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/mutex.h>
  #include <linux/slab.h>
  #include <linux/stacktrace.h>
  #include <linux/rculist.h>
  #include <linux/tracefs.h>
  
  #include "tracing_map.h"
  #include "trace.h"
  #include "trace_dynevent.h"
  
  #define SYNTH_SYSTEM		"synthetic"
  #define SYNTH_FIELDS_MAX	16
  
  #define STR_VAR_LEN_MAX		32 /* must be multiple of sizeof(u64) */
  
  struct hist_field;
  
  typedef u64 (*hist_field_fn_t) (struct hist_field *field,
  				struct tracing_map_elt *elt,
  				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
  
  enum field_op_id {
  	FIELD_OP_NONE,
  	FIELD_OP_PLUS,
  	FIELD_OP_MINUS,
  	FIELD_OP_UNARY_MINUS,
  };
  
  /*
   * 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			size;
  	unsigned int			offset;
  	unsigned int                    is_signed;
  	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;
  };
  
  static u64 hist_field_none(struct hist_field *field,
  			   struct tracing_map_elt *elt,
  			   struct ring_buffer_event *rbe,
  			   void *event)
  {
  	return 0;
  }
  
  static u64 hist_field_counter(struct hist_field *field,
  			      struct tracing_map_elt *elt,
  			      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 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 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_pstring(struct hist_field *hist_field,
  			      struct tracing_map_elt *elt,
  			      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 ring_buffer_event *rbe,
  			   void *event)
  {
  	struct hist_field *operand = hist_field->operands[0];
  
  	u64 val = operand->fn(operand, elt, rbe, event);
  
  	return (u64) ilog2(roundup_pow_of_two(val));
  }
  
  static u64 hist_field_plus(struct hist_field *hist_field,
  			   struct tracing_map_elt *elt,
  			   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, rbe, event);
  	u64 val2 = operand2->fn(operand2, elt, rbe, event);
  
  	return val1 + val2;
  }
  
  static u64 hist_field_minus(struct hist_field *hist_field,
  			    struct tracing_map_elt *elt,
  			    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, rbe, event);
  	u64 val2 = operand2->fn(operand2, elt, rbe, event);
  
  	return val1 - val2;
  }
  
  static u64 hist_field_unary_minus(struct hist_field *hist_field,
  				  struct tracing_map_elt *elt,
  				  struct ring_buffer_event *rbe,
  				  void *event)
  {
  	struct hist_field *operand = hist_field->operands[0];
  
  	s64 sval = (s64)operand->fn(operand, elt, 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 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,
  };
  
  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			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		*max_vars[SYNTH_FIELDS_MAX];
  	unsigned int			n_max_vars;
  	unsigned int			n_max_var_str;
  };
  
  static int synth_event_create(int argc, const char **argv);
  static int synth_event_show(struct seq_file *m, struct dyn_event *ev);
  static int synth_event_release(struct dyn_event *ev);
  static bool synth_event_is_busy(struct dyn_event *ev);
  static bool synth_event_match(const char *system, const char *event,
  			      struct dyn_event *ev);
  
  static struct dyn_event_operations synth_event_ops = {
  	.create = synth_event_create,
  	.show = synth_event_show,
  	.is_busy = synth_event_is_busy,
  	.free = synth_event_release,
  	.match = synth_event_match,
  };
  
  struct synth_field {
  	char *type;
  	char *name;
  	size_t size;
  	bool is_signed;
  	bool is_string;
  };
  
  struct synth_event {
  	struct dyn_event			devent;
  	int					ref;
  	char					*name;
  	struct synth_field			**fields;
  	unsigned int				n_fields;
  	unsigned int				n_u64;
  	struct trace_event_class		class;
  	struct trace_event_call			call;
  	struct tracepoint			*tp;
  };
  
  static bool is_synth_event(struct dyn_event *ev)
  {
  	return ev->ops == &synth_event_ops;
  }
  
  static struct synth_event *to_synth_event(struct dyn_event *ev)
  {
  	return container_of(ev, struct synth_event, devent);
  }
  
  static bool synth_event_is_busy(struct dyn_event *ev)
  {
  	struct synth_event *event = to_synth_event(ev);
  
  	return event->ref != 0;
  }
  
  static bool synth_event_match(const char *system, const char *event,
  			      struct dyn_event *ev)
  {
  	struct synth_event *sev = to_synth_event(ev);
  
  	return strcmp(sev->name, event) == 0 &&
  		(!system || strcmp(system, SYNTH_SYSTEM) == 0);
  }
  
  struct action_data;
  
  typedef void (*action_fn_t) (struct hist_trigger_data *hist_data,
  			     struct tracing_map_elt *elt, void *rec,
  			     struct ring_buffer_event *rbe,
  			     struct action_data *data, u64 *var_ref_vals);
  
  struct action_data {
  	action_fn_t		fn;
  	unsigned int		n_params;
  	char			*params[SYNTH_FIELDS_MAX];
  
  	union {
  		struct {
  			/*
  			 * 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 is the index of the
  			 * first param in the array to be passed to the synthetic
  			 * event invocation.
  			 */
  			unsigned int		var_ref_idx;
  			char			*match_event;
  			char			*match_event_system;
  			char			*synth_event_name;
  			struct synth_event	*synth_event;
  		} onmatch;
  
  		struct {
  			char			*var_str;
  			char			*fn_name;
  			unsigned int		max_var_ref_idx;
  			struct hist_field	*max_var;
  			struct hist_field	*var;
  		} onmax;
  	};
  };
  
  
  static char last_hist_cmd[MAX_FILTER_STR_VAL];
  static char hist_err_str[MAX_FILTER_STR_VAL];
  
  static void last_cmd_set(char *str)
  {
  	if (!str)
  		return;
  
  	strncpy(last_hist_cmd, str, MAX_FILTER_STR_VAL - 1);
  }
  
  static void hist_err(char *str, char *var)
  {
  	int maxlen = MAX_FILTER_STR_VAL - 1;
  
  	if (!str)
  		return;
  
  	if (strlen(hist_err_str))
  		return;
  
  	if (!var)
  		var = "";
  
  	if (strlen(hist_err_str) + strlen(str) + strlen(var) > maxlen)
  		return;
  
  	strcat(hist_err_str, str);
  	strcat(hist_err_str, var);
  }
  
  static void hist_err_event(char *str, char *system, char *event, char *var)
  {
  	char err[MAX_FILTER_STR_VAL];
  
  	if (system && var)
  		snprintf(err, MAX_FILTER_STR_VAL, "%s.%s.%s", system, event, var);
  	else if (system)
  		snprintf(err, MAX_FILTER_STR_VAL, "%s.%s", system, event);
  	else
  		strscpy(err, var, MAX_FILTER_STR_VAL);
  
  	hist_err(str, err);
  }
  
  static void hist_err_clear(void)
  {
  	hist_err_str[0] = '\0';
  }
  
  static bool have_hist_err(void)
  {
  	if (strlen(hist_err_str))
  		return true;
  
  	return false;
  }
  
  struct synth_trace_event {
  	struct trace_entry	ent;
  	u64			fields[];
  };
  
  static int synth_event_define_fields(struct trace_event_call *call)
  {
  	struct synth_trace_event trace;
  	int offset = offsetof(typeof(trace), fields);
  	struct synth_event *event = call->data;
  	unsigned int i, size, n_u64;
  	char *name, *type;
  	bool is_signed;
  	int ret = 0;
  
  	for (i = 0, n_u64 = 0; i < event->n_fields; i++) {
  		size = event->fields[i]->size;
  		is_signed = event->fields[i]->is_signed;
  		type = event->fields[i]->type;
  		name = event->fields[i]->name;
  		ret = trace_define_field(call, type, name, offset, size,
  					 is_signed, FILTER_OTHER);
  		if (ret)
  			break;
  
  		if (event->fields[i]->is_string) {
  			offset += STR_VAR_LEN_MAX;
  			n_u64 += STR_VAR_LEN_MAX / sizeof(u64);
  		} else {
  			offset += sizeof(u64);
  			n_u64++;
  		}
  	}
  
  	event->n_u64 = n_u64;
  
  	return ret;
  }
  
  static bool synth_field_signed(char *type)
  {
  	if (str_has_prefix(type, "u"))
  		return false;
  
  	return true;
  }
  
  static int synth_field_is_string(char *type)
  {
  	if (strstr(type, "char[") != NULL)
  		return true;
  
