text: /* SPDX-License-Identifier: GPL-2.0 */
  #ifndef _LINUX_JUMP_LABEL_H
  #define _LINUX_JUMP_LABEL_H
  
  /*
   * Jump label support
   *
   * Copyright (C) 2009-2012 Jason Baron <jbaron@redhat.com>
   * Copyright (C) 2011-2012 Red Hat, Inc., Peter Zijlstra
   *
   * DEPRECATED API:
   *
   * The use of 'struct static_key' directly, is now DEPRECATED. In addition
   * static_key_{true,false}() is also DEPRECATED. IE DO NOT use the following:
   *
   * struct static_key false = STATIC_KEY_INIT_FALSE;
   * struct static_key true = STATIC_KEY_INIT_TRUE;
   * static_key_true()
   * static_key_false()
   *
   * The updated API replacements are:
   *
   * DEFINE_STATIC_KEY_TRUE(key);
   * DEFINE_STATIC_KEY_FALSE(key);
   * DEFINE_STATIC_KEY_ARRAY_TRUE(keys, count);
   * DEFINE_STATIC_KEY_ARRAY_FALSE(keys, count);
   * static_branch_likely()
   * static_branch_unlikely()
   *
   * Jump labels provide an interface to generate dynamic branches using
   * self-modifying code. Assuming toolchain and architecture support, if we
   * define a "key" that is initially false via "DEFINE_STATIC_KEY_FALSE(key)",
   * an "if (static_branch_unlikely(&key))" statement is an unconditional branch
   * (which defaults to false - and the true block is placed out of line).
   * Similarly, we can define an initially true key via
   * "DEFINE_STATIC_KEY_TRUE(key)", and use it in the same
   * "if (static_branch_unlikely(&key))", in which case we will generate an
   * unconditional branch to the out-of-line true branch. Keys that are
   * initially true or false can be using in both static_branch_unlikely()
   * and static_branch_likely() statements.
   *
   * At runtime we can change the branch target by setting the key
   * to true via a call to static_branch_enable(), or false using
   * static_branch_disable(). If the direction of the branch is switched by
   * these calls then we run-time modify the branch target via a
   * no-op -> jump or jump -> no-op conversion. For example, for an
   * initially false key that is used in an "if (static_branch_unlikely(&key))"
   * statement, setting the key to true requires us to patch in a jump
   * to the out-of-line of true branch.
   *
   * In addition to static_branch_{enable,disable}, we can also reference count
   * the key or branch direction via static_branch_{inc,dec}. Thus,
   * static_branch_inc() can be thought of as a 'make more true' and
   * static_branch_dec() as a 'make more false'.
   *
   * Since this relies on modifying code, the branch modifying functions
   * must be considered absolute slow paths (machine wide synchronization etc.).
   * OTOH, since the affected branches are unconditional, their runtime overhead
   * will be absolutely minimal, esp. in the default (off) case where the total
   * effect is a single NOP of appropriate size. The on case will patch in a jump
   * to the out-of-line block.
   *
   * When the control is directly exposed to userspace, it is prudent to delay the
   * decrement to avoid high frequency code modifications which can (and do)
   * cause significant performance degradation. Struct static_key_deferred and
   * static_key_slow_dec_deferred() provide for this.
   *
   * Lacking toolchain and or architecture support, static keys fall back to a
   * simple conditional branch.
   *
   * Additional babbling in: Documentation/static-keys.txt
   */
  
  #ifndef __ASSEMBLY__
  
  #include <linux/types.h>
  #include <linux/compiler.h>
  
  extern bool static_key_initialized;
  
  #define STATIC_KEY_CHECK_USE(key) WARN(!static_key_initialized,		      \
  				    "%s(): static key '%pS' used before call to jump_label_init()", \
  				    __func__, (key))
  
  #ifdef CONFIG_JUMP_LABEL
  
  struct static_key {
  	atomic_t enabled;
  /*
   * Note:
   *   To make anonymous unions work with old compilers, the static
   *   initialization of them requires brackets. This creates a dependency
   *   on the order of the struct with the initializers. If any fields
   *   are added, STATIC_KEY_INIT_TRUE and STATIC_KEY_INIT_FALSE may need
   *   to be modified.
   *
   * bit 0 => 1 if key is initially true
   *	    0 if initially false
   * bit 1 => 1 if points to struct static_key_mod
   *	    0 if points to struct jump_entry
   */
  	union {
  		unsigned long type;
  		struct jump_entry *entries;
  		struct static_key_mod *next;
  	};
  };
  
  #else
  struct static_key {
  	atomic_t enabled;
  };
  #endif	/* CONFIG_JUMP_LABEL */
  #endif /* __ASSEMBLY__ */
  
