text: // SPDX-License-Identifier: GPL-2.0
  /*
   * trace_events_hist - trace event hist triggers
   *
   * Copyright (C) 2015 Tom Zanussi <tom.zanussi@linux.intel.com>
   */
  
  #include <linux/module.h>
  #include <linux/kallsyms.h>
  #include <linux/security.h>
  #include <linux/mutex.h>
  #include <linux/slab.h>
  #include <linux/stacktrace.h>
  #include <linux/rculist.h>
  #include <linux/tracefs.h>
  
  /* for gfp flag names */
  #include <linux/trace_events.h>
  #include <trace/events/mmflags.h>
  
  #include "tracing_map.h"
  #include "trace_synth.h"
  
  #define ERRORS								\
  	C(NONE,			"No error"),				\
  	C(DUPLICATE_VAR,	"Variable already defined"),		\
  	C(VAR_NOT_UNIQUE,	"Variable name not unique, need to use fully qualified name (subsys.event.var) for variable"), \
  	C(TOO_MANY_VARS,	"Too many variables defined"),		\
  	C(MALFORMED_ASSIGNMENT,	"Malformed assignment"),		\
  	C(NAMED_MISMATCH,	"Named hist trigger doesn't match existing named trigger (includes variables)"), \
  	C(TRIGGER_EEXIST,	"Hist trigger already exists"),		\
  	C(TRIGGER_ENOENT_CLEAR,	"Can't clear or continue a nonexistent hist trigger"), \
  	C(SET_CLOCK_FAIL,	"Couldn't set trace_clock"),		\
  	C(BAD_FIELD_MODIFIER,	"Invalid field modifier"),		\
  	C(TOO_MANY_SUBEXPR,	"Too many subexpressions (3 max)"),	\
  	C(TIMESTAMP_MISMATCH,	"Timestamp units in expression don't match"), \
  	C(TOO_MANY_FIELD_VARS,	"Too many field variables defined"),	\
  	C(EVENT_FILE_NOT_FOUND,	"Event file not found"),		\
  	C(HIST_NOT_FOUND,	"Matching event histogram not found"),	\
  	C(HIST_CREATE_FAIL,	"Couldn't create histogram for field"),	\
  	C(SYNTH_VAR_NOT_FOUND,	"Couldn't find synthetic variable"),	\
  	C(SYNTH_EVENT_NOT_FOUND,"Couldn't find synthetic event"),	\
  	C(SYNTH_TYPE_MISMATCH,	"Param type doesn't match synthetic event field type"), \
  	C(SYNTH_COUNT_MISMATCH,	"Param count doesn't match synthetic event field count"), \
  	C(FIELD_VAR_PARSE_FAIL,	"Couldn't parse field variable"),	\
  	C(VAR_CREATE_FIND_FAIL,	"Couldn't create or find variable"),	\
  	C(ONX_NOT_VAR,		"For onmax(x) or onchange(x), x must be a variable"), \
  	C(ONX_VAR_NOT_FOUND,	"Couldn't find onmax or onchange variable"), \
  	C(ONX_VAR_CREATE_FAIL,	"Couldn't create onmax or onchange variable"), \
  	C(FIELD_VAR_CREATE_FAIL,"Couldn't create field variable"),	\
  	C(TOO_MANY_PARAMS,	"Too many action params"),		\
  	C(PARAM_NOT_FOUND,	"Couldn't find param"),			\
  	C(INVALID_PARAM,	"Invalid action param"),		\
  	C(ACTION_NOT_FOUND,	"No action found"),			\
  	C(NO_SAVE_PARAMS,	"No params found for save()"),		\
  	C(TOO_MANY_SAVE_ACTIONS,"Can't have more than one save() action per hist"), \
  	C(ACTION_MISMATCH,	"Handler doesn't support action"),	\
  	C(NO_CLOSING_PAREN,	"No closing paren found"),		\
  	C(SUBSYS_NOT_FOUND,	"Missing subsystem"),			\
  	C(INVALID_SUBSYS_EVENT,	"Invalid subsystem or event name"),	\
  	C(INVALID_REF_KEY,	"Using variable references in keys not supported"), \
  	C(VAR_NOT_FOUND,	"Couldn't find variable"),		\
  	C(FIELD_NOT_FOUND,	"Couldn't find field"),			\
  	C(EMPTY_ASSIGNMENT,	"Empty assignment"),			\
  	C(INVALID_SORT_MODIFIER,"Invalid sort modifier"),		\
  	C(EMPTY_SORT_FIELD,	"Empty sort field"),			\
  	C(TOO_MANY_SORT_FIELDS,	"Too many sort fields (Max = 2)"),	\
  	C(INVALID_SORT_FIELD,	"Sort field must be a key or a val"),	\
  	C(INVALID_STR_OPERAND,	"String type can not be an operand in expression"), \
  	C(EXPECT_NUMBER,	"Expecting numeric literal"),		\
  	C(UNARY_MINUS_SUBEXPR,	"Unary minus not supported in sub-expressions"), \
  	C(DIVISION_BY_ZERO,	"Division by zero"),
  
  #undef C
  #define C(a, b)		HIST_ERR_##a
  
  enum { ERRORS };
  
  #undef C
  #define C(a, b)		b
  
  static const char *err_text[] = { ERRORS };
  
  struct hist_field;
  
  typedef u64 (*hist_field_fn_t) (struct hist_field *field,
  				struct tracing_map_elt *elt,
  				struct trace_buffer *buffer,
  				struct ring_buffer_event *rbe,
  				void *event);
  
  #define HIST_FIELD_OPERANDS_MAX	2
  #define HIST_FIELDS_MAX		(TRACING_MAP_FIELDS_MAX + TRACING_MAP_VARS_MAX)
  #define HIST_ACTIONS_MAX	8
  #define HIST_CONST_DIGITS_MAX	21
  #define HIST_DIV_SHIFT		20  /* For optimizing division by constants */
  
  enum field_op_id {
  	FIELD_OP_NONE,
  	FIELD_OP_PLUS,
  	FIELD_OP_MINUS,
  	FIELD_OP_UNARY_MINUS,
  	FIELD_OP_DIV,
  	FIELD_OP_MULT,
  };
  
  /*
   * A hist_var (histogram variable) contains variable information for
   * hist_fields having the HIST_FIELD_FL_VAR or HIST_FIELD_FL_VAR_REF
   * flag set.  A hist_var has a variable name e.g. ts0, and is
   * associated with a given histogram trigger, as specified by
   * hist_data.  The hist_var idx is the unique index assigned to the
   * variable by the hist trigger's tracing_map.  The idx is what is
   * used to set a variable's value and, by a variable reference, to
   * retrieve it.
   */
  struct hist_var {
  	char				*name;
  	struct hist_trigger_data	*hist_data;
  	unsigned int			idx;
  };
  
  struct hist_field {
  	struct ftrace_event_field	*field;
  	unsigned long			flags;
  	hist_field_fn_t			fn;
  	unsigned int			ref;
  	unsigned int			size;
  	unsigned int			offset;
  	unsigned int                    is_signed;
  	unsigned long			buckets;
  	const char			*type;
  	struct hist_field		*operands[HIST_FIELD_OPERANDS_MAX];
  	struct hist_trigger_data	*hist_data;
  
  	/*
  	 * Variable fields contain variable-specific info in var.
  	 */
  	struct hist_var			var;
  	enum field_op_id		operator;
  	char				*system;
  	char				*event_name;
  
  	/*
  	 * The name field is used for EXPR and VAR_REF fields.  VAR
  	 * fields contain the variable name in var.name.
  	 */
  	char				*name;
  
  	/*
  	 * When a histogram trigger is hit, if it has any references
  	 * to variables, the values of those variables are collected
  	 * into a var_ref_vals array by resolve_var_refs().  The
  	 * current value of each variable is read from the tracing_map
  	 * using the hist field's hist_var.idx and entered into the
  	 * var_ref_idx entry i.e. var_ref_vals[var_ref_idx].
  	 */
  	unsigned int			var_ref_idx;
  	bool                            read_once;
  
  	unsigned int			var_str_idx;
  
  	/* Numeric literals are represented as u64 */
  	u64				constant;
  	/* Used to optimize division by constants */
  	u64				div_multiplier;
  };
  
  static u64 hist_field_none(struct hist_field *field,
  			   struct tracing_map_elt *elt,
  			   struct trace_buffer *buffer,
  			   struct ring_buffer_event *rbe,
  			   void *event)
  {
  	return 0;
  }
  
  static u64 hist_field_const(struct hist_field *field,
  			   struct tracing_map_elt *elt,
  			   struct trace_buffer *buffer,
  			   struct ring_buffer_event *rbe,
  			   void *event)
  {
  	return field->constant;
  }
  
  static u64 hist_field_counter(struct hist_field *field,
  			      struct tracing_map_elt *elt,
  			      struct trace_buffer *buffer,
  			      struct ring_buffer_event *rbe,
  			      void *event)
  {
  	return 1;
  }
  
  static u64 hist_field_string(struct hist_field *hist_field,
  			     struct tracing_map_elt *elt,
  			     struct trace_buffer *buffer,
  			     struct ring_buffer_event *rbe,
  			     void *event)
  {
  	char *addr = (char *)(event + hist_field->field->offset);
  
  	return (u64)(unsigned long)addr;
  }
  
  static u64 hist_field_dynstring(struct hist_field *hist_field,
  				struct tracing_map_elt *elt,
  				struct trace_buffer *buffer,
  				struct ring_buffer_event *rbe,
  				void *event)
  {
  	u32 str_item = *(u32 *)(event + hist_field->field->offset);
  	int str_loc = str_item & 0xffff;
  	char *addr = (char *)(event + str_loc);
  
  	return (u64)(unsigned long)addr;
  }
  
  static u64 hist_field_reldynstring(struct hist_field *hist_field,
  				   struct tracing_map_elt *elt,
  				   struct trace_buffer *buffer,
  				   struct ring_buffer_event *rbe,
  				   void *event)
  {
  	u32 *item = event + hist_field->field->offset;
  	u32 str_item = *item;
  	int str_loc = str_item & 0xffff;
  	char *addr = (char *)&item[1] + str_loc;
  
  	return (u64)(unsigned long)addr;
  }
  
  static u64 hist_field_pstring(struct hist_field *hist_field,
  			      struct tracing_map_elt *elt,
  			      struct trace_buffer *buffer,
  			      struct ring_buffer_event *rbe,
  			      void *event)
  {
  	char **addr = (char **)(event + hist_field->field->offset);
  
  	return (u64)(unsigned long)*addr;
  }
  
  static u64 hist_field_log2(struct hist_field *hist_field,
  			   struct tracing_map_elt *elt,
  			   struct trace_buffer *buffer,
  			   struct ring_buffer_event *rbe,
  			   void *event)
  {
  	struct hist_field *operand = hist_field->operands[0];
  
  	u64 val = operand->fn(operand, elt, buffer, rbe, event);
  
  	return (u64) ilog2(roundup_pow_of_two(val));
  }
  
  static u64 hist_field_bucket(struct hist_field *hist_field,
  			     struct tracing_map_elt *elt,
  			     struct trace_buffer *buffer,
  			     struct ring_buffer_event *rbe,
  			     void *event)
  {
  	struct hist_field *operand = hist_field->operands[0];
  	unsigned long buckets = hist_field->buckets;
  
  	u64 val = operand->fn(operand, elt, buffer, rbe, event);
  
  	if (WARN_ON_ONCE(!buckets))
  		return val;
  
  	if (val >= LONG_MAX)
  		val = div64_ul(val, buckets);
  	else
  		val = (u64)((unsigned long)val / buckets);
  	return val * buckets;
  }
  
  static u64 hist_field_plus(struct hist_field *hist_field,
  			   struct tracing_map_elt *elt,
  			   struct trace_buffer *buffer,
  			   struct ring_buffer_event *rbe,
  			   void *event)
  {
  	struct hist_field *operand1 = hist_field->operands[0];
  	struct hist_field *operand2 = hist_field->operands[1];
  
  	u64 val1 = operand1->fn(operand1, elt, buffer, rbe, event);
  	u64 val2 = operand2->fn(operand2, elt, buffer, rbe, event);
  
  	return val1 + val2;
  }
  
  static u64 hist_field_minus(struct hist_field *hist_field,
  			    struct tracing_map_elt *elt,
  			    struct trace_buffer *buffer,
  			    struct ring_buffer_event *rbe,
  			    void *event)
  {
  	struct hist_field *operand1 = hist_field->operands[0];
  	struct hist_field *operand2 = hist_field->operands[1];
  
  	u64 val1 = operand1->fn(operand1, elt, buffer, rbe, event);
  	u64 val2 = operand2->fn(operand2, elt, buffer, rbe, event);
  
  	return val1 - val2;
  }
  
  static u64 hist_field_div(struct hist_field *hist_field,
  			   struct tracing_map_elt *elt,
  			   struct trace_buffer *buffer,
  			   struct ring_buffer_event *rbe,
  			   void *event)
  {
  	struct hist_field *operand1 = hist_field->operands[0];
  	struct hist_field *operand2 = hist_field->operands[1];
  
  	u64 val1 = operand1->fn(operand1, elt, buffer, rbe, event);
  	u64 val2 = operand2->fn(operand2, elt, buffer, rbe, event);
  
  	/* Return -1 for the undefined case */
  	if (!val2)
  		return -1;
  
  	/* Use shift if the divisor is a power of 2 */
  	if (!(val2 & (val2 - 1)))
  		return val1 >> __ffs64(val2);
  
  	return div64_u64(val1, val2);
  }
  
  static u64 div_by_power_of_two(struct hist_field *hist_field,
  				struct tracing_map_elt *elt,
  				struct trace_buffer *buffer,
  				struct ring_buffer_event *rbe,
  				void *event)
  {
  	struct hist_field *operand1 = hist_field->operands[0];
  	struct hist_field *operand2 = hist_field->operands[1];
  
  	u64 val1 = operand1->fn(operand1, elt, buffer, rbe, event);
  
  	return val1 >> __ffs64(operand2->constant);
  }
  
  static u64 div_by_not_power_of_two(struct hist_field *hist_field,
  				struct tracing_map_elt *elt,
  				struct trace_buffer *buffer,
  				struct ring_buffer_event *rbe,
  				void *event)
  {
  	struct hist_field *operand1 = hist_field->operands[0];
  	struct hist_field *operand2 = hist_field->operands[1];
  
  	u64 val1 = operand1->fn(operand1, elt, buffer, rbe, event);
  
  	return div64_u64(val1, operand2->constant);
  }
  
  static u64 div_by_mult_and_shift(struct hist_field *hist_field,
  				struct tracing_map_elt *elt,
  				struct trace_buffer *buffer,
  				struct ring_buffer_event *rbe,
  				void *event)
  {
  	struct hist_field *operand1 = hist_field->operands[0];
  	struct hist_field *operand2 = hist_field->operands[1];
  
  	u64 val1 = operand1->fn(operand1, elt, buffer, rbe, event);
  
  	/*
  	 * If the divisor is a constant, do a multiplication and shift instead.
  	 *
  	 * Choose Z = some power of 2. If Y <= Z, then:
  	 *     X / Y = (X * (Z / Y)) / Z
  	 *
  	 * (Z / Y) is a constant (mult) which is calculated at parse time, so:
  	 *     X / Y = (X * mult) / Z
  	 *
  	 * The division by Z can be replaced by a shift since Z is a power of 2:
  	 *     X / Y = (X * mult) >> HIST_DIV_SHIFT
  	 *
  	 * As long, as X < Z the results will not be off by more than 1.
  	 */
  	if (val1 < (1 << HIST_DIV_SHIFT)) {
  		u64 mult = operand2->div_multiplier;
  
  		return (val1 * mult + ((1 << HIST_DIV_SHIFT) - 1)) >> HIST_DIV_SHIFT;
  	}
  
  	return div64_u64(val1, operand2->constant);
  }
  
  static u64 hist_field_mult(struct hist_field *hist_field,
  			   struct tracing_map_elt *elt,
  			   struct trace_buffer *buffer,
  			   struct ring_buffer_event *rbe,
  			   void *event)
  {
  	struct hist_field *operand1 = hist_field->operands[0];
  	struct hist_field *operand2 = hist_field->operands[1];
  
  	u64 val1 = operand1->fn(operand1, elt, buffer, rbe, event);
  	u64 val2 = operand2->fn(operand2, elt, buffer, rbe, event);
  
  	return val1 * val2;
  }
  
  static u64 hist_field_unary_minus(struct hist_field *hist_field,
  				  struct tracing_map_elt *elt,
  				  struct trace_buffer *buffer,
  				  struct ring_buffer_event *rbe,
  				  void *event)
  {
  	struct hist_field *operand = hist_field->operands[0];
  
  	s64 sval = (s64)operand->fn(operand, elt, buffer, rbe, event);
  	u64 val = (u64)-sval;
  
  	return val;
  }
  
  #define DEFINE_HIST_FIELD_FN(type)					\
  	static u64 hist_field_##type(struct hist_field *hist_field,	\
  				     struct tracing_map_elt *elt,	\
  				     struct trace_buffer *buffer,	\
  				     struct ring_buffer_event *rbe,	\
  				     void *event)			\
  {									\
  	type *addr = (type *)(event + hist_field->field->offset);	\
  									\
  	return (u64)(unsigned long)*addr;				\
  }
  
  DEFINE_HIST_FIELD_FN(s64);
  DEFINE_HIST_FIELD_FN(u64);
  DEFINE_HIST_FIELD_FN(s32);
  DEFINE_HIST_FIELD_FN(u32);
  DEFINE_HIST_FIELD_FN(s16);
  DEFINE_HIST_FIELD_FN(u16);
  DEFINE_HIST_FIELD_FN(s8);
  DEFINE_HIST_FIELD_FN(u8);
  
  #define for_each_hist_field(i, hist_data)	\
  	for ((i) = 0; (i) < (hist_data)->n_fields; (i)++)
  
  #define for_each_hist_val_field(i, hist_data)	\
  	for ((i) = 0; (i) < (hist_data)->n_vals; (i)++)
  
  #define for_each_hist_key_field(i, hist_data)	\
  	for ((i) = (hist_data)->n_vals; (i) < (hist_data)->n_fields; (i)++)
  
  #define HIST_STACKTRACE_DEPTH	16
  #define HIST_STACKTRACE_SIZE	(HIST_STACKTRACE_DEPTH * sizeof(unsigned long))
  #define HIST_STACKTRACE_SKIP	5
  
  #define HITCOUNT_IDX		0
  #define HIST_KEY_SIZE_MAX	(MAX_FILTER_STR_VAL + HIST_STACKTRACE_SIZE)
  
  enum hist_field_flags {
  	HIST_FIELD_FL_HITCOUNT		= 1 << 0,
  	HIST_FIELD_FL_KEY		= 1 << 1,
  	HIST_FIELD_FL_STRING		= 1 << 2,
  	HIST_FIELD_FL_HEX		= 1 << 3,
  	HIST_FIELD_FL_SYM		= 1 << 4,
  	HIST_FIELD_FL_SYM_OFFSET	= 1 << 5,
  	HIST_FIELD_FL_EXECNAME		= 1 << 6,
  	HIST_FIELD_FL_SYSCALL		= 1 << 7,
  	HIST_FIELD_FL_STACKTRACE	= 1 << 8,
  	HIST_FIELD_FL_LOG2		= 1 << 9,
  	HIST_FIELD_FL_TIMESTAMP		= 1 << 10,
  	HIST_FIELD_FL_TIMESTAMP_USECS	= 1 << 11,
  	HIST_FIELD_FL_VAR		= 1 << 12,
  	HIST_FIELD_FL_EXPR		= 1 << 13,
  	HIST_FIELD_FL_VAR_REF		= 1 << 14,
  	HIST_FIELD_FL_CPU		= 1 << 15,
  	HIST_FIELD_FL_ALIAS		= 1 << 16,
  	HIST_FIELD_FL_BUCKET		= 1 << 17,
  	HIST_FIELD_FL_CONST		= 1 << 18,
  };
  
  struct var_defs {
  	unsigned int	n_vars;
  	char		*name[TRACING_MAP_VARS_MAX];
  	char		*expr[TRACING_MAP_VARS_MAX];
  };
  
  struct hist_trigger_attrs {
  	char		*keys_str;
  	char		*vals_str;
  	char		*sort_key_str;
  	char		*name;
  	char		*clock;
  	bool		pause;
  	bool		cont;
  	bool		clear;
  	bool		ts_in_usecs;
  	unsigned int	map_bits;
  
  	char		*assignment_str[TRACING_MAP_VARS_MAX];
  	unsigned int	n_assignments;
  
  	char		*action_str[HIST_ACTIONS_MAX];
  	unsigned int	n_actions;
  
  	struct var_defs	var_defs;
  };
  
  struct field_var {
  	struct hist_field	*var;
  	struct hist_field	*val;
  };
  
  struct field_var_hist {
  	struct hist_trigger_data	*hist_data;
  	char				*cmd;
  };
  
  struct hist_trigger_data {
  	struct hist_field               *fields[HIST_FIELDS_MAX];
  	unsigned int			n_vals;
  	unsigned int			n_keys;
  	unsigned int			n_fields;
  	unsigned int			n_vars;
  	unsigned int			n_var_str;
  	unsigned int			key_size;
  	struct tracing_map_sort_key	sort_keys[TRACING_MAP_SORT_KEYS_MAX];
  	unsigned int			n_sort_keys;
  	struct trace_event_file		*event_file;
  	struct hist_trigger_attrs	*attrs;
  	struct tracing_map		*map;
  	bool				enable_timestamps;
  	bool				remove;
  	struct hist_field               *var_refs[TRACING_MAP_VARS_MAX];
  	unsigned int			n_var_refs;
  
  	struct action_data		*actions[HIST_ACTIONS_MAX];
  	unsigned int			n_actions;
  
  	struct field_var		*field_vars[SYNTH_FIELDS_MAX];
  	unsigned int			n_field_vars;
  	unsigned int			n_field_var_str;
  	struct field_var_hist		*field_var_hists[SYNTH_FIELDS_MAX];
  	unsigned int			n_field_var_hists;
  
  	struct field_var		*save_vars[SYNTH_FIELDS_MAX];
  	unsigned int			n_save_vars;
  	unsigned int			n_save_var_str;
  };
  
  struct action_data;
  
  typedef void (*action_fn_t) (struct hist_trigger_data *hist_data,
  			     struct tracing_map_elt *elt,
  			     struct trace_buffer *buffer, void *rec,
  			     struct ring_buffer_event *rbe, void *key,
  			     struct action_data *data, u64 *var_ref_vals);
  
  typedef bool (*check_track_val_fn_t) (u64 track_val, u64 var_val);
  
  enum handler_id {
  	HANDLER_ONMATCH = 1,
  	HANDLER_ONMAX,
  	HANDLER_ONCHANGE,
  };
  
  enum action_id {
  	ACTION_SAVE = 1,
  	ACTION_TRACE,
  	ACTION_SNAPSHOT,
  };
  
  struct action_data {
  	enum handler_id		handler;
  	enum action_id		action;
  	char			*action_name;
  	action_fn_t		fn;
  
  	unsigned int		n_params;
  	char			*params[SYNTH_FIELDS_MAX];
  
  	/*
  	 * When a histogram trigger is hit, the values of any
  	 * references to variables, including variables being passed
  	 * as parameters to synthetic events, are collected into a
  	 * var_ref_vals array.  This var_ref_idx array is an array of
  	 * indices into the var_ref_vals array, one for each synthetic
  	 * event param, and is passed to the synthetic event
  	 * invocation.
  	 */
  	unsigned int		var_ref_idx[TRACING_MAP_VARS_MAX];
  	struct synth_event	*synth_event;
  	bool			use_trace_keyword;
  	char			*synth_event_name;
  
  	union {
  		struct {
  			char			*event;
  			char			*event_system;
  		} match_data;
  
  		struct {
  			/*
  			 * var_str contains the $-unstripped variable
  			 * name referenced by var_ref, and used when
  			 * printing the action.  Because var_ref
  			 * creation is deferred to create_actions(),
  			 * we need a per-action way to save it until
  			 * then, thus var_str.
  			 */
  			char			*var_str;
  
  			/*
  			 * var_ref refers to the variable being
  			 * tracked e.g onmax($var).
  			 */
  			struct hist_field	*var_ref;
  
  			/*
  			 * track_var contains the 'invisible' tracking
  			 * variable created to keep the current
  			 * e.g. max value.
  			 */
  			struct hist_field	*track_var;
  
  			check_track_val_fn_t	check_val;
  			action_fn_t		save_data;
  		} track_data;
  	};
  };
  
  struct track_data {
  	u64				track_val;
  	bool				updated;
  
  	unsigned int			key_len;
  	void				*key;
  	struct tracing_map_elt		elt;
  
  	struct action_data		*action_data;
  	struct hist_trigger_data	*hist_data;
  };
  
  struct hist_elt_data {
  	char *comm;
  	u64 *var_ref_vals;
  	char **field_var_str;
  	int n_field_var_str;
  };
  
  struct snapshot_context {
  	struct tracing_map_elt	*elt;
  	void			*key;
  };
  
  /*
   * Returns the specific division function to use if the divisor
   * is constant. This avoids extra branches when the trigger is hit.
   */
  static hist_field_fn_t hist_field_get_div_fn(struct hist_field *divisor)
  {
  	u64 div = divisor->constant;
  
  	if (!(div & (div - 1)))
  		return div_by_power_of_two;
  
