[mirror_ubuntu-artful-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;
/*
 * 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	/* 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 /* __ASSEMBLY__ */

#endif	/* _LINUX_JUMP_LABEL_H */
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	92	/*
b17ef2ed SRV	93	* Note:
	94	* To make anonymous unions work with old compilers, the static
	95	* initialization of them requires brackets. This creates a dependency
	96	* on the order of the struct with the initializers. If any fields
	97	* are added, STATIC_KEY_INIT_TRUE and STATIC_KEY_INIT_FALSE may need
	98	* to be modified.
	99	*
3821fd35 JB	100	* bit 0 => 1 if key is initially true
	101	* 0 if initially false
	102	* bit 1 => 1 if points to struct static_key_mod
	103	* 0 if points to struct jump_entry
	104	*/
	105	union {
	106	unsigned long type;
	107	struct jump_entry *entries;
	108	struct static_key_mod *next;
	109	};
d430d3d7 JB	110	};
d430d3d7 JB	111
ea5e9539 MG	112	#else
	113	struct static_key {
	114	atomic_t enabled;
	115	};
c0ccf6f9 AB	116	#endif /* HAVE_JUMP_LABEL */
	117	#endif /* __ASSEMBLY__ */
	118
	119	#ifdef HAVE_JUMP_LABEL
	120	#include <asm/jump_label.h>
	121	#endif
	122
	123	#ifndef __ASSEMBLY__
bf5438fc JB	124
bf5438fc JB	125	enum jump_label_type {
76b235c6 PZ	126	JUMP_LABEL_NOP = 0,
76b235c6 PZ	127	JUMP_LABEL_JMP,
bf5438fc JB	128	};
	129
	130	struct module;
	131
4c5ea0a9 PB	132	#ifdef HAVE_JUMP_LABEL
4c5ea0a9 PB	133
3821fd35 JB	134	#define JUMP_TYPE_FALSE 0UL
	135	#define JUMP_TYPE_TRUE 1UL
	136	#define JUMP_TYPE_LINKED 2UL
	137	#define JUMP_TYPE_MASK 3UL
c5905afb IM	138
	139	static __always_inline bool static_key_false(struct static_key *key)
	140	{
11276d53	141	return arch_static_branch(key, false);
c5905afb	142	}
d430d3d7	143
c5905afb IM	144	static __always_inline bool static_key_true(struct static_key *key)
c5905afb IM	145	{
11276d53	146	return !arch_static_branch(key, true);
c5905afb IM	147	}
c5905afb IM	148
bf5438fc JB	149	extern struct jump_entry __start___jump_table[];
	150	extern struct jump_entry __stop___jump_table[];
	151
97ce2c88	152	extern void jump_label_init(void);
91bad2f8 JB	153	extern void jump_label_lock(void);
91bad2f8 JB	154	extern void jump_label_unlock(void);
bf5438fc	155	extern void arch_jump_label_transform(struct jump_entry *entry,
37348804	156	enum jump_label_type type);
20284aa7 JF	157	extern void arch_jump_label_transform_static(struct jump_entry *entry,
20284aa7 JF	158	enum jump_label_type type);
4c3ef6d7	159	extern int jump_label_text_reserved(void start, void end);
c5905afb IM	160	extern void static_key_slow_inc(struct static_key *key);
c5905afb IM	161	extern void static_key_slow_dec(struct static_key *key);
d430d3d7	162	extern void jump_label_apply_nops(struct module *mod);
1f69bf9c JB	163	extern int static_key_count(struct static_key *key);
	164	extern void static_key_enable(struct static_key *key);
	165	extern void static_key_disable(struct static_key *key);
c5905afb	166
1f69bf9c JB	167	/*
	168	* We should be using ATOMIC_INIT() for initializing .enabled, but
	169	* the inclusion of atomic.h is problematic for inclusion of jump_label.h
	170	* in 'low-level' headers. Thus, we are initializing .enabled with a
	171	* raw value, but have added a BUILD_BUG_ON() to catch any issues in
	172	* jump_label_init() see: kernel/jump_label.c.