  	return false;
  }
  
  static int synth_field_string_size(char *type)
  {
  	char buf[4], *end, *start;
  	unsigned int len;
  	int size, err;
  
  	start = strstr(type, "char[");
  	if (start == NULL)
  		return -EINVAL;
  	start += sizeof("char[") - 1;
  
  	end = strchr(type, ']');
  	if (!end || end < start)
  		return -EINVAL;
  
  	len = end - start;
  	if (len > 3)
  		return -EINVAL;
  
  	strncpy(buf, start, len);
  	buf[len] = '\0';
  
  	err = kstrtouint(buf, 0, &size);
  	if (err)
  		return err;
  
  	if (size > STR_VAR_LEN_MAX)
  		return -EINVAL;
  
  	return size;
  }
  
  static int synth_field_size(char *type)
  {
  	int size = 0;
  
  	if (strcmp(type, "s64") == 0)
  		size = sizeof(s64);
  	else if (strcmp(type, "u64") == 0)
  		size = sizeof(u64);
  	else if (strcmp(type, "s32") == 0)
  		size = sizeof(s32);
  	else if (strcmp(type, "u32") == 0)
  		size = sizeof(u32);
  	else if (strcmp(type, "s16") == 0)
  		size = sizeof(s16);
  	else if (strcmp(type, "u16") == 0)
  		size = sizeof(u16);
  	else if (strcmp(type, "s8") == 0)
  		size = sizeof(s8);
  	else if (strcmp(type, "u8") == 0)
  		size = sizeof(u8);
  	else if (strcmp(type, "char") == 0)
  		size = sizeof(char);
  	else if (strcmp(type, "unsigned char") == 0)
  		size = sizeof(unsigned char);
  	else if (strcmp(type, "int") == 0)
  		size = sizeof(int);
  	else if (strcmp(type, "unsigned int") == 0)
  		size = sizeof(unsigned int);
  	else if (strcmp(type, "long") == 0)
  		size = sizeof(long);
  	else if (strcmp(type, "unsigned long") == 0)
  		size = sizeof(unsigned long);
  	else if (strcmp(type, "pid_t") == 0)
  		size = sizeof(pid_t);
  	else if (synth_field_is_string(type))
  		size = synth_field_string_size(type);
  
  	return size;
  }
  
  static const char *synth_field_fmt(char *type)
  {
  	const char *fmt = "%llu";
  
  	if (strcmp(type, "s64") == 0)
  		fmt = "%lld";
  	else if (strcmp(type, "u64") == 0)
  		fmt = "%llu";
  	else if (strcmp(type, "s32") == 0)
  		fmt = "%d";
  	else if (strcmp(type, "u32") == 0)
  		fmt = "%u";
  	else if (strcmp(type, "s16") == 0)
  		fmt = "%d";
  	else if (strcmp(type, "u16") == 0)
  		fmt = "%u";
  	else if (strcmp(type, "s8") == 0)
  		fmt = "%d";
  	else if (strcmp(type, "u8") == 0)
  		fmt = "%u";
  	else if (strcmp(type, "char") == 0)
  		fmt = "%d";
  	else if (strcmp(type, "unsigned char") == 0)
  		fmt = "%u";
  	else if (strcmp(type, "int") == 0)
  		fmt = "%d";
  	else if (strcmp(type, "unsigned int") == 0)
  		fmt = "%u";
  	else if (strcmp(type, "long") == 0)
  		fmt = "%ld";
  	else if (strcmp(type, "unsigned long") == 0)
  		fmt = "%lu";
  	else if (strcmp(type, "pid_t") == 0)
  		fmt = "%d";
  	else if (synth_field_is_string(type))
  		fmt = "%s";
  
  	return fmt;
  }
  
  static enum print_line_t print_synth_event(struct trace_iterator *iter,
  					   int flags,
  					   struct trace_event *event)
  {
  	struct trace_array *tr = iter->tr;
  	struct trace_seq *s = &iter->seq;
  	struct synth_trace_event *entry;
  	struct synth_event *se;
  	unsigned int i, n_u64;
  	char print_fmt[32];
  	const char *fmt;
  
  	entry = (struct synth_trace_event *)iter->ent;
  	se = container_of(event, struct synth_event, call.event);
  
  	trace_seq_printf(s, "%s: ", se->name);
  
  	for (i = 0, n_u64 = 0; i < se->n_fields; i++) {
  		if (trace_seq_has_overflowed(s))
  			goto end;
  
  		fmt = synth_field_fmt(se->fields[i]->type);
  
  		/* parameter types */
  		if (tr->trace_flags & TRACE_ITER_VERBOSE)
  			trace_seq_printf(s, "%s ", fmt);
  
  		snprintf(print_fmt, sizeof(print_fmt), "%%s=%s%%s", fmt);
  
  		/* parameter values */
  		if (se->fields[i]->is_string) {
  			trace_seq_printf(s, print_fmt, se->fields[i]->name,
  					 (char *)&entry->fields[n_u64],
  					 i == se->n_fields - 1 ? "" : " ");
  			n_u64 += STR_VAR_LEN_MAX / sizeof(u64);
  		} else {
  			trace_seq_printf(s, print_fmt, se->fields[i]->name,
  					 entry->fields[n_u64],
  					 i == se->n_fields - 1 ? "" : " ");
  			n_u64++;
  		}
  	}
  end:
  	trace_seq_putc(s, '\n');
  
  	return trace_handle_return(s);
  }
  
  static struct trace_event_functions synth_event_funcs = {
  	.trace		= print_synth_event
  };
  
  static notrace void trace_event_raw_event_synth(void *__data,
  						u64 *var_ref_vals,
  						unsigned int var_ref_idx)
  {
  	struct trace_event_file *trace_file = __data;
  	struct synth_trace_event *entry;
  	struct trace_event_buffer fbuffer;
  	struct ring_buffer *buffer;
  	struct synth_event *event;
  	unsigned int i, n_u64;
  	int fields_size = 0;
  
  	event = trace_file->event_call->data;
  
  	if (trace_trigger_soft_disabled(trace_file))
  		return;
  
  	fields_size = event->n_u64 * sizeof(u64);
  
  	/*
  	 * Avoid ring buffer recursion detection, as this event
  	 * is being performed within another event.
  	 */
  	buffer = trace_file->tr->trace_buffer.buffer;
  	ring_buffer_nest_start(buffer);
  
  	entry = trace_event_buffer_reserve(&fbuffer, trace_file,
  					   sizeof(*entry) + fields_size);
  	if (!entry)
  		goto out;
  
  	for (i = 0, n_u64 = 0; i < event->n_fields; i++) {
  		if (event->fields[i]->is_string) {
  			char *str_val = (char *)(long)var_ref_vals[var_ref_idx + i];
  			char *str_field = (char *)&entry->fields[n_u64];
  
  			strscpy(str_field, str_val, STR_VAR_LEN_MAX);
  			n_u64 += STR_VAR_LEN_MAX / sizeof(u64);
  		} else {
  			entry->fields[n_u64] = var_ref_vals[var_ref_idx + i];
  			n_u64++;
  		}
  	}
  
  	trace_event_buffer_commit(&fbuffer);
  out:
  	ring_buffer_nest_end(buffer);
  }
  
  static void free_synth_event_print_fmt(struct trace_event_call *call)
  {
  	if (call) {
  		kfree(call->print_fmt);
  		call->print_fmt = NULL;
  	}
  }
  
  static int __set_synth_event_print_fmt(struct synth_event *event,
  				       char *buf, int len)
  {
  	const char *fmt;
  	int pos = 0;
  	int i;
  
  	/* When len=0, we just calculate the needed length */
  #define LEN_OR_ZERO (len ? len - pos : 0)
  
  	pos += snprintf(buf + pos, LEN_OR_ZERO, "\"");
  	for (i = 0; i < event->n_fields; i++) {
  		fmt = synth_field_fmt(event->fields[i]->type);
  		pos += snprintf(buf + pos, LEN_OR_ZERO, "%s=%s%s",
  				event->fields[i]->name, fmt,
  				i == event->n_fields - 1 ? "" : ", ");
  	}
  	pos += snprintf(buf + pos, LEN_OR_ZERO, "\"");
  
  	for (i = 0; i < event->n_fields; i++) {
  		pos += snprintf(buf + pos, LEN_OR_ZERO,
  				", REC->%s", event->fields[i]->name);
  	}
  
  #undef LEN_OR_ZERO
  
  	/* return the length of print_fmt */
  	return pos;
  }
  
  static int set_synth_event_print_fmt(struct trace_event_call *call)
  {
  	struct synth_event *event = call->data;
  	char *print_fmt;
  	int len;
  