  	/* If the divisor is too large, do a regular division */
  	if (div > (1 << HIST_DIV_SHIFT))
  		return div_by_not_power_of_two;
  
  	divisor->div_multiplier = div64_u64((u64)(1 << HIST_DIV_SHIFT), div);
  	return div_by_mult_and_shift;
  }
  
  static void track_data_free(struct track_data *track_data)
  {
  	struct hist_elt_data *elt_data;
  
  	if (!track_data)
  		return;
  
  	kfree(track_data->key);
  
  	elt_data = track_data->elt.private_data;
  	if (elt_data) {
  		kfree(elt_data->comm);
  		kfree(elt_data);
  	}
  
  	kfree(track_data);
  }
  
  static struct track_data *track_data_alloc(unsigned int key_len,
  					   struct action_data *action_data,
  					   struct hist_trigger_data *hist_data)
  {
  	struct track_data *data = kzalloc(sizeof(*data), GFP_KERNEL);
  	struct hist_elt_data *elt_data;
  
  	if (!data)
  		return ERR_PTR(-ENOMEM);
  
  	data->key = kzalloc(key_len, GFP_KERNEL);
  	if (!data->key) {
  		track_data_free(data);
  		return ERR_PTR(-ENOMEM);
  	}
  
  	data->key_len = key_len;
  	data->action_data = action_data;
  	data->hist_data = hist_data;
  
  	elt_data = kzalloc(sizeof(*elt_data), GFP_KERNEL);
  	if (!elt_data) {
  		track_data_free(data);
  		return ERR_PTR(-ENOMEM);
  	}
  
  	data->elt.private_data = elt_data;
  
  	elt_data->comm = kzalloc(TASK_COMM_LEN, GFP_KERNEL);
  	if (!elt_data->comm) {
  		track_data_free(data);
  		return ERR_PTR(-ENOMEM);
  	}
  
  	return data;
  }
  
  #define HIST_PREFIX "hist:"
  
  static char *last_cmd;
  static char last_cmd_loc[MAX_FILTER_STR_VAL];
  
  static int errpos(char *str)
  {
  	if (!str || !last_cmd)
  		return 0;
  
  	return err_pos(last_cmd, str);
  }
  
  static void last_cmd_set(struct trace_event_file *file, char *str)
  {
  	const char *system = NULL, *name = NULL;
  	struct trace_event_call *call;
  	int len;
  
  	if (!str)
  		return;
  
  	/* sizeof() contains the nul byte */
  	len = sizeof(HIST_PREFIX) + strlen(str);
  	kfree(last_cmd);
  	last_cmd = kzalloc(len, GFP_KERNEL);
  	if (!last_cmd)
  		return;
  
  	strcpy(last_cmd, HIST_PREFIX);
  	/* Again, sizeof() contains the nul byte */
  	len -= sizeof(HIST_PREFIX);
  	strncat(last_cmd, str, len);
  
  	if (file) {
  		call = file->event_call;
  		system = call->class->system;
  		if (system) {
  			name = trace_event_name(call);
  			if (!name)
  				system = NULL;
  		}
  	}
  
  	if (system)
  		snprintf(last_cmd_loc, MAX_FILTER_STR_VAL, HIST_PREFIX "%s:%s", system, name);
  }
  
  static void hist_err(struct trace_array *tr, u8 err_type, u16 err_pos)
  {
  	if (!last_cmd)
  		return;
  
  	tracing_log_err(tr, last_cmd_loc, last_cmd, err_text,
  			err_type, err_pos);
  }
  
  static void hist_err_clear(void)
  {
  	if (last_cmd)
  		last_cmd[0] = '\0';
  	last_cmd_loc[0] = '\0';
  }
  
  typedef void (*synth_probe_func_t) (void *__data, u64 *var_ref_vals,
  				    unsigned int *var_ref_idx);
  
  static inline void trace_synth(struct synth_event *event, u64 *var_ref_vals,
  			       unsigned int *var_ref_idx)
  {
  	struct tracepoint *tp = event->tp;
  
  	if (unlikely(atomic_read(&tp->key.enabled) > 0)) {
  		struct tracepoint_func *probe_func_ptr;
  		synth_probe_func_t probe_func;
  		void *__data;
  
  		if (!(cpu_online(raw_smp_processor_id())))
  			return;
  
  		probe_func_ptr = rcu_dereference_sched((tp)->funcs);
  		if (probe_func_ptr) {
  			do {
  				probe_func = probe_func_ptr->func;
  				__data = probe_func_ptr->data;
  				probe_func(__data, var_ref_vals, var_ref_idx);
  			} while ((++probe_func_ptr)->func);
  		}
  	}
  }
  
  static void action_trace(struct hist_trigger_data *hist_data,
  			 struct tracing_map_elt *elt,
  			 struct trace_buffer *buffer, void *rec,
  			 struct ring_buffer_event *rbe, void *key,
  			 struct action_data *data, u64 *var_ref_vals)
  {
  	struct synth_event *event = data->synth_event;
  
  	trace_synth(event, var_ref_vals, data->var_ref_idx);
  }
  
  struct hist_var_data {
  	struct list_head list;
  	struct hist_trigger_data *hist_data;
  };
  
  static u64 hist_field_timestamp(struct hist_field *hist_field,
  				struct tracing_map_elt *elt,
  				struct trace_buffer *buffer,
  				struct ring_buffer_event *rbe,
  				void *event)
  {
  	struct hist_trigger_data *hist_data = hist_field->hist_data;
  	struct trace_array *tr = hist_data->event_file->tr;
  
  	u64 ts = ring_buffer_event_time_stamp(buffer, rbe);
  
  	if (hist_data->attrs->ts_in_usecs && trace_clock_in_ns(tr))
  		ts = ns2usecs(ts);
  
  	return ts;
  }
  
  static u64 hist_field_cpu(struct hist_field *hist_field,
  			  struct tracing_map_elt *elt,
  			  struct trace_buffer *buffer,
  			  struct ring_buffer_event *rbe,
  			  void *event)
  {
  	int cpu = smp_processor_id();
  
  	return cpu;
  }
  
  /**
   * check_field_for_var_ref - Check if a VAR_REF field references a variable
   * @hist_field: The VAR_REF field to check
   * @var_data: The hist trigger that owns the variable
   * @var_idx: The trigger variable identifier
   *
   * Check the given VAR_REF field to see whether or not it references
   * the given variable associated with the given trigger.
   *
   * Return: The VAR_REF field if it does reference the variable, NULL if not
   */
  static struct hist_field *
  check_field_for_var_ref(struct hist_field *hist_field,
  			struct hist_trigger_data *var_data,
  			unsigned int var_idx)
  {
  	WARN_ON(!(hist_field && hist_field->flags & HIST_FIELD_FL_VAR_REF));
  
  	if (hist_field && hist_field->var.idx == var_idx &&
  	    hist_field->var.hist_data == var_data)
  		return hist_field;
  
  	return NULL;
  }
  
  /**
   * find_var_ref - Check if a trigger has a reference to a trigger variable
   * @hist_data: The hist trigger that might have a reference to the variable
   * @var_data: The hist trigger that owns the variable
   * @var_idx: The trigger variable identifier
   *
   * Check the list of var_refs[] on the first hist trigger to see
   * whether any of them are references to the variable on the second
   * trigger.
   *
   * Return: The VAR_REF field referencing the variable if so, NULL if not
   */
  static struct hist_field *find_var_ref(struct hist_trigger_data *hist_data,
  				       struct hist_trigger_data *var_data,
  				       unsigned int var_idx)
  {
  	struct hist_field *hist_field;
  	unsigned int i;
  
  	for (i = 0; i < hist_data->n_var_refs; i++) {
  		hist_field = hist_data->var_refs[i];
  		if (check_field_for_var_ref(hist_field, var_data, var_idx))
  			return hist_field;
  	}
  
  	return NULL;
  }
  
  /**
   * find_any_var_ref - Check if there is a reference to a given trigger variable
   * @hist_data: The hist trigger
   * @var_idx: The trigger variable identifier
   *
   * Check to see whether the given variable is currently referenced by
   * any other trigger.
   *
   * The trigger the variable is defined on is explicitly excluded - the
   * assumption being that a self-reference doesn't prevent a trigger
   * from being removed.
   *
   * Return: The VAR_REF field referencing the variable if so, NULL if not
   */
  static struct hist_field *find_any_var_ref(struct hist_trigger_data *hist_data,
  					   unsigned int var_idx)
  {
  	struct trace_array *tr = hist_data->event_file->tr;
  	struct hist_field *found = NULL;
  	struct hist_var_data *var_data;
  
  	list_for_each_entry(var_data, &tr->hist_vars, list) {
  		if (var_data->hist_data == hist_data)
  			continue;
  		found = find_var_ref(var_data->hist_data, hist_data, var_idx);
  		if (found)
  			break;
  	}
  
  	return found;
  }
  
  /**
   * check_var_refs - Check if there is a reference to any of trigger's variables
   * @hist_data: The hist trigger
   *
   * A trigger can define one or more variables.  If any one of them is
   * currently referenced by any other trigger, this function will
   * determine that.
  
   * Typically used to determine whether or not a trigger can be removed
   * - if there are any references to a trigger's variables, it cannot.
   *
   * Return: True if there is a reference to any of trigger's variables
   */
  static bool check_var_refs(struct hist_trigger_data *hist_data)
  {
  	struct hist_field *field;
  	bool found = false;
  	int i;
  
  	for_each_hist_field(i, hist_data) {
  		field = hist_data->fields[i];
  		if (field && field->flags & HIST_FIELD_FL_VAR) {
  			if (find_any_var_ref(hist_data, field->var.idx)) {
  				found = true;
  				break;
  			}
  		}
  	}
  
  	return found;
  }
  
  static struct hist_var_data *find_hist_vars(struct hist_trigger_data *hist_data)
  {
  	struct trace_array *tr = hist_data->event_file->tr;
  	struct hist_var_data *var_data, *found = NULL;
  
  	list_for_each_entry(var_data, &tr->hist_vars, list) {
  		if (var_data->hist_data == hist_data) {
  			found = var_data;
  			break;
  		}
  	}
  
  	return found;
  }
  
  static bool field_has_hist_vars(struct hist_field *hist_field,
  				unsigned int level)
  {
  	int i;
  
  	if (level > 3)
  		return false;
  
  	if (!hist_field)
  		return false;
  
  	if (hist_field->flags & HIST_FIELD_FL_VAR ||
  	    hist_field->flags & HIST_FIELD_FL_VAR_REF)
  		return true;
  
  	for (i = 0; i < HIST_FIELD_OPERANDS_MAX; i++) {
  		struct hist_field *operand;
  
  		operand = hist_field->operands[i];
  		if (field_has_hist_vars(operand, level + 1))
  			return true;
  	}
  
  	return false;
  }
  
  static bool has_hist_vars(struct hist_trigger_data *hist_data)
  {
  	struct hist_field *hist_field;
  	int i;
  
  	for_each_hist_field(i, hist_data) {
  		hist_field = hist_data->fields[i];
  		if (field_has_hist_vars(hist_field, 0))
  			return true;
  	}
  
  	return false;
  }
  
  static int save_hist_vars(struct hist_trigger_data *hist_data)
  {
  	struct trace_array *tr = hist_data->event_file->tr;
  	struct hist_var_data *var_data;
  
  	var_data = find_hist_vars(hist_data);
  	if (var_data)
  		return 0;
  
  	if (tracing_check_open_get_tr(tr))
  		return -ENODEV;
  
  	var_data = kzalloc(sizeof(*var_data), GFP_KERNEL);
  	if (!var_data) {
  		trace_array_put(tr);
  		return -ENOMEM;
  	}
  
  	var_data->hist_data = hist_data;
  	list_add(&var_data->list, &tr->hist_vars);
  
  	return 0;
  }
  
  static void remove_hist_vars(struct hist_trigger_data *hist_data)
  {
  	struct trace_array *tr = hist_data->event_file->tr;
  	struct hist_var_data *var_data;
  
  	var_data = find_hist_vars(hist_data);
  	if (!var_data)
  		return;
  
  	if (WARN_ON(check_var_refs(hist_data)))
  		return;
  
  	list_del(&var_data->list);
  
  	kfree(var_data);
  
  	trace_array_put(tr);
  }
  
  static struct hist_field *find_var_field(struct hist_trigger_data *hist_data,
  					 const char *var_name)
  {
  	struct hist_field *hist_field, *found = NULL;
  	int i;
  
  	for_each_hist_field(i, hist_data) {
  		hist_field = hist_data->fields[i];
  		if (hist_field && hist_field->flags & HIST_FIELD_FL_VAR &&
  		    strcmp(hist_field->var.name, var_name) == 0) {
  			found = hist_field;
  			break;
  		}
  	}
  
  	return found;
  }
  
  static struct hist_field *find_var(struct hist_trigger_data *hist_data,
  				   struct trace_event_file *file,
  				   const char *var_name)
  {
  	struct hist_trigger_data *test_data;
  	struct event_trigger_data *test;
  	struct hist_field *hist_field;
  
  	lockdep_assert_held(&event_mutex);
  
  	hist_field = find_var_field(hist_data, var_name);
  	if (hist_field)
  		return hist_field;
  
  	list_for_each_entry(test, &file->triggers, list) {
  		if (test->cmd_ops->trigger_type == ETT_EVENT_HIST) {
  			test_data = test->private_data;
  			hist_field = find_var_field(test_data, var_name);
  			if (hist_field)
  				return hist_field;
  		}
  	}
  
  	return NULL;
  }
  
  static struct trace_event_file *find_var_file(struct trace_array *tr,
  					      char *system,
  					      char *event_name,
  					      char *var_name)
  {
  	struct hist_trigger_data *var_hist_data;
  	struct hist_var_data *var_data;
  	struct trace_event_file *file, *found = NULL;
  
  	if (system)
  		return find_event_file(tr, system, event_name);
  
  	list_for_each_entry(var_data, &tr->hist_vars, list) {
  		var_hist_data = var_data->hist_data;
  		file = var_hist_data->event_file;
  		if (file == found)
  			continue;
  
  		if (find_var_field(var_hist_data, var_name)) {
  			if (found) {
  				hist_err(tr, HIST_ERR_VAR_NOT_UNIQUE, errpos(var_name));
  				return NULL;
  			}
  
  			found = file;
  		}
  	}
  
  	return found;
  }
  
  static struct hist_field *find_file_var(struct trace_event_file *file,
  					const char *var_name)
  {
  	struct hist_trigger_data *test_data;
  	struct event_trigger_data *test;
  	struct hist_field *hist_field;
  
  	lockdep_assert_held(&event_mutex);
  
  	list_for_each_entry(test, &file->triggers, list) {
  		if (test->cmd_ops->trigger_type == ETT_EVENT_HIST) {
  			test_data = test->private_data;
  			hist_field = find_var_field(test_data, var_name);
  			if (hist_field)
  				return hist_field;
  		}
  	}
  
  	return NULL;
  }
  
  static struct hist_field *
  find_match_var(struct hist_trigger_data *hist_data, char *var_name)
  {
  	struct trace_array *tr = hist_data->event_file->tr;
  	struct hist_field *hist_field, *found = NULL;
  	struct trace_event_file *file;
  	unsigned int i;
  
  	for (i = 0; i < hist_data->n_actions; i++) {
  		struct action_data *data = hist_data->actions[i];
  
  		if (data->handler == HANDLER_ONMATCH) {
  			char *system = data->match_data.event_system;
  			char *event_name = data->match_data.event;
  
  			file = find_var_file(tr, system, event_name, var_name);
  			if (!file)
  				continue;
  			hist_field = find_file_var(file, var_name);
  			if (hist_field) {
  				if (found) {
  					hist_err(tr, HIST_ERR_VAR_NOT_UNIQUE,
  						 errpos(var_name));
  					return ERR_PTR(-EINVAL);
  				}
  
  				found = hist_field;
  			}
  		}
  	}
  	return found;
  }
  
  static struct hist_field *find_event_var(struct hist_trigger_data *hist_data,
  					 char *system,
  					 char *event_name,
  					 char *var_name)
  {
  	struct trace_array *tr = hist_data->event_file->tr;
  	struct hist_field *hist_field = NULL;
  	struct trace_event_file *file;
  
  	if (!system || !event_name) {
  		hist_field = find_match_var(hist_data, var_name);
  		if (IS_ERR(hist_field))
  			return NULL;
  		if (hist_field)
  			return hist_field;
  	}
  
  	file = find_var_file(tr, system, event_name, var_name);
  	if (!file)
  		return NULL;
  
  	hist_field = find_file_var(file, var_name);
  
  	return hist_field;
  }
  
  static u64 hist_field_var_ref(struct hist_field *hist_field,
  			      struct tracing_map_elt *elt,
  			      struct trace_buffer *buffer,
  			      struct ring_buffer_event *rbe,
  			      void *event)
  {
  	struct hist_elt_data *elt_data;
  	u64 var_val = 0;
  
  	if (WARN_ON_ONCE(!elt))
  		return var_val;
  
  	elt_data = elt->private_data;
  	var_val = elt_data->var_ref_vals[hist_field->var_ref_idx];
  
  	return var_val;
  }
  
  static bool resolve_var_refs(struct hist_trigger_data *hist_data, void *key,
  			     u64 *var_ref_vals, bool self)
  {
  	struct hist_trigger_data *var_data;
  	struct tracing_map_elt *var_elt;
  	struct hist_field *hist_field;
  	unsigned int i, var_idx;
  	bool resolved = true;
  	u64 var_val = 0;
  
  	for (i = 0; i < hist_data->n_var_refs; i++) {
  		hist_field = hist_data->var_refs[i];
  		var_idx = hist_field->var.idx;
  		var_data = hist_field->var.hist_data;
  
  		if (var_data == NULL) {
  			resolved = false;
  			break;
  		}
  
  		if ((self && var_data != hist_data) ||
  		    (!self && var_data == hist_data))
  			continue;
  
  		var_elt = tracing_map_lookup(var_data->map, key);
  		if (!var_elt) {
  			resolved = false;
  			break;
  		}
  
  		if (!tracing_map_var_set(var_elt, var_idx)) {
  			resolved = false;
  			break;
  		}
  
  		if (self || !hist_field->read_once)
  			var_val = tracing_map_read_var(var_elt, var_idx);
  		else
  			var_val = tracing_map_read_var_once(var_elt, var_idx);
  
  		var_ref_vals[i] = var_val;
  	}
  
  	return resolved;
  }
  
  static const char *hist_field_name(struct hist_field *field,
  				   unsigned int level)
  {
  	const char *field_name = "";
  
  	if (level > 1)
  		return field_name;
  
  	if (field->field)
  		field_name = field->field->name;
  	else if (field->flags & HIST_FIELD_FL_LOG2 ||
  		 field->flags & HIST_FIELD_FL_ALIAS ||
  		 field->flags & HIST_FIELD_FL_BUCKET)
  		field_name = hist_field_name(field->operands[0], ++level);
  	else if (field->flags & HIST_FIELD_FL_CPU)
  		field_name = "common_cpu";
  	else if (field->flags & HIST_FIELD_FL_EXPR ||
  		 field->flags & HIST_FIELD_FL_VAR_REF) {
  		if (field->system) {
  			static char full_name[MAX_FILTER_STR_VAL];
  
  			strcat(full_name, field->system);
  			strcat(full_name, ".");
  			strcat(full_name, field->event_name);
  			strcat(full_name, ".");
  			strcat(full_name, field->name);
  			field_name = full_name;
  		} else
  			field_name = field->name;
  	} else if (field->flags & HIST_FIELD_FL_TIMESTAMP)
  		field_name = "common_timestamp";
  
  	if (field_name == NULL)
  		field_name = "";
  
  	return field_name;
  }
  
  static hist_field_fn_t select_value_fn(int field_size, int field_is_signed)
  {
  	hist_field_fn_t fn = NULL;
  
  	switch (field_size) {
  	case 8:
  		if (field_is_signed)
  			fn = hist_field_s64;
  		else
  			fn = hist_field_u64;
  		break;
  	case 4:
  		if (field_is_signed)
  			fn = hist_field_s32;
  		else
  			fn = hist_field_u32;
  		break;
  	case 2:
  		if (field_is_signed)
  			fn = hist_field_s16;
  		else
  			fn = hist_field_u16;
  		break;
  	case 1:
  		if (field_is_signed)
  			fn = hist_field_s8;
  		else
  			fn = hist_field_u8;
  		break;
  	}
  
  	return fn;
  }
  
  static int parse_map_size(char *str)
  {
  	unsigned long size, map_bits;
  	int ret;
  
  	ret = kstrtoul(str, 0, &size);
  	if (ret)
  		goto out;
  
  	map_bits = ilog2(roundup_pow_of_two(size));
  	if (map_bits < TRACING_MAP_BITS_MIN ||
  	    map_bits > TRACING_MAP_BITS_MAX)
  		ret = -EINVAL;
  	else
  		ret = map_bits;
   out:
  	return ret;
  }
  
  static void destroy_hist_trigger_attrs(struct hist_trigger_attrs *attrs)
  {
  	unsigned int i;
  
  	if (!attrs)
  		return;
  
  	for (i = 0; i < attrs->n_assignments; i++)
  		kfree(attrs->assignment_str[i]);
  
  	for (i = 0; i < attrs->n_actions; i++)
  		kfree(attrs->action_str[i]);
  
  	kfree(attrs->name);
  	kfree(attrs->sort_key_str);
  	kfree(attrs->keys_str);
  	kfree(attrs->vals_str);
  	kfree(attrs->clock);
  	kfree(attrs);
  }
  
  static int parse_action(char *str, struct hist_trigger_attrs *attrs)
  {
  	int ret = -EINVAL;
  
  	if (attrs->n_actions >= HIST_ACTIONS_MAX)
  		return ret;
  
  	if ((str_has_prefix(str, "onmatch(")) ||
  	    (str_has_prefix(str, "onmax(")) ||
  	    (str_has_prefix(str, "onchange("))) {
  		attrs->action_str[attrs->n_actions] = kstrdup(str, GFP_KERNEL);
  		if (!attrs->action_str[attrs->n_actions]) {
  			ret = -ENOMEM;
  			return ret;
  		}
  		attrs->n_actions++;
  		ret = 0;
  	}
  	return ret;
  }
  
  static int parse_assignment(struct trace_array *tr,
  			    char *str, struct hist_trigger_attrs *attrs)
  {
  	int len, ret = 0;
  
  	if ((len = str_has_prefix(str, "key=")) ||
  	    (len = str_has_prefix(str, "keys="))) {
  		attrs->keys_str = kstrdup(str + len, GFP_KERNEL);
  		if (!attrs->keys_str) {
  			ret = -ENOMEM;
  			goto out;
  		}
  	} else if ((len = str_has_prefix(str, "val=")) ||
  		   (len = str_has_prefix(str, "vals=")) ||
  		   (len = str_has_prefix(str, "values="))) {
  		attrs->vals_str = kstrdup(str + len, GFP_KERNEL);
  		if (!attrs->vals_str) {
  			ret = -ENOMEM;
  			goto out;
  		}
  	} else if ((len = str_has_prefix(str, "sort="))) {
  		attrs->sort_key_str = kstrdup(str + len, GFP_KERNEL);
  		if (!attrs->sort_key_str) {
  			ret = -ENOMEM;
  			goto out;
  		}
  	} else if (str_has_prefix(str, "name=")) {
  		attrs->name = kstrdup(str, GFP_KERNEL);
  		if (!attrs->name) {
  			ret = -ENOMEM;
  			goto out;
  		}
  	} else if ((len = str_has_prefix(str, "clock="))) {
  		str += len;
  
  		str = strstrip(str);
  		attrs->clock = kstrdup(str, GFP_KERNEL);
  		if (!attrs->clock) {
  			ret = -ENOMEM;
  			goto out;
  		}
  	} else if ((len = str_has_prefix(str, "size="))) {
  		int map_bits = parse_map_size(str + len);
  
  		if (map_bits < 0) {
  			ret = map_bits;
  			goto out;
  		}
  		attrs->map_bits = map_bits;
  	} else {
  		char *assignment;
  
  		if (attrs->n_assignments == TRACING_MAP_VARS_MAX) {
  			hist_err(tr, HIST_ERR_TOO_MANY_VARS, errpos(str));
  			ret = -EINVAL;
  			goto out;
  		}
  
  		assignment = kstrdup(str, GFP_KERNEL);
  		if (!assignment) {
  			ret = -ENOMEM;
  			goto out;
  		}
  
  		attrs->assignment_str[attrs->n_assignments++] = assignment;
  	}
   out:
  	return ret;
  }
  
  static struct hist_trigger_attrs *
  parse_hist_trigger_attrs(struct trace_array *tr, char *trigger_str)
  {
  	struct hist_trigger_attrs *attrs;
  	int ret = 0;
  
  	attrs = kzalloc(sizeof(*attrs), GFP_KERNEL);
  	if (!attrs)
  		return ERR_PTR(-ENOMEM);
  
  	while (trigger_str) {
  		char *str = strsep(&trigger_str, ":");
  		char *rhs;
  
  		rhs = strchr(str, '=');
  		if (rhs) {
  			if (!strlen(++rhs)) {
  				ret = -EINVAL;
  				hist_err(tr, HIST_ERR_EMPTY_ASSIGNMENT, errpos(str));
  				goto free;
  			}
  			ret = parse_assignment(tr, str, attrs);
  			if (ret)
  				goto free;
  		} else if (strcmp(str, "pause") == 0)
  			attrs->pause = true;
  		else if ((strcmp(str, "cont") == 0) ||
  			 (strcmp(str, "continue") == 0))
  			attrs->cont = true;
  		else if (strcmp(str, "clear") == 0)
  			attrs->clear = true;
  		else {
  			ret = parse_action(str, attrs);
  			if (ret)
  				goto free;
  		}
  	}
  
  	if (!attrs->keys_str) {
  		ret = -EINVAL;
  		goto free;
  	}
  
  	if (!attrs->clock) {
  		attrs->clock = kstrdup("global", GFP_KERNEL);
  		if (!attrs->clock) {
  			ret = -ENOMEM;
  			goto free;
  		}
  	}
  
  	return attrs;
   free:
  	destroy_hist_trigger_attrs(attrs);
  
  	return ERR_PTR(ret);
  }
  
  static inline void save_comm(char *comm, struct task_struct *task)
  {
  	if (!task->pid) {
  		strcpy(comm, "<idle>");
  		return;
  	}
  
  	if (WARN_ON_ONCE(task->pid < 0)) {
  		strcpy(comm, "<XXX>");
  		return;
  	}
  
  	strncpy(comm, task->comm, TASK_COMM_LEN);
  }
  
  static void hist_elt_data_free(struct hist_elt_data *elt_data)
  {
  	unsigned int i;
  
  	for (i = 0; i < elt_data->n_field_var_str; i++)
  		kfree(elt_data->field_var_str[i]);
  
  	kfree(elt_data->field_var_str);
  
  	kfree(elt_data->comm);
  	kfree(elt_data);
  }
  
  static void hist_trigger_elt_data_free(struct tracing_map_elt *elt)
  {
  	struct hist_elt_data *elt_data = elt->private_data;
  
  	hist_elt_data_free(elt_data);
  }
  
  static int hist_trigger_elt_data_alloc(struct tracing_map_elt *elt)
  {
  	struct hist_trigger_data *hist_data = elt->map->private_data;
  	unsigned int size = TASK_COMM_LEN;
  	struct hist_elt_data *elt_data;
  	struct hist_field *hist_field;
  	unsigned int i, n_str;
  
  	elt_data = kzalloc(sizeof(*elt_data), GFP_KERNEL);
  	if (!elt_data)
  		return -ENOMEM;
  
  	for_each_hist_field(i, hist_data) {
  		hist_field = hist_data->fields[i];
  
  		if (hist_field->flags & HIST_FIELD_FL_EXECNAME) {
  			elt_data->comm = kzalloc(size, GFP_KERNEL);
  			if (!elt_data->comm) {
  				kfree(elt_data);
  				return -ENOMEM;
  			}
  			break;
  		}
  	}
  
  	n_str = hist_data->n_field_var_str + hist_data->n_save_var_str +
  		hist_data->n_var_str;
  	if (n_str > SYNTH_FIELDS_MAX) {
  		hist_elt_data_free(elt_data);
  		return -EINVAL;
  	}
  
