[mirror_ubuntu-bionic-kernel.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);
 * 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
 */

#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;
/*
 * 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	/* 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_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 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 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 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 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);
ef0da55a CM	24	* DEFINE_STATIC_KEY_ARRAY_TRUE(keys, count);
ef0da55a CM	25	* DEFINE_STATIC_KEY_ARRAY_FALSE(keys, count);
1975dbc2 JC	26	* static_branch_likely()
1975dbc2 JC	27	* static_branch_unlikely()
412758cb	28	*
efb3040d	29	* Jump labels provide an interface to generate dynamic branches using
412758cb JB	30	* self-modifying code. Assuming toolchain and architecture support, if we
	31	* define a "key" that is initially false via "DEFINE_STATIC_KEY_FALSE(key)",
	32	* an "if (static_branch_unlikely(&key))" statement is an unconditional branch
	33	* (which defaults to false - and the true block is placed out of line).
	34	* Similarly, we can define an initially true key via
	35	* "DEFINE_STATIC_KEY_TRUE(key)", and use it in the same
	36	* "if (static_branch_unlikely(&key))", in which case we will generate an
	37	* unconditional branch to the out-of-line true branch. Keys that are
	38	* initially true or false can be using in both static_branch_unlikely()
	39	* and static_branch_likely() statements.
efb3040d	40	*
412758cb JB	41	* At runtime we can change the branch target by setting the key
	42	* to true via a call to static_branch_enable(), or false using
	43	* static_branch_disable(). If the direction of the branch is switched by
	44	* these calls then we run-time modify the branch target via a
	45	* no-op -> jump or jump -> no-op conversion. For example, for an
	46	* initially false key that is used in an "if (static_branch_unlikely(&key))"
	47	* statement, setting the key to true requires us to patch in a jump
	48	* to the out-of-line of true branch.
efb3040d	49	*
1975dbc2	50	* In addition to static_branch_{enable,disable}, we can also reference count
412758cb JB	51	* the key or branch direction via static_branch_{inc,dec}. Thus,
412758cb JB	52	* static_branch_inc() can be thought of as a 'make more true' and
1975dbc2	53	* static_branch_dec() as a 'make more false'.
412758cb JB	54	*
412758cb JB	55	* Since this relies on modifying code, the branch modifying functions
efb3040d	56	* must be considered absolute slow paths (machine wide synchronization etc.).
fd3cbdc0	57	* OTOH, since the affected branches are unconditional, their runtime overhead
efb3040d PZ	58	* will be absolutely minimal, esp. in the default (off) case where the total
	59	* effect is a single NOP of appropriate size. The on case will patch in a jump
	60	* to the out-of-line block.
	61	*
fd3cbdc0	62	* When the control is directly exposed to userspace, it is prudent to delay the
efb3040d	63	* decrement to avoid high frequency code modifications which can (and do)
c5905afb IM	64	* cause significant performance degradation. Struct static_key_deferred and
c5905afb IM	65	* static_key_slow_dec_deferred() provide for this.
efb3040d	66	*
412758cb JB	67	* Lacking toolchain and or architecture support, static keys fall back to a
412758cb JB	68	* simple conditional branch.