  #ifdef CONFIG_JUMP_LABEL
  #include <asm/jump_label.h>
  
  #ifndef __ASSEMBLY__
  #ifdef CONFIG_HAVE_ARCH_JUMP_LABEL_RELATIVE
  
  struct jump_entry {
  	s32 code;
  	s32 target;
  	long key;	// key may be far away from the core kernel under KASLR
  };
  
  static inline unsigned long jump_entry_code(const struct jump_entry *entry)
  {
  	return (unsigned long)&entry->code + entry->code;
  }
  
  static inline unsigned long jump_entry_target(const struct jump_entry *entry)
  {
  	return (unsigned long)&entry->target + entry->target;
  }
  
  static inline struct static_key *jump_entry_key(const struct jump_entry *entry)
  {
  	long offset = entry->key & ~3L;
  
  	return (struct static_key *)((unsigned long)&entry->key + offset);
  }
  
  #else
  
  static inline unsigned long jump_entry_code(const struct jump_entry *entry)
  {
  	return entry->code;
  }
  
  static inline unsigned long jump_entry_target(const struct jump_entry *entry)
  {
  	return entry->target;
  }
  
  static inline struct static_key *jump_entry_key(const struct jump_entry *entry)
  {
  	return (struct static_key *)((unsigned long)entry->key & ~3UL);
  }
  
  #endif
  
  static inline bool jump_entry_is_branch(const struct jump_entry *entry)
  {
  	return (unsigned long)entry->key & 1UL;
  }
  
  static inline bool jump_entry_is_init(const struct jump_entry *entry)
  {
  	return (unsigned long)entry->key & 2UL;
  }
  
  static inline void jump_entry_set_init(struct jump_entry *entry)
  {
  	entry->key |= 2;
  }
  
  #endif
  #endif
  
  #ifndef __ASSEMBLY__
  
  enum jump_label_type {
  	JUMP_LABEL_NOP = 0,
  	JUMP_LABEL_JMP,
  };
  
  struct module;
  
  #ifdef CONFIG_JUMP_LABEL
  
  #define JUMP_TYPE_FALSE		0UL
  #define JUMP_TYPE_TRUE		1UL
  #define JUMP_TYPE_LINKED	2UL
  #define JUMP_TYPE_MASK		3UL
  
  static __always_inline bool static_key_false(struct static_key *key)
  {
  	return arch_static_branch(key, false);
  }
  
  static __always_inline bool static_key_true(struct static_key *key)
  {
  	return !arch_static_branch(key, true);
  }
  
  extern struct jump_entry __start___jump_table[];
  extern struct jump_entry __stop___jump_table[];
  
  extern void jump_label_init(void);
  extern void jump_label_lock(void);
  extern void jump_label_unlock(void);
  extern void arch_jump_label_transform(struct jump_entry *entry,
  				      enum jump_label_type type);
  extern void arch_jump_label_transform_static(struct jump_entry *entry,
  					     enum jump_label_type type);
  extern bool arch_jump_label_transform_queue(struct jump_entry *entry,
  					    enum jump_label_type type);
  extern void arch_jump_label_transform_apply(void);
  extern int jump_label_text_reserved(void *start, void *end);
  extern void static_key_slow_inc(struct static_key *key);
  extern void static_key_slow_dec(struct static_key *key);
  extern void static_key_slow_inc_cpuslocked(struct static_key *key);
  extern void static_key_slow_dec_cpuslocked(struct static_key *key);
  extern void jump_label_apply_nops(struct module *mod);
  extern int static_key_count(struct static_key *key);
  extern void static_key_enable(struct static_key *key);
  extern void static_key_disable(struct static_key *key);
  extern void static_key_enable_cpuslocked(struct static_key *key);
  extern void static_key_disable_cpuslocked(struct static_key *key);
  
  /*
   * We should be using ATOMIC_INIT() for initializing .enabled, but
   * the inclusion of atomic.h is problematic for inclusion of jump_label.h
   * in 'low-level' headers. Thus, we are initializing .enabled with a
   * raw value, but have added a BUILD_BUG_ON() to catch any issues in
   * jump_label_init() see: kernel/jump_label.c.
   */
  #define STATIC_KEY_INIT_TRUE					\
  	{ .enabled = { 1 },					\
  	  { .entries = (void *)JUMP_TYPE_TRUE } }
  #define STATIC_KEY_INIT_FALSE					\
  	{ .enabled = { 0 },					\
  	  { .entries = (void *)JUMP_TYPE_FALSE } }
  
