[linux-2.6-block.git] / include / linux / jump_label.h

#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);
 * 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
 */

#if defined(CC_HAVE_ASM_GOTO) && defined(CONFIG_JUMP_LABEL)
# define HAVE_JUMP_LABEL
#endif

#ifndef __ASSEMBLY__

#include <linux/types.h>
#include <linux/compiler.h>

extern bool static_key_initialized;

#define STATIC_KEY_CHECK_USE() WARN(!static_key_initialized,		      \
				    "%s used before call to jump_label_init", \
				    __func__)

#ifdef HAVE_JUMP_LABEL

struct static_key {
	atomic_t enabled;
/* Set lsb bit to 1 if branch is default true, 0 ot */
	struct jump_entry *entries;
#ifdef CONFIG_MODULES
	struct static_key_mod *next;
#endif
};

#else
struct static_key {
	atomic_t enabled;
};
#endif	/* HAVE_JUMP_LABEL */
#endif /* __ASSEMBLY__ */

#ifdef HAVE_JUMP_LABEL
#include <asm/jump_label.h>
#endif

#ifndef __ASSEMBLY__

enum jump_label_type {
	JUMP_LABEL_NOP = 0,
	JUMP_LABEL_JMP,
};

struct module;

#ifdef HAVE_JUMP_LABEL

#define JUMP_TYPE_FALSE	0UL
#define JUMP_TYPE_TRUE	1UL
#define JUMP_TYPE_MASK	1UL

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 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 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);

/*
 * 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  /* !HAVE_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();
	atomic_inc(&key->enabled);
}

static inline void static_key_slow_dec(struct static_key *key)
{
	STATIC_KEY_CHECK_USE();
	atomic_dec(&key->enabled);
}

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)
{
	int count = static_key_count(key);

	WARN_ON_ONCE(count < 0 || count > 1);

	if (!count)
		static_key_slow_inc(key);
}

static inline void static_key_disable(struct static_key *key)
{
	int count = static_key_count(key);

	WARN_ON_ONCE(count < 0 || count > 1);

	if (count)
		static_key_slow_dec(key);
}

#define STATIC_KEY_INIT_TRUE	{ .enabled = ATOMIC_INIT(1) }
#define STATIC_KEY_INIT_FALSE	{ .enabled = ATOMIC_INIT(0) }

#endif	/* HAVE_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_FALSE(name)	\
	struct static_key_false name = 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 HAVE_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();				\
	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();				\
	branch;									\
})

#else /* !HAVE_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 /* HAVE_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)

/*
 * 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)