  	BUILD_BUG_ON(STR_VAR_LEN_MAX & (sizeof(u64) - 1));
  
  	size = STR_VAR_LEN_MAX;
  
  	elt_data->field_var_str = kcalloc(n_str, sizeof(char *), GFP_KERNEL);
  	if (!elt_data->field_var_str) {
  		hist_elt_data_free(elt_data);
  		return -EINVAL;
  	}
  	elt_data->n_field_var_str = n_str;
  
  	for (i = 0; i < n_str; i++) {
  		elt_data->field_var_str[i] = kzalloc(size, GFP_KERNEL);
  		if (!elt_data->field_var_str[i]) {
  			hist_elt_data_free(elt_data);
  			return -ENOMEM;
  		}
  	}
  
  	elt->private_data = elt_data;
  
  	return 0;
  }
  
  static void hist_trigger_elt_data_init(struct tracing_map_elt *elt)
  {
  	struct hist_elt_data *elt_data = elt->private_data;
  
  	if (elt_data->comm)
  		save_comm(elt_data->comm, current);
  }
  
  static const struct tracing_map_ops hist_trigger_elt_data_ops = {
  	.elt_alloc	= hist_trigger_elt_data_alloc,
  	.elt_free	= hist_trigger_elt_data_free,
  	.elt_init	= hist_trigger_elt_data_init,
  };
  
  static const char *get_hist_field_flags(struct hist_field *hist_field)
  {
  	const char *flags_str = NULL;
  
  	if (hist_field->flags & HIST_FIELD_FL_HEX)
  		flags_str = "hex";
  	else if (hist_field->flags & HIST_FIELD_FL_SYM)
  		flags_str = "sym";
  	else if (hist_field->flags & HIST_FIELD_FL_SYM_OFFSET)
  		flags_str = "sym-offset";
  	else if (hist_field->flags & HIST_FIELD_FL_EXECNAME)
  		flags_str = "execname";
  	else if (hist_field->flags & HIST_FIELD_FL_SYSCALL)
  		flags_str = "syscall";
  	else if (hist_field->flags & HIST_FIELD_FL_LOG2)
  		flags_str = "log2";
  	else if (hist_field->flags & HIST_FIELD_FL_BUCKET)
  		flags_str = "buckets";
  	else if (hist_field->flags & HIST_FIELD_FL_TIMESTAMP_USECS)
  		flags_str = "usecs";
  
  	return flags_str;
  }
  
  static void expr_field_str(struct hist_field *field, char *expr)
  {
  	if (field->flags & HIST_FIELD_FL_VAR_REF)
  		strcat(expr, "$");
  	else if (field->flags & HIST_FIELD_FL_CONST) {
  		char str[HIST_CONST_DIGITS_MAX];
  
  		snprintf(str, HIST_CONST_DIGITS_MAX, "%llu", field->constant);
  		strcat(expr, str);
  	}
  
  	strcat(expr, hist_field_name(field, 0));
  
  	if (field->flags && !(field->flags & HIST_FIELD_FL_VAR_REF)) {
  		const char *flags_str = get_hist_field_flags(field);
  
  		if (flags_str) {
  			strcat(expr, ".");
  			strcat(expr, flags_str);
  		}
  	}
  }
  
  static char *expr_str(struct hist_field *field, unsigned int level)
  {
  	char *expr;
  
  	if (level > 1)
  		return NULL;
  
  	expr = kzalloc(MAX_FILTER_STR_VAL, GFP_KERNEL);
  	if (!expr)
  		return NULL;
  
  	if (!field->operands[0]) {
  		expr_field_str(field, expr);
  		return expr;
  	}
  
  	if (field->operator == FIELD_OP_UNARY_MINUS) {
  		char *subexpr;
  
  		strcat(expr, "-(");
  		subexpr = expr_str(field->operands[0], ++level);
  		if (!subexpr) {
  			kfree(expr);
  			return NULL;
  		}
  		strcat(expr, subexpr);
  		strcat(expr, ")");
  
  		kfree(subexpr);
  
  		return expr;
  	}
  
  	expr_field_str(field->operands[0], expr);
  
  	switch (field->operator) {
  	case FIELD_OP_MINUS:
  		strcat(expr, "-");
  		break;
  	case FIELD_OP_PLUS:
  		strcat(expr, "+");
  		break;
  	case FIELD_OP_DIV:
  		strcat(expr, "/");
  		break;
  	case FIELD_OP_MULT:
  		strcat(expr, "*");
  		break;
  	default:
  		kfree(expr);
  		return NULL;
  	}
  
  	expr_field_str(field->operands[1], expr);
  
  	return expr;
  }
  
  /*
   * If field_op != FIELD_OP_NONE, *sep points to the root operator
   * of the expression tree to be evaluated.
   */
  static int contains_operator(char *str, char **sep)
  {
  	enum field_op_id field_op = FIELD_OP_NONE;
  	char *minus_op, *plus_op, *div_op, *mult_op;
  
  
  	/*
  	 * Report the last occurrence of the operators first, so that the
  	 * expression is evaluated left to right. This is important since
  	 * subtraction and division are not associative.
  	 *
  	 *	e.g
  	 *		64/8/4/2 is 1, i.e 64/8/4/2 = ((64/8)/4)/2
  	 *		14-7-5-2 is 0, i.e 14-7-5-2 = ((14-7)-5)-2
  	 */
  
  	/*
  	 * First, find lower precedence addition and subtraction
  	 * since the expression will be evaluated recursively.
  	 */
  	minus_op = strrchr(str, '-');
  	if (minus_op) {
  		/*
  		 * Unary minus is not supported in sub-expressions. If
  		 * present, it is always the next root operator.
  		 */
  		if (minus_op == str) {
  			field_op = FIELD_OP_UNARY_MINUS;
  			goto out;
  		}
  
  		field_op = FIELD_OP_MINUS;
  	}
  
  	plus_op = strrchr(str, '+');
  	if (plus_op || minus_op) {
  		/*
  		 * For operators of the same precedence use to rightmost as the
  		 * root, so that the expression is evaluated left to right.
  		 */
  		if (plus_op > minus_op)
  			field_op = FIELD_OP_PLUS;
  		goto out;
  	}
  
  	/*
  	 * Multiplication and division have higher precedence than addition and
  	 * subtraction.
  	 */
  	div_op = strrchr(str, '/');
  	if (div_op)
  		field_op = FIELD_OP_DIV;
  
  	mult_op = strrchr(str, '*');
  	/*
  	 * For operators of the same precedence use to rightmost as the
  	 * root, so that the expression is evaluated left to right.
  	 */
  	if (mult_op > div_op)
  		field_op = FIELD_OP_MULT;
  
  out:
  	if (sep) {
  		switch (field_op) {
  		case FIELD_OP_UNARY_MINUS:
  		case FIELD_OP_MINUS:
  			*sep = minus_op;
  			break;
  		case FIELD_OP_PLUS:
  			*sep = plus_op;
  			break;
  		case FIELD_OP_DIV:
  			*sep = div_op;
  			break;
  		case FIELD_OP_MULT:
  			*sep = mult_op;
  			break;
  		case FIELD_OP_NONE:
  		default:
  			*sep = NULL;
  			break;
  		}
  	}
  
  	return field_op;
  }
  
  static void get_hist_field(struct hist_field *hist_field)
  {
  	hist_field->ref++;
  }
  
  static void __destroy_hist_field(struct hist_field *hist_field)
  {
  	if (--hist_field->ref > 1)
  		return;
  
  	kfree(hist_field->var.name);
  	kfree(hist_field->name);
  
  	/* Can likely be a const */
  	kfree_const(hist_field->type);
  
  	kfree(hist_field->system);
  	kfree(hist_field->event_name);
  
  	kfree(hist_field);
  }
  
  static void destroy_hist_field(struct hist_field *hist_field,
  			       unsigned int level)
  {
  	unsigned int i;
  
  	if (level > 3)
  		return;
  
  	if (!hist_field)
  		return;
  
  	if (hist_field->flags & HIST_FIELD_FL_VAR_REF)
  		return; /* var refs will be destroyed separately */
  
  	for (i = 0; i < HIST_FIELD_OPERANDS_MAX; i++)
  		destroy_hist_field(hist_field->operands[i], level + 1);
  
  	__destroy_hist_field(hist_field);
  }
  
  static struct hist_field *create_hist_field(struct hist_trigger_data *hist_data,
  					    struct ftrace_event_field *field,
  					    unsigned long flags,
  					    char *var_name)
  {
  	struct hist_field *hist_field;
  
  	if (field && is_function_field(field))
  		return NULL;
  
  	hist_field = kzalloc(sizeof(struct hist_field), GFP_KERNEL);
  	if (!hist_field)
  		return NULL;
  
  	hist_field->ref = 1;
  
  	hist_field->hist_data = hist_data;
  
  	if (flags & HIST_FIELD_FL_EXPR || flags & HIST_FIELD_FL_ALIAS)
  		goto out; /* caller will populate */
  
  	if (flags & HIST_FIELD_FL_VAR_REF) {
  		hist_field->fn = hist_field_var_ref;
  		goto out;
  	}
  
  	if (flags & HIST_FIELD_FL_HITCOUNT) {
  		hist_field->fn = hist_field_counter;
  		hist_field->size = sizeof(u64);
  		hist_field->type = "u64";
  		goto out;
  	}
  
  	if (flags & HIST_FIELD_FL_CONST) {
  		hist_field->fn = hist_field_const;
  		hist_field->size = sizeof(u64);
  		hist_field->type = kstrdup("u64", GFP_KERNEL);
  		if (!hist_field->type)
  			goto free;
  		goto out;
  	}
  
  	if (flags & HIST_FIELD_FL_STACKTRACE) {
  		hist_field->fn = hist_field_none;
  		goto out;
  	}
  
  	if (flags & (HIST_FIELD_FL_LOG2 | HIST_FIELD_FL_BUCKET)) {
  		unsigned long fl = flags & ~(HIST_FIELD_FL_LOG2 | HIST_FIELD_FL_BUCKET);
  		hist_field->fn = flags & HIST_FIELD_FL_LOG2 ? hist_field_log2 :
  			hist_field_bucket;
  		hist_field->operands[0] = create_hist_field(hist_data, field, fl, NULL);
  		hist_field->size = hist_field->operands[0]->size;
  		hist_field->type = kstrdup_const(hist_field->operands[0]->type, GFP_KERNEL);
  		if (!hist_field->type)
  			goto free;
  		goto out;
  	}
  
  	if (flags & HIST_FIELD_FL_TIMESTAMP) {
  		hist_field->fn = hist_field_timestamp;
  		hist_field->size = sizeof(u64);
  		hist_field->type = "u64";
  		goto out;
  	}
  
  	if (flags & HIST_FIELD_FL_CPU) {
  		hist_field->fn = hist_field_cpu;
  		hist_field->size = sizeof(int);
  		hist_field->type = "unsigned int";
  		goto out;
  	}
  
  	if (WARN_ON_ONCE(!field))
  		goto out;
  
  	/* Pointers to strings are just pointers and dangerous to dereference */
  	if (is_string_field(field) &&
  	    (field->filter_type != FILTER_PTR_STRING)) {
  		flags |= HIST_FIELD_FL_STRING;
  
  		hist_field->size = MAX_FILTER_STR_VAL;
  		hist_field->type = kstrdup_const(field->type, GFP_KERNEL);
  		if (!hist_field->type)
  			goto free;
  
  		if (field->filter_type == FILTER_STATIC_STRING) {
  			hist_field->fn = hist_field_string;
  			hist_field->size = field->size;
  		} else if (field->filter_type == FILTER_DYN_STRING) {
  			hist_field->fn = hist_field_dynstring;
  		} else if (field->filter_type == FILTER_RDYN_STRING)
  			hist_field->fn = hist_field_reldynstring;
  		else
  			hist_field->fn = hist_field_pstring;
  	} else {
  		hist_field->size = field->size;
  		hist_field->is_signed = field->is_signed;
  		hist_field->type = kstrdup_const(field->type, GFP_KERNEL);
  		if (!hist_field->type)
  			goto free;
  
  		hist_field->fn = select_value_fn(field->size,
  						 field->is_signed);
  		if (!hist_field->fn) {
  			destroy_hist_field(hist_field, 0);
  			return NULL;
  		}
  	}
   out:
  	hist_field->field = field;
  	hist_field->flags = flags;
  
  	if (var_name) {
  		hist_field->var.name = kstrdup(var_name, GFP_KERNEL);
  		if (!hist_field->var.name)
  			goto free;
  	}
  
  	return hist_field;
   free:
  	destroy_hist_field(hist_field, 0);
  	return NULL;
  }
  
  static void destroy_hist_fields(struct hist_trigger_data *hist_data)
  {
  	unsigned int i;
  
  	for (i = 0; i < HIST_FIELDS_MAX; i++) {
  		if (hist_data->fields[i]) {
  			destroy_hist_field(hist_data->fields[i], 0);
  			hist_data->fields[i] = NULL;
  		}
  	}
  
  	for (i = 0; i < hist_data->n_var_refs; i++) {
  		WARN_ON(!(hist_data->var_refs[i]->flags & HIST_FIELD_FL_VAR_REF));
  		__destroy_hist_field(hist_data->var_refs[i]);
  		hist_data->var_refs[i] = NULL;
  	}
  }
  
  static int init_var_ref(struct hist_field *ref_field,
  			struct hist_field *var_field,
  			char *system, char *event_name)
  {
  	int err = 0;
  
  	ref_field->var.idx = var_field->var.idx;
  	ref_field->var.hist_data = var_field->hist_data;
  	ref_field->size = var_field->size;
  	ref_field->is_signed = var_field->is_signed;
  	ref_field->flags |= var_field->flags &
  		(HIST_FIELD_FL_TIMESTAMP | HIST_FIELD_FL_TIMESTAMP_USECS);
  
  	if (system) {
  		ref_field->system = kstrdup(system, GFP_KERNEL);
  		if (!ref_field->system)
  			return -ENOMEM;
  	}
  
  	if (event_name) {
  		ref_field->event_name = kstrdup(event_name, GFP_KERNEL);
  		if (!ref_field->event_name) {
  			err = -ENOMEM;
  			goto free;
  		}
  	}
  
  	if (var_field->var.name) {
  		ref_field->name = kstrdup(var_field->var.name, GFP_KERNEL);
  		if (!ref_field->name) {
  			err = -ENOMEM;
  			goto free;
  		}
  	} else if (var_field->name) {
  		ref_field->name = kstrdup(var_field->name, GFP_KERNEL);
  		if (!ref_field->name) {
  			err = -ENOMEM;
  			goto free;
  		}
  	}
  
  	ref_field->type = kstrdup_const(var_field->type, GFP_KERNEL);
  	if (!ref_field->type) {
  		err = -ENOMEM;
  		goto free;
  	}
   out:
  	return err;
   free:
  	kfree(ref_field->system);
  	kfree(ref_field->event_name);
  	kfree(ref_field->name);
  
  	goto out;
  }
  
  static int find_var_ref_idx(struct hist_trigger_data *hist_data,
  			    struct hist_field *var_field)
  {
  	struct hist_field *ref_field;
  	int i;
  
  	for (i = 0; i < hist_data->n_var_refs; i++) {
  		ref_field = hist_data->var_refs[i];
  		if (ref_field->var.idx == var_field->var.idx &&
  		    ref_field->var.hist_data == var_field->hist_data)
  			return i;
  	}
  
  	return -ENOENT;
  }
  
  /**
   * create_var_ref - Create a variable reference and attach it to trigger
   * @hist_data: The trigger that will be referencing the variable
   * @var_field: The VAR field to create a reference to
   * @system: The optional system string
   * @event_name: The optional event_name string
   *
   * Given a variable hist_field, create a VAR_REF hist_field that
   * represents a reference to it.
   *
   * This function also adds the reference to the trigger that
   * now references the variable.
   *
   * Return: The VAR_REF field if successful, NULL if not
   */
  static struct hist_field *create_var_ref(struct hist_trigger_data *hist_data,
  					 struct hist_field *var_field,
  					 char *system, char *event_name)
  {
  	unsigned long flags = HIST_FIELD_FL_VAR_REF;
  	struct hist_field *ref_field;
  	int i;
  
  	/* Check if the variable already exists */
  	for (i = 0; i < hist_data->n_var_refs; i++) {
  		ref_field = hist_data->var_refs[i];
  		if (ref_field->var.idx == var_field->var.idx &&
  		    ref_field->var.hist_data == var_field->hist_data) {
  			get_hist_field(ref_field);
  			return ref_field;
  		}
  	}
  
  	ref_field = create_hist_field(var_field->hist_data, NULL, flags, NULL);
  	if (ref_field) {
  		if (init_var_ref(ref_field, var_field, system, event_name)) {
  			destroy_hist_field(ref_field, 0);
  			return NULL;
  		}
  
  		hist_data->var_refs[hist_data->n_var_refs] = ref_field;
  		ref_field->var_ref_idx = hist_data->n_var_refs++;
  	}
  
  	return ref_field;
  }
  
  static bool is_var_ref(char *var_name)
  {
  	if (!var_name || strlen(var_name) < 2 || var_name[0] != '$')
  		return false;
  
  	return true;
  }
  
  static char *field_name_from_var(struct hist_trigger_data *hist_data,
  				 char *var_name)
  {
  	char *name, *field;
  	unsigned int i;
  
  	for (i = 0; i < hist_data->attrs->var_defs.n_vars; i++) {
  		name = hist_data->attrs->var_defs.name[i];
  
  		if (strcmp(var_name, name) == 0) {
  			field = hist_data->attrs->var_defs.expr[i];
  			if (contains_operator(field, NULL) || is_var_ref(field))
  				continue;
  			return field;
  		}
  	}
  
  	return NULL;
  }
  
  static char *local_field_var_ref(struct hist_trigger_data *hist_data,
  				 char *system, char *event_name,
  				 char *var_name)
  {
  	struct trace_event_call *call;
  
  	if (system && event_name) {
  		call = hist_data->event_file->event_call;
  
  		if (strcmp(system, call->class->system) != 0)
  			return NULL;
  
  		if (strcmp(event_name, trace_event_name(call)) != 0)
  			return NULL;
  	}
  
  	if (!!system != !!event_name)
  		return NULL;
  
  	if (!is_var_ref(var_name))
  		return NULL;
  
  	var_name++;
  
  	return field_name_from_var(hist_data, var_name);
  }
  
  static struct hist_field *parse_var_ref(struct hist_trigger_data *hist_data,
  					char *system, char *event_name,
  					char *var_name)
  {
  	struct hist_field *var_field = NULL, *ref_field = NULL;
  	struct trace_array *tr = hist_data->event_file->tr;
  
  	if (!is_var_ref(var_name))
  		return NULL;
  
  	var_name++;
  
  	var_field = find_event_var(hist_data, system, event_name, var_name);
  	if (var_field)
  		ref_field = create_var_ref(hist_data, var_field,
  					   system, event_name);
  
  	if (!ref_field)
  		hist_err(tr, HIST_ERR_VAR_NOT_FOUND, errpos(var_name));
  
  	return ref_field;
  }
  
  static struct ftrace_event_field *
  parse_field(struct hist_trigger_data *hist_data, struct trace_event_file *file,
  	    char *field_str, unsigned long *flags, unsigned long *buckets)
  {
  	struct ftrace_event_field *field = NULL;
  	char *field_name, *modifier, *str;
  	struct trace_array *tr = file->tr;
  
  	modifier = str = kstrdup(field_str, GFP_KERNEL);
  	if (!modifier)
  		return ERR_PTR(-ENOMEM);
  
  	field_name = strsep(&modifier, ".");
  	if (modifier) {
  		if (strcmp(modifier, "hex") == 0)
  			*flags |= HIST_FIELD_FL_HEX;
  		else if (strcmp(modifier, "sym") == 0)
  			*flags |= HIST_FIELD_FL_SYM;
  		/*
  		 * 'sym-offset' occurrences in the trigger string are modified
  		 * to 'symXoffset' to simplify arithmetic expression parsing.
  		 */
  		else if (strcmp(modifier, "symXoffset") == 0)
  			*flags |= HIST_FIELD_FL_SYM_OFFSET;
  		else if ((strcmp(modifier, "execname") == 0) &&
  			 (strcmp(field_name, "common_pid") == 0))
  			*flags |= HIST_FIELD_FL_EXECNAME;
  		else if (strcmp(modifier, "syscall") == 0)
  			*flags |= HIST_FIELD_FL_SYSCALL;
  		else if (strcmp(modifier, "log2") == 0)
  			*flags |= HIST_FIELD_FL_LOG2;
  		else if (strcmp(modifier, "usecs") == 0)
  			*flags |= HIST_FIELD_FL_TIMESTAMP_USECS;
  		else if (strncmp(modifier, "bucket", 6) == 0) {
  			int ret;
  
  			modifier += 6;
  
  			if (*modifier == 's')
  				modifier++;
  			if (*modifier != '=')
  				goto error;
  			modifier++;
  			ret = kstrtoul(modifier, 0, buckets);
  			if (ret || !(*buckets))
  				goto error;
  			*flags |= HIST_FIELD_FL_BUCKET;
  		} else {
   error:
  			hist_err(tr, HIST_ERR_BAD_FIELD_MODIFIER, errpos(modifier));
  			field = ERR_PTR(-EINVAL);
  			goto out;
  		}
  	}
  
  	if (strcmp(field_name, "common_timestamp") == 0) {
  		*flags |= HIST_FIELD_FL_TIMESTAMP;
  		hist_data->enable_timestamps = true;
  		if (*flags & HIST_FIELD_FL_TIMESTAMP_USECS)
  			hist_data->attrs->ts_in_usecs = true;
  	} else if (strcmp(field_name, "common_cpu") == 0)
  		*flags |= HIST_FIELD_FL_CPU;
  	else {
  		field = trace_find_event_field(file->event_call, field_name);
  		if (!field || !field->size) {
  			/*
  			 * For backward compatibility, if field_name
  			 * was "cpu", then we treat this the same as
  			 * common_cpu. This also works for "CPU".
  			 */
  			if (field && field->filter_type == FILTER_CPU) {
  				*flags |= HIST_FIELD_FL_CPU;
  			} else {
  				hist_err(tr, HIST_ERR_FIELD_NOT_FOUND,
  					 errpos(field_name));
  				field = ERR_PTR(-EINVAL);
  				goto out;
  			}
  		}
  	}
   out:
  	kfree(str);
  
  	return field;
  }
  
  static struct hist_field *create_alias(struct hist_trigger_data *hist_data,
  				       struct hist_field *var_ref,
  				       char *var_name)
  {
  	struct hist_field *alias = NULL;
  	unsigned long flags = HIST_FIELD_FL_ALIAS | HIST_FIELD_FL_VAR;
  
  	alias = create_hist_field(hist_data, NULL, flags, var_name);
  	if (!alias)
  		return NULL;
  
  	alias->fn = var_ref->fn;
  	alias->operands[0] = var_ref;
  
  	if (init_var_ref(alias, var_ref, var_ref->system, var_ref->event_name)) {
  		destroy_hist_field(alias, 0);
  		return NULL;
  	}
  
  	alias->var_ref_idx = var_ref->var_ref_idx;
  
  	return alias;
  }
  
  static struct hist_field *parse_const(struct hist_trigger_data *hist_data,
  				      char *str, char *var_name,
  				      unsigned long *flags)
  {
  	struct trace_array *tr = hist_data->event_file->tr;
  	struct hist_field *field = NULL;
  	u64 constant;
  
  	if (kstrtoull(str, 0, &constant)) {
  		hist_err(tr, HIST_ERR_EXPECT_NUMBER, errpos(str));
  		return NULL;
  	}
  
  	*flags |= HIST_FIELD_FL_CONST;
  	field = create_hist_field(hist_data, NULL, *flags, var_name);
  	if (!field)
  		return NULL;
  
  	field->constant = constant;
  
  	return field;
  }
  
  static struct hist_field *parse_atom(struct hist_trigger_data *hist_data,
  				     struct trace_event_file *file, char *str,
  				     unsigned long *flags, char *var_name)
  {
  	char *s, *ref_system = NULL, *ref_event = NULL, *ref_var = str;
  	struct ftrace_event_field *field = NULL;
  	struct hist_field *hist_field = NULL;
  	unsigned long buckets = 0;
  	int ret = 0;
  
  	if (isdigit(str[0])) {
  		hist_field = parse_const(hist_data, str, var_name, flags);
  		if (!hist_field) {
  			ret = -EINVAL;
  			goto out;
  		}
  		return hist_field;
  	}
  
  	s = strchr(str, '.');
  	if (s) {
  		s = strchr(++s, '.');
  		if (s) {
  			ref_system = strsep(&str, ".");
  			if (!str) {
  				ret = -EINVAL;
  				goto out;
  			}
  			ref_event = strsep(&str, ".");
  			if (!str) {
  				ret = -EINVAL;
  				goto out;
  			}
  			ref_var = str;
  		}
  	}
  
  	s = local_field_var_ref(hist_data, ref_system, ref_event, ref_var);
  	if (!s) {
  		hist_field = parse_var_ref(hist_data, ref_system,
  					   ref_event, ref_var);
  		if (hist_field) {
  			if (var_name) {
  				hist_field = create_alias(hist_data, hist_field, var_name);
  				if (!hist_field) {
  					ret = -ENOMEM;
  					goto out;
  				}
  			}
  			return hist_field;
  		}
  	} else
  		str = s;
  
  	field = parse_field(hist_data, file, str, flags, &buckets);
  	if (IS_ERR(field)) {
  		ret = PTR_ERR(field);
  		goto out;
  	}
  
  	hist_field = create_hist_field(hist_data, field, *flags, var_name);
  	if (!hist_field) {
  		ret = -ENOMEM;
  		goto out;
  	}
  	hist_field->buckets = buckets;
  
  	return hist_field;
   out:
  	return ERR_PTR(ret);
  }
  
  static struct hist_field *parse_expr(struct hist_trigger_data *hist_data,
  				     struct trace_event_file *file,
  				     char *str, unsigned long flags,
  				     char *var_name, unsigned int *n_subexprs);
  
  static struct hist_field *parse_unary(struct hist_trigger_data *hist_data,
  				      struct trace_event_file *file,
  				      char *str, unsigned long flags,
  				      char *var_name, unsigned int *n_subexprs)
  {
  	struct hist_field *operand1, *expr = NULL;
  	unsigned long operand_flags;
  	int ret = 0;
  	char *s;
  