  	/* First: called with 0 length to calculate the needed length */
  	len = __set_synth_event_print_fmt(event, NULL, 0);
  
  	print_fmt = kmalloc(len + 1, GFP_KERNEL);
  	if (!print_fmt)
  		return -ENOMEM;
  
  	/* Second: actually write the @print_fmt */
  	__set_synth_event_print_fmt(event, print_fmt, len + 1);
  	call->print_fmt = print_fmt;
  
  	return 0;
  }
  
  static void free_synth_field(struct synth_field *field)
  {
  	kfree(field->type);
  	kfree(field->name);
  	kfree(field);
  }
  
  static struct synth_field *parse_synth_field(int argc, const char **argv,
  					     int *consumed)
  {
  	struct synth_field *field;
  	const char *prefix = NULL, *field_type = argv[0], *field_name, *array;
  	int len, ret = 0;
  
  	if (field_type[0] == ';')
  		field_type++;
  
  	if (!strcmp(field_type, "unsigned")) {
  		if (argc < 3)
  			return ERR_PTR(-EINVAL);
  		prefix = "unsigned ";
  		field_type = argv[1];
  		field_name = argv[2];
  		*consumed = 3;
  	} else {
  		field_name = argv[1];
  		*consumed = 2;
  	}
  
  	field = kzalloc(sizeof(*field), GFP_KERNEL);
  	if (!field)
  		return ERR_PTR(-ENOMEM);
  
  	len = strlen(field_name);
  	array = strchr(field_name, '[');
  	if (array)
  		len -= strlen(array);
  	else if (field_name[len - 1] == ';')
  		len--;
  
  	field->name = kmemdup_nul(field_name, len, GFP_KERNEL);
  	if (!field->name) {
  		ret = -ENOMEM;
  		goto free;
  	}
  
  	if (field_type[0] == ';')
  		field_type++;
  	len = strlen(field_type) + 1;
  	if (array)
  		len += strlen(array);
  	if (prefix)
  		len += strlen(prefix);
  
  	field->type = kzalloc(len, GFP_KERNEL);
  	if (!field->type) {
  		ret = -ENOMEM;
  		goto free;
  	}
  	if (prefix)
  		strcat(field->type, prefix);
  	strcat(field->type, field_type);
  	if (array) {
  		strcat(field->type, array);
  		if (field->type[len - 1] == ';')
  			field->type[len - 1] = '\0';
  	}
  
  	field->size = synth_field_size(field->type);
  	if (!field->size) {
  		ret = -EINVAL;
  		goto free;
  	}
  
  	if (synth_field_is_string(field->type))
  		field->is_string = true;
  
  	field->is_signed = synth_field_signed(field->type);
  
   out:
  	return field;
   free:
  	free_synth_field(field);
  	field = ERR_PTR(ret);
  	goto out;
  }
  
  static void free_synth_tracepoint(struct tracepoint *tp)
  {
  	if (!tp)
  		return;
  
  	kfree(tp->name);
  	kfree(tp);
  }
  
  static struct tracepoint *alloc_synth_tracepoint(char *name)
  {
  	struct tracepoint *tp;
  
  	tp = kzalloc(sizeof(*tp), GFP_KERNEL);
  	if (!tp)
  		return ERR_PTR(-ENOMEM);
  
  	tp->name = kstrdup(name, GFP_KERNEL);
  	if (!tp->name) {
  		kfree(tp);
  		return ERR_PTR(-ENOMEM);
  	}
  
  	return tp;
  }
  
  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 struct synth_event *find_synth_event(const char *name)
  {
  	struct dyn_event *pos;
  	struct synth_event *event;
  
  	for_each_dyn_event(pos) {
  		if (!is_synth_event(pos))
  			continue;
  		event = to_synth_event(pos);
  		if (strcmp(event->name, name) == 0)
  			return event;
  	}
  
  	return NULL;
  }
  
  static int register_synth_event(struct synth_event *event)
  {
  	struct trace_event_call *call = &event->call;
  	int ret = 0;
  
  	event->call.class = &event->class;
  	event->class.system = kstrdup(SYNTH_SYSTEM, GFP_KERNEL);
  	if (!event->class.system) {
  		ret = -ENOMEM;
  		goto out;
  	}
  
  	event->tp = alloc_synth_tracepoint(event->name);
  	if (IS_ERR(event->tp)) {
  		ret = PTR_ERR(event->tp);
  		event->tp = NULL;
  		goto out;
  	}
  
  	INIT_LIST_HEAD(&call->class->fields);
  	call->event.funcs = &synth_event_funcs;
  	call->class->define_fields = synth_event_define_fields;
  
  	ret = register_trace_event(&call->event);
  	if (!ret) {
  		ret = -ENODEV;
  		goto out;
  	}
  	call->flags = TRACE_EVENT_FL_TRACEPOINT;
  	call->class->reg = trace_event_reg;
  	call->class->probe = trace_event_raw_event_synth;
  	call->data = event;
  	call->tp = event->tp;
  
  	ret = trace_add_event_call(call);
  	if (ret) {
  		pr_warn("Failed to register synthetic event: %s\n",
  			trace_event_name(call));
  		goto err;
  	}
  
  	ret = set_synth_event_print_fmt(call);
  	if (ret < 0) {
  		trace_remove_event_call(call);
  		goto err;
  	}
   out:
  	return ret;
   err:
  	unregister_trace_event(&call->event);
  	goto out;
  }
  
  static int unregister_synth_event(struct synth_event *event)
  {
  	struct trace_event_call *call = &event->call;
  	int ret;
  
  	ret = trace_remove_event_call(call);
  
  	return ret;
  }
  
  static void free_synth_event(struct synth_event *event)
  {
  	unsigned int i;
  
  	if (!event)
  		return;
  
  	for (i = 0; i < event->n_fields; i++)
  		free_synth_field(event->fields[i]);
  
  	kfree(event->fields);
  	kfree(event->name);
  	kfree(event->class.system);
  	free_synth_tracepoint(event->tp);
  	free_synth_event_print_fmt(&event->call);
  	kfree(event);
  }
  
  static struct synth_event *alloc_synth_event(const char *name, int n_fields,
  					     struct synth_field **fields)
  {
  	struct synth_event *event;
  	unsigned int i;
  
  	event = kzalloc(sizeof(*event), GFP_KERNEL);
  	if (!event) {
  		event = ERR_PTR(-ENOMEM);
  		goto out;
  	}
  
  	event->name = kstrdup(name, GFP_KERNEL);
  	if (!event->name) {
  		kfree(event);
  		event = ERR_PTR(-ENOMEM);
  		goto out;
  	}
  
  	event->fields = kcalloc(n_fields, sizeof(*event->fields), GFP_KERNEL);
  	if (!event->fields) {
  		free_synth_event(event);
  		event = ERR_PTR(-ENOMEM);
  		goto out;
  	}
  
  	dyn_event_init(&event->devent, &synth_event_ops);
  
  	for (i = 0; i < n_fields; i++)
  		event->fields[i] = fields[i];
  
  	event->n_fields = n_fields;
   out:
  	return event;
  }
  
  static void action_trace(struct hist_trigger_data *hist_data,
  			 struct tracing_map_elt *elt, void *rec,
  			 struct ring_buffer_event *rbe,
  			 struct action_data *data, u64 *var_ref_vals)
  {
  	struct synth_event *event = data->onmatch.synth_event;
  
  	trace_synth(event, var_ref_vals, data->onmatch.var_ref_idx);
  }
  
  struct hist_var_data {
  	struct list_head list;
  	struct hist_trigger_data *hist_data;
  };
  
  static int __create_synth_event(int argc, const char *name, const char **argv)
  {
  	struct synth_field *field, *fields[SYNTH_FIELDS_MAX];
  	struct synth_event *event = NULL;
  	int i, consumed = 0, n_fields = 0, ret = 0;
  