#endif	/* _LINUX_JUMP_LABEL_H */

#endif /* __ASSEMBLY__ */
Commit	Line	Data
bf5438fc JB	1	#ifndef _LINUX_JUMP_LABEL_H
	2	#define _LINUX_JUMP_LABEL_H
	3
efb3040d PZ	4	/*
	5	* Jump label support
	6	*
	7	* Copyright (C) 2009-2012 Jason Baron <jbaron@redhat.com>
90eec103	8	* Copyright (C) 2011-2012 Red Hat, Inc., Peter Zijlstra
efb3040d	9	*
412758cb JB	10	* DEPRECATED API:
	11	*
	12	* The use of 'struct static_key' directly, is now DEPRECATED. In addition
	13	* static_key_{true,false}() is also DEPRECATED. IE DO NOT use the following:
	14	*
	15	* struct static_key false = STATIC_KEY_INIT_FALSE;
	16	* struct static_key true = STATIC_KEY_INIT_TRUE;
	17	* static_key_true()
	18	* static_key_false()
	19	*
	20	* The updated API replacements are:
	21	*
	22	* DEFINE_STATIC_KEY_TRUE(key);
	23	* DEFINE_STATIC_KEY_FALSE(key);
1975dbc2 JC	24	* static_branch_likely()
1975dbc2 JC	25	* static_branch_unlikely()
412758cb	26	*
efb3040d	27	* Jump labels provide an interface to generate dynamic branches using
412758cb JB	28	* self-modifying code. Assuming toolchain and architecture support, if we
	29	* define a "key" that is initially false via "DEFINE_STATIC_KEY_FALSE(key)",
	30	* an "if (static_branch_unlikely(&key))" statement is an unconditional branch
	31	* (which defaults to false - and the true block is placed out of line).
	32	* Similarly, we can define an initially true key via
	33	* "DEFINE_STATIC_KEY_TRUE(key)", and use it in the same
	34	* "if (static_branch_unlikely(&key))", in which case we will generate an
	35	* unconditional branch to the out-of-line true branch. Keys that are
	36	* initially true or false can be using in both static_branch_unlikely()
	37	* and static_branch_likely() statements.
efb3040d	38	*
412758cb JB	39	* At runtime we can change the branch target by setting the key
	40	* to true via a call to static_branch_enable(), or false using
	41	* static_branch_disable(). If the direction of the branch is switched by
	42	* these calls then we run-time modify the branch target via a
	43	* no-op -> jump or jump -> no-op conversion. For example, for an
	44	* initially false key that is used in an "if (static_branch_unlikely(&key))"
	45	* statement, setting the key to true requires us to patch in a jump
	46	* to the out-of-line of true branch.
efb3040d	47	*
1975dbc2	48	* In addition to static_branch_{enable,disable}, we can also reference count
412758cb JB	49	* the key or branch direction via static_branch_{inc,dec}. Thus,
412758cb JB	50	* static_branch_inc() can be thought of as a 'make more true' and
1975dbc2	51	* static_branch_dec() as a 'make more false'.
412758cb JB	52	*
412758cb JB	53	* Since this relies on modifying code, the branch modifying functions
efb3040d	54	* must be considered absolute slow paths (machine wide synchronization etc.).
fd3cbdc0	55	* OTOH, since the affected branches are unconditional, their runtime overhead
efb3040d PZ	56	* will be absolutely minimal, esp. in the default (off) case where the total
	57	* effect is a single NOP of appropriate size. The on case will patch in a jump
	58	* to the out-of-line block.
	59	*
fd3cbdc0	60	* When the control is directly exposed to userspace, it is prudent to delay the
efb3040d	61	* decrement to avoid high frequency code modifications which can (and do)
c5905afb IM	62	* cause significant performance degradation. Struct static_key_deferred and
c5905afb IM	63	* static_key_slow_dec_deferred() provide for this.
efb3040d	64	*