  	/* Unary minus operator, increment n_subexprs */
  	++*n_subexprs;
  
  	/* we support only -(xxx) i.e. explicit parens required */
  
  	if (*n_subexprs > 3) {
  		hist_err(file->tr, HIST_ERR_TOO_MANY_SUBEXPR, errpos(str));
  		ret = -EINVAL;
  		goto free;
  	}
  
  	str++; /* skip leading '-' */
  
  	s = strchr(str, '(');
  	if (s)
  		str++;
  	else {
  		ret = -EINVAL;
  		goto free;
  	}
  
  	s = strrchr(str, ')');
  	if (s) {
  		 /* unary minus not supported in sub-expressions */
  		if (*(s+1) != '\0') {
  			hist_err(file->tr, HIST_ERR_UNARY_MINUS_SUBEXPR,
  				 errpos(str));
  			ret = -EINVAL;
  			goto free;
  		}
  		*s = '\0';
  	}
  	else {
  		ret = -EINVAL; /* no closing ')' */
  		goto free;
  	}
  
  	flags |= HIST_FIELD_FL_EXPR;
  	expr = create_hist_field(hist_data, NULL, flags, var_name);
  	if (!expr) {
  		ret = -ENOMEM;
  		goto free;
  	}
  
  	operand_flags = 0;
  	operand1 = parse_expr(hist_data, file, str, operand_flags, NULL, n_subexprs);
  	if (IS_ERR(operand1)) {
  		ret = PTR_ERR(operand1);
  		goto free;
  	}
  	if (operand1->flags & HIST_FIELD_FL_STRING) {
  		/* String type can not be the operand of unary operator. */
  		hist_err(file->tr, HIST_ERR_INVALID_STR_OPERAND, errpos(str));
  		destroy_hist_field(operand1, 0);
  		ret = -EINVAL;
  		goto free;
  	}
  
  	expr->flags |= operand1->flags &
  		(HIST_FIELD_FL_TIMESTAMP | HIST_FIELD_FL_TIMESTAMP_USECS);
  	expr->fn = hist_field_unary_minus;
  	expr->operands[0] = operand1;
  	expr->size = operand1->size;
  	expr->is_signed = operand1->is_signed;
  	expr->operator = FIELD_OP_UNARY_MINUS;
  	expr->name = expr_str(expr, 0);
  	expr->type = kstrdup_const(operand1->type, GFP_KERNEL);
  	if (!expr->type) {
  		ret = -ENOMEM;
  		goto free;
  	}
  
  	return expr;
   free:
  	destroy_hist_field(expr, 0);
  	return ERR_PTR(ret);
  }
  
  /*
   * If the operands are var refs, return pointers the
   * variable(s) referenced in var1 and var2, else NULL.
   */
  static int check_expr_operands(struct trace_array *tr,
  			       struct hist_field *operand1,
  			       struct hist_field *operand2,
  			       struct hist_field **var1,
  			       struct hist_field **var2)
  {
  	unsigned long operand1_flags = operand1->flags;
  	unsigned long operand2_flags = operand2->flags;
  
  	if ((operand1_flags & HIST_FIELD_FL_VAR_REF) ||
  	    (operand1_flags & HIST_FIELD_FL_ALIAS)) {
  		struct hist_field *var;
  
  		var = find_var_field(operand1->var.hist_data, operand1->name);
  		if (!var)
  			return -EINVAL;
  		operand1_flags = var->flags;
  		*var1 = var;
  	}
  
  	if ((operand2_flags & HIST_FIELD_FL_VAR_REF) ||
  	    (operand2_flags & HIST_FIELD_FL_ALIAS)) {
  		struct hist_field *var;
  
  		var = find_var_field(operand2->var.hist_data, operand2->name);
  		if (!var)
  			return -EINVAL;
  		operand2_flags = var->flags;
  		*var2 = var;
  	}
  
  	if ((operand1_flags & HIST_FIELD_FL_TIMESTAMP_USECS) !=
  	    (operand2_flags & HIST_FIELD_FL_TIMESTAMP_USECS)) {
  		hist_err(tr, HIST_ERR_TIMESTAMP_MISMATCH, 0);
  		return -EINVAL;
  	}
  
  	return 0;
  }
  
  static struct hist_field *parse_expr(struct hist_trigger_data *hist_data,
  				     struct trace_event_file *file,
  				     char *str, unsigned long flags,
  				     char *var_name, unsigned int *n_subexprs)
  {
  	struct hist_field *operand1 = NULL, *operand2 = NULL, *expr = NULL;
  	struct hist_field *var1 = NULL, *var2 = NULL;
  	unsigned long operand_flags, operand2_flags;
  	int field_op, ret = -EINVAL;
  	char *sep, *operand1_str;
  	hist_field_fn_t op_fn;
  	bool combine_consts;
  
  	if (*n_subexprs > 3) {
  		hist_err(file->tr, HIST_ERR_TOO_MANY_SUBEXPR, errpos(str));
  		return ERR_PTR(-EINVAL);
  	}
  
  	field_op = contains_operator(str, &sep);
  
  	if (field_op == FIELD_OP_NONE)
  		return parse_atom(hist_data, file, str, &flags, var_name);
  
  	if (field_op == FIELD_OP_UNARY_MINUS)
  		return parse_unary(hist_data, file, str, flags, var_name, n_subexprs);
  
  	/* Binary operator found, increment n_subexprs */
  	++*n_subexprs;
  
  	/* Split the expression string at the root operator */
  	if (!sep)
  		return ERR_PTR(-EINVAL);
  
  	*sep = '\0';
  	operand1_str = str;
  	str = sep+1;
  
  	/* Binary operator requires both operands */
  	if (*operand1_str == '\0' || *str == '\0')
  		return ERR_PTR(-EINVAL);
  
  	operand_flags = 0;
  
  	/* LHS of string is an expression e.g. a+b in a+b+c */
  	operand1 = parse_expr(hist_data, file, operand1_str, operand_flags, NULL, n_subexprs);
  	if (IS_ERR(operand1))
  		return ERR_CAST(operand1);
  
  	if (operand1->flags & HIST_FIELD_FL_STRING) {
  		hist_err(file->tr, HIST_ERR_INVALID_STR_OPERAND, errpos(operand1_str));
  		ret = -EINVAL;
  		goto free_op1;
  	}
  
  	/* RHS of string is another expression e.g. c in a+b+c */
  	operand_flags = 0;
  	operand2 = parse_expr(hist_data, file, str, operand_flags, NULL, n_subexprs);
  	if (IS_ERR(operand2)) {
  		ret = PTR_ERR(operand2);
  		goto free_op1;
  	}
  	if (operand2->flags & HIST_FIELD_FL_STRING) {
  		hist_err(file->tr, HIST_ERR_INVALID_STR_OPERAND, errpos(str));
  		ret = -EINVAL;
  		goto free_operands;
  	}
  
  	switch (field_op) {
  	case FIELD_OP_MINUS:
  		op_fn = hist_field_minus;
  		break;
  	case FIELD_OP_PLUS:
  		op_fn = hist_field_plus;
  		break;
  	case FIELD_OP_DIV:
  		op_fn = hist_field_div;
  		break;
  	case FIELD_OP_MULT:
  		op_fn = hist_field_mult;
  		break;
  	default:
  		ret = -EINVAL;
  		goto free_operands;
  	}
  
  	ret = check_expr_operands(file->tr, operand1, operand2, &var1, &var2);
  	if (ret)
  		goto free_operands;
  
  	operand_flags = var1 ? var1->flags : operand1->flags;
  	operand2_flags = var2 ? var2->flags : operand2->flags;
  
  	/*
  	 * If both operands are constant, the expression can be
  	 * collapsed to a single constant.
  	 */
  	combine_consts = operand_flags & operand2_flags & HIST_FIELD_FL_CONST;
  
  	flags |= combine_consts ? HIST_FIELD_FL_CONST : HIST_FIELD_FL_EXPR;
  
  	flags |= operand1->flags &
  		(HIST_FIELD_FL_TIMESTAMP | HIST_FIELD_FL_TIMESTAMP_USECS);
  
  	expr = create_hist_field(hist_data, NULL, flags, var_name);
  	if (!expr) {
  		ret = -ENOMEM;
  		goto free_operands;
  	}
  
  	operand1->read_once = true;
  	operand2->read_once = true;
  
  	/* The operands are now owned and free'd by 'expr' */
  	expr->operands[0] = operand1;
  	expr->operands[1] = operand2;
  
  	if (field_op == FIELD_OP_DIV &&
  			operand2_flags & HIST_FIELD_FL_CONST) {
  		u64 divisor = var2 ? var2->constant : operand2->constant;
  
  		if (!divisor) {
  			hist_err(file->tr, HIST_ERR_DIVISION_BY_ZERO, errpos(str));
  			ret = -EDOM;
  			goto free_expr;
  		}
  
  		/*
  		 * Copy the divisor here so we don't have to look it up
  		 * later if this is a var ref
  		 */
  		operand2->constant = divisor;
  		op_fn = hist_field_get_div_fn(operand2);
  	}
  
  	if (combine_consts) {
  		if (var1)
  			expr->operands[0] = var1;
  		if (var2)
  			expr->operands[1] = var2;
  
  		expr->constant = op_fn(expr, NULL, NULL, NULL, NULL);
  
  		expr->operands[0] = NULL;
  		expr->operands[1] = NULL;
  
  		/*
  		 * var refs won't be destroyed immediately
  		 * See: destroy_hist_field()
  		 */
  		destroy_hist_field(operand2, 0);
  		destroy_hist_field(operand1, 0);
  
  		expr->name = expr_str(expr, 0);
  	} else {
  		expr->fn = op_fn;
  
  		/* The operand sizes should be the same, so just pick one */
  		expr->size = operand1->size;
  		expr->is_signed = operand1->is_signed;
  
  		expr->operator = field_op;
  		expr->type = kstrdup_const(operand1->type, GFP_KERNEL);
  		if (!expr->type) {
  			ret = -ENOMEM;
  			goto free_expr;
  		}
  
  		expr->name = expr_str(expr, 0);
  	}
  
  	return expr;
  
  free_operands:
  	destroy_hist_field(operand2, 0);
  free_op1:
  	destroy_hist_field(operand1, 0);
  	return ERR_PTR(ret);
  
  free_expr:
  	destroy_hist_field(expr, 0);
  	return ERR_PTR(ret);
  }
  
  static char *find_trigger_filter(struct hist_trigger_data *hist_data,
  				 struct trace_event_file *file)
  {
  	struct event_trigger_data *test;
  
  	lockdep_assert_held(&event_mutex);
  
  	list_for_each_entry(test, &file->triggers, list) {
  		if (test->cmd_ops->trigger_type == ETT_EVENT_HIST) {
  			if (test->private_data == hist_data)
  				return test->filter_str;
  		}
  	}
  
  	return NULL;
  }
  
  static struct event_command trigger_hist_cmd;
  static int event_hist_trigger_parse(struct event_command *cmd_ops,
  				    struct trace_event_file *file,
  				    char *glob, char *cmd, char *param);
  
  static bool compatible_keys(struct hist_trigger_data *target_hist_data,
  			    struct hist_trigger_data *hist_data,
  			    unsigned int n_keys)
  {
  	struct hist_field *target_hist_field, *hist_field;
  	unsigned int n, i, j;
  
  	if (hist_data->n_fields - hist_data->n_vals != n_keys)
  		return false;
  
  	i = hist_data->n_vals;
  	j = target_hist_data->n_vals;
  
  	for (n = 0; n < n_keys; n++) {
  		hist_field = hist_data->fields[i + n];
  		target_hist_field = target_hist_data->fields[j + n];
  
  		if (strcmp(hist_field->type, target_hist_field->type) != 0)
  			return false;
  		if (hist_field->size != target_hist_field->size)
  			return false;
  		if (hist_field->is_signed != target_hist_field->is_signed)
  			return false;
  	}
  
  	return true;
  }
  
  static struct hist_trigger_data *
  find_compatible_hist(struct hist_trigger_data *target_hist_data,
  		     struct trace_event_file *file)
  {
  	struct hist_trigger_data *hist_data;
  	struct event_trigger_data *test;
  	unsigned int n_keys;
  
  	lockdep_assert_held(&event_mutex);
  
  	n_keys = target_hist_data->n_fields - target_hist_data->n_vals;
  
  	list_for_each_entry(test, &file->triggers, list) {
  		if (test->cmd_ops->trigger_type == ETT_EVENT_HIST) {
  			hist_data = test->private_data;
  
  			if (compatible_keys(target_hist_data, hist_data, n_keys))
  				return hist_data;
  		}
  	}
  
  	return NULL;
  }
  
  static struct trace_event_file *event_file(struct trace_array *tr,
  					   char *system, char *event_name)
  {
  	struct trace_event_file *file;
  
  	file = __find_event_file(tr, system, event_name);
  	if (!file)
  		return ERR_PTR(-EINVAL);
  
  	return file;
  }
  
  static struct hist_field *
  find_synthetic_field_var(struct hist_trigger_data *target_hist_data,
  			 char *system, char *event_name, char *field_name)
  {
  	struct hist_field *event_var;
  	char *synthetic_name;
  
  	synthetic_name = kzalloc(MAX_FILTER_STR_VAL, GFP_KERNEL);
  	if (!synthetic_name)
  		return ERR_PTR(-ENOMEM);
  
  	strcpy(synthetic_name, "synthetic_");
  	strcat(synthetic_name, field_name);
  
  	event_var = find_event_var(target_hist_data, system, event_name, synthetic_name);
  
  	kfree(synthetic_name);
  
  	return event_var;
  }
  
  /**
   * create_field_var_hist - Automatically create a histogram and var for a field
   * @target_hist_data: The target hist trigger
   * @subsys_name: Optional subsystem name
   * @event_name: Optional event name
   * @field_name: The name of the field (and the resulting variable)
   *
   * Hist trigger actions fetch data from variables, not directly from
   * events.  However, for convenience, users are allowed to directly
   * specify an event field in an action, which will be automatically
   * converted into a variable on their behalf.
   *
   * If a user specifies a field on an event that isn't the event the
   * histogram currently being defined (the target event histogram), the
   * only way that can be accomplished is if a new hist trigger is
   * created and the field variable defined on that.
   *
   * This function creates a new histogram compatible with the target
   * event (meaning a histogram with the same key as the target
   * histogram), and creates a variable for the specified field, but
   * with 'synthetic_' prepended to the variable name in order to avoid
   * collision with normal field variables.
   *
   * Return: The variable created for the field.
   */
  static struct hist_field *
  create_field_var_hist(struct hist_trigger_data *target_hist_data,
  		      char *subsys_name, char *event_name, char *field_name)
  {
  	struct trace_array *tr = target_hist_data->event_file->tr;
  	struct hist_trigger_data *hist_data;
  	unsigned int i, n, first = true;
  	struct field_var_hist *var_hist;
  	struct trace_event_file *file;
  	struct hist_field *key_field;
  	struct hist_field *event_var;
  	char *saved_filter;
  	char *cmd;
  	int ret;
  
  	if (target_hist_data->n_field_var_hists >= SYNTH_FIELDS_MAX) {
  		hist_err(tr, HIST_ERR_TOO_MANY_FIELD_VARS, errpos(field_name));
  		return ERR_PTR(-EINVAL);
  	}
  
  	file = event_file(tr, subsys_name, event_name);
  
  	if (IS_ERR(file)) {
  		hist_err(tr, HIST_ERR_EVENT_FILE_NOT_FOUND, errpos(field_name));
  		ret = PTR_ERR(file);
  		return ERR_PTR(ret);
  	}
  
  	/*
  	 * Look for a histogram compatible with target.  We'll use the
  	 * found histogram specification to create a new matching
  	 * histogram with our variable on it.  target_hist_data is not
  	 * yet a registered histogram so we can't use that.
  	 */
  	hist_data = find_compatible_hist(target_hist_data, file);
  	if (!hist_data) {
  		hist_err(tr, HIST_ERR_HIST_NOT_FOUND, errpos(field_name));
  		return ERR_PTR(-EINVAL);
  	}
  
  	/* See if a synthetic field variable has already been created */
  	event_var = find_synthetic_field_var(target_hist_data, subsys_name,
  					     event_name, field_name);
  	if (!IS_ERR_OR_NULL(event_var))
  		return event_var;
  
  	var_hist = kzalloc(sizeof(*var_hist), GFP_KERNEL);
  	if (!var_hist)
  		return ERR_PTR(-ENOMEM);
  
  	cmd = kzalloc(MAX_FILTER_STR_VAL, GFP_KERNEL);
  	if (!cmd) {
  		kfree(var_hist);
  		return ERR_PTR(-ENOMEM);
  	}
  
  	/* Use the same keys as the compatible histogram */
  	strcat(cmd, "keys=");
  
  	for_each_hist_key_field(i, hist_data) {
  		key_field = hist_data->fields[i];
  		if (!first)
  			strcat(cmd, ",");
  		strcat(cmd, key_field->field->name);
  		first = false;
  	}
  
  	/* Create the synthetic field variable specification */
  	strcat(cmd, ":synthetic_");
  	strcat(cmd, field_name);
  	strcat(cmd, "=");
  	strcat(cmd, field_name);
  
  	/* Use the same filter as the compatible histogram */
  	saved_filter = find_trigger_filter(hist_data, file);
  	if (saved_filter) {
  		strcat(cmd, " if ");
  		strcat(cmd, saved_filter);
  	}
  
  	var_hist->cmd = kstrdup(cmd, GFP_KERNEL);
  	if (!var_hist->cmd) {
  		kfree(cmd);
  		kfree(var_hist);
  		return ERR_PTR(-ENOMEM);
  	}
  
  	/* Save the compatible histogram information */
  	var_hist->hist_data = hist_data;
  
  	/* Create the new histogram with our variable */
  	ret = event_hist_trigger_parse(&trigger_hist_cmd, file,
  				       "", "hist", cmd);
  	if (ret) {
  		kfree(cmd);
  		kfree(var_hist->cmd);
  		kfree(var_hist);
  		hist_err(tr, HIST_ERR_HIST_CREATE_FAIL, errpos(field_name));
  		return ERR_PTR(ret);
  	}
  
  	kfree(cmd);
  
  	/* If we can't find the variable, something went wrong */
  	event_var = find_synthetic_field_var(target_hist_data, subsys_name,
  					     event_name, field_name);
  	if (IS_ERR_OR_NULL(event_var)) {
  		kfree(var_hist->cmd);
  		kfree(var_hist);
  		hist_err(tr, HIST_ERR_SYNTH_VAR_NOT_FOUND, errpos(field_name));
  		return ERR_PTR(-EINVAL);
  	}
  
  	n = target_hist_data->n_field_var_hists;
  	target_hist_data->field_var_hists[n] = var_hist;
  	target_hist_data->n_field_var_hists++;
  
  	return event_var;
  }
  
  static struct hist_field *
  find_target_event_var(struct hist_trigger_data *hist_data,
  		      char *subsys_name, char *event_name, char *var_name)
  {
  	struct trace_event_file *file = hist_data->event_file;
  	struct hist_field *hist_field = NULL;
  
  	if (subsys_name) {
  		struct trace_event_call *call;
  
  		if (!event_name)
  			return NULL;
  
  		call = file->event_call;
  
  		if (strcmp(subsys_name, call->class->system) != 0)
  			return NULL;
  
  		if (strcmp(event_name, trace_event_name(call)) != 0)
  			return NULL;
  	}
  
  	hist_field = find_var_field(hist_data, var_name);
  
  	return hist_field;
  }
  
  static inline void __update_field_vars(struct tracing_map_elt *elt,
  				       struct trace_buffer *buffer,
  				       struct ring_buffer_event *rbe,
  				       void *rec,
  				       struct field_var **field_vars,
  				       unsigned int n_field_vars,
  				       unsigned int field_var_str_start)
  {
  	struct hist_elt_data *elt_data = elt->private_data;
  	unsigned int i, j, var_idx;
  	u64 var_val;
  
  	for (i = 0, j = field_var_str_start; i < n_field_vars; i++) {
  		struct field_var *field_var = field_vars[i];
  		struct hist_field *var = field_var->var;
  		struct hist_field *val = field_var->val;
  
  		var_val = val->fn(val, elt, buffer, rbe, rec);
  		var_idx = var->var.idx;
  
  		if (val->flags & HIST_FIELD_FL_STRING) {
  			char *str = elt_data->field_var_str[j++];
  			char *val_str = (char *)(uintptr_t)var_val;
  			unsigned int size;
  
  			size = min(val->size, STR_VAR_LEN_MAX);
  			strscpy(str, val_str, size);
  			var_val = (u64)(uintptr_t)str;
  		}
  		tracing_map_set_var(elt, var_idx, var_val);
  	}
  }
  
  static void update_field_vars(struct hist_trigger_data *hist_data,
  			      struct tracing_map_elt *elt,
  			      struct trace_buffer *buffer,
  			      struct ring_buffer_event *rbe,
  			      void *rec)
  {
  	__update_field_vars(elt, buffer, rbe, rec, hist_data->field_vars,
  			    hist_data->n_field_vars, 0);
  }
  
  static void save_track_data_vars(struct hist_trigger_data *hist_data,
  				 struct tracing_map_elt *elt,
  				 struct trace_buffer *buffer,  void *rec,
  				 struct ring_buffer_event *rbe, void *key,
  				 struct action_data *data, u64 *var_ref_vals)
  {
  	__update_field_vars(elt, buffer, rbe, rec, hist_data->save_vars,
  			    hist_data->n_save_vars, hist_data->n_field_var_str);
  }
  
  static struct hist_field *create_var(struct hist_trigger_data *hist_data,
  				     struct trace_event_file *file,
  				     char *name, int size, const char *type)
  {
  	struct hist_field *var;
  	int idx;
  
  	if (find_var(hist_data, file, name) && !hist_data->remove) {
  		var = ERR_PTR(-EINVAL);
  		goto out;
  	}
  
  	var = kzalloc(sizeof(struct hist_field), GFP_KERNEL);
  	if (!var) {
  		var = ERR_PTR(-ENOMEM);
  		goto out;
  	}
  
  	idx = tracing_map_add_var(hist_data->map);
  	if (idx < 0) {
  		kfree(var);
  		var = ERR_PTR(-EINVAL);
  		goto out;
  	}
  
  	var->ref = 1;
  	var->flags = HIST_FIELD_FL_VAR;
  	var->var.idx = idx;
  	var->var.hist_data = var->hist_data = hist_data;
  	var->size = size;
  	var->var.name = kstrdup(name, GFP_KERNEL);
  	var->type = kstrdup_const(type, GFP_KERNEL);
  	if (!var->var.name || !var->type) {
  		kfree_const(var->type);
  		kfree(var->var.name);
  		kfree(var);
  		var = ERR_PTR(-ENOMEM);
  	}
   out:
  	return var;
  }
  
  static struct field_var *create_field_var(struct hist_trigger_data *hist_data,
  					  struct trace_event_file *file,
  					  char *field_name)
  {
  	struct hist_field *val = NULL, *var = NULL;
  	unsigned long flags = HIST_FIELD_FL_VAR;
  	struct trace_array *tr = file->tr;
  	struct field_var *field_var;
  	int ret = 0;
  
  	if (hist_data->n_field_vars >= SYNTH_FIELDS_MAX) {
  		hist_err(tr, HIST_ERR_TOO_MANY_FIELD_VARS, errpos(field_name));
  		ret = -EINVAL;
  		goto err;
  	}
  
  	val = parse_atom(hist_data, file, field_name, &flags, NULL);
  	if (IS_ERR(val)) {
  		hist_err(tr, HIST_ERR_FIELD_VAR_PARSE_FAIL, errpos(field_name));
  		ret = PTR_ERR(val);
  		goto err;
  	}
  
  	var = create_var(hist_data, file, field_name, val->size, val->type);
  	if (IS_ERR(var)) {
  		hist_err(tr, HIST_ERR_VAR_CREATE_FIND_FAIL, errpos(field_name));
  		kfree(val);
  		ret = PTR_ERR(var);
  		goto err;
  	}
  
  	field_var = kzalloc(sizeof(struct field_var), GFP_KERNEL);
  	if (!field_var) {
  		kfree(val);
  		kfree(var);
  		ret =  -ENOMEM;
  		goto err;
  	}
  
  	field_var->var = var;
  	field_var->val = val;
   out:
  	return field_var;
   err:
  	field_var = ERR_PTR(ret);
  	goto out;
  }
  
  /**
   * create_target_field_var - Automatically create a variable for a field
   * @target_hist_data: The target hist trigger
   * @subsys_name: Optional subsystem name
   * @event_name: Optional event name
   * @var_name: The name of the field (and the resulting variable)
   *
   * Hist trigger actions fetch data from variables, not directly from
   * events.  However, for convenience, users are allowed to directly
   * specify an event field in an action, which will be automatically
   * converted into a variable on their behalf.
  