  	/*
  	 * Argument syntax:
  	 *  - Add synthetic event: <event_name> field[;field] ...
  	 *  - Remove synthetic event: !<event_name> field[;field] ...
  	 *      where 'field' = type field_name
  	 */
  
  	if (name[0] == '\0' || argc < 1)
  		return -EINVAL;
  
  	mutex_lock(&event_mutex);
  
  	event = find_synth_event(name);
  	if (event) {
  		ret = -EEXIST;
  		goto out;
  	}
  
  	for (i = 0; i < argc - 1; i++) {
  		if (strcmp(argv[i], ";") == 0)
  			continue;
  		if (n_fields == SYNTH_FIELDS_MAX) {
  			ret = -EINVAL;
  			goto err;
  		}
  
  		field = parse_synth_field(argc - i, &argv[i], &consumed);
  		if (IS_ERR(field)) {
  			ret = PTR_ERR(field);
  			goto err;
  		}
  		fields[n_fields++] = field;
  		i += consumed - 1;
  	}
  
  	if (i < argc && strcmp(argv[i], ";") != 0) {
  		ret = -EINVAL;
  		goto err;
  	}
  
  	event = alloc_synth_event(name, n_fields, fields);
  	if (IS_ERR(event)) {
  		ret = PTR_ERR(event);
  		event = NULL;
  		goto err;
  	}
  	ret = register_synth_event(event);
  	if (!ret)
  		dyn_event_add(&event->devent);
  	else
  		free_synth_event(event);
   out:
  	mutex_unlock(&event_mutex);
  
  	return ret;
   err:
  	for (i = 0; i < n_fields; i++)
  		free_synth_field(fields[i]);
  
  	goto out;
  }
  
  static int create_or_delete_synth_event(int argc, char **argv)
  {
  	const char *name = argv[0];
  	struct synth_event *event = NULL;
  	int ret;
  
  	/* trace_run_command() ensures argc != 0 */
  	if (name[0] == '!') {
  		mutex_lock(&event_mutex);
  		event = find_synth_event(name + 1);
  		if (event) {
  			if (event->ref)
  				ret = -EBUSY;
  			else {
  				ret = unregister_synth_event(event);
  				if (!ret) {
  					dyn_event_remove(&event->devent);
  					free_synth_event(event);
  				}
  			}
  		} else
  			ret = -ENOENT;
  		mutex_unlock(&event_mutex);
  		return ret;
  	}
  
  	ret = __create_synth_event(argc - 1, name, (const char **)argv + 1);
  	return ret == -ECANCELED ? -EINVAL : ret;
  }
  
  static int synth_event_create(int argc, const char **argv)
  {
  	const char *name = argv[0];
  	int len;
  
  	if (name[0] != 's' || name[1] != ':')
  		return -ECANCELED;
  	name += 2;
  
  	/* This interface accepts group name prefix */
  	if (strchr(name, '/')) {
  		len = sizeof(SYNTH_SYSTEM "/") - 1;
  		if (strncmp(name, SYNTH_SYSTEM "/", len))
  			return -EINVAL;
  		name += len;
  	}
  	return __create_synth_event(argc - 1, name, argv + 1);
  }
  
  static int synth_event_release(struct dyn_event *ev)
  {
  	struct synth_event *event = to_synth_event(ev);
  	int ret;
  
  	if (event->ref)
  		return -EBUSY;
  
  	ret = unregister_synth_event(event);
  	if (ret)
  		return ret;
  
  	dyn_event_remove(ev);
  	free_synth_event(event);
  	return 0;
  }
  
  static int __synth_event_show(struct seq_file *m, struct synth_event *event)
  {
  	struct synth_field *field;
  	unsigned int i;
  
  	seq_printf(m, "%s\t", event->name);
  
  	for (i = 0; i < event->n_fields; i++) {
  		field = event->fields[i];
  
  		/* parameter values */
  		seq_printf(m, "%s %s%s", field->type, field->name,
  			   i == event->n_fields - 1 ? "" : "; ");
  	}
  
  	seq_putc(m, '\n');
  
  	return 0;
  }
  
  static int synth_event_show(struct seq_file *m, struct dyn_event *ev)
  {
  	struct synth_event *event = to_synth_event(ev);
  
  	seq_printf(m, "s:%s/", event->class.system);
  
  	return __synth_event_show(m, event);
  }
  
  static int synth_events_seq_show(struct seq_file *m, void *v)
  {
  	struct dyn_event *ev = v;
  
  	if (!is_synth_event(ev))
  		return 0;
  
  	return __synth_event_show(m, to_synth_event(ev));
  }
  
  static const struct seq_operations synth_events_seq_op = {
  	.start	= dyn_event_seq_start,
  	.next	= dyn_event_seq_next,
  	.stop	= dyn_event_seq_stop,
  	.show	= synth_events_seq_show,
  };
  
  static int synth_events_open(struct inode *inode, struct file *file)
  {
  	int ret;
  
  	if ((file->f_mode & FMODE_WRITE) && (file->f_flags & O_TRUNC)) {
  		ret = dyn_events_release_all(&synth_event_ops);
  		if (ret < 0)
  			return ret;
  	}
  
  	return seq_open(file, &synth_events_seq_op);
  }
  
  static ssize_t synth_events_write(struct file *file,
  				  const char __user *buffer,
  				  size_t count, loff_t *ppos)
  {
  	return trace_parse_run_command(file, buffer, count, ppos,
  				       create_or_delete_synth_event);
  }
  
  static const struct file_operations synth_events_fops = {
  	.open           = synth_events_open,
  	.write		= synth_events_write,
  	.read           = seq_read,
  	.llseek         = seq_lseek,
  	.release        = seq_release,
  };
  
  static u64 hist_field_timestamp(struct hist_field *hist_field,
  				struct tracing_map_elt *elt,
  				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(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 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 (trace_array_get(tr) < 0)
  		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;
  
  	hist_field = find_var_field(hist_data, var_name);
  	if (hist_field)
  		return hist_field;
  
  	list_for_each_entry_rcu(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_event("Variable name not unique, need to use fully qualified name (subsys.event.var) for variable: ", system, event_name, 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;
  
  	list_for_each_entry_rcu(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->fn == action_trace) {
  			char *system = data->onmatch.match_event_system;
  			char *event_name = data->onmatch.match_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_event("Variable name not unique, need to use fully qualified name (subsys.event.var) for variable: ", system, event_name, 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;
  }
  
  struct hist_elt_data {
  	char *comm;
  	u64 *var_ref_vals;
  	char *field_var_str[SYNTH_FIELDS_MAX];
  };
  
  static u64 hist_field_var_ref(struct hist_field *hist_field,
  			      struct tracing_map_elt *elt,
  			      struct ring_buffer_event *rbe,
  			      void *event)
  {
  	struct hist_elt_data *elt_data;
  	u64 var_val = 0;
  
  	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_name = hist_field_name(field->operands[0], ++level);
  	else if (field->flags & HIST_FIELD_FL_CPU)
  		field_name = "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;
  
  	strsep(&str, "=");
  	if (!str) {
  		ret = -EINVAL;
  		goto out;
  	}
  
  	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("))) {
  		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(char *str, struct hist_trigger_attrs *attrs)
  {
  	int ret = 0;
  
  	if ((str_has_prefix(str, "key=")) ||
  	    (str_has_prefix(str, "keys="))) {
  		attrs->keys_str = kstrdup(str, GFP_KERNEL);
  		if (!attrs->keys_str) {
  			ret = -ENOMEM;
  			goto out;
  		}
  	} else if ((str_has_prefix(str, "val=")) ||
  		   (str_has_prefix(str, "vals=")) ||
  		   (str_has_prefix(str, "values="))) {
  		attrs->vals_str = kstrdup(str, GFP_KERNEL);
  		if (!attrs->vals_str) {
  			ret = -ENOMEM;
  			goto out;
  		}
  	} else if (str_has_prefix(str, "sort=")) {
  		attrs->sort_key_str = kstrdup(str, 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 (str_has_prefix(str, "clock=")) {
  		strsep(&str, "=");
  		if (!str) {
  			ret = -EINVAL;
  			goto out;
  		}
  
  		str = strstrip(str);
  		attrs->clock = kstrdup(str, GFP_KERNEL);
  		if (!attrs->clock) {
  			ret = -ENOMEM;
  			goto out;
  		}
  	} else if (str_has_prefix(str, "size=")) {
  		int map_bits = parse_map_size(str);
  
  		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("Too many variables defined: ", 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(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, ":");
  
  		if (strchr(str, '=')) {
  			ret = parse_assignment(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;
  	}
  
  	memcpy(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 < SYNTH_FIELDS_MAX; i++)
  		kfree(elt_data->field_var_str[i]);
  
  	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 *key_field;
  	unsigned int i, n_str;
  
  	elt_data = kzalloc(sizeof(*elt_data), GFP_KERNEL);
  	if (!elt_data)
  		return -ENOMEM;
  
  	for_each_hist_key_field(i, hist_data) {
  		key_field = hist_data->fields[i];
  
  		if (key_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_max_var_str;
  
  	size = STR_VAR_LEN_MAX;
  