	173	*/
11276d53	174	#define STATIC_KEY_INIT_TRUE \
1f69bf9c	175	{ .enabled = { 1 }, \
cd8d860d	176	{ .entries = (void *)JUMP_TYPE_TRUE } }
11276d53	177	#define STATIC_KEY_INIT_FALSE \
1f69bf9c	178	{ .enabled = { 0 }, \
cd8d860d	179	{ .entries = (void *)JUMP_TYPE_FALSE } }
bf5438fc	180
97ce2c88	181	#else /* !HAVE_JUMP_LABEL */
bf5438fc	182
1f69bf9c JB	183	#include <linux/atomic.h>
	184	#include <linux/bug.h>
	185
4c5ea0a9 PB	186	static inline int static_key_count(struct static_key *key)
	187	{
	188	return atomic_read(&key->enabled);
	189	}
	190
97ce2c88 JF	191	static __always_inline void jump_label_init(void)
97ce2c88 JF	192	{
c4b2c0c5	193	static_key_initialized = true;
97ce2c88 JF	194	}
97ce2c88 JF	195
c5905afb IM	196	static __always_inline bool static_key_false(struct static_key *key)
c5905afb IM	197	{
ea5e9539	198	if (unlikely(static_key_count(key) > 0))
c5905afb IM	199	return true;
	200	return false;
	201	}
	202
	203	static __always_inline bool static_key_true(struct static_key *key)
d430d3d7	204	{
ea5e9539	205	if (likely(static_key_count(key) > 0))
d430d3d7 JB	206	return true;
	207	return false;
	208	}
bf5438fc	209
c5905afb	210	static inline void static_key_slow_inc(struct static_key *key)
d430d3d7	211	{
c4b2c0c5	212	STATIC_KEY_CHECK_USE();
d430d3d7 JB	213	atomic_inc(&key->enabled);
d430d3d7 JB	214	}
bf5438fc	215
c5905afb	216	static inline void static_key_slow_dec(struct static_key *key)
bf5438fc	217	{
c4b2c0c5	218	STATIC_KEY_CHECK_USE();
d430d3d7	219	atomic_dec(&key->enabled);
bf5438fc JB	220	}
bf5438fc JB	221
4c3ef6d7 JB	222	static inline int jump_label_text_reserved(void start, void end)
	223	{
	224	return 0;
	225	}
	226
91bad2f8 JB	227	static inline void jump_label_lock(void) {}
	228	static inline void jump_label_unlock(void) {}
	229
d430d3d7 JB	230	static inline int jump_label_apply_nops(struct module *mod)
	231	{
	232	return 0;
	233	}
b2029520	234
e33886b3 PZ	235	static inline void static_key_enable(struct static_key *key)
	236	{
	237	int count = static_key_count(key);
	238
	239	WARN_ON_ONCE(count < 0 \|\| count > 1);
	240
	241	if (!count)
	242	static_key_slow_inc(key);
	243	}
	244
	245	static inline void static_key_disable(struct static_key *key)
	246	{
	247	int count = static_key_count(key);
	248
	249	WARN_ON_ONCE(count < 0 \|\| count > 1);
	250
	251	if (count)
	252	static_key_slow_dec(key);
	253	}
	254
1f69bf9c JB	255	#define STATIC_KEY_INIT_TRUE { .enabled = ATOMIC_INIT(1) }
	256	#define STATIC_KEY_INIT_FALSE { .enabled = ATOMIC_INIT(0) }
	257
	258	#endif /* HAVE_JUMP_LABEL */
	259
	260	#define STATIC_KEY_INIT STATIC_KEY_INIT_FALSE
	261	#define jump_label_enabled static_key_enabled
	262
11276d53 PZ	263	/* -------------------------------------------------------------------------- */
	264
	265	/*
	266	* Two type wrappers around static_key, such that we can use compile time
	267	* type differentiation to emit the right code.
	268	*
	269	* All the below code is macros in order to play type games.
	270	*/
	271
	272	struct static_key_true {
	273	struct static_key key;
	274	};
	275
	276	struct static_key_false {
	277	struct static_key key;
	278	};
	279
	280	#define STATIC_KEY_TRUE_INIT (struct static_key_true) { .key = STATIC_KEY_INIT_TRUE, }
	281	#define STATIC_KEY_FALSE_INIT (struct static_key_false){ .key = STATIC_KEY_INIT_FALSE, }
	282
	283	#define DEFINE_STATIC_KEY_TRUE(name) \
	284	struct static_key_true name = STATIC_KEY_TRUE_INIT
	285
b8fb0378 TL	286	#define DECLARE_STATIC_KEY_TRUE(name) \
	287	extern struct static_key_true name
	288
11276d53 PZ	289	#define DEFINE_STATIC_KEY_FALSE(name) \
	290	struct static_key_false name = STATIC_KEY_FALSE_INIT
	291
b8fb0378 TL	292	#define DECLARE_STATIC_KEY_FALSE(name) \
	293	extern struct static_key_false name
	294
ef0da55a CM	295	#define DEFINE_STATIC_KEY_ARRAY_TRUE(name, count) \
	296	struct static_key_true name[count] = { \
	297	[0 ... (count) - 1] = STATIC_KEY_TRUE_INIT, \
	298	}
	299
	300	#define DEFINE_STATIC_KEY_ARRAY_FALSE(name, count) \
	301	struct static_key_false name[count] = { \
	302	[0 ... (count) - 1] = STATIC_KEY_FALSE_INIT, \
	303	}
	304
fa128fd7 TH	305	extern bool ____wrong_branch_error(void);
	306
	307	#define static_key_enabled(x) \
	308	({ \
	309	if (!__builtin_types_compatible_p(typeof(*x), struct static_key) && \
	310	!__builtin_types_compatible_p(typeof(*x), struct static_key_true) &&\
	311	!__builtin_types_compatible_p(typeof(*x), struct static_key_false)) \
	312	____wrong_branch_error(); \
	313	static_key_count((struct static_key *)x) > 0; \
	314	})
	315
11276d53 PZ	316	#ifdef HAVE_JUMP_LABEL
	317
	318	/*
	319	* Combine the right initial value (type) with the right branch order
	320	* to generate the desired result.