   * This function creates a field variable with the name var_name on
   * the hist trigger currently being defined on the target event.  If
   * subsys_name and event_name are specified, this function simply
   * verifies that they do in fact match the target event subsystem and
   * event name.
   *
   * Return: The variable created for the field.
   */
  static struct field_var *
  create_target_field_var(struct hist_trigger_data *target_hist_data,
  			char *subsys_name, char *event_name, char *var_name)
  {
  	struct trace_event_file *file = target_hist_data->event_file;
  
  	if (subsys_name) {
  		struct trace_event_call *call;
  
  		if (!event_name)
  			return NULL;
  
  		call = file->event_call;
  
  		if (strcmp(subsys_name, call->class->system) != 0)
  			return NULL;
  
  		if (strcmp(event_name, trace_event_name(call)) != 0)
  			return NULL;
  	}
  
  	return create_field_var(target_hist_data, file, var_name);
  }
  
  static bool check_track_val_max(u64 track_val, u64 var_val)
  {
  	if (var_val <= track_val)
  		return false;
  
  	return true;
  }
  
  static bool check_track_val_changed(u64 track_val, u64 var_val)
  {
  	if (var_val == track_val)
  		return false;
  
  	return true;
  }
  
  static u64 get_track_val(struct hist_trigger_data *hist_data,
  			 struct tracing_map_elt *elt,
  			 struct action_data *data)
  {
  	unsigned int track_var_idx = data->track_data.track_var->var.idx;
  	u64 track_val;
  
  	track_val = tracing_map_read_var(elt, track_var_idx);
  
  	return track_val;
  }
  
  static void save_track_val(struct hist_trigger_data *hist_data,
  			   struct tracing_map_elt *elt,
  			   struct action_data *data, u64 var_val)
  {
  	unsigned int track_var_idx = data->track_data.track_var->var.idx;
  
  	tracing_map_set_var(elt, track_var_idx, var_val);
  }
  
  static void save_track_data(struct hist_trigger_data *hist_data,
  			    struct tracing_map_elt *elt,
  			    struct trace_buffer *buffer, void *rec,
  			    struct ring_buffer_event *rbe, void *key,
  			    struct action_data *data, u64 *var_ref_vals)
  {
  	if (data->track_data.save_data)
  		data->track_data.save_data(hist_data, elt, buffer, rec, rbe,
  					   key, data, var_ref_vals);
  }
  
  static bool check_track_val(struct tracing_map_elt *elt,
  			    struct action_data *data,
  			    u64 var_val)
  {
  	struct hist_trigger_data *hist_data;
  	u64 track_val;
  
  	hist_data = data->track_data.track_var->hist_data;
  	track_val = get_track_val(hist_data, elt, data);
  
  	return data->track_data.check_val(track_val, var_val);
  }
  
  #ifdef CONFIG_TRACER_SNAPSHOT
  static bool cond_snapshot_update(struct trace_array *tr, void *cond_data)
  {
  	/* called with tr->max_lock held */
  	struct track_data *track_data = tr->cond_snapshot->cond_data;
  	struct hist_elt_data *elt_data, *track_elt_data;
  	struct snapshot_context *context = cond_data;
  	struct action_data *action;
  	u64 track_val;
  
  	if (!track_data)
  		return false;
  
  	action = track_data->action_data;
  
  	track_val = get_track_val(track_data->hist_data, context->elt,
  				  track_data->action_data);
  
  	if (!action->track_data.check_val(track_data->track_val, track_val))
  		return false;
  
  	track_data->track_val = track_val;
  	memcpy(track_data->key, context->key, track_data->key_len);
  
  	elt_data = context->elt->private_data;
  	track_elt_data = track_data->elt.private_data;
  	if (elt_data->comm)
  		strncpy(track_elt_data->comm, elt_data->comm, TASK_COMM_LEN);
  
  	track_data->updated = true;
  
  	return true;
  }
  
  static void save_track_data_snapshot(struct hist_trigger_data *hist_data,
  				     struct tracing_map_elt *elt,
  				     struct trace_buffer *buffer, void *rec,
  				     struct ring_buffer_event *rbe, void *key,
  				     struct action_data *data,
  				     u64 *var_ref_vals)
  {
  	struct trace_event_file *file = hist_data->event_file;
  	struct snapshot_context context;
  
  	context.elt = elt;
  	context.key = key;
  
  	tracing_snapshot_cond(file->tr, &context);
  }
  
  static void hist_trigger_print_key(struct seq_file *m,
  				   struct hist_trigger_data *hist_data,
  				   void *key,
  				   struct tracing_map_elt *elt);
  
  static struct action_data *snapshot_action(struct hist_trigger_data *hist_data)
  {
  	unsigned int i;
  
  	if (!hist_data->n_actions)
  		return NULL;
  
  	for (i = 0; i < hist_data->n_actions; i++) {
  		struct action_data *data = hist_data->actions[i];
  
  		if (data->action == ACTION_SNAPSHOT)
  			return data;
  	}
  
  	return NULL;
  }
  
  static void track_data_snapshot_print(struct seq_file *m,
  				      struct hist_trigger_data *hist_data)
  {
  	struct trace_event_file *file = hist_data->event_file;
  	struct track_data *track_data;
  	struct action_data *action;
  
  	track_data = tracing_cond_snapshot_data(file->tr);
  	if (!track_data)
  		return;
  
  	if (!track_data->updated)
  		return;
  
  	action = snapshot_action(hist_data);
  	if (!action)
  		return;
  
  	seq_puts(m, "\nSnapshot taken (see tracing/snapshot).  Details:\n");
  	seq_printf(m, "\ttriggering value { %s(%s) }: %10llu",
  		   action->handler == HANDLER_ONMAX ? "onmax" : "onchange",
  		   action->track_data.var_str, track_data->track_val);
  
  	seq_puts(m, "\ttriggered by event with key: ");
  	hist_trigger_print_key(m, hist_data, track_data->key, &track_data->elt);
  	seq_putc(m, '\n');
  }
  #else
  static bool cond_snapshot_update(struct trace_array *tr, void *cond_data)
  {
  	return false;
  }
  static void save_track_data_snapshot(struct hist_trigger_data *hist_data,
  				     struct tracing_map_elt *elt,
  				     struct trace_buffer *buffer, void *rec,
  				     struct ring_buffer_event *rbe, void *key,
  				     struct action_data *data,
  				     u64 *var_ref_vals) {}
  static void track_data_snapshot_print(struct seq_file *m,
  				      struct hist_trigger_data *hist_data) {}
  #endif /* CONFIG_TRACER_SNAPSHOT */
  
  static void track_data_print(struct seq_file *m,
  			     struct hist_trigger_data *hist_data,
  			     struct tracing_map_elt *elt,
  			     struct action_data *data)
  {
  	u64 track_val = get_track_val(hist_data, elt, data);
  	unsigned int i, save_var_idx;
  
  	if (data->handler == HANDLER_ONMAX)
  		seq_printf(m, "\n\tmax: %10llu", track_val);
  	else if (data->handler == HANDLER_ONCHANGE)
  		seq_printf(m, "\n\tchanged: %10llu", track_val);
  
  	if (data->action == ACTION_SNAPSHOT)
  		return;
  
  	for (i = 0; i < hist_data->n_save_vars; i++) {
  		struct hist_field *save_val = hist_data->save_vars[i]->val;
  		struct hist_field *save_var = hist_data->save_vars[i]->var;
  		u64 val;
  
  		save_var_idx = save_var->var.idx;
  
  		val = tracing_map_read_var(elt, save_var_idx);
  
  		if (save_val->flags & HIST_FIELD_FL_STRING) {
  			seq_printf(m, "  %s: %-32s", save_var->var.name,
  				   (char *)(uintptr_t)(val));
  		} else
  			seq_printf(m, "  %s: %10llu", save_var->var.name, val);
  	}
  }
  
  static void ontrack_action(struct hist_trigger_data *hist_data,
  			   struct tracing_map_elt *elt,
  			   struct trace_buffer *buffer, void *rec,
  			   struct ring_buffer_event *rbe, void *key,
  			   struct action_data *data, u64 *var_ref_vals)
  {
  	u64 var_val = var_ref_vals[data->track_data.var_ref->var_ref_idx];
  
  	if (check_track_val(elt, data, var_val)) {
  		save_track_val(hist_data, elt, data, var_val);
  		save_track_data(hist_data, elt, buffer, rec, rbe,
  				key, data, var_ref_vals);
  	}
  }
  
  static void action_data_destroy(struct action_data *data)
  {
  	unsigned int i;
  
  	lockdep_assert_held(&event_mutex);
  
  	kfree(data->action_name);
  
  	for (i = 0; i < data->n_params; i++)
  		kfree(data->params[i]);
  
  	if (data->synth_event)
  		data->synth_event->ref--;
  
  	kfree(data->synth_event_name);
  
  	kfree(data);
  }
  
  static void track_data_destroy(struct hist_trigger_data *hist_data,
  			       struct action_data *data)
  {
  	struct trace_event_file *file = hist_data->event_file;
  
  	destroy_hist_field(data->track_data.track_var, 0);
  
  	if (data->action == ACTION_SNAPSHOT) {
  		struct track_data *track_data;
  
  		track_data = tracing_cond_snapshot_data(file->tr);
  		if (track_data && track_data->hist_data == hist_data) {
  			tracing_snapshot_cond_disable(file->tr);
  			track_data_free(track_data);
  		}
  	}
  
  	kfree(data->track_data.var_str);
  
  	action_data_destroy(data);
  }
  
  static int action_create(struct hist_trigger_data *hist_data,
  			 struct action_data *data);
  
  static int track_data_create(struct hist_trigger_data *hist_data,
  			     struct action_data *data)
  {
  	struct hist_field *var_field, *ref_field, *track_var = NULL;
  	struct trace_event_file *file = hist_data->event_file;
  	struct trace_array *tr = file->tr;
  	char *track_data_var_str;
  	int ret = 0;
  
  	track_data_var_str = data->track_data.var_str;
  	if (track_data_var_str[0] != '$') {
  		hist_err(tr, HIST_ERR_ONX_NOT_VAR, errpos(track_data_var_str));
  		return -EINVAL;
  	}
  	track_data_var_str++;
  
  	var_field = find_target_event_var(hist_data, NULL, NULL, track_data_var_str);
  	if (!var_field) {
  		hist_err(tr, HIST_ERR_ONX_VAR_NOT_FOUND, errpos(track_data_var_str));
  		return -EINVAL;
  	}
  
  	ref_field = create_var_ref(hist_data, var_field, NULL, NULL);
  	if (!ref_field)
  		return -ENOMEM;
  
  	data->track_data.var_ref = ref_field;
  
  	if (data->handler == HANDLER_ONMAX)
  		track_var = create_var(hist_data, file, "__max", sizeof(u64), "u64");
  	if (IS_ERR(track_var)) {
  		hist_err(tr, HIST_ERR_ONX_VAR_CREATE_FAIL, 0);
  		ret = PTR_ERR(track_var);
  		goto out;
  	}
  
  	if (data->handler == HANDLER_ONCHANGE)
  		track_var = create_var(hist_data, file, "__change", sizeof(u64), "u64");
  	if (IS_ERR(track_var)) {
  		hist_err(tr, HIST_ERR_ONX_VAR_CREATE_FAIL, 0);
  		ret = PTR_ERR(track_var);
  		goto out;
  	}
  	data->track_data.track_var = track_var;
  
  	ret = action_create(hist_data, data);
   out:
  	return ret;
  }
  
  static int parse_action_params(struct trace_array *tr, char *params,
  			       struct action_data *data)
  {
  	char *param, *saved_param;
  	bool first_param = true;
  	int ret = 0;
  
  	while (params) {
  		if (data->n_params >= SYNTH_FIELDS_MAX) {
  			hist_err(tr, HIST_ERR_TOO_MANY_PARAMS, 0);
  			goto out;
  		}
  
  		param = strsep(&params, ",");
  		if (!param) {
  			hist_err(tr, HIST_ERR_PARAM_NOT_FOUND, 0);
  			ret = -EINVAL;
  			goto out;
  		}
  
  		param = strstrip(param);
  		if (strlen(param) < 2) {
  			hist_err(tr, HIST_ERR_INVALID_PARAM, errpos(param));
  			ret = -EINVAL;
  			goto out;
  		}
  
  		saved_param = kstrdup(param, GFP_KERNEL);
  		if (!saved_param) {
  			ret = -ENOMEM;
  			goto out;
  		}
  
  		if (first_param && data->use_trace_keyword) {
  			data->synth_event_name = saved_param;
  			first_param = false;
  			continue;
  		}
  		first_param = false;
  
  		data->params[data->n_params++] = saved_param;
  	}
   out:
  	return ret;
  }
  
  static int action_parse(struct trace_array *tr, char *str, struct action_data *data,
  			enum handler_id handler)
  {
  	char *action_name;
  	int ret = 0;
  
  	strsep(&str, ".");
  	if (!str) {
  		hist_err(tr, HIST_ERR_ACTION_NOT_FOUND, 0);
  		ret = -EINVAL;
  		goto out;
  	}
  
  	action_name = strsep(&str, "(");
  	if (!action_name || !str) {
  		hist_err(tr, HIST_ERR_ACTION_NOT_FOUND, 0);
  		ret = -EINVAL;
  		goto out;
  	}
  
  	if (str_has_prefix(action_name, "save")) {
  		char *params = strsep(&str, ")");
  
  		if (!params) {
  			hist_err(tr, HIST_ERR_NO_SAVE_PARAMS, 0);
  			ret = -EINVAL;
  			goto out;
  		}
  
  		ret = parse_action_params(tr, params, data);
  		if (ret)
  			goto out;
  
  		if (handler == HANDLER_ONMAX)
  			data->track_data.check_val = check_track_val_max;
  		else if (handler == HANDLER_ONCHANGE)
  			data->track_data.check_val = check_track_val_changed;
  		else {
  			hist_err(tr, HIST_ERR_ACTION_MISMATCH, errpos(action_name));
  			ret = -EINVAL;
  			goto out;
  		}
  
  		data->track_data.save_data = save_track_data_vars;
  		data->fn = ontrack_action;
  		data->action = ACTION_SAVE;
  	} else if (str_has_prefix(action_name, "snapshot")) {
  		char *params = strsep(&str, ")");
  
  		if (!str) {
  			hist_err(tr, HIST_ERR_NO_CLOSING_PAREN, errpos(params));
  			ret = -EINVAL;
  			goto out;
  		}
  
  		if (handler == HANDLER_ONMAX)
  			data->track_data.check_val = check_track_val_max;
  		else if (handler == HANDLER_ONCHANGE)
  			data->track_data.check_val = check_track_val_changed;
  		else {
  			hist_err(tr, HIST_ERR_ACTION_MISMATCH, errpos(action_name));
  			ret = -EINVAL;
  			goto out;
  		}
  
  		data->track_data.save_data = save_track_data_snapshot;
  		data->fn = ontrack_action;
  		data->action = ACTION_SNAPSHOT;
  	} else {
  		char *params = strsep(&str, ")");
  
  		if (str_has_prefix(action_name, "trace"))
  			data->use_trace_keyword = true;
  
  		if (params) {
  			ret = parse_action_params(tr, params, data);
  			if (ret)
  				goto out;
  		}
  
  		if (handler == HANDLER_ONMAX)
  			data->track_data.check_val = check_track_val_max;
  		else if (handler == HANDLER_ONCHANGE)
  			data->track_data.check_val = check_track_val_changed;
  
  		if (handler != HANDLER_ONMATCH) {
  			data->track_data.save_data = action_trace;
  			data->fn = ontrack_action;
  		} else
  			data->fn = action_trace;
  
  		data->action = ACTION_TRACE;
  	}
  
  	data->action_name = kstrdup(action_name, GFP_KERNEL);
  	if (!data->action_name) {
  		ret = -ENOMEM;
  		goto out;
  	}
  
  	data->handler = handler;
   out:
  	return ret;
  }
  
  static struct action_data *track_data_parse(struct hist_trigger_data *hist_data,
  					    char *str, enum handler_id handler)
  {
  	struct action_data *data;
  	int ret = -EINVAL;
  	char *var_str;
  
  	data = kzalloc(sizeof(*data), GFP_KERNEL);
  	if (!data)
  		return ERR_PTR(-ENOMEM);
  
  	var_str = strsep(&str, ")");
  	if (!var_str || !str) {
  		ret = -EINVAL;
  		goto free;
  	}
  
  	data->track_data.var_str = kstrdup(var_str, GFP_KERNEL);
  	if (!data->track_data.var_str) {
  		ret = -ENOMEM;
  		goto free;
  	}
  
  	ret = action_parse(hist_data->event_file->tr, str, data, handler);
  	if (ret)
  		goto free;
   out:
  	return data;
   free:
  	track_data_destroy(hist_data, data);
  	data = ERR_PTR(ret);
  	goto out;
  }
  
  static void onmatch_destroy(struct action_data *data)
  {
  	kfree(data->match_data.event);
  	kfree(data->match_data.event_system);
  
  	action_data_destroy(data);
  }
  
  static void destroy_field_var(struct field_var *field_var)
  {
  	if (!field_var)
  		return;
  
  	destroy_hist_field(field_var->var, 0);
  	destroy_hist_field(field_var->val, 0);
  
  	kfree(field_var);
  }
  
  static void destroy_field_vars(struct hist_trigger_data *hist_data)
  {
  	unsigned int i;
  
  	for (i = 0; i < hist_data->n_field_vars; i++)
  		destroy_field_var(hist_data->field_vars[i]);
  
  	for (i = 0; i < hist_data->n_save_vars; i++)
  		destroy_field_var(hist_data->save_vars[i]);
  }
  
  static void save_field_var(struct hist_trigger_data *hist_data,
  			   struct field_var *field_var)
  {
  	hist_data->field_vars[hist_data->n_field_vars++] = field_var;
  
  	if (field_var->val->flags & HIST_FIELD_FL_STRING)
  		hist_data->n_field_var_str++;
  }
  
  
  static int check_synth_field(struct synth_event *event,
  			     struct hist_field *hist_field,
  			     unsigned int field_pos)
  {
  	struct synth_field *field;
  
  	if (field_pos >= event->n_fields)
  		return -EINVAL;
  
  	field = event->fields[field_pos];
  
  	/*
  	 * A dynamic string synth field can accept static or
  	 * dynamic. A static string synth field can only accept a
  	 * same-sized static string, which is checked for later.
  	 */
  	if (strstr(hist_field->type, "char[") && field->is_string
  	    && field->is_dynamic)
  		return 0;
  
  	if (strcmp(field->type, hist_field->type) != 0) {
  		if (field->size != hist_field->size ||
  		    (!field->is_string && field->is_signed != hist_field->is_signed))
  			return -EINVAL;
  	}
  
  	return 0;
  }
  
  static struct hist_field *
  trace_action_find_var(struct hist_trigger_data *hist_data,
  		      struct action_data *data,
  		      char *system, char *event, char *var)
  {
  	struct trace_array *tr = hist_data->event_file->tr;
  	struct hist_field *hist_field;
  
  	var++; /* skip '$' */
  
  	hist_field = find_target_event_var(hist_data, system, event, var);
  	if (!hist_field) {
  		if (!system && data->handler == HANDLER_ONMATCH) {
  			system = data->match_data.event_system;
  			event = data->match_data.event;
  		}
  
  		hist_field = find_event_var(hist_data, system, event, var);
  	}
  
  	if (!hist_field)
  		hist_err(tr, HIST_ERR_PARAM_NOT_FOUND, errpos(var));
  
  	return hist_field;
  }
  
  static struct hist_field *
  trace_action_create_field_var(struct hist_trigger_data *hist_data,
  			      struct action_data *data, char *system,
  			      char *event, char *var)
  {
  	struct hist_field *hist_field = NULL;
  	struct field_var *field_var;
  
  	/*
  	 * First try to create a field var on the target event (the
  	 * currently being defined).  This will create a variable for
  	 * unqualified fields on the target event, or if qualified,
  	 * target fields that have qualified names matching the target.
  	 */
  	field_var = create_target_field_var(hist_data, system, event, var);
  
  	if (field_var && !IS_ERR(field_var)) {
  		save_field_var(hist_data, field_var);
  		hist_field = field_var->var;
  	} else {
  		field_var = NULL;
  		/*
  		 * If no explicit system.event is specified, default to
  		 * looking for fields on the onmatch(system.event.xxx)
  		 * event.
  		 */
  		if (!system && data->handler == HANDLER_ONMATCH) {
  			system = data->match_data.event_system;
  			event = data->match_data.event;
  		}
  
  		if (!event)
  			goto free;
  		/*
  		 * At this point, we're looking at a field on another
  		 * event.  Because we can't modify a hist trigger on
  		 * another event to add a variable for a field, we need
  		 * to create a new trigger on that event and create the
  		 * variable at the same time.
  		 */
  		hist_field = create_field_var_hist(hist_data, system, event, var);
  		if (IS_ERR(hist_field))
  			goto free;
  	}
   out:
  	return hist_field;
   free:
  	destroy_field_var(field_var);
  	hist_field = NULL;
  	goto out;
  }
  
  static int trace_action_create(struct hist_trigger_data *hist_data,
  			       struct action_data *data)
  {
  	struct trace_array *tr = hist_data->event_file->tr;
  	char *event_name, *param, *system = NULL;
  	struct hist_field *hist_field, *var_ref;
  	unsigned int i;
  	unsigned int field_pos = 0;
  	struct synth_event *event;
  	char *synth_event_name;
  	int var_ref_idx, ret = 0;
  
  	lockdep_assert_held(&event_mutex);
  
  	if (data->use_trace_keyword)
  		synth_event_name = data->synth_event_name;
  	else
  		synth_event_name = data->action_name;
  
  	event = find_synth_event(synth_event_name);
  	if (!event) {
  		hist_err(tr, HIST_ERR_SYNTH_EVENT_NOT_FOUND, errpos(synth_event_name));
  		return -EINVAL;
  	}
  
  	event->ref++;
  
  	for (i = 0; i < data->n_params; i++) {
  		char *p;
  
  		p = param = kstrdup(data->params[i], GFP_KERNEL);
  		if (!param) {
  			ret = -ENOMEM;
  			goto err;
  		}
  
  		system = strsep(&param, ".");
  		if (!param) {
  			param = (char *)system;
  			system = event_name = NULL;
  		} else {
  			event_name = strsep(&param, ".");
  			if (!param) {
  				kfree(p);
  				ret = -EINVAL;
  				goto err;
  			}
  		}
  
  		if (param[0] == '$')
  			hist_field = trace_action_find_var(hist_data, data,
  							   system, event_name,
  							   param);
  		else
  			hist_field = trace_action_create_field_var(hist_data,
  								   data,
  								   system,
  								   event_name,
  								   param);
  
  		if (!hist_field) {
  			kfree(p);
  			ret = -EINVAL;
  			goto err;
  		}
  
  		if (check_synth_field(event, hist_field, field_pos) == 0) {
  			var_ref = create_var_ref(hist_data, hist_field,
  						 system, event_name);
  			if (!var_ref) {
  				kfree(p);
  				ret = -ENOMEM;
  				goto err;
  			}
  
  			var_ref_idx = find_var_ref_idx(hist_data, var_ref);
  			if (WARN_ON(var_ref_idx < 0)) {
  				kfree(p);
  				ret = var_ref_idx;
  				goto err;
  			}
  
  			data->var_ref_idx[i] = var_ref_idx;
  
  			field_pos++;
  			kfree(p);
  			continue;
  		}
  
  		hist_err(tr, HIST_ERR_SYNTH_TYPE_MISMATCH, errpos(param));
  		kfree(p);
  		ret = -EINVAL;
  		goto err;
  	}
  
  	if (field_pos != event->n_fields) {
  		hist_err(tr, HIST_ERR_SYNTH_COUNT_MISMATCH, errpos(event->name));
  		ret = -EINVAL;
  		goto err;
  	}
  
  	data->synth_event = event;
   out:
  	return ret;
   err:
  	event->ref--;
  
  	goto out;
  }
  
  static int action_create(struct hist_trigger_data *hist_data,
  			 struct action_data *data)
  {
  	struct trace_event_file *file = hist_data->event_file;
  	struct trace_array *tr = file->tr;
  	struct track_data *track_data;
  	struct field_var *field_var;
  	unsigned int i;
  	char *param;
  	int ret = 0;
  
  	if (data->action == ACTION_TRACE)
  		return trace_action_create(hist_data, data);
  
  	if (data->action == ACTION_SNAPSHOT) {
  		track_data = track_data_alloc(hist_data->key_size, data, hist_data);
  		if (IS_ERR(track_data)) {
  			ret = PTR_ERR(track_data);
  			goto out;
  		}
  
  		ret = tracing_snapshot_cond_enable(file->tr, track_data,
  						   cond_snapshot_update);
  		if (ret)
  			track_data_free(track_data);
  
  		goto out;
  	}
  
  	if (data->action == ACTION_SAVE) {
  		if (hist_data->n_save_vars) {
  			ret = -EEXIST;
  			hist_err(tr, HIST_ERR_TOO_MANY_SAVE_ACTIONS, 0);
  			goto out;
  		}
  
  		for (i = 0; i < data->n_params; i++) {
  			param = kstrdup(data->params[i], GFP_KERNEL);
  			if (!param) {
  				ret = -ENOMEM;
  				goto out;
  			}
  
  			field_var = create_target_field_var(hist_data, NULL, NULL, param);
  			if (IS_ERR(field_var)) {
  				hist_err(tr, HIST_ERR_FIELD_VAR_CREATE_FAIL,
  					 errpos(param));
  				ret = PTR_ERR(field_var);
  				kfree(param);
  				goto out;
  			}
  
  			hist_data->save_vars[hist_data->n_save_vars++] = field_var;
  			if (field_var->val->flags & HIST_FIELD_FL_STRING)
  				hist_data->n_save_var_str++;
  			kfree(param);
  		}
  	}
   out:
  	return ret;
  }
  
  static int onmatch_create(struct hist_trigger_data *hist_data,
  			  struct action_data *data)
  {
  	return action_create(hist_data, data);
  }
  
  static struct action_data *onmatch_parse(struct trace_array *tr, char *str)
  {
  	char *match_event, *match_event_system;
  	struct action_data *data;
  	int ret = -EINVAL;
  
  	data = kzalloc(sizeof(*data), GFP_KERNEL);
  	if (!data)
  		return ERR_PTR(-ENOMEM);
  
  	match_event = strsep(&str, ")");
  	if (!match_event || !str) {
  		hist_err(tr, HIST_ERR_NO_CLOSING_PAREN, errpos(match_event));
  		goto free;
  	}
  
  	match_event_system = strsep(&match_event, ".");
  	if (!match_event) {
  		hist_err(tr, HIST_ERR_SUBSYS_NOT_FOUND, errpos(match_event_system));
  		goto free;
  	}
  
  	if (IS_ERR(event_file(tr, match_event_system, match_event))) {
  		hist_err(tr, HIST_ERR_INVALID_SUBSYS_EVENT, errpos(match_event));
  		goto free;
  	}
  
  	data->match_data.event = kstrdup(match_event, GFP_KERNEL);
  	if (!data->match_data.event) {
  		ret = -ENOMEM;
  		goto free;
  	}
  
  	data->match_data.event_system = kstrdup(match_event_system, GFP_KERNEL);
  	if (!data->match_data.event_system) {
  		ret = -ENOMEM;
  		goto free;
  	}
  
  	ret = action_parse(tr, str, data, HANDLER_ONMATCH);
  	if (ret)
  		goto free;
   out:
  	return data;
   free:
  	onmatch_destroy(data);
  	data = ERR_PTR(ret);
  	goto out;
  }
  
  static int create_hitcount_val(struct hist_trigger_data *hist_data)
  {
  	hist_data->fields[HITCOUNT_IDX] =
  		create_hist_field(hist_data, NULL, HIST_FIELD_FL_HITCOUNT, NULL);
  	if (!hist_data->fields[HITCOUNT_IDX])
  		return -ENOMEM;
  
  	hist_data->n_vals++;
  	hist_data->n_fields++;
  
  	if (WARN_ON(hist_data->n_vals > TRACING_MAP_VALS_MAX))
  		return -EINVAL;
  
  	return 0;
  }
  
  static int __create_val_field(struct hist_trigger_data *hist_data,
  			      unsigned int val_idx,
  			      struct trace_event_file *file,
  			      char *var_name, char *field_str,
  			      unsigned long flags)
  {
  	struct hist_field *hist_field;
  	int ret = 0, n_subexprs = 0;
  
  	hist_field = parse_expr(hist_data, file, field_str, flags, var_name, &n_subexprs);
  	if (IS_ERR(hist_field)) {
  		ret = PTR_ERR(hist_field);
  		goto out;
  	}
  
  	hist_data->fields[val_idx] = hist_field;
  