  #else  /* !CONFIG_JUMP_LABEL */
  
  #include <linux/atomic.h>
  #include <linux/bug.h>
  
  static inline int static_key_count(struct static_key *key)
  {
  	return atomic_read(&key->enabled);
  }
  
  static __always_inline void jump_label_init(void)
  {
  	static_key_initialized = true;
  }
  
  static __always_inline bool static_key_false(struct static_key *key)
  {
  	if (unlikely(static_key_count(key) > 0))
  		return true;
  	return false;
  }
  
  static __always_inline bool static_key_true(struct static_key *key)
  {
  	if (likely(static_key_count(key) > 0))
  		return true;
  	return false;
  }
  
  static inline void static_key_slow_inc(struct static_key *key)
  {
  	STATIC_KEY_CHECK_USE(key);
  	atomic_inc(&key->enabled);
  }
  
  static inline void static_key_slow_dec(struct static_key *key)
  {
  	STATIC_KEY_CHECK_USE(key);
  	atomic_dec(&key->enabled);
  }
  
  #define static_key_slow_inc_cpuslocked(key) static_key_slow_inc(key)
  #define static_key_slow_dec_cpuslocked(key) static_key_slow_dec(key)
  
  static inline int jump_label_text_reserved(void *start, void *end)
  {
  	return 0;
  }
  
  static inline void jump_label_lock(void) {}
  static inline void jump_label_unlock(void) {}
  
  static inline int jump_label_apply_nops(struct module *mod)
  {
  	return 0;
  }
  
  static inline void static_key_enable(struct static_key *key)
  {
  	STATIC_KEY_CHECK_USE(key);
  
  	if (atomic_read(&key->enabled) != 0) {
  		WARN_ON_ONCE(atomic_read(&key->enabled) != 1);
  		return;
  	}
  	atomic_set(&key->enabled, 1);
  }
  
  static inline void static_key_disable(struct static_key *key)
  {
  	STATIC_KEY_CHECK_USE(key);
  
  	if (atomic_read(&key->enabled) != 1) {
  		WARN_ON_ONCE(atomic_read(&key->enabled) != 0);
  		return;
  	}
  	atomic_set(&key->enabled, 0);
  }
  
  #define static_key_enable_cpuslocked(k)		static_key_enable((k))
  #define static_key_disable_cpuslocked(k)	static_key_disable((k))
  
  #define STATIC_KEY_INIT_TRUE	{ .enabled = ATOMIC_INIT(1) }
  #define STATIC_KEY_INIT_FALSE	{ .enabled = ATOMIC_INIT(0) }
  
  #endif	/* CONFIG_JUMP_LABEL */
  
  #define STATIC_KEY_INIT STATIC_KEY_INIT_FALSE
  #define jump_label_enabled static_key_enabled
  
  /* -------------------------------------------------------------------------- */
  
  /*
   * Two type wrappers around static_key, such that we can use compile time
   * type differentiation to emit the right code.
   *
   * All the below code is macros in order to play type games.
   */
  
  struct static_key_true {
  	struct static_key key;
  };
  
  struct static_key_false {
  	struct static_key key;
  };
  
  #define STATIC_KEY_TRUE_INIT  (struct static_key_true) { .key = STATIC_KEY_INIT_TRUE,  }
  #define STATIC_KEY_FALSE_INIT (struct static_key_false){ .key = STATIC_KEY_INIT_FALSE, }
  
  #define DEFINE_STATIC_KEY_TRUE(name)	\
  	struct static_key_true name = STATIC_KEY_TRUE_INIT
  
  #define DEFINE_STATIC_KEY_TRUE_RO(name)	\
  	struct static_key_true name __ro_after_init = STATIC_KEY_TRUE_INIT
  
  #define DECLARE_STATIC_KEY_TRUE(name)	\
  	extern struct static_key_true name
  
  #define DEFINE_STATIC_KEY_FALSE(name)	\
  	struct static_key_false name = STATIC_KEY_FALSE_INIT
  
  #define DEFINE_STATIC_KEY_FALSE_RO(name)	\
  	struct static_key_false name __ro_after_init = STATIC_KEY_FALSE_INIT
  
  #define DECLARE_STATIC_KEY_FALSE(name)	\
  	extern struct static_key_false name
  
  #define DEFINE_STATIC_KEY_ARRAY_TRUE(name, count)		\
  	struct static_key_true name[count] = {			\
  		[0 ... (count) - 1] = STATIC_KEY_TRUE_INIT,	\
  	}
  
  #define DEFINE_STATIC_KEY_ARRAY_FALSE(name, count)		\
  	struct static_key_false name[count] = {			\
  		[0 ... (count) - 1] = STATIC_KEY_FALSE_INIT,	\
  	}
  
  extern bool ____wrong_branch_error(void);
  