  	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_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, "$");
  
  	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;
  	default:
  		kfree(expr);
  		return NULL;
  	}
  
  	expr_field_str(field->operands[1], expr);
  
  	return expr;
  }
  
  static int contains_operator(char *str)
  {
  	enum field_op_id field_op = FIELD_OP_NONE;
  	char *op;
  
  	op = strpbrk(str, "+-");
  	if (!op)
  		return FIELD_OP_NONE;
  
  	switch (*op) {
  	case '-':
  		if (*str == '-')
  			field_op = FIELD_OP_UNARY_MINUS;
  		else
  			field_op = FIELD_OP_MINUS;
  		break;
  	case '+':
  		field_op = FIELD_OP_PLUS;
  		break;
  	default:
  		break;
  	}
  
  	return field_op;
  }
  
  static void __destroy_hist_field(struct hist_field *hist_field)
  {
  	kfree(hist_field->var.name);
  	kfree(hist_field->name);
  	kfree(hist_field->type);
  
  	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->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 = 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) {
  		unsigned long fl = flags & ~HIST_FIELD_FL_LOG2;
  		hist_field->fn = hist_field_log2;
  		hist_field->operands[0] = create_hist_field(hist_data, field, fl, NULL);
  		hist_field->size = hist_field->operands[0]->size;
  		hist_field->type = kstrdup(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 = kstrdup("u64", GFP_KERNEL);
  		if (!hist_field->type)
  			goto free;
  		goto out;
  	}
  
  	if (flags & HIST_FIELD_FL_CPU) {
  		hist_field->fn = hist_field_cpu;
  		hist_field->size = sizeof(int);
  		hist_field->type = kstrdup("unsigned int", GFP_KERNEL);
  		if (!hist_field->type)
  			goto free;
  		goto out;
  	}
  
  	if (WARN_ON_ONCE(!field))
  		goto out;
  
  	if (is_string_field(field)) {
  		flags |= HIST_FIELD_FL_STRING;
  
  		hist_field->size = MAX_FILTER_STR_VAL;
  		hist_field->type = kstrdup(field->type, GFP_KERNEL);
  		if (!hist_field->type)
  			goto free;
  
  		if (field->filter_type == FILTER_STATIC_STRING)
  			hist_field->fn = hist_field_string;
  		else if (field->filter_type == FILTER_DYN_STRING)
  			hist_field->fn = hist_field_dynstring;
  		else
  			hist_field->fn = hist_field_pstring;
  	} else {
  		hist_field->size = field->size;
  		hist_field->is_signed = field->is_signed;
  		hist_field->type = kstrdup(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(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;
  }
  
  /**
   * 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;
  
  	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) || 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;
  
  	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_event("Couldn't find variable: $",
  			       system, event_name, 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)
  {
  	struct ftrace_event_field *field = NULL;
  	char *field_name, *modifier, *str;
  
  	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;
  		else if (strcmp(modifier, "sym-offset") == 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 {
  			hist_err("Invalid field modifier: ", 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, "cpu") == 0)
  		*flags |= HIST_FIELD_FL_CPU;
  	else {
  		field = trace_find_event_field(file->event_call, field_name);
  		if (!field || !field->size) {
  			hist_err("Couldn't find field: ", 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;
  	}
  
  	return alias;
  }
  
  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;
  	int ret = 0;
  
  	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);
  	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;
  	}
  
  	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 level);
  
  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 level)
  {
  	struct hist_field *operand1, *expr = NULL;
  	unsigned long operand_flags;
  	int ret = 0;
  	char *s;
  
  	/* we support only -(xxx) i.e. explicit parens required */
  
  	if (level > 3) {
  		hist_err("Too many subexpressions (3 max): ", str);
  		ret = -EINVAL;
  		goto free;
  	}
  
  	str++; /* skip leading '-' */
  
  	s = strchr(str, '(');
  	if (s)
  		str++;
  	else {
  		ret = -EINVAL;
  		goto free;
  	}
  
  	s = strrchr(str, ')');
  	if (s)
  		*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, ++level);
  	if (IS_ERR(operand1)) {
  		ret = PTR_ERR(operand1);
  		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->operator = FIELD_OP_UNARY_MINUS;
  	expr->name = expr_str(expr, 0);
  	expr->type = kstrdup(operand1->type, GFP_KERNEL);
  	if (!expr->type) {
  		ret = -ENOMEM;
  		goto free;
  	}
  
  	return expr;
   free:
  	destroy_hist_field(expr, 0);
  	return ERR_PTR(ret);
  }
  
  static int check_expr_operands(struct hist_field *operand1,
  			       struct hist_field *operand2)
  {
  	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;
  	}
  
  	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;
  	}
  
  	if ((operand1_flags & HIST_FIELD_FL_TIMESTAMP_USECS) !=
  	    (operand2_flags & HIST_FIELD_FL_TIMESTAMP_USECS)) {
  		hist_err("Timestamp units in expression don't match", NULL);
  		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 level)
  {
  	struct hist_field *operand1 = NULL, *operand2 = NULL, *expr = NULL;
  	unsigned long operand_flags;
  	int field_op, ret = -EINVAL;
  	char *sep, *operand1_str;
  
  	if (level > 3) {
  		hist_err("Too many subexpressions (3 max): ", str);
  		return ERR_PTR(-EINVAL);
  	}
  
  	field_op = contains_operator(str);
  
  	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, ++level);
  
  	switch (field_op) {
  	case FIELD_OP_MINUS:
  		sep = "-";
  		break;
  	case FIELD_OP_PLUS:
  		sep = "+";
  		break;
  	default:
  		goto free;
  	}
  
  	operand1_str = strsep(&str, sep);
  	if (!operand1_str || !str)
  		goto free;
  
  	operand_flags = 0;
  	operand1 = parse_atom(hist_data, file, operand1_str,
  			      &operand_flags, NULL);
  	if (IS_ERR(operand1)) {
  		ret = PTR_ERR(operand1);
  		operand1 = NULL;
  		goto free;
  	}
  
  	/* rest of string could be another expression e.g. b+c in a+b+c */
  	operand_flags = 0;
  	operand2 = parse_expr(hist_data, file, str, operand_flags, NULL, ++level);
  	if (IS_ERR(operand2)) {
  		ret = PTR_ERR(operand2);
  		operand2 = NULL;
  		goto free;
  	}
  
  	ret = check_expr_operands(operand1, operand2);
  	if (ret)
  		goto free;
  
  	flags |= 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;
  	}
  
  	operand1->read_once = true;
  	operand2->read_once = true;
  
  	expr->operands[0] = operand1;
  	expr->operands[1] = operand2;
  	expr->operator = field_op;
  	expr->name = expr_str(expr, 0);
  	expr->type = kstrdup(operand1->type, GFP_KERNEL);
  	if (!expr->type) {
  		ret = -ENOMEM;
  		goto free;
  	}
  
  	switch (field_op) {
  	case FIELD_OP_MINUS:
  		expr->fn = hist_field_minus;
  		break;
  	case FIELD_OP_PLUS:
  		expr->fn = hist_field_plus;
  		break;
  	default:
  		ret = -EINVAL;
  		goto free;
  	}
  
  	return expr;
   free:
  	destroy_hist_field(operand1, 0);
  	destroy_hist_field(operand2, 0);
  	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;
  
  	list_for_each_entry_rcu(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_func(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;
  
  	n_keys = target_hist_data->n_fields - target_hist_data->n_vals;
  
  	list_for_each_entry_rcu(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_field *event_var = ERR_PTR(-EINVAL);
  	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;
  	char *saved_filter;
  	char *cmd;
  	int ret;
  
  	if (target_hist_data->n_field_var_hists >= SYNTH_FIELDS_MAX) {
  		hist_err_event("onmatch: Too many field variables defined: ",
  			       subsys_name, event_name, field_name);
  		return ERR_PTR(-EINVAL);
  	}
  
  	file = event_file(tr, subsys_name, event_name);
  
  	if (IS_ERR(file)) {
  		hist_err_event("onmatch: Event file not found: ",
  			       subsys_name, event_name, 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_event("onmatch: Matching event histogram not found: ",
  			       subsys_name, event_name, 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_func(&trigger_hist_cmd, file,
  				      "", "hist", cmd);
  	if (ret) {
  		kfree(cmd);
  		kfree(var_hist->cmd);
  		kfree(var_hist);
  		hist_err_event("onmatch: Couldn't create histogram for field: ",
  			       subsys_name, event_name, 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_event("onmatch: Couldn't find synthetic variable: ",
  			       subsys_name, event_name, 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 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, 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;
  