  	++hist_data->n_vals;
  	++hist_data->n_fields;
  
  	if (WARN_ON(hist_data->n_vals > TRACING_MAP_VALS_MAX + TRACING_MAP_VARS_MAX))
  		ret = -EINVAL;
   out:
  	return ret;
  }
  
  static int create_val_field(struct hist_trigger_data *hist_data,
  			    unsigned int val_idx,
  			    struct trace_event_file *file,
  			    char *field_str)
  {
  	if (WARN_ON(val_idx >= TRACING_MAP_VALS_MAX))
  		return -EINVAL;
  
  	return __create_val_field(hist_data, val_idx, file, NULL, field_str, 0);
  }
  
  static const char *no_comm = "(no comm)";
  
  static u64 hist_field_execname(struct hist_field *hist_field,
  			       struct tracing_map_elt *elt,
  			       struct trace_buffer *buffer,
  			       struct ring_buffer_event *rbe,
  			       void *event)
  {
  	struct hist_elt_data *elt_data;
  
  	if (WARN_ON_ONCE(!elt))
  		return (u64)(unsigned long)no_comm;
  
  	elt_data = elt->private_data;
  
  	if (WARN_ON_ONCE(!elt_data->comm))
  		return (u64)(unsigned long)no_comm;
  
  	return (u64)(unsigned long)(elt_data->comm);
  }
  
  /* Convert a var that points to common_pid.execname to a string */
  static void update_var_execname(struct hist_field *hist_field)
  {
  	hist_field->flags = HIST_FIELD_FL_STRING | HIST_FIELD_FL_VAR |
  		HIST_FIELD_FL_EXECNAME;
  	hist_field->size = MAX_FILTER_STR_VAL;
  	hist_field->is_signed = 0;
  
  	kfree_const(hist_field->type);
  	hist_field->type = "char[]";
  
  	hist_field->fn = hist_field_execname;
  }
  
  static int create_var_field(struct hist_trigger_data *hist_data,
  			    unsigned int val_idx,
  			    struct trace_event_file *file,
  			    char *var_name, char *expr_str)
  {
  	struct trace_array *tr = hist_data->event_file->tr;
  	unsigned long flags = 0;
  	int ret;
  
  	if (WARN_ON(val_idx >= TRACING_MAP_VALS_MAX + TRACING_MAP_VARS_MAX))
  		return -EINVAL;
  
  	if (find_var(hist_data, file, var_name) && !hist_data->remove) {
  		hist_err(tr, HIST_ERR_DUPLICATE_VAR, errpos(var_name));
  		return -EINVAL;
  	}
  
  	flags |= HIST_FIELD_FL_VAR;
  	hist_data->n_vars++;
  	if (WARN_ON(hist_data->n_vars > TRACING_MAP_VARS_MAX))
  		return -EINVAL;
  
  	ret = __create_val_field(hist_data, val_idx, file, var_name, expr_str, flags);
  
  	if (!ret && hist_data->fields[val_idx]->flags & HIST_FIELD_FL_EXECNAME)
  		update_var_execname(hist_data->fields[val_idx]);
  
  	if (!ret && hist_data->fields[val_idx]->flags & HIST_FIELD_FL_STRING)
  		hist_data->fields[val_idx]->var_str_idx = hist_data->n_var_str++;
  
  	return ret;
  }
  
  static int create_val_fields(struct hist_trigger_data *hist_data,
  			     struct trace_event_file *file)
  {
  	char *fields_str, *field_str;
  	unsigned int i, j = 1;
  	int ret;
  
  	ret = create_hitcount_val(hist_data);
  	if (ret)
  		goto out;
  
  	fields_str = hist_data->attrs->vals_str;
  	if (!fields_str)
  		goto out;
  
  	for (i = 0, j = 1; i < TRACING_MAP_VALS_MAX &&
  		     j < TRACING_MAP_VALS_MAX; i++) {
  		field_str = strsep(&fields_str, ",");
  		if (!field_str)
  			break;
  
  		if (strcmp(field_str, "hitcount") == 0)
  			continue;
  
  		ret = create_val_field(hist_data, j++, file, field_str);
  		if (ret)
  			goto out;
  	}
  
  	if (fields_str && (strcmp(fields_str, "hitcount") != 0))
  		ret = -EINVAL;
   out:
  	return ret;
  }
  
  static int create_key_field(struct hist_trigger_data *hist_data,
  			    unsigned int key_idx,
  			    unsigned int key_offset,
  			    struct trace_event_file *file,
  			    char *field_str)
  {
  	struct trace_array *tr = hist_data->event_file->tr;
  	struct hist_field *hist_field = NULL;
  	unsigned long flags = 0;
  	unsigned int key_size;
  	int ret = 0, n_subexprs = 0;
  
  	if (WARN_ON(key_idx >= HIST_FIELDS_MAX))
  		return -EINVAL;
  
  	flags |= HIST_FIELD_FL_KEY;
  
  	if (strcmp(field_str, "stacktrace") == 0) {
  		flags |= HIST_FIELD_FL_STACKTRACE;
  		key_size = sizeof(unsigned long) * HIST_STACKTRACE_DEPTH;
  		hist_field = create_hist_field(hist_data, NULL, flags, NULL);
  	} else {
  		hist_field = parse_expr(hist_data, file, field_str, flags,
  					NULL, &n_subexprs);
  		if (IS_ERR(hist_field)) {
  			ret = PTR_ERR(hist_field);
  			goto out;
  		}
  
  		if (field_has_hist_vars(hist_field, 0))	{
  			hist_err(tr, HIST_ERR_INVALID_REF_KEY, errpos(field_str));
  			destroy_hist_field(hist_field, 0);
  			ret = -EINVAL;
  			goto out;
  		}
  
  		key_size = hist_field->size;
  	}
  
  	hist_data->fields[key_idx] = hist_field;
  
  	key_size = ALIGN(key_size, sizeof(u64));
  	hist_data->fields[key_idx]->size = key_size;
  	hist_data->fields[key_idx]->offset = key_offset;
  
  	hist_data->key_size += key_size;
  
  	if (hist_data->key_size > HIST_KEY_SIZE_MAX) {
  		ret = -EINVAL;
  		goto out;
  	}
  
  	hist_data->n_keys++;
  	hist_data->n_fields++;
  
  	if (WARN_ON(hist_data->n_keys > TRACING_MAP_KEYS_MAX))
  		return -EINVAL;
  
  	ret = key_size;
   out:
  	return ret;
  }
  
  static int create_key_fields(struct hist_trigger_data *hist_data,
  			     struct trace_event_file *file)
  {
  	unsigned int i, key_offset = 0, n_vals = hist_data->n_vals;
  	char *fields_str, *field_str;
  	int ret = -EINVAL;
  
  	fields_str = hist_data->attrs->keys_str;
  	if (!fields_str)
  		goto out;
  
  	for (i = n_vals; i < n_vals + TRACING_MAP_KEYS_MAX; i++) {
  		field_str = strsep(&fields_str, ",");
  		if (!field_str)
  			break;
  		ret = create_key_field(hist_data, i, key_offset,
  				       file, field_str);
  		if (ret < 0)
  			goto out;
  		key_offset += ret;
  	}
  	if (fields_str) {
  		ret = -EINVAL;
  		goto out;
  	}
  	ret = 0;
   out:
  	return ret;
  }
  
  static int create_var_fields(struct hist_trigger_data *hist_data,
  			     struct trace_event_file *file)
  {
  	unsigned int i, j = hist_data->n_vals;
  	int ret = 0;
  
  	unsigned int n_vars = hist_data->attrs->var_defs.n_vars;
  
  	for (i = 0; i < n_vars; i++) {
  		char *var_name = hist_data->attrs->var_defs.name[i];
  		char *expr = hist_data->attrs->var_defs.expr[i];
  
  		ret = create_var_field(hist_data, j++, file, var_name, expr);
  		if (ret)
  			goto out;
  	}
   out:
  	return ret;
  }
  
  static void free_var_defs(struct hist_trigger_data *hist_data)
  {
  	unsigned int i;
  
  	for (i = 0; i < hist_data->attrs->var_defs.n_vars; i++) {
  		kfree(hist_data->attrs->var_defs.name[i]);
  		kfree(hist_data->attrs->var_defs.expr[i]);
  	}
  
  	hist_data->attrs->var_defs.n_vars = 0;
  }
  
  static int parse_var_defs(struct hist_trigger_data *hist_data)
  {
  	struct trace_array *tr = hist_data->event_file->tr;
  	char *s, *str, *var_name, *field_str;
  	unsigned int i, j, n_vars = 0;
  	int ret = 0;
  
  	for (i = 0; i < hist_data->attrs->n_assignments; i++) {
  		str = hist_data->attrs->assignment_str[i];
  		for (j = 0; j < TRACING_MAP_VARS_MAX; j++) {
  			field_str = strsep(&str, ",");
  			if (!field_str)
  				break;
  
  			var_name = strsep(&field_str, "=");
  			if (!var_name || !field_str) {
  				hist_err(tr, HIST_ERR_MALFORMED_ASSIGNMENT,
  					 errpos(var_name));
  				ret = -EINVAL;
  				goto free;
  			}
  
  			if (n_vars == TRACING_MAP_VARS_MAX) {
  				hist_err(tr, HIST_ERR_TOO_MANY_VARS, errpos(var_name));
  				ret = -EINVAL;
  				goto free;
  			}
  
  			s = kstrdup(var_name, GFP_KERNEL);
  			if (!s) {
  				ret = -ENOMEM;
  				goto free;
  			}
  			hist_data->attrs->var_defs.name[n_vars] = s;
  
  			s = kstrdup(field_str, GFP_KERNEL);
  			if (!s) {
  				ret = -ENOMEM;
  				goto free;
  			}
  			hist_data->attrs->var_defs.expr[n_vars++] = s;
  
  			hist_data->attrs->var_defs.n_vars = n_vars;
  		}
  	}
  
  	return ret;
   free:
  	free_var_defs(hist_data);
  
  	return ret;
  }
  
  static int create_hist_fields(struct hist_trigger_data *hist_data,
  			      struct trace_event_file *file)
  {
  	int ret;
  
  	ret = parse_var_defs(hist_data);
  	if (ret)
  		goto out;
  
  	ret = create_val_fields(hist_data, file);
  	if (ret)
  		goto out;
  
  	ret = create_var_fields(hist_data, file);
  	if (ret)
  		goto out;
  
  	ret = create_key_fields(hist_data, file);
  	if (ret)
  		goto out;
   out:
  	free_var_defs(hist_data);
  
  	return ret;
  }
  
  static int is_descending(struct trace_array *tr, const char *str)
  {
  	if (!str)
  		return 0;
  
  	if (strcmp(str, "descending") == 0)
  		return 1;
  
  	if (strcmp(str, "ascending") == 0)
  		return 0;
  
  	hist_err(tr, HIST_ERR_INVALID_SORT_MODIFIER, errpos((char *)str));
  
  	return -EINVAL;
  }
  
  static int create_sort_keys(struct hist_trigger_data *hist_data)
  {
  	struct trace_array *tr = hist_data->event_file->tr;
  	char *fields_str = hist_data->attrs->sort_key_str;
  	struct tracing_map_sort_key *sort_key;
  	int descending, ret = 0;
  	unsigned int i, j, k;
  
  	hist_data->n_sort_keys = 1; /* we always have at least one, hitcount */
  
  	if (!fields_str)
  		goto out;
  
  	for (i = 0; i < TRACING_MAP_SORT_KEYS_MAX; i++) {
  		struct hist_field *hist_field;
  		char *field_str, *field_name;
  		const char *test_name;
  
  		sort_key = &hist_data->sort_keys[i];
  
  		field_str = strsep(&fields_str, ",");
  		if (!field_str)
  			break;
  
  		if (!*field_str) {
  			ret = -EINVAL;
  			hist_err(tr, HIST_ERR_EMPTY_SORT_FIELD, errpos("sort="));
  			break;
  		}
  
  		if ((i == TRACING_MAP_SORT_KEYS_MAX - 1) && fields_str) {
  			hist_err(tr, HIST_ERR_TOO_MANY_SORT_FIELDS, errpos("sort="));
  			ret = -EINVAL;
  			break;
  		}
  
  		field_name = strsep(&field_str, ".");
  		if (!field_name || !*field_name) {
  			ret = -EINVAL;
  			hist_err(tr, HIST_ERR_EMPTY_SORT_FIELD, errpos("sort="));
  			break;
  		}
  
  		if (strcmp(field_name, "hitcount") == 0) {
  			descending = is_descending(tr, field_str);
  			if (descending < 0) {
  				ret = descending;
  				break;
  			}
  			sort_key->descending = descending;
  			continue;
  		}
  
  		for (j = 1, k = 1; j < hist_data->n_fields; j++) {
  			unsigned int idx;
  
  			hist_field = hist_data->fields[j];
  			if (hist_field->flags & HIST_FIELD_FL_VAR)
  				continue;
  
  			idx = k++;
  
  			test_name = hist_field_name(hist_field, 0);
  
  			if (strcmp(field_name, test_name) == 0) {
  				sort_key->field_idx = idx;
  				descending = is_descending(tr, field_str);
  				if (descending < 0) {
  					ret = descending;
  					goto out;
  				}
  				sort_key->descending = descending;
  				break;
  			}
  		}
  		if (j == hist_data->n_fields) {
  			ret = -EINVAL;
  			hist_err(tr, HIST_ERR_INVALID_SORT_FIELD, errpos(field_name));
  			break;
  		}
  	}
  
  	hist_data->n_sort_keys = i;
   out:
  	return ret;
  }
  
  static void destroy_actions(struct hist_trigger_data *hist_data)
  {
  	unsigned int i;
  
  	for (i = 0; i < hist_data->n_actions; i++) {
  		struct action_data *data = hist_data->actions[i];
  
  		if (data->handler == HANDLER_ONMATCH)
  			onmatch_destroy(data);
  		else if (data->handler == HANDLER_ONMAX ||
  			 data->handler == HANDLER_ONCHANGE)
  			track_data_destroy(hist_data, data);
  		else
  			kfree(data);
  	}
  }
  
  static int parse_actions(struct hist_trigger_data *hist_data)
  {
  	struct trace_array *tr = hist_data->event_file->tr;
  	struct action_data *data;
  	unsigned int i;
  	int ret = 0;
  	char *str;
  	int len;
  
  	for (i = 0; i < hist_data->attrs->n_actions; i++) {
  		str = hist_data->attrs->action_str[i];
  
  		if ((len = str_has_prefix(str, "onmatch("))) {
  			char *action_str = str + len;
  
  			data = onmatch_parse(tr, action_str);
  			if (IS_ERR(data)) {
  				ret = PTR_ERR(data);
  				break;
  			}
  		} else if ((len = str_has_prefix(str, "onmax("))) {
  			char *action_str = str + len;
  
  			data = track_data_parse(hist_data, action_str,
  						HANDLER_ONMAX);
  			if (IS_ERR(data)) {
  				ret = PTR_ERR(data);
  				break;
  			}
  		} else if ((len = str_has_prefix(str, "onchange("))) {
  			char *action_str = str + len;
  
  			data = track_data_parse(hist_data, action_str,
  						HANDLER_ONCHANGE);
  			if (IS_ERR(data)) {
  				ret = PTR_ERR(data);
  				break;
  			}
  		} else {
  			ret = -EINVAL;
  			break;
  		}
  
  		hist_data->actions[hist_data->n_actions++] = data;
  	}
  
  	return ret;
  }
  
  static int create_actions(struct hist_trigger_data *hist_data)
  {
  	struct action_data *data;
  	unsigned int i;
  	int ret = 0;
  
  	for (i = 0; i < hist_data->attrs->n_actions; i++) {
  		data = hist_data->actions[i];
  
  		if (data->handler == HANDLER_ONMATCH) {
  			ret = onmatch_create(hist_data, data);
  			if (ret)
  				break;
  		} else if (data->handler == HANDLER_ONMAX ||
  			   data->handler == HANDLER_ONCHANGE) {
  			ret = track_data_create(hist_data, data);
  			if (ret)
  				break;
  		} else {
  			ret = -EINVAL;
  			break;
  		}
  	}
  
  	return ret;
  }
  
  static void print_actions(struct seq_file *m,
  			  struct hist_trigger_data *hist_data,
  			  struct tracing_map_elt *elt)
  {
  	unsigned int i;
  
  	for (i = 0; i < hist_data->n_actions; i++) {
  		struct action_data *data = hist_data->actions[i];
  
  		if (data->action == ACTION_SNAPSHOT)
  			continue;
  
  		if (data->handler == HANDLER_ONMAX ||
  		    data->handler == HANDLER_ONCHANGE)
  			track_data_print(m, hist_data, elt, data);
  	}
  }
  
  static void print_action_spec(struct seq_file *m,
  			      struct hist_trigger_data *hist_data,
  			      struct action_data *data)
  {
  	unsigned int i;
  
  	if (data->action == ACTION_SAVE) {
  		for (i = 0; i < hist_data->n_save_vars; i++) {
  			seq_printf(m, "%s", hist_data->save_vars[i]->var->var.name);
  			if (i < hist_data->n_save_vars - 1)
  				seq_puts(m, ",");
  		}
  	} else if (data->action == ACTION_TRACE) {
  		if (data->use_trace_keyword)
  			seq_printf(m, "%s", data->synth_event_name);
  		for (i = 0; i < data->n_params; i++) {
  			if (i || data->use_trace_keyword)
  				seq_puts(m, ",");
  			seq_printf(m, "%s", data->params[i]);
  		}
  	}
  }
  
  static void print_track_data_spec(struct seq_file *m,
  				  struct hist_trigger_data *hist_data,
  				  struct action_data *data)
  {
  	if (data->handler == HANDLER_ONMAX)
  		seq_puts(m, ":onmax(");
  	else if (data->handler == HANDLER_ONCHANGE)
  		seq_puts(m, ":onchange(");
  	seq_printf(m, "%s", data->track_data.var_str);
  	seq_printf(m, ").%s(", data->action_name);
  
  	print_action_spec(m, hist_data, data);
  
  	seq_puts(m, ")");
  }
  
  static void print_onmatch_spec(struct seq_file *m,
  			       struct hist_trigger_data *hist_data,
  			       struct action_data *data)
  {
  	seq_printf(m, ":onmatch(%s.%s).", data->match_data.event_system,
  		   data->match_data.event);
  
  	seq_printf(m, "%s(", data->action_name);
  
  	print_action_spec(m, hist_data, data);
  
  	seq_puts(m, ")");
  }
  
  static bool actions_match(struct hist_trigger_data *hist_data,
  			  struct hist_trigger_data *hist_data_test)
  {
  	unsigned int i, j;
  
  	if (hist_data->n_actions != hist_data_test->n_actions)
  		return false;
  
  	for (i = 0; i < hist_data->n_actions; i++) {
  		struct action_data *data = hist_data->actions[i];
  		struct action_data *data_test = hist_data_test->actions[i];
  		char *action_name, *action_name_test;
  
  		if (data->handler != data_test->handler)
  			return false;
  		if (data->action != data_test->action)
  			return false;
  
  		if (data->n_params != data_test->n_params)
  			return false;
  
  		for (j = 0; j < data->n_params; j++) {
  			if (strcmp(data->params[j], data_test->params[j]) != 0)
  				return false;
  		}
  
  		if (data->use_trace_keyword)
  			action_name = data->synth_event_name;
  		else
  			action_name = data->action_name;
  
  		if (data_test->use_trace_keyword)
  			action_name_test = data_test->synth_event_name;
  		else
  			action_name_test = data_test->action_name;
  
  		if (strcmp(action_name, action_name_test) != 0)
  			return false;
  
  		if (data->handler == HANDLER_ONMATCH) {
  			if (strcmp(data->match_data.event_system,
  				   data_test->match_data.event_system) != 0)
  				return false;
  			if (strcmp(data->match_data.event,
  				   data_test->match_data.event) != 0)
  				return false;
  		} else if (data->handler == HANDLER_ONMAX ||
  			   data->handler == HANDLER_ONCHANGE) {
  			if (strcmp(data->track_data.var_str,
  				   data_test->track_data.var_str) != 0)
  				return false;
  		}
  	}
  
  	return true;
  }
  
  
  static void print_actions_spec(struct seq_file *m,
  			       struct hist_trigger_data *hist_data)
  {
  	unsigned int i;
  
  	for (i = 0; i < hist_data->n_actions; i++) {
  		struct action_data *data = hist_data->actions[i];
  
  		if (data->handler == HANDLER_ONMATCH)
  			print_onmatch_spec(m, hist_data, data);
  		else if (data->handler == HANDLER_ONMAX ||
  			 data->handler == HANDLER_ONCHANGE)
  			print_track_data_spec(m, hist_data, data);
  	}
  }
  
  static void destroy_field_var_hists(struct hist_trigger_data *hist_data)
  {
  	unsigned int i;
  
  	for (i = 0; i < hist_data->n_field_var_hists; i++) {
  		kfree(hist_data->field_var_hists[i]->cmd);
  		kfree(hist_data->field_var_hists[i]);
  	}
  }
  
  static void destroy_hist_data(struct hist_trigger_data *hist_data)
  {
  	if (!hist_data)
  		return;
  
  	destroy_hist_trigger_attrs(hist_data->attrs);
  	destroy_hist_fields(hist_data);
  	tracing_map_destroy(hist_data->map);
  
  	destroy_actions(hist_data);
  	destroy_field_vars(hist_data);
  	destroy_field_var_hists(hist_data);
  
  	kfree(hist_data);
  }
  
  static int create_tracing_map_fields(struct hist_trigger_data *hist_data)
  {
  	struct tracing_map *map = hist_data->map;
  	struct ftrace_event_field *field;
  	struct hist_field *hist_field;
  	int i, idx = 0;
  
  	for_each_hist_field(i, hist_data) {
  		hist_field = hist_data->fields[i];
  		if (hist_field->flags & HIST_FIELD_FL_KEY) {
  			tracing_map_cmp_fn_t cmp_fn;
  
  			field = hist_field->field;
  
  			if (hist_field->flags & HIST_FIELD_FL_STACKTRACE)
  				cmp_fn = tracing_map_cmp_none;
  			else if (!field || hist_field->flags & HIST_FIELD_FL_CPU)
  				cmp_fn = tracing_map_cmp_num(hist_field->size,
  							     hist_field->is_signed);
  			else if (is_string_field(field))
  				cmp_fn = tracing_map_cmp_string;
  			else
  				cmp_fn = tracing_map_cmp_num(field->size,
  							     field->is_signed);
  			idx = tracing_map_add_key_field(map,
  							hist_field->offset,
  							cmp_fn);
  		} else if (!(hist_field->flags & HIST_FIELD_FL_VAR))
  			idx = tracing_map_add_sum_field(map);
  
  		if (idx < 0)
  			return idx;
  
  		if (hist_field->flags & HIST_FIELD_FL_VAR) {
  			idx = tracing_map_add_var(map);
  			if (idx < 0)
  				return idx;
  			hist_field->var.idx = idx;
  			hist_field->var.hist_data = hist_data;
  		}
  	}
  
  	return 0;
  }
  
  static struct hist_trigger_data *
  create_hist_data(unsigned int map_bits,
  		 struct hist_trigger_attrs *attrs,
  		 struct trace_event_file *file,
  		 bool remove)
  {
  	const struct tracing_map_ops *map_ops = NULL;
  	struct hist_trigger_data *hist_data;
  	int ret = 0;
  
  	hist_data = kzalloc(sizeof(*hist_data), GFP_KERNEL);
  	if (!hist_data)
  		return ERR_PTR(-ENOMEM);
  
  	hist_data->attrs = attrs;
  	hist_data->remove = remove;
  	hist_data->event_file = file;
  
  	ret = parse_actions(hist_data);
  	if (ret)
  		goto free;
  
  	ret = create_hist_fields(hist_data, file);
  	if (ret)
  		goto free;
  
  	ret = create_sort_keys(hist_data);
  	if (ret)
  		goto free;
  
  	map_ops = &hist_trigger_elt_data_ops;
  
  	hist_data->map = tracing_map_create(map_bits, hist_data->key_size,
  					    map_ops, hist_data);
  	if (IS_ERR(hist_data->map)) {
  		ret = PTR_ERR(hist_data->map);
  		hist_data->map = NULL;
  		goto free;
  	}
  
  	ret = create_tracing_map_fields(hist_data);
  	if (ret)
  		goto free;
   out:
  	return hist_data;
   free:
  	hist_data->attrs = NULL;
  
  	destroy_hist_data(hist_data);
  
  	hist_data = ERR_PTR(ret);
  
  	goto out;
  }
  
  static void hist_trigger_elt_update(struct hist_trigger_data *hist_data,
  				    struct tracing_map_elt *elt,
  				    struct trace_buffer *buffer, void *rec,
  				    struct ring_buffer_event *rbe,
  				    u64 *var_ref_vals)
  {
  	struct hist_elt_data *elt_data;
  	struct hist_field *hist_field;
  	unsigned int i, var_idx;
  	u64 hist_val;
  
  	elt_data = elt->private_data;
  	elt_data->var_ref_vals = var_ref_vals;
  
  	for_each_hist_val_field(i, hist_data) {
  		hist_field = hist_data->fields[i];
  		hist_val = hist_field->fn(hist_field, elt, buffer, rbe, rec);
  		if (hist_field->flags & HIST_FIELD_FL_VAR) {
  			var_idx = hist_field->var.idx;
  
  			if (hist_field->flags & HIST_FIELD_FL_STRING) {
  				unsigned int str_start, var_str_idx, idx;
  				char *str, *val_str;
  				unsigned int size;
  
  				str_start = hist_data->n_field_var_str +
  					hist_data->n_save_var_str;
  				var_str_idx = hist_field->var_str_idx;
  				idx = str_start + var_str_idx;
  
  				str = elt_data->field_var_str[idx];
  				val_str = (char *)(uintptr_t)hist_val;
  
  				size = min(hist_field->size, STR_VAR_LEN_MAX);
  				strscpy(str, val_str, size);
  
  				hist_val = (u64)(uintptr_t)str;
  			}
  			tracing_map_set_var(elt, var_idx, hist_val);
  			continue;
  		}
  		tracing_map_update_sum(elt, i, hist_val);
  	}
  
  	for_each_hist_key_field(i, hist_data) {
  		hist_field = hist_data->fields[i];
  		if (hist_field->flags & HIST_FIELD_FL_VAR) {
  			hist_val = hist_field->fn(hist_field, elt, buffer, rbe, rec);
  			var_idx = hist_field->var.idx;
  			tracing_map_set_var(elt, var_idx, hist_val);
  		}
  	}
  
  	update_field_vars(hist_data, elt, buffer, rbe, rec);
  }
  
  static inline void add_to_key(char *compound_key, void *key,
  			      struct hist_field *key_field, void *rec)
  {
  	size_t size = key_field->size;
  
  	if (key_field->flags & HIST_FIELD_FL_STRING) {
  		struct ftrace_event_field *field;
  
  		field = key_field->field;
  		if (field->filter_type == FILTER_DYN_STRING ||
  		    field->filter_type == FILTER_RDYN_STRING)
  			size = *(u32 *)(rec + field->offset) >> 16;
  		else if (field->filter_type == FILTER_STATIC_STRING)
  			size = field->size;
  