  #define static_key_enabled(x)							\
  ({										\
  	if (!__builtin_types_compatible_p(typeof(*x), struct static_key) &&	\
  	    !__builtin_types_compatible_p(typeof(*x), struct static_key_true) &&\
  	    !__builtin_types_compatible_p(typeof(*x), struct static_key_false))	\
  		____wrong_branch_error();					\
  	static_key_count((struct static_key *)x) > 0;				\
  })
  
  #ifdef CONFIG_JUMP_LABEL
  
  /*
   * Combine the right initial value (type) with the right branch order
   * to generate the desired result.
   *
   *
   * type\branch|	likely (1)	      |	unlikely (0)
   * -----------+-----------------------+------------------
   *            |                       |
   *  true (1)  |	   ...		      |	   ...
   *            |    NOP		      |	   JMP L
   *            |    <br-stmts>	      |	1: ...
   *            |	L: ...		      |
   *            |			      |
   *            |			      |	L: <br-stmts>
   *            |			      |	   jmp 1b
   *            |                       |
   * -----------+-----------------------+------------------
   *            |                       |
   *  false (0) |	   ...		      |	   ...
   *            |    JMP L	      |	   NOP
   *            |    <br-stmts>	      |	1: ...
   *            |	L: ...		      |
   *            |			      |
   *            |			      |	L: <br-stmts>
   *            |			      |	   jmp 1b
   *            |                       |
   * -----------+-----------------------+------------------
   *
   * The initial value is encoded in the LSB of static_key::entries,
   * type: 0 = false, 1 = true.
   *
   * The branch type is encoded in the LSB of jump_entry::key,
   * branch: 0 = unlikely, 1 = likely.
   *
   * This gives the following logic table:
   *
   *	enabled	type	branch	  instuction
   * -----------------------------+-----------
   *	0	0	0	| NOP
   *	0	0	1	| JMP
   *	0	1	0	| NOP
   *	0	1	1	| JMP
   *
   *	1	0	0	| JMP
   *	1	0	1	| NOP
   *	1	1	0	| JMP
   *	1	1	1	| NOP
   *
   * Which gives the following functions:
   *
   *   dynamic: instruction = enabled ^ branch
   *   static:  instruction = type ^ branch
   *
   * See jump_label_type() / jump_label_init_type().
   */
  
  #define static_branch_likely(x)							\
  ({										\
  	bool branch;								\
  	if (__builtin_types_compatible_p(typeof(*x), struct static_key_true))	\
  		branch = !arch_static_branch(&(x)->key, true);			\
  	else if (__builtin_types_compatible_p(typeof(*x), struct static_key_false)) \
  		branch = !arch_static_branch_jump(&(x)->key, true);		\
  	else									\
  		branch = ____wrong_branch_error();				\
  	likely(branch);								\
  })
  
  #define static_branch_unlikely(x)						\
  ({										\
  	bool branch;								\
  	if (__builtin_types_compatible_p(typeof(*x), struct static_key_true))	\
  		branch = arch_static_branch_jump(&(x)->key, false);		\
  	else if (__builtin_types_compatible_p(typeof(*x), struct static_key_false)) \
  		branch = arch_static_branch(&(x)->key, false);			\
  	else									\
  		branch = ____wrong_branch_error();				\
  	unlikely(branch);							\
  })
  
  #else /* !CONFIG_JUMP_LABEL */
  
  #define static_branch_likely(x)		likely(static_key_enabled(&(x)->key))
  #define static_branch_unlikely(x)	unlikely(static_key_enabled(&(x)->key))
  
  #endif /* CONFIG_JUMP_LABEL */
  
  /*
   * Advanced usage; refcount, branch is enabled when: count != 0
   */
  
  #define static_branch_inc(x)		static_key_slow_inc(&(x)->key)
  #define static_branch_dec(x)		static_key_slow_dec(&(x)->key)
  #define static_branch_inc_cpuslocked(x)	static_key_slow_inc_cpuslocked(&(x)->key)
  #define static_branch_dec_cpuslocked(x)	static_key_slow_dec_cpuslocked(&(x)->key)
  
  /*
   * Normal usage; boolean enable/disable.
   */
  
  #define static_branch_enable(x)			static_key_enable(&(x)->key)
  #define static_branch_disable(x)		static_key_disable(&(x)->key)
  #define static_branch_enable_cpuslocked(x)	static_key_enable_cpuslocked(&(x)->key)
  #define static_branch_disable_cpuslocked(x)	static_key_disable_cpuslocked(&(x)->key)
  
  #endif /* __ASSEMBLY__ */
  
  #endif	/* _LINUX_JUMP_LABEL_H */
  