  			strscpy(str, val_str, STR_VAR_LEN_MAX);
  			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 ring_buffer_event *rbe,
  			      void *rec)
  {
  	__update_field_vars(elt, rbe, rec, hist_data->field_vars,
  			    hist_data->n_field_vars, 0);
  }
  
  static void update_max_vars(struct hist_trigger_data *hist_data,
  			    struct tracing_map_elt *elt,
  			    struct ring_buffer_event *rbe,
  			    void *rec)
  {
  	__update_field_vars(elt, rbe, rec, hist_data->max_vars,
  			    hist_data->n_max_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->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(type, GFP_KERNEL);
  	if (!var->var.name || !var->type) {
  		kfree(var->var.name);
  		kfree(var->type);
  		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 field_var *field_var;
  	int ret = 0;
  
  	if (hist_data->n_field_vars >= SYNTH_FIELDS_MAX) {
  		hist_err("Too many field variables defined: ", field_name);
  		ret = -EINVAL;
  		goto err;
  	}
  
  	val = parse_atom(hist_data, file, field_name, &flags, NULL);
  	if (IS_ERR(val)) {
  		hist_err("Couldn't parse field variable: ", 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("Couldn't create or find variable: ", 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 void onmax_print(struct seq_file *m,
  			struct hist_trigger_data *hist_data,
  			struct tracing_map_elt *elt,
  			struct action_data *data)
  {
  	unsigned int i, save_var_idx, max_idx = data->onmax.max_var->var.idx;
  
  	seq_printf(m, "\n\tmax: %10llu", tracing_map_read_var(elt, max_idx));
  
  	for (i = 0; i < hist_data->n_max_vars; i++) {
  		struct hist_field *save_val = hist_data->max_vars[i]->val;
  		struct hist_field *save_var = hist_data->max_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 onmax_save(struct hist_trigger_data *hist_data,
  		       struct tracing_map_elt *elt, void *rec,
  		       struct ring_buffer_event *rbe,
  		       struct action_data *data, u64 *var_ref_vals)
  {
  	unsigned int max_idx = data->onmax.max_var->var.idx;
  	unsigned int max_var_ref_idx = data->onmax.max_var_ref_idx;
  
  	u64 var_val, max_val;
  
  	var_val = var_ref_vals[max_var_ref_idx];
  	max_val = tracing_map_read_var(elt, max_idx);
  
  	if (var_val <= max_val)
  		return;
  
  	tracing_map_set_var(elt, max_idx, var_val);
  
  	update_max_vars(hist_data, elt, rbe, rec);
  }
  
  static void onmax_destroy(struct action_data *data)
  {
  	unsigned int i;
  
  	destroy_hist_field(data->onmax.max_var, 0);
  	destroy_hist_field(data->onmax.var, 0);
  
  	kfree(data->onmax.var_str);
  	kfree(data->onmax.fn_name);
  
  	for (i = 0; i < data->n_params; i++)
  		kfree(data->params[i]);
  
  	kfree(data);
  }
  
  static int onmax_create(struct hist_trigger_data *hist_data,
  			struct action_data *data)
  {
  	struct trace_event_file *file = hist_data->event_file;
  	struct hist_field *var_field, *ref_field, *max_var;
  	unsigned int var_ref_idx = hist_data->n_var_refs;
  	struct field_var *field_var;
  	char *onmax_var_str, *param;
  	unsigned int i;
  	int ret = 0;
  
  	onmax_var_str = data->onmax.var_str;
  	if (onmax_var_str[0] != '$') {
  		hist_err("onmax: For onmax(x), x must be a variable: ", onmax_var_str);
  		return -EINVAL;
  	}
  	onmax_var_str++;
  
  	var_field = find_target_event_var(hist_data, NULL, NULL, onmax_var_str);
  	if (!var_field) {
  		hist_err("onmax: Couldn't find onmax variable: ", onmax_var_str);
  		return -EINVAL;
  	}
  
  	ref_field = create_var_ref(hist_data, var_field, NULL, NULL);
  	if (!ref_field)
  		return -ENOMEM;
  
  	data->onmax.var = ref_field;
  
  	data->fn = onmax_save;
  	data->onmax.max_var_ref_idx = var_ref_idx;
  	max_var = create_var(hist_data, file, "max", sizeof(u64), "u64");
  	if (IS_ERR(max_var)) {
  		hist_err("onmax: Couldn't create onmax variable: ", "max");
  		ret = PTR_ERR(max_var);
  		goto out;
  	}
  	data->onmax.max_var = max_var;
  
  	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("onmax: Couldn't create field variable: ", param);
  			ret = PTR_ERR(field_var);
  			kfree(param);
  			goto out;
  		}
  
  		hist_data->max_vars[hist_data->n_max_vars++] = field_var;
  		if (field_var->val->flags & HIST_FIELD_FL_STRING)
  			hist_data->n_max_var_str++;
  
  		kfree(param);
  	}
   out:
  	return ret;
  }
  
  static int parse_action_params(char *params, struct action_data *data)
  {
  	char *param, *saved_param;
  	int ret = 0;
  
  	while (params) {
  		if (data->n_params >= SYNTH_FIELDS_MAX)
  			goto out;
  
  		param = strsep(&params, ",");
  		if (!param) {
  			ret = -EINVAL;
  			goto out;
  		}
  
  		param = strstrip(param);
  		if (strlen(param) < 2) {
  			hist_err("Invalid action param: ", param);
  			ret = -EINVAL;
  			goto out;
  		}
  
  		saved_param = kstrdup(param, GFP_KERNEL);
  		if (!saved_param) {
  			ret = -ENOMEM;
  			goto out;
  		}
  
  		data->params[data->n_params++] = saved_param;
  	}
   out:
  	return ret;
  }
  
  static struct action_data *onmax_parse(char *str)
  {
  	char *onmax_fn_name, *onmax_var_str;
  	struct action_data *data;
  	int ret = -EINVAL;
  
  	data = kzalloc(sizeof(*data), GFP_KERNEL);
  	if (!data)
  		return ERR_PTR(-ENOMEM);
  
  	onmax_var_str = strsep(&str, ")");
  	if (!onmax_var_str || !str) {
  		ret = -EINVAL;
  		goto free;
  	}
  
  	data->onmax.var_str = kstrdup(onmax_var_str, GFP_KERNEL);
  	if (!data->onmax.var_str) {
  		ret = -ENOMEM;
  		goto free;
  	}
  
  	strsep(&str, ".");
  	if (!str)
  		goto free;
  
  	onmax_fn_name = strsep(&str, "(");
  	if (!onmax_fn_name || !str)
  		goto free;
  
  	if (str_has_prefix(onmax_fn_name, "save")) {
  		char *params = strsep(&str, ")");
  
  		if (!params) {
  			ret = -EINVAL;
  			goto free;
  		}
  
  		ret = parse_action_params(params, data);
  		if (ret)
  			goto free;
  	} else
  		goto free;
  
  	data->onmax.fn_name = kstrdup(onmax_fn_name, GFP_KERNEL);
  	if (!data->onmax.fn_name) {
  		ret = -ENOMEM;
  		goto free;
  	}
   out:
  	return data;
   free:
  	onmax_destroy(data);
  	data = ERR_PTR(ret);
  	goto out;
  }
  
  static void onmatch_destroy(struct action_data *data)
  {
  	unsigned int i;
  
  	lockdep_assert_held(&event_mutex);
  
  	kfree(data->onmatch.match_event);
  	kfree(data->onmatch.match_event_system);
  	kfree(data->onmatch.synth_event_name);
  
  	for (i = 0; i < data->n_params; i++)
  		kfree(data->params[i]);
  
  	if (data->onmatch.synth_event)
  		data->onmatch.synth_event->ref--;
  
  	kfree(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]);
  }
  
  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];
  
  	if (strcmp(field->type, hist_field->type) != 0)
  		return -EINVAL;
  
  	return 0;
  }
  
  static struct hist_field *
  onmatch_find_var(struct hist_trigger_data *hist_data, struct action_data *data,
  		 char *system, char *event, char *var)
  {
  	struct hist_field *hist_field;
  
  	var++; /* skip '$' */
  
  	hist_field = find_target_event_var(hist_data, system, event, var);
  	if (!hist_field) {
  		if (!system) {
  			system = data->onmatch.match_event_system;
  			event = data->onmatch.match_event;
  		}
  
  		hist_field = find_event_var(hist_data, system, event, var);
  	}
  
  	if (!hist_field)
  		hist_err_event("onmatch: Couldn't find onmatch param: $", system, event, var);
  
  	return hist_field;
  }
  
  static struct hist_field *
  onmatch_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 specfied, default to
  		 * looking for fields on the onmatch(system.event.xxx)
  		 * event.
  		 */
  		if (!system) {
  			system = data->onmatch.match_event_system;
  			event = data->onmatch.match_event;
  		}
  