412758cb JB	65	* Lacking toolchain and or architecture support, static keys fall back to a
412758cb JB	66	* simple conditional branch.
c5905afb	67	*
412758cb	68	* Additional babbling in: Documentation/static-keys.txt
fd3cbdc0	69	*/
efb3040d	70
c0ccf6f9 AB	71	#if defined(CC_HAVE_ASM_GOTO) && defined(CONFIG_JUMP_LABEL)
	72	# define HAVE_JUMP_LABEL
	73	#endif
	74
	75	#ifndef __ASSEMBLY__
	76
d430d3d7 JB	77	#include <linux/types.h>
d430d3d7 JB	78	#include <linux/compiler.h>
c4b2c0c5 HFS	79
	80	extern bool static_key_initialized;
	81
	82	#define STATIC_KEY_CHECK_USE() WARN(!static_key_initialized, \
	83	"%s used before call to jump_label_init", \
	84	__func__)
d430d3d7	85
c0ccf6f9	86	#ifdef HAVE_JUMP_LABEL
d430d3d7	87
c5905afb	88	struct static_key {
d430d3d7	89	atomic_t enabled;
c5905afb	90	/* Set lsb bit to 1 if branch is default true, 0 ot */
d430d3d7 JB	91	struct jump_entry *entries;
d430d3d7 JB	92	#ifdef CONFIG_MODULES
c5905afb	93	struct static_key_mod *next;
d430d3d7 JB	94	#endif
	95	};
	96
ea5e9539 MG	97	#else
	98	struct static_key {
	99	atomic_t enabled;
	100	};
c0ccf6f9 AB	101	#endif /* HAVE_JUMP_LABEL */
	102	#endif /* __ASSEMBLY__ */
	103
	104	#ifdef HAVE_JUMP_LABEL
	105	#include <asm/jump_label.h>
	106	#endif
	107
	108	#ifndef __ASSEMBLY__
bf5438fc JB	109
bf5438fc JB	110	enum jump_label_type {
76b235c6 PZ	111	JUMP_LABEL_NOP = 0,
76b235c6 PZ	112	JUMP_LABEL_JMP,
bf5438fc JB	113	};
	114
	115	struct module;
	116
4c5ea0a9 PB	117	#ifdef HAVE_JUMP_LABEL
4c5ea0a9 PB	118
a1efb01f PZ	119	#define JUMP_TYPE_FALSE 0UL
	120	#define JUMP_TYPE_TRUE 1UL
	121	#define JUMP_TYPE_MASK 1UL
c5905afb IM	122
	123	static __always_inline bool static_key_false(struct static_key *key)
	124	{
11276d53	125	return arch_static_branch(key, false);
c5905afb	126	}
d430d3d7	127
c5905afb IM	128	static __always_inline bool static_key_true(struct static_key *key)
c5905afb IM	129	{
11276d53	130	return !arch_static_branch(key, true);
c5905afb IM	131	}
c5905afb IM	132
bf5438fc JB	133	extern struct jump_entry __start___jump_table[];
	134	extern struct jump_entry __stop___jump_table[];
	135
97ce2c88	136	extern void jump_label_init(void);
91bad2f8 JB	137	extern void jump_label_lock(void);
91bad2f8 JB	138	extern void jump_label_unlock(void);
bf5438fc	139	extern void arch_jump_label_transform(struct jump_entry *entry,
37348804	140	enum jump_label_type type);
20284aa7 JF	141	extern void arch_jump_label_transform_static(struct jump_entry *entry,
20284aa7 JF	142	enum jump_label_type type);
4c3ef6d7	143	extern int jump_label_text_reserved(void start, void end);
c5905afb IM	144	extern void static_key_slow_inc(struct static_key *key);
c5905afb IM	145	extern void static_key_slow_dec(struct static_key *key);
d430d3d7	146	extern void jump_label_apply_nops(struct module *mod);
1f69bf9c JB	147	extern int static_key_count(struct static_key *key);
	148	extern void static_key_enable(struct static_key *key);
	149	extern void static_key_disable(struct static_key *key);
c5905afb	150
1f69bf9c JB	151	/*
	152	* We should be using ATOMIC_INIT() for initializing .enabled, but
	153	* the inclusion of atomic.h is problematic for inclusion of jump_label.h
	154	* in 'low-level' headers. Thus, we are initializing .enabled with a
	155	* raw value, but have added a BUILD_BUG_ON() to catch any issues in
	156	* jump_label_init() see: kernel/jump_label.c.
	157	*/
11276d53	158	#define STATIC_KEY_INIT_TRUE \
1f69bf9c	159	{ .enabled = { 1 }, \
11276d53 PZ	160	.entries = (void *)JUMP_TYPE_TRUE }
11276d53 PZ	161	#define STATIC_KEY_INIT_FALSE \