  		/* ensure NULL-termination */
  		if (size > key_field->size - 1)
  			size = key_field->size - 1;
  
  		strncpy(compound_key + key_field->offset, (char *)key, size);
  	} else
  		memcpy(compound_key + key_field->offset, key, size);
  }
  
  static void
  hist_trigger_actions(struct hist_trigger_data *hist_data,
  		     struct tracing_map_elt *elt,
  		     struct trace_buffer *buffer, void *rec,
  		     struct ring_buffer_event *rbe, void *key,
  		     u64 *var_ref_vals)
  {
  	struct action_data *data;
  	unsigned int i;
  
  	for (i = 0; i < hist_data->n_actions; i++) {
  		data = hist_data->actions[i];
  		data->fn(hist_data, elt, buffer, rec, rbe, key, data, var_ref_vals);
  	}
  }
  
  static void event_hist_trigger(struct event_trigger_data *data,
  			       struct trace_buffer *buffer, void *rec,
  			       struct ring_buffer_event *rbe)
  {
  	struct hist_trigger_data *hist_data = data->private_data;
  	bool use_compound_key = (hist_data->n_keys > 1);
  	unsigned long entries[HIST_STACKTRACE_DEPTH];
  	u64 var_ref_vals[TRACING_MAP_VARS_MAX];
  	char compound_key[HIST_KEY_SIZE_MAX];
  	struct tracing_map_elt *elt = NULL;
  	struct hist_field *key_field;
  	u64 field_contents;
  	void *key = NULL;
  	unsigned int i;
  
  	memset(compound_key, 0, hist_data->key_size);
  
  	for_each_hist_key_field(i, hist_data) {
  		key_field = hist_data->fields[i];
  
  		if (key_field->flags & HIST_FIELD_FL_STACKTRACE) {
  			memset(entries, 0, HIST_STACKTRACE_SIZE);
  			stack_trace_save(entries, HIST_STACKTRACE_DEPTH,
  					 HIST_STACKTRACE_SKIP);
  			key = entries;
  		} else {
  			field_contents = key_field->fn(key_field, elt, buffer, rbe, rec);
  			if (key_field->flags & HIST_FIELD_FL_STRING) {
  				key = (void *)(unsigned long)field_contents;
  				use_compound_key = true;
  			} else
  				key = (void *)&field_contents;
  		}
  
  		if (use_compound_key)
  			add_to_key(compound_key, key, key_field, rec);
  	}
  
  	if (use_compound_key)
  		key = compound_key;
  
  	if (hist_data->n_var_refs &&
  	    !resolve_var_refs(hist_data, key, var_ref_vals, false))
  		return;
  
  	elt = tracing_map_insert(hist_data->map, key);
  	if (!elt)
  		return;
  
  	hist_trigger_elt_update(hist_data, elt, buffer, rec, rbe, var_ref_vals);
  
  	if (resolve_var_refs(hist_data, key, var_ref_vals, true))
  		hist_trigger_actions(hist_data, elt, buffer, rec, rbe, key, var_ref_vals);
  }
  
  static void hist_trigger_stacktrace_print(struct seq_file *m,
  					  unsigned long *stacktrace_entries,
  					  unsigned int max_entries)
  {
  	unsigned int spaces = 8;
  	unsigned int i;
  
  	for (i = 0; i < max_entries; i++) {
  		if (!stacktrace_entries[i])
  			return;
  
  		seq_printf(m, "%*c", 1 + spaces, ' ');
  		seq_printf(m, "%pS\n", (void*)stacktrace_entries[i]);
  	}
  }
  
  static void hist_trigger_print_key(struct seq_file *m,
  				   struct hist_trigger_data *hist_data,
  				   void *key,
  				   struct tracing_map_elt *elt)
  {
  	struct hist_field *key_field;
  	bool multiline = false;
  	const char *field_name;
  	unsigned int i;
  	u64 uval;
  
  	seq_puts(m, "{ ");
  
  	for_each_hist_key_field(i, hist_data) {
  		key_field = hist_data->fields[i];
  
  		if (i > hist_data->n_vals)
  			seq_puts(m, ", ");
  
  		field_name = hist_field_name(key_field, 0);
  
  		if (key_field->flags & HIST_FIELD_FL_HEX) {
  			uval = *(u64 *)(key + key_field->offset);
  			seq_printf(m, "%s: %llx", field_name, uval);
  		} else if (key_field->flags & HIST_FIELD_FL_SYM) {
  			uval = *(u64 *)(key + key_field->offset);
  			seq_printf(m, "%s: [%llx] %-45ps", field_name,
  				   uval, (void *)(uintptr_t)uval);
  		} else if (key_field->flags & HIST_FIELD_FL_SYM_OFFSET) {
  			uval = *(u64 *)(key + key_field->offset);
  			seq_printf(m, "%s: [%llx] %-55pS", field_name,
  				   uval, (void *)(uintptr_t)uval);
  		} else if (key_field->flags & HIST_FIELD_FL_EXECNAME) {
  			struct hist_elt_data *elt_data = elt->private_data;
  			char *comm;
  
  			if (WARN_ON_ONCE(!elt_data))
  				return;
  
  			comm = elt_data->comm;
  
  			uval = *(u64 *)(key + key_field->offset);
  			seq_printf(m, "%s: %-16s[%10llu]", field_name,
  				   comm, uval);
  		} else if (key_field->flags & HIST_FIELD_FL_SYSCALL) {
  			const char *syscall_name;
  
  			uval = *(u64 *)(key + key_field->offset);
  			syscall_name = get_syscall_name(uval);
  			if (!syscall_name)
  				syscall_name = "unknown_syscall";
  
  			seq_printf(m, "%s: %-30s[%3llu]", field_name,
  				   syscall_name, uval);
  		} else if (key_field->flags & HIST_FIELD_FL_STACKTRACE) {
  			seq_puts(m, "stacktrace:\n");
  			hist_trigger_stacktrace_print(m,
  						      key + key_field->offset,
  						      HIST_STACKTRACE_DEPTH);
  			multiline = true;
  		} else if (key_field->flags & HIST_FIELD_FL_LOG2) {
  			seq_printf(m, "%s: ~ 2^%-2llu", field_name,
  				   *(u64 *)(key + key_field->offset));
  		} else if (key_field->flags & HIST_FIELD_FL_BUCKET) {
  			unsigned long buckets = key_field->buckets;
  			uval = *(u64 *)(key + key_field->offset);
  			seq_printf(m, "%s: ~ %llu-%llu", field_name,
  				   uval, uval + buckets -1);
  		} else if (key_field->flags & HIST_FIELD_FL_STRING) {
  			seq_printf(m, "%s: %-50s", field_name,
  				   (char *)(key + key_field->offset));
  		} else {
  			uval = *(u64 *)(key + key_field->offset);
  			seq_printf(m, "%s: %10llu", field_name, uval);
  		}
  	}
  
  	if (!multiline)
  		seq_puts(m, " ");
  
  	seq_puts(m, "}");
  }
  
  static void hist_trigger_entry_print(struct seq_file *m,
  				     struct hist_trigger_data *hist_data,
  				     void *key,
  				     struct tracing_map_elt *elt)
  {
  	const char *field_name;
  	unsigned int i;
  
  	hist_trigger_print_key(m, hist_data, key, elt);
  
  	seq_printf(m, " hitcount: %10llu",
  		   tracing_map_read_sum(elt, HITCOUNT_IDX));
  
  	for (i = 1; i < hist_data->n_vals; i++) {
  		field_name = hist_field_name(hist_data->fields[i], 0);
  
  		if (hist_data->fields[i]->flags & HIST_FIELD_FL_VAR ||
  		    hist_data->fields[i]->flags & HIST_FIELD_FL_EXPR)
  			continue;
  
  		if (hist_data->fields[i]->flags & HIST_FIELD_FL_HEX) {
  			seq_printf(m, "  %s: %10llx", field_name,
  				   tracing_map_read_sum(elt, i));
  		} else {
  			seq_printf(m, "  %s: %10llu", field_name,
  				   tracing_map_read_sum(elt, i));
  		}
  	}
  
  	print_actions(m, hist_data, elt);
  
  	seq_puts(m, "\n");
  }
  
  static int print_entries(struct seq_file *m,
  			 struct hist_trigger_data *hist_data)
  {
  	struct tracing_map_sort_entry **sort_entries = NULL;
  	struct tracing_map *map = hist_data->map;
  	int i, n_entries;
  
  	n_entries = tracing_map_sort_entries(map, hist_data->sort_keys,
  					     hist_data->n_sort_keys,
  					     &sort_entries);
  	if (n_entries < 0)
  		return n_entries;
  
  	for (i = 0; i < n_entries; i++)
  		hist_trigger_entry_print(m, hist_data,
  					 sort_entries[i]->key,
  					 sort_entries[i]->elt);
  
  	tracing_map_destroy_sort_entries(sort_entries, n_entries);
  
  	return n_entries;
  }
  
  static void hist_trigger_show(struct seq_file *m,
  			      struct event_trigger_data *data, int n)
  {
  	struct hist_trigger_data *hist_data;
  	int n_entries;
  
  	if (n > 0)
  		seq_puts(m, "\n\n");
  
  	seq_puts(m, "# event histogram\n#\n# trigger info: ");
  	data->ops->print(m, data->ops, data);
  	seq_puts(m, "#\n\n");
  
  	hist_data = data->private_data;
  	n_entries = print_entries(m, hist_data);
  	if (n_entries < 0)
  		n_entries = 0;
  
  	track_data_snapshot_print(m, hist_data);
  
  	seq_printf(m, "\nTotals:\n    Hits: %llu\n    Entries: %u\n    Dropped: %llu\n",
  		   (u64)atomic64_read(&hist_data->map->hits),
  		   n_entries, (u64)atomic64_read(&hist_data->map->drops));
  }
  
  static int hist_show(struct seq_file *m, void *v)
  {
  	struct event_trigger_data *data;
  	struct trace_event_file *event_file;
  	int n = 0, ret = 0;
  
  	mutex_lock(&event_mutex);
  
  	event_file = event_file_data(m->private);
  	if (unlikely(!event_file)) {
  		ret = -ENODEV;
  		goto out_unlock;
  	}
  
  	list_for_each_entry(data, &event_file->triggers, list) {
  		if (data->cmd_ops->trigger_type == ETT_EVENT_HIST)
  			hist_trigger_show(m, data, n++);
  	}
  
   out_unlock:
  	mutex_unlock(&event_mutex);
  
  	return ret;
  }
  
  static int event_hist_open(struct inode *inode, struct file *file)
  {
  	int ret;
  
  	ret = security_locked_down(LOCKDOWN_TRACEFS);
  	if (ret)
  		return ret;
  
  	return single_open(file, hist_show, file);
  }
  
  const struct file_operations event_hist_fops = {
  	.open = event_hist_open,
  	.read = seq_read,
  	.llseek = seq_lseek,
  	.release = single_release,
  };
  
  #ifdef CONFIG_HIST_TRIGGERS_DEBUG
  static void hist_field_debug_show_flags(struct seq_file *m,
  					unsigned long flags)
  {
  	seq_puts(m, "      flags:\n");
  
  	if (flags & HIST_FIELD_FL_KEY)
  		seq_puts(m, "        HIST_FIELD_FL_KEY\n");
  	else if (flags & HIST_FIELD_FL_HITCOUNT)
  		seq_puts(m, "        VAL: HIST_FIELD_FL_HITCOUNT\n");
  	else if (flags & HIST_FIELD_FL_VAR)
  		seq_puts(m, "        HIST_FIELD_FL_VAR\n");
  	else if (flags & HIST_FIELD_FL_VAR_REF)
  		seq_puts(m, "        HIST_FIELD_FL_VAR_REF\n");
  	else
  		seq_puts(m, "        VAL: normal u64 value\n");
  
  	if (flags & HIST_FIELD_FL_ALIAS)
  		seq_puts(m, "        HIST_FIELD_FL_ALIAS\n");
  	else if (flags & HIST_FIELD_FL_CONST)
  		seq_puts(m, "        HIST_FIELD_FL_CONST\n");
  }
  
  static int hist_field_debug_show(struct seq_file *m,
  				 struct hist_field *field, unsigned long flags)
  {
  	if ((field->flags & flags) != flags) {
  		seq_printf(m, "ERROR: bad flags - %lx\n", flags);
  		return -EINVAL;
  	}
  
  	hist_field_debug_show_flags(m, field->flags);
  	if (field->field)
  		seq_printf(m, "      ftrace_event_field name: %s\n",
  			   field->field->name);
  
  	if (field->flags & HIST_FIELD_FL_VAR) {
  		seq_printf(m, "      var.name: %s\n", field->var.name);
  		seq_printf(m, "      var.idx (into tracing_map_elt.vars[]): %u\n",
  			   field->var.idx);
  	}
  
  	if (field->flags & HIST_FIELD_FL_CONST)
  		seq_printf(m, "      constant: %llu\n", field->constant);
  
  	if (field->flags & HIST_FIELD_FL_ALIAS)
  		seq_printf(m, "      var_ref_idx (into hist_data->var_refs[]): %u\n",
  			   field->var_ref_idx);
  
  	if (field->flags & HIST_FIELD_FL_VAR_REF) {
  		seq_printf(m, "      name: %s\n", field->name);
  		seq_printf(m, "      var.idx (into tracing_map_elt.vars[]): %u\n",
  			   field->var.idx);
  		seq_printf(m, "      var.hist_data: %p\n", field->var.hist_data);
  		seq_printf(m, "      var_ref_idx (into hist_data->var_refs[]): %u\n",
  			   field->var_ref_idx);
  		if (field->system)
  			seq_printf(m, "      system: %s\n", field->system);
  		if (field->event_name)
  			seq_printf(m, "      event_name: %s\n", field->event_name);
  	}
  
  	seq_printf(m, "      type: %s\n", field->type);
  	seq_printf(m, "      size: %u\n", field->size);
  	seq_printf(m, "      is_signed: %u\n", field->is_signed);
  
  	return 0;
  }
  
  static int field_var_debug_show(struct seq_file *m,
  				struct field_var *field_var, unsigned int i,
  				bool save_vars)
  {
  	const char *vars_name = save_vars ? "save_vars" : "field_vars";
  	struct hist_field *field;
  	int ret = 0;
  
  	seq_printf(m, "\n    hist_data->%s[%d]:\n", vars_name, i);
  
  	field = field_var->var;
  
  	seq_printf(m, "\n      %s[%d].var:\n", vars_name, i);
  
  	hist_field_debug_show_flags(m, field->flags);
  	seq_printf(m, "      var.name: %s\n", field->var.name);
  	seq_printf(m, "      var.idx (into tracing_map_elt.vars[]): %u\n",
  		   field->var.idx);
  
  	field = field_var->val;
  
  	seq_printf(m, "\n      %s[%d].val:\n", vars_name, i);
  	if (field->field)
  		seq_printf(m, "      ftrace_event_field name: %s\n",
  			   field->field->name);
  	else {
  		ret = -EINVAL;
  		goto out;
  	}
  
  	seq_printf(m, "      type: %s\n", field->type);
  	seq_printf(m, "      size: %u\n", field->size);
  	seq_printf(m, "      is_signed: %u\n", field->is_signed);
  out:
  	return ret;
  }
  
  static int hist_action_debug_show(struct seq_file *m,
  				  struct action_data *data, int i)
  {
  	int ret = 0;
  
  	if (data->handler == HANDLER_ONMAX ||
  	    data->handler == HANDLER_ONCHANGE) {
  		seq_printf(m, "\n    hist_data->actions[%d].track_data.var_ref:\n", i);
  		ret = hist_field_debug_show(m, data->track_data.var_ref,
  					    HIST_FIELD_FL_VAR_REF);
  		if (ret)
  			goto out;
  
  		seq_printf(m, "\n    hist_data->actions[%d].track_data.track_var:\n", i);
  		ret = hist_field_debug_show(m, data->track_data.track_var,
  					    HIST_FIELD_FL_VAR);
  		if (ret)
  			goto out;
  	}
  
  	if (data->handler == HANDLER_ONMATCH) {
  		seq_printf(m, "\n    hist_data->actions[%d].match_data.event_system: %s\n",
  			   i, data->match_data.event_system);
  		seq_printf(m, "    hist_data->actions[%d].match_data.event: %s\n",
  			   i, data->match_data.event);
  	}
  out:
  	return ret;
  }
  
  static int hist_actions_debug_show(struct seq_file *m,
  				   struct hist_trigger_data *hist_data)
  {
  	int i, ret = 0;
  
  	if (hist_data->n_actions)
  		seq_puts(m, "\n  action tracking variables (for onmax()/onchange()/onmatch()):\n");
  
  	for (i = 0; i < hist_data->n_actions; i++) {
  		struct action_data *action = hist_data->actions[i];
  
  		ret = hist_action_debug_show(m, action, i);
  		if (ret)
  			goto out;
  	}
  
  	if (hist_data->n_save_vars)
  		seq_puts(m, "\n  save action variables (save() params):\n");
  
  	for (i = 0; i < hist_data->n_save_vars; i++) {
  		ret = field_var_debug_show(m, hist_data->save_vars[i], i, true);
  		if (ret)
  			goto out;
  	}
  out:
  	return ret;
  }
  
  static void hist_trigger_debug_show(struct seq_file *m,
  				    struct event_trigger_data *data, int n)
  {
  	struct hist_trigger_data *hist_data;
  	int i, ret;
  
  	if (n > 0)
  		seq_puts(m, "\n\n");
  
  	seq_puts(m, "# event histogram\n#\n# trigger info: ");
  	data->ops->print(m, data->ops, data);
  	seq_puts(m, "#\n\n");
  
  	hist_data = data->private_data;
  
  	seq_printf(m, "hist_data: %p\n\n", hist_data);
  	seq_printf(m, "  n_vals: %u\n", hist_data->n_vals);
  	seq_printf(m, "  n_keys: %u\n", hist_data->n_keys);
  	seq_printf(m, "  n_fields: %u\n", hist_data->n_fields);
  
  	seq_puts(m, "\n  val fields:\n\n");
  
  	seq_puts(m, "    hist_data->fields[0]:\n");
  	ret = hist_field_debug_show(m, hist_data->fields[0],
  				    HIST_FIELD_FL_HITCOUNT);
  	if (ret)
  		return;
  
  	for (i = 1; i < hist_data->n_vals; i++) {
  		seq_printf(m, "\n    hist_data->fields[%d]:\n", i);
  		ret = hist_field_debug_show(m, hist_data->fields[i], 0);
  		if (ret)
  			return;
  	}
  
  	seq_puts(m, "\n  key fields:\n");
  
  	for (i = hist_data->n_vals; i < hist_data->n_fields; i++) {
  		seq_printf(m, "\n    hist_data->fields[%d]:\n", i);
  		ret = hist_field_debug_show(m, hist_data->fields[i],
  					    HIST_FIELD_FL_KEY);
  		if (ret)
  			return;
  	}
  
  	if (hist_data->n_var_refs)
  		seq_puts(m, "\n  variable reference fields:\n");
  
  	for (i = 0; i < hist_data->n_var_refs; i++) {
  		seq_printf(m, "\n    hist_data->var_refs[%d]:\n", i);
  		ret = hist_field_debug_show(m, hist_data->var_refs[i],
  					    HIST_FIELD_FL_VAR_REF);
  		if (ret)
  			return;
  	}
  
  	if (hist_data->n_field_vars)
  		seq_puts(m, "\n  field variables:\n");
  
  	for (i = 0; i < hist_data->n_field_vars; i++) {
  		ret = field_var_debug_show(m, hist_data->field_vars[i], i, false);
  		if (ret)
  			return;
  	}
  
  	ret = hist_actions_debug_show(m, hist_data);
  	if (ret)
  		return;
  }
  
  static int hist_debug_show(struct seq_file *m, void *v)
  {
  	struct event_trigger_data *data;
  	struct trace_event_file *event_file;
  	int n = 0, ret = 0;
  
  	mutex_lock(&event_mutex);
  
  	event_file = event_file_data(m->private);
  	if (unlikely(!event_file)) {
  		ret = -ENODEV;
  		goto out_unlock;
  	}
  
  	list_for_each_entry(data, &event_file->triggers, list) {
  		if (data->cmd_ops->trigger_type == ETT_EVENT_HIST)
  			hist_trigger_debug_show(m, data, n++);
  	}
  
   out_unlock:
  	mutex_unlock(&event_mutex);
  
  	return ret;
  }
  
  static int event_hist_debug_open(struct inode *inode, struct file *file)
  {
  	int ret;
  
  	ret = security_locked_down(LOCKDOWN_TRACEFS);
  	if (ret)
  		return ret;
  
  	return single_open(file, hist_debug_show, file);
  }
  
  const struct file_operations event_hist_debug_fops = {
  	.open = event_hist_debug_open,
  	.read = seq_read,
  	.llseek = seq_lseek,
  	.release = single_release,
  };
  #endif
  
  static void hist_field_print(struct seq_file *m, struct hist_field *hist_field)
  {
  	const char *field_name = hist_field_name(hist_field, 0);
  
  	if (hist_field->var.name)
  		seq_printf(m, "%s=", hist_field->var.name);
  
  	if (hist_field->flags & HIST_FIELD_FL_CPU)
  		seq_puts(m, "common_cpu");
  	else if (hist_field->flags & HIST_FIELD_FL_CONST)
  		seq_printf(m, "%llu", hist_field->constant);
  	else if (field_name) {
  		if (hist_field->flags & HIST_FIELD_FL_VAR_REF ||
  		    hist_field->flags & HIST_FIELD_FL_ALIAS)
  			seq_putc(m, '$');
  		seq_printf(m, "%s", field_name);
  	} else if (hist_field->flags & HIST_FIELD_FL_TIMESTAMP)
  		seq_puts(m, "common_timestamp");
  
  	if (hist_field->flags) {
  		if (!(hist_field->flags & HIST_FIELD_FL_VAR_REF) &&
  		    !(hist_field->flags & HIST_FIELD_FL_EXPR)) {
  			const char *flags = get_hist_field_flags(hist_field);
  
  			if (flags)
  				seq_printf(m, ".%s", flags);
  		}
  	}
  	if (hist_field->buckets)
  		seq_printf(m, "=%ld", hist_field->buckets);
  }
  
  static int event_hist_trigger_print(struct seq_file *m,
  				    struct event_trigger_ops *ops,
  				    struct event_trigger_data *data)
  {
  	struct hist_trigger_data *hist_data = data->private_data;
  	struct hist_field *field;
  	bool have_var = false;
  	unsigned int i;
  
  	seq_puts(m, HIST_PREFIX);
  
  	if (data->name)
  		seq_printf(m, "%s:", data->name);
  
  	seq_puts(m, "keys=");
  
  	for_each_hist_key_field(i, hist_data) {
  		field = hist_data->fields[i];
  
  		if (i > hist_data->n_vals)
  			seq_puts(m, ",");
  
  		if (field->flags & HIST_FIELD_FL_STACKTRACE)
  			seq_puts(m, "stacktrace");
  		else
  			hist_field_print(m, field);
  	}
  
  	seq_puts(m, ":vals=");
  
  	for_each_hist_val_field(i, hist_data) {
  		field = hist_data->fields[i];
  		if (field->flags & HIST_FIELD_FL_VAR) {
  			have_var = true;
  			continue;
  		}
  
  		if (i == HITCOUNT_IDX)
  			seq_puts(m, "hitcount");
  		else {
  			seq_puts(m, ",");
  			hist_field_print(m, field);
  		}
  	}
  
  	if (have_var) {
  		unsigned int n = 0;
  
  		seq_puts(m, ":");
  
  		for_each_hist_val_field(i, hist_data) {
  			field = hist_data->fields[i];
  
  			if (field->flags & HIST_FIELD_FL_VAR) {
  				if (n++)
  					seq_puts(m, ",");
  				hist_field_print(m, field);
  			}
  		}
  	}
  
  	seq_puts(m, ":sort=");
  
  	for (i = 0; i < hist_data->n_sort_keys; i++) {
  		struct tracing_map_sort_key *sort_key;
  		unsigned int idx, first_key_idx;
  