  		/*
  		 * 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 onmatch_create(struct hist_trigger_data *hist_data,
  			  struct trace_event_file *file,
  			  struct action_data *data)
  {
  	char *event_name, *param, *system = NULL;
  	struct hist_field *hist_field, *var_ref;
  	unsigned int i, var_ref_idx;
  	unsigned int field_pos = 0;
  	struct synth_event *event;
  	int ret = 0;
  
  	lockdep_assert_held(&event_mutex);
  
  	event = find_synth_event(data->onmatch.synth_event_name);
  	if (!event) {
  		hist_err("onmatch: Couldn't find synthetic event: ", data->onmatch.synth_event_name);
  		return -EINVAL;
  	}
  	event->ref++;
  
  	var_ref_idx = hist_data->n_var_refs;
  
  	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 = onmatch_find_var(hist_data, data, system,
  						      event_name, param);
  		else
  			hist_field = onmatch_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;
  			}
  
  			field_pos++;
  			kfree(p);
  			continue;
  		}
  
  		hist_err_event("onmatch: Param type doesn't match synthetic event field type: ",
  			       system, event_name, param);
  		kfree(p);
  		ret = -EINVAL;
  		goto err;
  	}
  
  	if (field_pos != event->n_fields) {
  		hist_err("onmatch: Param count doesn't match synthetic event field count: ", event->name);
  		ret = -EINVAL;
  		goto err;
  	}
  
  	data->fn = action_trace;
  	data->onmatch.synth_event = event;
  	data->onmatch.var_ref_idx = var_ref_idx;
   out:
  	return ret;
   err:
  	event->ref--;
  
  	goto out;
  }
  
  static struct action_data *onmatch_parse(struct trace_array *tr, char *str)
  {
  	char *match_event, *match_event_system;
  	char *synth_event_name, *params;
  	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("onmatch: Missing closing paren: ", match_event);
  		goto free;
  	}
  
  	match_event_system = strsep(&match_event, ".");
  	if (!match_event) {
  		hist_err("onmatch: Missing subsystem for match event: ", match_event_system);
  		goto free;
  	}
  
  	if (IS_ERR(event_file(tr, match_event_system, match_event))) {
  		hist_err_event("onmatch: Invalid subsystem or event name: ",
  			       match_event_system, match_event, NULL);
  		goto free;
  	}
  
  	data->onmatch.match_event = kstrdup(match_event, GFP_KERNEL);
  	if (!data->onmatch.match_event) {
  		ret = -ENOMEM;
  		goto free;
  	}
  
  	data->onmatch.match_event_system = kstrdup(match_event_system, GFP_KERNEL);
  	if (!data->onmatch.match_event_system) {
  		ret = -ENOMEM;
  		goto free;
  	}
  
  	strsep(&str, ".");
  	if (!str) {
  		hist_err("onmatch: Missing . after onmatch(): ", str);
  		goto free;
  	}
  
  	synth_event_name = strsep(&str, "(");
  	if (!synth_event_name || !str) {
  		hist_err("onmatch: Missing opening paramlist paren: ", synth_event_name);
  		goto free;
  	}
  
  	data->onmatch.synth_event_name = kstrdup(synth_event_name, GFP_KERNEL);
  	if (!data->onmatch.synth_event_name) {
  		ret = -ENOMEM;
  		goto free;
  	}
  
  	params = strsep(&str, ")");
  	if (!params || !str || (str && strlen(str))) {
  		hist_err("onmatch: Missing closing paramlist paren: ", params);
  		goto free;
  	}
  
  	ret = parse_action_params(params, data);
  	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;
  
  	hist_field = parse_expr(hist_data, file, field_str, flags, var_name, 0);
  	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 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)
  {
  	unsigned long flags = 0;
  
  	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("Variable already defined: ", 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;
  
  	return __create_val_field(hist_data, val_idx, file, var_name, expr_str, flags);
  }
  
  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;
  
  	strsep(&fields_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 hist_field *hist_field = NULL;
  
  	unsigned long flags = 0;
  	unsigned int key_size;
  	int ret = 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, 0);
  		if (IS_ERR(hist_field)) {
  			ret = PTR_ERR(hist_field);
  			goto out;
  		}
  
  		if (hist_field->flags & HIST_FIELD_FL_VAR_REF) {
  			hist_err("Using variable references as keys not supported: ", 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;
  
  	strsep(&fields_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)
  {
  	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("Malformed assignment: ", var_name);
  				ret = -EINVAL;
  				goto free;
  			}
  
  			if (n_vars == TRACING_MAP_VARS_MAX) {
  				hist_err("Too many variables defined: ", 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) {
  				kfree(hist_data->attrs->var_defs.name[n_vars]);
  				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(const char *str)
  {
  	if (!str)
  		return 0;
  
  	if (strcmp(str, "descending") == 0)
  		return 1;
  
  	if (strcmp(str, "ascending") == 0)
  		return 0;
  
  	return -EINVAL;
  }
  
  static int create_sort_keys(struct hist_trigger_data *hist_data)
  {
  	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;
  
  	strsep(&fields_str, "=");
  	if (!fields_str) {
  		ret = -EINVAL;
  		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) {
  			if (i == 0)
  				ret = -EINVAL;
  			break;
  		}
  
  		if ((i == TRACING_MAP_SORT_KEYS_MAX - 1) && fields_str) {
  			ret = -EINVAL;
  			break;
  		}
  
  		field_name = strsep(&field_str, ".");
  		if (!field_name) {
  			ret = -EINVAL;
  			break;
  		}
  
  		if (strcmp(field_name, "hitcount") == 0) {
  			descending = is_descending(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(field_str);
  				if (descending < 0) {
  					ret = descending;
  					goto out;
  				}
  				sort_key->descending = descending;
  				break;
  			}
  		}
  		if (j == hist_data->n_fields) {
  			ret = -EINVAL;
  			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->fn == action_trace)
  			onmatch_destroy(data);
  		else if (data->fn == onmax_save)
  			onmax_destroy(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;
  			}
  			data->fn = action_trace;
  		} else if ((len = str_has_prefix(str, "onmax("))) {
  			char *action_str = str + len;
  
  			data = onmax_parse(action_str);
  			if (IS_ERR(data)) {
  				ret = PTR_ERR(data);
  				break;
  			}
  			data->fn = onmax_save;
  		} 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 trace_event_file *file)
  {
  	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->fn == action_trace) {
  			ret = onmatch_create(hist_data, file, data);
  			if (ret)
  				return ret;
  		} else if (data->fn == onmax_save) {
  			ret = onmax_create(hist_data, data);
  			if (ret)
  				return ret;
  		}
  	}
  
  	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->fn == onmax_save)
  			onmax_print(m, hist_data, elt, data);
  	}
  }
  
  static void print_onmax_spec(struct seq_file *m,
  			     struct hist_trigger_data *hist_data,
  			     struct action_data *data)
  {
  	unsigned int i;
  
  	seq_puts(m, ":onmax(");
  	seq_printf(m, "%s", data->onmax.var_str);
  	seq_printf(m, ").%s(", data->onmax.fn_name);
  
  	for (i = 0; i < hist_data->n_max_vars; i++) {
  		seq_printf(m, "%s", hist_data->max_vars[i]->var->var.name);
  		if (i < hist_data->n_max_vars - 1)
  			seq_puts(m, ",");
  	}
  	seq_puts(m, ")");
  }
  
  static void print_onmatch_spec(struct seq_file *m,
  			       struct hist_trigger_data *hist_data,
  			       struct action_data *data)
  {
  	unsigned int i;
  
  	seq_printf(m, ":onmatch(%s.%s).", data->onmatch.match_event_system,
  		   data->onmatch.match_event);
  
  	seq_printf(m, "%s(", data->onmatch.synth_event->name);
  
  	for (i = 0; i < data->n_params; i++) {
  		if (i)
  			seq_puts(m, ",");
  		seq_printf(m, "%s", data->params[i]);
  	}
  