c5905afb	69	*
412758cb	70	* Additional babbling in: Documentation/static-keys.txt
fd3cbdc0	71	*/
efb3040d	72
c0ccf6f9 AB	73	#if defined(CC_HAVE_ASM_GOTO) && defined(CONFIG_JUMP_LABEL)
	74	# define HAVE_JUMP_LABEL
	75	#endif
	76
	77	#ifndef __ASSEMBLY__
	78
d430d3d7 JB	79	#include <linux/types.h>
d430d3d7 JB	80	#include <linux/compiler.h>
c4b2c0c5 HFS	81
	82	extern bool static_key_initialized;
	83
	84	#define STATIC_KEY_CHECK_USE() WARN(!static_key_initialized, \
	85	"%s used before call to jump_label_init", \
	86	__func__)
d430d3d7	87
c0ccf6f9	88	#ifdef HAVE_JUMP_LABEL
d430d3d7	89
c5905afb	90	struct static_key {
d430d3d7	91	atomic_t enabled;
3821fd35 JB	92	/*
	93	* bit 0 => 1 if key is initially true
	94	* 0 if initially false
	95	* bit 1 => 1 if points to struct static_key_mod
	96	* 0 if points to struct jump_entry
	97	*/
	98	union {
	99	unsigned long type;
	100	struct jump_entry *entries;
	101	struct static_key_mod *next;
	102	};
d430d3d7 JB	103	};
d430d3d7 JB	104
ea5e9539 MG	105	#else
	106	struct static_key {
	107	atomic_t enabled;
	108	};
c0ccf6f9 AB	109	#endif /* HAVE_JUMP_LABEL */
	110	#endif /* __ASSEMBLY__ */
	111
	112	#ifdef HAVE_JUMP_LABEL
	113	#include <asm/jump_label.h>
	114	#endif
	115
	116	#ifndef __ASSEMBLY__
bf5438fc JB	117
bf5438fc JB	118	enum jump_label_type {
76b235c6 PZ	119	JUMP_LABEL_NOP = 0,
76b235c6 PZ	120	JUMP_LABEL_JMP,
bf5438fc JB	121	};
	122
	123	struct module;
	124
4c5ea0a9 PB	125	#ifdef HAVE_JUMP_LABEL
4c5ea0a9 PB	126
3821fd35 JB	127	#define JUMP_TYPE_FALSE 0UL
	128	#define JUMP_TYPE_TRUE 1UL
	129	#define JUMP_TYPE_LINKED 2UL
	130	#define JUMP_TYPE_MASK 3UL
c5905afb IM	131
	132	static __always_inline bool static_key_false(struct static_key *key)
	133	{
11276d53	134	return arch_static_branch(key, false);
c5905afb	135	}
d430d3d7	136
c5905afb IM	137	static __always_inline bool static_key_true(struct static_key *key)
c5905afb IM	138	{
11276d53	139	return !arch_static_branch(key, true);
c5905afb IM	140	}
c5905afb IM	141
bf5438fc JB	142	extern struct jump_entry __start___jump_table[];
	143	extern struct jump_entry __stop___jump_table[];
	144
97ce2c88	145	extern void jump_label_init(void);
91bad2f8 JB	146	extern void jump_label_lock(void);
91bad2f8 JB	147	extern void jump_label_unlock(void);
bf5438fc	148	extern void arch_jump_label_transform(struct jump_entry *entry,
37348804	149	enum jump_label_type type);
20284aa7 JF	150	extern void arch_jump_label_transform_static(struct jump_entry *entry,
20284aa7 JF	151	enum jump_label_type type);
4c3ef6d7	152	extern int jump_label_text_reserved(void start, void end);
c5905afb IM	153	extern void static_key_slow_inc(struct static_key *key);
c5905afb IM	154	extern void static_key_slow_dec(struct static_key *key);
d430d3d7	155	extern void jump_label_apply_nops(struct module *mod);
1f69bf9c JB	156	extern int static_key_count(struct static_key *key);
	157	extern void static_key_enable(struct static_key *key);
	158	extern void static_key_disable(struct static_key *key);
c5905afb	159
1f69bf9c JB	160	/*
	161	* We should be using ATOMIC_INIT() for initializing .enabled, but
	162	* the inclusion of atomic.h is problematic for inclusion of jump_label.h
	163	* in 'low-level' headers. Thus, we are initializing .enabled with a
	164	* raw value, but have added a BUILD_BUG_ON() to catch any issues in
	165	* jump_label_init() see: kernel/jump_label.c.