1f69bf9c	162	{ .enabled = { 0 }, \
11276d53	163	.entries = (void *)JUMP_TYPE_FALSE }
bf5438fc	164
97ce2c88	165	#else /* !HAVE_JUMP_LABEL */
bf5438fc	166
1f69bf9c JB	167	#include <linux/atomic.h>
	168	#include <linux/bug.h>
	169
4c5ea0a9 PB	170	static inline int static_key_count(struct static_key *key)
	171	{
	172	return atomic_read(&key->enabled);
	173	}
	174
97ce2c88 JF	175	static __always_inline void jump_label_init(void)
97ce2c88 JF	176	{
c4b2c0c5	177	static_key_initialized = true;
97ce2c88 JF	178	}
97ce2c88 JF	179
c5905afb IM	180	static __always_inline bool static_key_false(struct static_key *key)
c5905afb IM	181	{
ea5e9539	182	if (unlikely(static_key_count(key) > 0))
c5905afb IM	183	return true;
	184	return false;
	185	}
	186
	187	static __always_inline bool static_key_true(struct static_key *key)
d430d3d7	188	{
ea5e9539	189	if (likely(static_key_count(key) > 0))
d430d3d7 JB	190	return true;
	191	return false;
	192	}
bf5438fc	193
c5905afb	194	static inline void static_key_slow_inc(struct static_key *key)
d430d3d7	195	{
c4b2c0c5	196	STATIC_KEY_CHECK_USE();
d430d3d7 JB	197	atomic_inc(&key->enabled);
d430d3d7 JB	198	}
bf5438fc	199
c5905afb	200	static inline void static_key_slow_dec(struct static_key *key)
bf5438fc	201	{
c4b2c0c5	202	STATIC_KEY_CHECK_USE();
d430d3d7	203	atomic_dec(&key->enabled);
bf5438fc JB	204	}
bf5438fc JB	205
4c3ef6d7 JB	206	static inline int jump_label_text_reserved(void start, void end)
	207	{
	208	return 0;
	209	}
	210
91bad2f8 JB	211	static inline void jump_label_lock(void) {}
	212	static inline void jump_label_unlock(void) {}
	213
d430d3d7 JB	214	static inline int jump_label_apply_nops(struct module *mod)
	215	{
	216	return 0;
	217	}
b2029520	218
e33886b3 PZ	219	static inline void static_key_enable(struct static_key *key)
	220	{
	221	int count = static_key_count(key);
	222
	223	WARN_ON_ONCE(count < 0 \|\| count > 1);
	224
	225	if (!count)
	226	static_key_slow_inc(key);
	227	}
	228
	229	static inline void static_key_disable(struct static_key *key)
	230	{
	231	int count = static_key_count(key);
	232
	233	WARN_ON_ONCE(count < 0 \|\| count > 1);
	234
	235	if (count)
	236	static_key_slow_dec(key);
	237	}
	238
1f69bf9c JB	239	#define STATIC_KEY_INIT_TRUE { .enabled = ATOMIC_INIT(1) }
	240	#define STATIC_KEY_INIT_FALSE { .enabled = ATOMIC_INIT(0) }
	241
	242	#endif /* HAVE_JUMP_LABEL */
	243
	244	#define STATIC_KEY_INIT STATIC_KEY_INIT_FALSE
	245	#define jump_label_enabled static_key_enabled
	246
11276d53 PZ	247	/* -------------------------------------------------------------------------- */
	248
	249	/*
	250	* Two type wrappers around static_key, such that we can use compile time
	251	* type differentiation to emit the right code.
	252	*
	253	* All the below code is macros in order to play type games.
	254	*/
	255
	256	struct static_key_true {
	257	struct static_key key;
	258	};
	259
	260	struct static_key_false {
	261	struct static_key key;
	262	};
	263
	264	#define STATIC_KEY_TRUE_INIT (struct static_key_true) { .key = STATIC_KEY_INIT_TRUE, }
	265	#define STATIC_KEY_FALSE_INIT (struct static_key_false){ .key = STATIC_KEY_INIT_FALSE, }
	266
	267	#define DEFINE_STATIC_KEY_TRUE(name) \
	268	struct static_key_true name = STATIC_KEY_TRUE_INIT
	269
	270	#define DEFINE_STATIC_KEY_FALSE(name) \
	271	struct static_key_false name = STATIC_KEY_FALSE_INIT
	272
fa128fd7 TH	273	extern bool ____wrong_branch_error(void);
	274
	275	#define static_key_enabled(x) \
	276	({ \