  	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];
  
  		if (data->fn != data_test->fn)
  			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->fn == action_trace) {
  			if (strcmp(data->onmatch.synth_event_name,
  				   data_test->onmatch.synth_event_name) != 0)
  				return false;
  			if (strcmp(data->onmatch.match_event_system,
  				   data_test->onmatch.match_event_system) != 0)
  				return false;
  			if (strcmp(data->onmatch.match_event,
  				   data_test->onmatch.match_event) != 0)
  				return false;
  		} else if (data->fn == onmax_save) {
  			if (strcmp(data->onmax.var_str,
  				   data_test->onmax.var_str) != 0)
  				return false;
  			if (strcmp(data->onmax.fn_name,
  				   data_test->onmax.fn_name) != 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->fn == action_trace)
  			print_onmatch_spec(m, hist_data, data);
  		else if (data->fn == onmax_save)
  			print_onmax_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)
  				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, 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, rbe, rec);
  		if (hist_field->flags & HIST_FIELD_FL_VAR) {
  			var_idx = hist_field->var.idx;
  			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, rbe, rec);
  			var_idx = hist_field->var.idx;
  			tracing_map_set_var(elt, var_idx, hist_val);
  		}
  	}
  
  	update_field_vars(hist_data, elt, 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)
  			size = *(u32 *)(rec + field->offset) >> 16;
  		else if (field->filter_type == FILTER_PTR_STRING)
  			size = strlen(key);
  		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;
  	}
  
  	memcpy(compound_key + key_field->offset, key, size);
  }
  
  static void
  hist_trigger_actions(struct hist_trigger_data *hist_data,
  		     struct tracing_map_elt *elt, void *rec,
  		     struct ring_buffer_event *rbe, 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, rec, rbe, data, var_ref_vals);
  	}
  }
  
  static void event_hist_trigger(struct event_trigger_data *data, 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 stack_trace stacktrace;
  	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) {
  			stacktrace.max_entries = HIST_STACKTRACE_DEPTH;
  			stacktrace.entries = entries;
  			stacktrace.nr_entries = 0;
  			stacktrace.skip = HIST_STACKTRACE_SKIP;
  
  			memset(stacktrace.entries, 0, HIST_STACKTRACE_SIZE);
  			save_stack_trace(&stacktrace);
  
  			key = entries;
  		} else {
  			field_contents = key_field->fn(key_field, elt, 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, rec, rbe, var_ref_vals);
  
  	if (resolve_var_refs(hist_data, key, var_ref_vals, true))
  		hist_trigger_actions(hist_data, elt, rec, rbe, var_ref_vals);
  }
  
  static void hist_trigger_stacktrace_print(struct seq_file *m,
  					  unsigned long *stacktrace_entries,
  					  unsigned int max_entries)
  {
  	char str[KSYM_SYMBOL_LEN];
  	unsigned int spaces = 8;
  	unsigned int i;
  
  	for (i = 0; i < max_entries; i++) {
  		if (stacktrace_entries[i] == ULONG_MAX)
  			return;
  
  		seq_printf(m, "%*c", 1 + spaces, ' ');
  		sprint_symbol(str, stacktrace_entries[i]);
  		seq_printf(m, "%s\n", str);
  	}
  }
  
  static void
  hist_trigger_entry_print(struct seq_file *m,
  			 struct hist_trigger_data *hist_data, void *key,
  			 struct tracing_map_elt *elt)
  {
  	struct hist_field *key_field;
  	char str[KSYM_SYMBOL_LEN];
  	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);
  			sprint_symbol_no_offset(str, uval);
  			seq_printf(m, "%s: [%llx] %-45s", field_name,
  				   uval, str);
  		} else if (key_field->flags & HIST_FIELD_FL_SYM_OFFSET) {
  			uval = *(u64 *)(key + key_field->offset);
  			sprint_symbol(str, uval);
  			seq_printf(m, "%s: [%llx] %-55s", field_name,
  				   uval, str);
  		} 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_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, "}");
  
  	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;
  
  	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_rcu(data, &event_file->triggers, list) {
  		if (data->cmd_ops->trigger_type == ETT_EVENT_HIST)
  			hist_trigger_show(m, data, n++);
  	}
  
  	if (have_hist_err()) {
  		seq_printf(m, "\nERROR: %s\n", hist_err_str);
  		seq_printf(m, "  Last command: %s\n", last_hist_cmd);
  	}
  
   out_unlock:
  	mutex_unlock(&event_mutex);
  
  	return ret;
  }
  
  static int event_hist_open(struct inode *inode, struct file *file)
  {
  	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,
  };
  
  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, "cpu");
  	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);
  		}
  	}
  }
  
  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:");
  
  	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_func(&trigger_hist_cmd, file,
  					      "!hist", "hist", cmd);
  	}
  }
  
  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 = {
  	.func			= 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 = {
  	.func			= 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_ops *ops,
  				 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;
  	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("Named hist trigger doesn't match existing named trigger (includes variables): ", hist_data->attrs->name);
  				ret = -EINVAL;
  				goto out;
  			}
  		}
  	}
  
  	if (hist_data->attrs->name && !named_data)
  		goto new;
  
  	list_for_each_entry_rcu(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("Hist trigger already exists", NULL);
  				ret = -EEXIST;
  			}
  			goto out;
  		}
  	}
   new:
  	if (hist_data->attrs->cont || hist_data->attrs->clear) {
  		hist_err("Can't clear or continue a nonexistent hist trigger", NULL);
  		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("Couldn't set trace_clock: ", clock);
  			goto out;
  		}
  
  		tracing_set_time_stamp_abs(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;
  
  	if (hist_data->attrs->name)
  		named_data = find_named_trigger(hist_data->attrs->name);
  
  	list_for_each_entry_rcu(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;
  
  	if (hist_data->attrs->name)
  		named_data = find_named_trigger(hist_data->attrs->name);
  
  	list_for_each_entry_rcu(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_ops *ops,
  				    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;
  
  	if (hist_data->attrs->name)
  		named_data = find_named_trigger(hist_data->attrs->name);
  
  	list_for_each_entry_rcu(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_time_stamp_abs(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;
  
  	list_for_each_entry_rcu(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_time_stamp_abs(file->tr, false);
  			if (test->ops->free)
  				test->ops->free(test->ops, test);
  		}
  	}
  }
  
  static int event_hist_trigger_func(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;
  	int ret = 0;
  
  	lockdep_assert_held(&event_mutex);
  
  	if (glob && strlen(glob)) {
  		last_cmd_set(param);
  		hist_err_clear();
  	}
  
  	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 (p);
  
  	if (!p)
  		param = NULL;
  	else {
  		*(p - 1) = '\0';
  		param = strstrip(p);
  		trigger = strstrip(trigger);
  	}
  
  	attrs = parse_hist_trigger_attrs(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_ops, 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_ops, 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, file);
  	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_ops, 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,
  	.func			= event_hist_trigger_func,
  	.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, 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) {
  		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, void *rec,
  			  struct ring_buffer_event *event)
  {
  	if (!data->count)
  		return;
  
  	if (data->count != -1)
  		(data->count)--;
  
  	hist_enable_trigger(data, rec, event);
  }
  
  static struct event_trigger_ops hist_enable_trigger_ops = {
  	.func			= 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 = {
  	.func			= 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 = {
  	.func			= 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 = {
  	.func			= 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,
  	.func			= event_enable_trigger_func,
  	.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,
  	.func			= event_enable_trigger_func,
  	.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;
  }
  
  static __init int trace_events_hist_init(void)
  {
  	struct dentry *entry = NULL;
  	struct dentry *d_tracer;
  	int err = 0;
  
  	err = dyn_event_register(&synth_event_ops);
  	if (err) {
  		pr_warn("Could not register synth_event_ops\n");
  		return err;
  	}
  
  	d_tracer = tracing_init_dentry();
  	if (IS_ERR(d_tracer)) {
  		err = PTR_ERR(d_tracer);
  		goto err;
  	}
  
  	entry = tracefs_create_file("synthetic_events", 0644, d_tracer,
  				    NULL, &synth_events_fops);
  	if (!entry) {
  		err = -ENODEV;
  		goto err;
  	}
  
  	return err;
   err:
  	pr_warn("Could not create tracefs 'synthetic_events' entry\n");
  
  	return err;
  }
  
  fs_initcall(trace_events_hist_init);
  