	166	*/
11276d53	167	#define STATIC_KEY_INIT_TRUE \
1f69bf9c	168	{ .enabled = { 1 }, \
cd8d860d	169	{ .entries = (void *)JUMP_TYPE_TRUE } }
11276d53	170	#define STATIC_KEY_INIT_FALSE \
1f69bf9c	171	{ .enabled = { 0 }, \
cd8d860d	172	{ .entries = (void *)JUMP_TYPE_FALSE } }
bf5438fc	173
97ce2c88	174	#else /* !HAVE_JUMP_LABEL */
bf5438fc	175
1f69bf9c JB	176	#include <linux/atomic.h>
	177	#include <linux/bug.h>
	178
4c5ea0a9 PB	179	static inline int static_key_count(struct static_key *key)
	180	{
	181	return atomic_read(&key->enabled);
	182	}
	183
97ce2c88 JF	184	static __always_inline void jump_label_init(void)
97ce2c88 JF	185	{
c4b2c0c5	186	static_key_initialized = true;
97ce2c88 JF	187	}
97ce2c88 JF	188
c5905afb IM	189	static __always_inline bool static_key_false(struct static_key *key)
c5905afb IM	190	{
ea5e9539	191	if (unlikely(static_key_count(key) > 0))
c5905afb IM	192	return true;
	193	return false;
	194	}
	195
	196	static __always_inline bool static_key_true(struct static_key *key)
d430d3d7	197	{
ea5e9539	198	if (likely(static_key_count(key) > 0))
d430d3d7 JB	199	return true;
	200	return false;
	201	}
bf5438fc	202
c5905afb	203	static inline void static_key_slow_inc(struct static_key *key)
d430d3d7	204	{
c4b2c0c5	205	STATIC_KEY_CHECK_USE();
d430d3d7 JB	206	atomic_inc(&key->enabled);
d430d3d7 JB	207	}
bf5438fc	208
c5905afb	209	static inline void static_key_slow_dec(struct static_key *key)
bf5438fc	210	{
c4b2c0c5	211	STATIC_KEY_CHECK_USE();
d430d3d7	212	atomic_dec(&key->enabled);
bf5438fc JB	213	}
bf5438fc JB	214
4c3ef6d7 JB	215	static inline int jump_label_text_reserved(void start, void end)
	216	{
	217	return 0;
	218	}
	219
91bad2f8 JB	220	static inline void jump_label_lock(void) {}
	221	static inline void jump_label_unlock(void) {}
	222
d430d3d7 JB	223	static inline int jump_label_apply_nops(struct module *mod)
	224	{
	225	return 0;
	226	}
b2029520	227
e33886b3 PZ	228	static inline void static_key_enable(struct static_key *key)
	229	{
	230	int count = static_key_count(key);
	231
	232	WARN_ON_ONCE(count < 0 \|\| count > 1);
	233
	234	if (!count)
	235	static_key_slow_inc(key);
	236	}
	237
	238	static inline void static_key_disable(struct static_key *key)
	239	{
	240	int count = static_key_count(key);
	241
	242	WARN_ON_ONCE(count < 0 \|\| count > 1);
	243
	244	if (count)
	245	static_key_slow_dec(key);
	246	}
	247
1f69bf9c JB	248	#define STATIC_KEY_INIT_TRUE { .enabled = ATOMIC_INIT(1) }
	249	#define STATIC_KEY_INIT_FALSE { .enabled = ATOMIC_INIT(0) }
	250
	251	#endif /* HAVE_JUMP_LABEL */
	252
	253	#define STATIC_KEY_INIT STATIC_KEY_INIT_FALSE
	254	#define jump_label_enabled static_key_enabled
	255
11276d53 PZ	256	/* -------------------------------------------------------------------------- */
	257
	258	/*
	259	* Two type wrappers around static_key, such that we can use compile time
	260	* type differentiation to emit the right code.
	261	*
	262	* All the below code is macros in order to play type games.
	263	*/
	264
	265	struct static_key_true {
	266	struct static_key key;
	267	};
	268
	269	struct static_key_false {
	270	struct static_key key;
	271	};
	272
	273	#define STATIC_KEY_TRUE_INIT (struct static_key_true) { .key = STATIC_KEY_INIT_TRUE, }
	274	#define STATIC_KEY_FALSE_INIT (struct static_key_false){ .key = STATIC_KEY_INIT_FALSE, }
	275
	276	#define DEFINE_STATIC_KEY_TRUE(name) \
	277	struct static_key_true name = STATIC_KEY_TRUE_INIT
	278
b8fb0378 TL	279	#define DECLARE_STATIC_KEY_TRUE(name) \
	280	extern struct static_key_true name
	281
11276d53 PZ	282	#define DEFINE_STATIC_KEY_FALSE(name) \
	283	struct static_key_false name = STATIC_KEY_FALSE_INIT
	284
b8fb0378 TL	285	#define DECLARE_STATIC_KEY_FALSE(name) \
	286	extern struct static_key_false name
	287
ef0da55a CM	288	#define DEFINE_STATIC_KEY_ARRAY_TRUE(name, count) \
	289	struct static_key_true name[count] = { \
	290	[0 ... (count) - 1] = STATIC_KEY_TRUE_INIT, \
	291	}
	292
	293	#define DEFINE_STATIC_KEY_ARRAY_FALSE(name, count) \
	294	struct static_key_false name[count] = { \
	295	[0 ... (count) - 1] = STATIC_KEY_FALSE_INIT, \
	296	}
	297
fa128fd7 TH	298	extern bool ____wrong_branch_error(void);
	299
	300	#define static_key_enabled(x) \
	301	({ \
	302	if (!__builtin_types_compatible_p(typeof(*x), struct static_key) && \
	303	!__builtin_types_compatible_p(typeof(*x), struct static_key_true) &&\
	304	!__builtin_types_compatible_p(typeof(*x), struct static_key_false)) \
	305	____wrong_branch_error(); \
	306	static_key_count((struct static_key *)x) > 0; \
	307	})
	308
11276d53 PZ	309	#ifdef HAVE_JUMP_LABEL
	310
	311	/*
	312	* Combine the right initial value (type) with the right branch order
	313	* to generate the desired result.