	277	if (!__builtin_types_compatible_p(typeof(*x), struct static_key) && \
	278	!__builtin_types_compatible_p(typeof(*x), struct static_key_true) &&\
	279	!__builtin_types_compatible_p(typeof(*x), struct static_key_false)) \
	280	____wrong_branch_error(); \
	281	static_key_count((struct static_key *)x) > 0; \
	282	})
	283
11276d53 PZ	284	#ifdef HAVE_JUMP_LABEL
	285
	286	/*
	287	* Combine the right initial value (type) with the right branch order
	288	* to generate the desired result.
	289	*
	290	*
	291	* type\branch\| likely (1) \| unlikely (0)
	292	* -----------+-----------------------+------------------
	293	* \| \|
	294	* true (1) \| ... \| ...
	295	* \| NOP \| JMP L
	296	* \| <br-stmts> \| 1: ...
	297	* \| L: ... \|
	298	* \| \|
	299	* \| \| L: <br-stmts>
	300	* \| \| jmp 1b
	301	* \| \|
	302	* -----------+-----------------------+------------------
	303	* \| \|
	304	* false (0) \| ... \| ...
	305	* \| JMP L \| NOP
	306	* \| <br-stmts> \| 1: ...
	307	* \| L: ... \|
	308	* \| \|
	309	* \| \| L: <br-stmts>
	310	* \| \| jmp 1b
	311	* \| \|
	312	* -----------+-----------------------+------------------
	313	*
	314	* The initial value is encoded in the LSB of static_key::entries,
	315	* type: 0 = false, 1 = true.
	316	*
	317	* The branch type is encoded in the LSB of jump_entry::key,
	318	* branch: 0 = unlikely, 1 = likely.
	319	*
	320	* This gives the following logic table:
	321	*
	322	* enabled type branch instuction
	323	* -----------------------------+-----------
	324	* 0 0 0 \| NOP
	325	* 0 0 1 \| JMP
	326	* 0 1 0 \| NOP
	327	* 0 1 1 \| JMP
	328	*
	329	* 1 0 0 \| JMP
	330	* 1 0 1 \| NOP
	331	* 1 1 0 \| JMP
	332	* 1 1 1 \| NOP
	333	*
	334	* Which gives the following functions:
	335	*
	336	* dynamic: instruction = enabled ^ branch
	337	* static: instruction = type ^ branch
	338	*
	339	* See jump_label_type() / jump_label_init_type().
	340	*/
	341
11276d53 PZ	342	#define static_branch_likely(x) \
	343	({ \
	344	bool branch; \
	345	if (__builtin_types_compatible_p(typeof(*x), struct static_key_true)) \
	346	branch = !arch_static_branch(&(x)->key, true); \
	347	else if (__builtin_types_compatible_p(typeof(*x), struct static_key_false)) \
	348	branch = !arch_static_branch_jump(&(x)->key, true); \
	349	else \
	350	branch = ____wrong_branch_error(); \
	351	branch; \
	352	})
	353
	354	#define static_branch_unlikely(x) \
	355	({ \
	356	bool branch; \
	357	if (__builtin_types_compatible_p(typeof(*x), struct static_key_true)) \
	358	branch = arch_static_branch_jump(&(x)->key, false); \
	359	else if (__builtin_types_compatible_p(typeof(*x), struct static_key_false)) \
	360	branch = arch_static_branch(&(x)->key, false); \
	361	else \
	362	branch = ____wrong_branch_error(); \
	363	branch; \
	364	})
	365
	366	#else /* !HAVE_JUMP_LABEL */
	367
	368	#define static_branch_likely(x) likely(static_key_enabled(&(x)->key))
	369	#define static_branch_unlikely(x) unlikely(static_key_enabled(&(x)->key))
	370
	371	#endif /* HAVE_JUMP_LABEL */
	372
	373	/*
	374	* Advanced usage; refcount, branch is enabled when: count != 0
	375	*/
	376
	377	#define static_branch_inc(x) static_key_slow_inc(&(x)->key)
	378	#define static_branch_dec(x) static_key_slow_dec(&(x)->key)
	379
	380	/*
	381	* Normal usage; boolean enable/disable.
	382	*/
	383
	384	#define static_branch_enable(x) static_key_enable(&(x)->key)
	385	#define static_branch_disable(x) static_key_disable(&(x)->key)
	386
97ce2c88	387	#endif /* _LINUX_JUMP_LABEL_H */
c0ccf6f9 AB	388
c0ccf6f9 AB	389	#endif /* __ASSEMBLY__ */