  		/* skip VAR vals */
  		first_key_idx = hist_data->n_vals - hist_data->n_vars;
  
  		sort_key = &hist_data->sort_keys[i];
  		idx = sort_key->field_idx;
  
  		if (WARN_ON(idx >= HIST_FIELDS_MAX))
  			return -EINVAL;
  
  		if (i > 0)
  			seq_puts(m, ",");
  
  		if (idx == HITCOUNT_IDX)
  			seq_puts(m, "hitcount");
  		else {
  			if (idx >= first_key_idx)
  				idx += hist_data->n_vars;
  			hist_field_print(m, hist_data->fields[idx]);
  		}
  
  		if (sort_key->descending)
  			seq_puts(m, ".descending");
  	}
  	seq_printf(m, ":size=%u", (1 << hist_data->map->map_bits));
  	if (hist_data->enable_timestamps)
  		seq_printf(m, ":clock=%s", hist_data->attrs->clock);
  
  	print_actions_spec(m, hist_data);
  
  	if (data->filter_str)
  		seq_printf(m, " if %s", data->filter_str);
  
  	if (data->paused)
  		seq_puts(m, " [paused]");
  	else
  		seq_puts(m, " [active]");
  
  	seq_putc(m, '\n');
  
  	return 0;
  }
  
  static int event_hist_trigger_init(struct event_trigger_ops *ops,
  				   struct event_trigger_data *data)
  {
  	struct hist_trigger_data *hist_data = data->private_data;
  
  	if (!data->ref && hist_data->attrs->name)
  		save_named_trigger(hist_data->attrs->name, data);
  
  	data->ref++;
  
  	return 0;
  }
  
  static void unregister_field_var_hists(struct hist_trigger_data *hist_data)
  {
  	struct trace_event_file *file;
  	unsigned int i;
  	char *cmd;
  	int ret;
  
  	for (i = 0; i < hist_data->n_field_var_hists; i++) {
  		file = hist_data->field_var_hists[i]->hist_data->event_file;
  		cmd = hist_data->field_var_hists[i]->cmd;
  		ret = event_hist_trigger_parse(&trigger_hist_cmd, file,
  					       "!hist", "hist", cmd);
  		WARN_ON_ONCE(ret < 0);
  	}
  }
  
  static void event_hist_trigger_free(struct event_trigger_ops *ops,
  				    struct event_trigger_data *data)
  {
  	struct hist_trigger_data *hist_data = data->private_data;
  
  	if (WARN_ON_ONCE(data->ref <= 0))
  		return;
  
  	data->ref--;
  	if (!data->ref) {
  		if (data->name)
  			del_named_trigger(data);
  
  		trigger_data_free(data);
  
  		remove_hist_vars(hist_data);
  
  		unregister_field_var_hists(hist_data);
  
  		destroy_hist_data(hist_data);
  	}
  }
  
  static struct event_trigger_ops event_hist_trigger_ops = {
  	.trigger		= event_hist_trigger,
  	.print			= event_hist_trigger_print,
  	.init			= event_hist_trigger_init,
  	.free			= event_hist_trigger_free,
  };
  
  static int event_hist_trigger_named_init(struct event_trigger_ops *ops,
  					 struct event_trigger_data *data)
  {
  	data->ref++;
  
  	save_named_trigger(data->named_data->name, data);
  
  	event_hist_trigger_init(ops, data->named_data);
  
  	return 0;
  }
  
  static void event_hist_trigger_named_free(struct event_trigger_ops *ops,
  					  struct event_trigger_data *data)
  {
  	if (WARN_ON_ONCE(data->ref <= 0))
  		return;
  
  	event_hist_trigger_free(ops, data->named_data);
  
  	data->ref--;
  	if (!data->ref) {
  		del_named_trigger(data);
  		trigger_data_free(data);
  	}
  }
  
  static struct event_trigger_ops event_hist_trigger_named_ops = {
  	.trigger		= event_hist_trigger,
  	.print			= event_hist_trigger_print,
  	.init			= event_hist_trigger_named_init,
  	.free			= event_hist_trigger_named_free,
  };
  
  static struct event_trigger_ops *event_hist_get_trigger_ops(char *cmd,
  							    char *param)
  {
  	return &event_hist_trigger_ops;
  }
  
  static void hist_clear(struct event_trigger_data *data)
  {
  	struct hist_trigger_data *hist_data = data->private_data;
  
  	if (data->name)
  		pause_named_trigger(data);
  
  	tracepoint_synchronize_unregister();
  
  	tracing_map_clear(hist_data->map);
  
  	if (data->name)
  		unpause_named_trigger(data);
  }
  
  static bool compatible_field(struct ftrace_event_field *field,
  			     struct ftrace_event_field *test_field)
  {
  	if (field == test_field)
  		return true;
  	if (field == NULL || test_field == NULL)
  		return false;
  	if (strcmp(field->name, test_field->name) != 0)
  		return false;
  	if (strcmp(field->type, test_field->type) != 0)
  		return false;
  	if (field->size != test_field->size)
  		return false;
  	if (field->is_signed != test_field->is_signed)
  		return false;
  
  	return true;
  }
  
  static bool hist_trigger_match(struct event_trigger_data *data,
  			       struct event_trigger_data *data_test,
  			       struct event_trigger_data *named_data,
  			       bool ignore_filter)
  {
  	struct tracing_map_sort_key *sort_key, *sort_key_test;
  	struct hist_trigger_data *hist_data, *hist_data_test;
  	struct hist_field *key_field, *key_field_test;
  	unsigned int i;
  
  	if (named_data && (named_data != data_test) &&
  	    (named_data != data_test->named_data))
  		return false;
  
  	if (!named_data && is_named_trigger(data_test))
  		return false;
  
  	hist_data = data->private_data;
  	hist_data_test = data_test->private_data;
  
  	if (hist_data->n_vals != hist_data_test->n_vals ||
  	    hist_data->n_fields != hist_data_test->n_fields ||
  	    hist_data->n_sort_keys != hist_data_test->n_sort_keys)
  		return false;
  
  	if (!ignore_filter) {
  		if ((data->filter_str && !data_test->filter_str) ||
  		   (!data->filter_str && data_test->filter_str))
  			return false;
  	}
  
  	for_each_hist_field(i, hist_data) {
  		key_field = hist_data->fields[i];
  		key_field_test = hist_data_test->fields[i];
  
  		if (key_field->flags != key_field_test->flags)
  			return false;
  		if (!compatible_field(key_field->field, key_field_test->field))
  			return false;
  		if (key_field->offset != key_field_test->offset)
  			return false;
  		if (key_field->size != key_field_test->size)
  			return false;
  		if (key_field->is_signed != key_field_test->is_signed)
  			return false;
  		if (!!key_field->var.name != !!key_field_test->var.name)
  			return false;
  		if (key_field->var.name &&
  		    strcmp(key_field->var.name, key_field_test->var.name) != 0)
  			return false;
  	}
  
  	for (i = 0; i < hist_data->n_sort_keys; i++) {
  		sort_key = &hist_data->sort_keys[i];
  		sort_key_test = &hist_data_test->sort_keys[i];
  
  		if (sort_key->field_idx != sort_key_test->field_idx ||
  		    sort_key->descending != sort_key_test->descending)
  			return false;
  	}
  
  	if (!ignore_filter && data->filter_str &&
  	    (strcmp(data->filter_str, data_test->filter_str) != 0))
  		return false;
  
  	if (!actions_match(hist_data, hist_data_test))
  		return false;
  
  	return true;
  }
  
  static int hist_register_trigger(char *glob,
  				 struct event_trigger_data *data,
  				 struct trace_event_file *file)
  {
  	struct hist_trigger_data *hist_data = data->private_data;
  	struct event_trigger_data *test, *named_data = NULL;
  	struct trace_array *tr = file->tr;
  	int ret = 0;
  
  	if (hist_data->attrs->name) {
  		named_data = find_named_trigger(hist_data->attrs->name);
  		if (named_data) {
  			if (!hist_trigger_match(data, named_data, named_data,
  						true)) {
  				hist_err(tr, HIST_ERR_NAMED_MISMATCH, errpos(hist_data->attrs->name));
  				ret = -EINVAL;
  				goto out;
  			}
  		}
  	}
  
  	if (hist_data->attrs->name && !named_data)
  		goto new;
  
  	lockdep_assert_held(&event_mutex);
  
  	list_for_each_entry(test, &file->triggers, list) {
  		if (test->cmd_ops->trigger_type == ETT_EVENT_HIST) {
  			if (!hist_trigger_match(data, test, named_data, false))
  				continue;
  			if (hist_data->attrs->pause)
  				test->paused = true;
  			else if (hist_data->attrs->cont)
  				test->paused = false;
  			else if (hist_data->attrs->clear)
  				hist_clear(test);
  			else {
  				hist_err(tr, HIST_ERR_TRIGGER_EEXIST, 0);
  				ret = -EEXIST;
  			}
  			goto out;
  		}
  	}
   new:
  	if (hist_data->attrs->cont || hist_data->attrs->clear) {
  		hist_err(tr, HIST_ERR_TRIGGER_ENOENT_CLEAR, 0);
  		ret = -ENOENT;
  		goto out;
  	}
  
  	if (hist_data->attrs->pause)
  		data->paused = true;
  
  	if (named_data) {
  		data->private_data = named_data->private_data;
  		set_named_trigger_data(data, named_data);
  		data->ops = &event_hist_trigger_named_ops;
  	}
  
  	if (data->ops->init) {
  		ret = data->ops->init(data->ops, data);
  		if (ret < 0)
  			goto out;
  	}
  
  	if (hist_data->enable_timestamps) {
  		char *clock = hist_data->attrs->clock;
  
  		ret = tracing_set_clock(file->tr, hist_data->attrs->clock);
  		if (ret) {
  			hist_err(tr, HIST_ERR_SET_CLOCK_FAIL, errpos(clock));
  			goto out;
  		}
  
  		tracing_set_filter_buffering(file->tr, true);
  	}
  
  	if (named_data)
  		destroy_hist_data(hist_data);
  
  	ret++;
   out:
  	return ret;
  }
  
  static int hist_trigger_enable(struct event_trigger_data *data,
  			       struct trace_event_file *file)
  {
  	int ret = 0;
  
  	list_add_tail_rcu(&data->list, &file->triggers);
  
  	update_cond_flag(file);
  
  	if (trace_event_trigger_enable_disable(file, 1) < 0) {
  		list_del_rcu(&data->list);
  		update_cond_flag(file);
  		ret--;
  	}
  
  	return ret;
  }
  
  static bool have_hist_trigger_match(struct event_trigger_data *data,
  				    struct trace_event_file *file)
  {
  	struct hist_trigger_data *hist_data = data->private_data;
  	struct event_trigger_data *test, *named_data = NULL;
  	bool match = false;
  
  	lockdep_assert_held(&event_mutex);
  
  	if (hist_data->attrs->name)
  		named_data = find_named_trigger(hist_data->attrs->name);
  
  	list_for_each_entry(test, &file->triggers, list) {
  		if (test->cmd_ops->trigger_type == ETT_EVENT_HIST) {
  			if (hist_trigger_match(data, test, named_data, false)) {
  				match = true;
  				break;
  			}
  		}
  	}
  
  	return match;
  }
  
  static bool hist_trigger_check_refs(struct event_trigger_data *data,
  				    struct trace_event_file *file)
  {
  	struct hist_trigger_data *hist_data = data->private_data;
  	struct event_trigger_data *test, *named_data = NULL;
  
  	lockdep_assert_held(&event_mutex);
  
  	if (hist_data->attrs->name)
  		named_data = find_named_trigger(hist_data->attrs->name);
  
  	list_for_each_entry(test, &file->triggers, list) {
  		if (test->cmd_ops->trigger_type == ETT_EVENT_HIST) {
  			if (!hist_trigger_match(data, test, named_data, false))
  				continue;
  			hist_data = test->private_data;
  			if (check_var_refs(hist_data))
  				return true;
  			break;
  		}
  	}
  
  	return false;
  }
  
  static void hist_unregister_trigger(char *glob,
  				    struct event_trigger_data *data,
  				    struct trace_event_file *file)
  {
  	struct hist_trigger_data *hist_data = data->private_data;
  	struct event_trigger_data *test, *named_data = NULL;
  	bool unregistered = false;
  
  	lockdep_assert_held(&event_mutex);
  
  	if (hist_data->attrs->name)
  		named_data = find_named_trigger(hist_data->attrs->name);
  
  	list_for_each_entry(test, &file->triggers, list) {
  		if (test->cmd_ops->trigger_type == ETT_EVENT_HIST) {
  			if (!hist_trigger_match(data, test, named_data, false))
  				continue;
  			unregistered = true;
  			list_del_rcu(&test->list);
  			trace_event_trigger_enable_disable(file, 0);
  			update_cond_flag(file);
  			break;
  		}
  	}
  
  	if (unregistered && test->ops->free)
  		test->ops->free(test->ops, test);
  
  	if (hist_data->enable_timestamps) {
  		if (!hist_data->remove || unregistered)
  			tracing_set_filter_buffering(file->tr, false);
  	}
  }
  
  static bool hist_file_check_refs(struct trace_event_file *file)
  {
  	struct hist_trigger_data *hist_data;
  	struct event_trigger_data *test;
  
  	lockdep_assert_held(&event_mutex);
  
  	list_for_each_entry(test, &file->triggers, list) {
  		if (test->cmd_ops->trigger_type == ETT_EVENT_HIST) {
  			hist_data = test->private_data;
  			if (check_var_refs(hist_data))
  				return true;
  		}
  	}
  
  	return false;
  }
  
  static void hist_unreg_all(struct trace_event_file *file)
  {
  	struct event_trigger_data *test, *n;
  	struct hist_trigger_data *hist_data;
  	struct synth_event *se;
  	const char *se_name;
  
  	lockdep_assert_held(&event_mutex);
  
  	if (hist_file_check_refs(file))
  		return;
  
  	list_for_each_entry_safe(test, n, &file->triggers, list) {
  		if (test->cmd_ops->trigger_type == ETT_EVENT_HIST) {
  			hist_data = test->private_data;
  			list_del_rcu(&test->list);
  			trace_event_trigger_enable_disable(file, 0);
  
  			se_name = trace_event_name(file->event_call);
  			se = find_synth_event(se_name);
  			if (se)
  				se->ref--;
  
  			update_cond_flag(file);
  			if (hist_data->enable_timestamps)
  				tracing_set_filter_buffering(file->tr, false);
  			if (test->ops->free)
  				test->ops->free(test->ops, test);
  		}
  	}
  }
  
  static int event_hist_trigger_parse(struct event_command *cmd_ops,
  				    struct trace_event_file *file,
  				    char *glob, char *cmd, char *param)
  {
  	unsigned int hist_trigger_bits = TRACING_MAP_BITS_DEFAULT;
  	struct event_trigger_data *trigger_data;
  	struct hist_trigger_attrs *attrs;
  	struct event_trigger_ops *trigger_ops;
  	struct hist_trigger_data *hist_data;
  	struct synth_event *se;
  	const char *se_name;
  	bool remove = false;
  	char *trigger, *p, *start;
  	int ret = 0;
  
  	lockdep_assert_held(&event_mutex);
  
  	WARN_ON(!glob);
  
  	if (strlen(glob)) {
  		hist_err_clear();
  		last_cmd_set(file, param);
  	}
  
  	if (!param)
  		return -EINVAL;
  
  	if (glob[0] == '!')
  		remove = true;
  
  	/*
  	 * separate the trigger from the filter (k:v [if filter])
  	 * allowing for whitespace in the trigger
  	 */
  	p = trigger = param;
  	do {
  		p = strstr(p, "if");
  		if (!p)
  			break;
  		if (p == param)
  			return -EINVAL;
  		if (*(p - 1) != ' ' && *(p - 1) != '\t') {
  			p++;
  			continue;
  		}
  		if (p >= param + strlen(param) - (sizeof("if") - 1) - 1)
  			return -EINVAL;
  		if (*(p + sizeof("if") - 1) != ' ' && *(p + sizeof("if") - 1) != '\t') {
  			p++;
  			continue;
  		}
  		break;
  	} while (1);
  
  	if (!p)
  		param = NULL;
  	else {
  		*(p - 1) = '\0';
  		param = strstrip(p);
  		trigger = strstrip(trigger);
  	}
  
  	/*
  	 * To simplify arithmetic expression parsing, replace occurrences of
  	 * '.sym-offset' modifier with '.symXoffset'
  	 */
  	start = strstr(trigger, ".sym-offset");
  	while (start) {
  		*(start + 4) = 'X';
  		start = strstr(start + 11, ".sym-offset");
  	}
  
  	attrs = parse_hist_trigger_attrs(file->tr, trigger);
  	if (IS_ERR(attrs))
  		return PTR_ERR(attrs);
  
  	if (attrs->map_bits)
  		hist_trigger_bits = attrs->map_bits;
  
  	hist_data = create_hist_data(hist_trigger_bits, attrs, file, remove);
  	if (IS_ERR(hist_data)) {
  		destroy_hist_trigger_attrs(attrs);
  		return PTR_ERR(hist_data);
  	}
  
  	trigger_ops = cmd_ops->get_trigger_ops(cmd, trigger);
  
  	trigger_data = kzalloc(sizeof(*trigger_data), GFP_KERNEL);
  	if (!trigger_data) {
  		ret = -ENOMEM;
  		goto out_free;
  	}
  
  	trigger_data->count = -1;
  	trigger_data->ops = trigger_ops;
  	trigger_data->cmd_ops = cmd_ops;
  
  	INIT_LIST_HEAD(&trigger_data->list);
  	RCU_INIT_POINTER(trigger_data->filter, NULL);
  
  	trigger_data->private_data = hist_data;
  
  	/* if param is non-empty, it's supposed to be a filter */
  	if (param && cmd_ops->set_filter) {
  		ret = cmd_ops->set_filter(param, trigger_data, file);
  		if (ret < 0)
  			goto out_free;
  	}
  
  	if (remove) {
  		if (!have_hist_trigger_match(trigger_data, file))
  			goto out_free;
  
  		if (hist_trigger_check_refs(trigger_data, file)) {
  			ret = -EBUSY;
  			goto out_free;
  		}
  
  		cmd_ops->unreg(glob+1, trigger_data, file);
  		se_name = trace_event_name(file->event_call);
  		se = find_synth_event(se_name);
  		if (se)
  			se->ref--;
  		ret = 0;
  		goto out_free;
  	}
  
  	ret = cmd_ops->reg(glob, trigger_data, file);
  	/*
  	 * The above returns on success the # of triggers registered,
  	 * but if it didn't register any it returns zero.  Consider no
  	 * triggers registered a failure too.
  	 */
  	if (!ret) {
  		if (!(attrs->pause || attrs->cont || attrs->clear))
  			ret = -ENOENT;
  		goto out_free;
  	} else if (ret < 0)
  		goto out_free;
  
  	if (get_named_trigger_data(trigger_data))
  		goto enable;
  
  	if (has_hist_vars(hist_data))
  		save_hist_vars(hist_data);
  
  	ret = create_actions(hist_data);
  	if (ret)
  		goto out_unreg;
  
  	ret = tracing_map_init(hist_data->map);
  	if (ret)
  		goto out_unreg;
  enable:
  	ret = hist_trigger_enable(trigger_data, file);
  	if (ret)
  		goto out_unreg;
  
  	se_name = trace_event_name(file->event_call);
  	se = find_synth_event(se_name);
  	if (se)
  		se->ref++;
  	/* Just return zero, not the number of registered triggers */
  	ret = 0;
   out:
  	if (ret == 0)
  		hist_err_clear();
  
  	return ret;
   out_unreg:
  	cmd_ops->unreg(glob+1, trigger_data, file);
   out_free:
  	if (cmd_ops->set_filter)
  		cmd_ops->set_filter(NULL, trigger_data, NULL);
  
  	remove_hist_vars(hist_data);
  
  	kfree(trigger_data);
  
  	destroy_hist_data(hist_data);
  	goto out;
  }
  
  static struct event_command trigger_hist_cmd = {
  	.name			= "hist",
  	.trigger_type		= ETT_EVENT_HIST,
  	.flags			= EVENT_CMD_FL_NEEDS_REC,
  	.parse			= event_hist_trigger_parse,
  	.reg			= hist_register_trigger,
  	.unreg			= hist_unregister_trigger,
  	.unreg_all		= hist_unreg_all,
  	.get_trigger_ops	= event_hist_get_trigger_ops,
  	.set_filter		= set_trigger_filter,
  };
  
  __init int register_trigger_hist_cmd(void)
  {
  	int ret;
  
  	ret = register_event_command(&trigger_hist_cmd);
  	WARN_ON(ret < 0);
  
  	return ret;
  }
  
  static void
  hist_enable_trigger(struct event_trigger_data *data,
  		    struct trace_buffer *buffer,  void *rec,
  		    struct ring_buffer_event *event)
  {
  	struct enable_trigger_data *enable_data = data->private_data;
  	struct event_trigger_data *test;
  
  	list_for_each_entry_rcu(test, &enable_data->file->triggers, list,
  				lockdep_is_held(&event_mutex)) {
  		if (test->cmd_ops->trigger_type == ETT_EVENT_HIST) {
  			if (enable_data->enable)
  				test->paused = false;
  			else
  				test->paused = true;
  		}
  	}
  }
  
  static void
  hist_enable_count_trigger(struct event_trigger_data *data,
  			  struct trace_buffer *buffer,  void *rec,
  			  struct ring_buffer_event *event)
  {
  	if (!data->count)
  		return;
  
  	if (data->count != -1)
  		(data->count)--;
  
  	hist_enable_trigger(data, buffer, rec, event);
  }
  
  static struct event_trigger_ops hist_enable_trigger_ops = {
  	.trigger		= hist_enable_trigger,
  	.print			= event_enable_trigger_print,
  	.init			= event_trigger_init,
  	.free			= event_enable_trigger_free,
  };
  
  static struct event_trigger_ops hist_enable_count_trigger_ops = {
  	.trigger		= hist_enable_count_trigger,
  	.print			= event_enable_trigger_print,
  	.init			= event_trigger_init,
  	.free			= event_enable_trigger_free,
  };
  
  static struct event_trigger_ops hist_disable_trigger_ops = {
  	.trigger		= hist_enable_trigger,
  	.print			= event_enable_trigger_print,
  	.init			= event_trigger_init,
  	.free			= event_enable_trigger_free,
  };
  
  static struct event_trigger_ops hist_disable_count_trigger_ops = {
  	.trigger		= hist_enable_count_trigger,
  	.print			= event_enable_trigger_print,
  	.init			= event_trigger_init,
  	.free			= event_enable_trigger_free,
  };
  
  static struct event_trigger_ops *
  hist_enable_get_trigger_ops(char *cmd, char *param)
  {
  	struct event_trigger_ops *ops;
  	bool enable;
  
  	enable = (strcmp(cmd, ENABLE_HIST_STR) == 0);
  
  	if (enable)
  		ops = param ? &hist_enable_count_trigger_ops :
  			&hist_enable_trigger_ops;
  	else
  		ops = param ? &hist_disable_count_trigger_ops :
  			&hist_disable_trigger_ops;
  
  	return ops;
  }
  
  static void hist_enable_unreg_all(struct trace_event_file *file)
  {
  	struct event_trigger_data *test, *n;
  
  	list_for_each_entry_safe(test, n, &file->triggers, list) {
  		if (test->cmd_ops->trigger_type == ETT_HIST_ENABLE) {
  			list_del_rcu(&test->list);
  			update_cond_flag(file);
  			trace_event_trigger_enable_disable(file, 0);
  			if (test->ops->free)
  				test->ops->free(test->ops, test);
  		}
  	}
  }
  
  static struct event_command trigger_hist_enable_cmd = {
  	.name			= ENABLE_HIST_STR,
  	.trigger_type		= ETT_HIST_ENABLE,
  	.parse			= event_enable_trigger_parse,
  	.reg			= event_enable_register_trigger,
  	.unreg			= event_enable_unregister_trigger,
  	.unreg_all		= hist_enable_unreg_all,
  	.get_trigger_ops	= hist_enable_get_trigger_ops,
  	.set_filter		= set_trigger_filter,
  };
  
  static struct event_command trigger_hist_disable_cmd = {
  	.name			= DISABLE_HIST_STR,
  	.trigger_type		= ETT_HIST_ENABLE,
  	.parse			= event_enable_trigger_parse,
  	.reg			= event_enable_register_trigger,
  	.unreg			= event_enable_unregister_trigger,
  	.unreg_all		= hist_enable_unreg_all,
  	.get_trigger_ops	= hist_enable_get_trigger_ops,
  	.set_filter		= set_trigger_filter,
  };
  
  static __init void unregister_trigger_hist_enable_disable_cmds(void)
  {
  	unregister_event_command(&trigger_hist_enable_cmd);
  	unregister_event_command(&trigger_hist_disable_cmd);
  }
  
  __init int register_trigger_hist_enable_disable_cmds(void)
  {
  	int ret;
  
  	ret = register_event_command(&trigger_hist_enable_cmd);
  	if (WARN_ON(ret < 0))
  		return ret;
  	ret = register_event_command(&trigger_hist_disable_cmd);
  	if (WARN_ON(ret < 0))
  		unregister_trigger_hist_enable_disable_cmds();
  
  	return ret;
  }
  