	314	*
	315	*
	316	* type\branch\| likely (1) \| unlikely (0)
	317	* -----------+-----------------------+------------------
	318	* \| \|
	319	* true (1) \| ... \| ...
	320	* \| NOP \| JMP L
	321	* \| <br-stmts> \| 1: ...
	322	* \| L: ... \|
	323	* \| \|
	324	* \| \| L: <br-stmts>
	325	* \| \| jmp 1b
	326	* \| \|
	327	* -----------+-----------------------+------------------
	328	* \| \|
	329	* false (0) \| ... \| ...
	330	* \| JMP L \| NOP
	331	* \| <br-stmts> \| 1: ...
	332	* \| L: ... \|
	333	* \| \|
	334	* \| \| L: <br-stmts>
	335	* \| \| jmp 1b
	336	* \| \|
	337	* -----------+-----------------------+------------------
	338	*
	339	* The initial value is encoded in the LSB of static_key::entries,
	340	* type: 0 = false, 1 = true.
	341	*
	342	* The branch type is encoded in the LSB of jump_entry::key,
	343	* branch: 0 = unlikely, 1 = likely.
	344	*
	345	* This gives the following logic table:
	346	*
	347	* enabled type branch instuction
	348	* -----------------------------+-----------
	349	* 0 0 0 \| NOP
	350	* 0 0 1 \| JMP
	351	* 0 1 0 \| NOP
	352	* 0 1 1 \| JMP
	353	*
	354	* 1 0 0 \| JMP
	355	* 1 0 1 \| NOP
	356	* 1 1 0 \| JMP
	357	* 1 1 1 \| NOP
	358	*
	359	* Which gives the following functions:
	360	*
	361	* dynamic: instruction = enabled ^ branch
	362	* static: instruction = type ^ branch
	363	*
	364	* See jump_label_type() / jump_label_init_type().
	365	*/
	366
11276d53 PZ	367	#define static_branch_likely(x) \
	368	({ \
	369	bool branch; \
	370	if (__builtin_types_compatible_p(typeof(*x), struct static_key_true)) \
	371	branch = !arch_static_branch(&(x)->key, true); \
	372	else if (__builtin_types_compatible_p(typeof(*x), struct static_key_false)) \
	373	branch = !arch_static_branch_jump(&(x)->key, true); \
	374	else \
	375	branch = ____wrong_branch_error(); \
	376	branch; \
	377	})
	378
	379	#define static_branch_unlikely(x) \
	380	({ \
	381	bool branch; \
	382	if (__builtin_types_compatible_p(typeof(*x), struct static_key_true)) \
	383	branch = arch_static_branch_jump(&(x)->key, false); \
	384	else if (__builtin_types_compatible_p(typeof(*x), struct static_key_false)) \
	385	branch = arch_static_branch(&(x)->key, false); \
	386	else \
	387	branch = ____wrong_branch_error(); \
	388	branch; \
	389	})
	390
	391	#else /* !HAVE_JUMP_LABEL */
	392
	393	#define static_branch_likely(x) likely(static_key_enabled(&(x)->key))
	394	#define static_branch_unlikely(x) unlikely(static_key_enabled(&(x)->key))
	395
	396	#endif /* HAVE_JUMP_LABEL */
	397
	398	/*
	399	* Advanced usage; refcount, branch is enabled when: count != 0
	400	*/
	401
	402	#define static_branch_inc(x) static_key_slow_inc(&(x)->key)
	403	#define static_branch_dec(x) static_key_slow_dec(&(x)->key)
	404
	405	/*
	406	* Normal usage; boolean enable/disable.
	407	*/
	408
	409	#define static_branch_enable(x) static_key_enable(&(x)->key)
	410	#define static_branch_disable(x) static_key_disable(&(x)->key)
	411
97ce2c88	412	#endif /* _LINUX_JUMP_LABEL_H */
c0ccf6f9 AB	413
c0ccf6f9 AB	414	#endif /* __ASSEMBLY__ */