	321	*
	322	*
	323	* type\branch\| likely (1) \| unlikely (0)
	324	* -----------+-----------------------+------------------
	325	* \| \|
	326	* true (1) \| ... \| ...
	327	* \| NOP \| JMP L
	328	* \| <br-stmts> \| 1: ...
	329	* \| L: ... \|
	330	* \| \|
	331	* \| \| L: <br-stmts>
	332	* \| \| jmp 1b
	333	* \| \|
	334	* -----------+-----------------------+------------------
	335	* \| \|
	336	* false (0) \| ... \| ...
	337	* \| JMP L \| NOP
	338	* \| <br-stmts> \| 1: ...
	339	* \| L: ... \|
	340	* \| \|
	341	* \| \| L: <br-stmts>
	342	* \| \| jmp 1b
	343	* \| \|
	344	* -----------+-----------------------+------------------
	345	*
	346	* The initial value is encoded in the LSB of static_key::entries,
	347	* type: 0 = false, 1 = true.
	348	*
	349	* The branch type is encoded in the LSB of jump_entry::key,
	350	* branch: 0 = unlikely, 1 = likely.
	351	*
	352	* This gives the following logic table:
	353	*
	354	* enabled type branch instuction
	355	* -----------------------------+-----------
	356	* 0 0 0 \| NOP
	357	* 0 0 1 \| JMP
	358	* 0 1 0 \| NOP
	359	* 0 1 1 \| JMP
	360	*
	361	* 1 0 0 \| JMP
	362	* 1 0 1 \| NOP
	363	* 1 1 0 \| JMP
	364	* 1 1 1 \| NOP
	365	*
	366	* Which gives the following functions:
	367	*
	368	* dynamic: instruction = enabled ^ branch
	369	* static: instruction = type ^ branch
	370	*
	371	* See jump_label_type() / jump_label_init_type().
	372	*/
	373
11276d53 PZ	374	#define static_branch_likely(x) \
	375	({ \
	376	bool branch; \
	377	if (__builtin_types_compatible_p(typeof(*x), struct static_key_true)) \
	378	branch = !arch_static_branch(&(x)->key, true); \
	379	else if (__builtin_types_compatible_p(typeof(*x), struct static_key_false)) \
	380	branch = !arch_static_branch_jump(&(x)->key, true); \
	381	else \
	382	branch = ____wrong_branch_error(); \
	383	branch; \
	384	})
	385
	386	#define static_branch_unlikely(x) \
	387	({ \
	388	bool branch; \
	389	if (__builtin_types_compatible_p(typeof(*x), struct static_key_true)) \
	390	branch = arch_static_branch_jump(&(x)->key, false); \
	391	else if (__builtin_types_compatible_p(typeof(*x), struct static_key_false)) \
	392	branch = arch_static_branch(&(x)->key, false); \
	393	else \
	394	branch = ____wrong_branch_error(); \
	395	branch; \
	396	})
	397
	398	#else /* !HAVE_JUMP_LABEL */
	399
	400	#define static_branch_likely(x) likely(static_key_enabled(&(x)->key))
	401	#define static_branch_unlikely(x) unlikely(static_key_enabled(&(x)->key))
	402
	403	#endif /* HAVE_JUMP_LABEL */
	404
	405	/*
	406	* Advanced usage; refcount, branch is enabled when: count != 0
	407	*/
	408
	409	#define static_branch_inc(x) static_key_slow_inc(&(x)->key)
	410	#define static_branch_dec(x) static_key_slow_dec(&(x)->key)
	411
	412	/*
	413	* Normal usage; boolean enable/disable.
	414	*/
	415
	416	#define static_branch_enable(x) static_key_enable(&(x)->key)
	417	#define static_branch_disable(x) static_key_disable(&(x)->key)
	418
c0ccf6f9	419	#endif /* __ASSEMBLY__ */
85b36c93 LR	420
85b36c93 LR	421	#endif /* _LINUX_JUMP_LABEL_H */