| /* 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/staging/static-keys.rst |
| */ |
| |
| #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, bool set) |
| { |
| if (set) |
| entry->key |= 2; |
| else |
| entry->key &= ~2; |
| } |
| |
| static inline int jump_entry_size(struct jump_entry *entry) |
| { |
| #ifdef JUMP_LABEL_NOP_SIZE |
| return JUMP_LABEL_NOP_SIZE; |
| #else |
| return arch_jump_entry_size(entry); |
| #endif |
| } |
| |
| #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_notrace(static_key_count(key) > 0)) |
| return true; |
| return false; |
| } |
| |
| static __always_inline bool static_key_true(struct static_key *key) |
| { |
| if (likely_notrace(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, \ |
| } |
| |
| #define _DEFINE_STATIC_KEY_1(name) DEFINE_STATIC_KEY_TRUE(name) |
| #define _DEFINE_STATIC_KEY_0(name) DEFINE_STATIC_KEY_FALSE(name) |
| #define DEFINE_STATIC_KEY_MAYBE(cfg, name) \ |
| __PASTE(_DEFINE_STATIC_KEY_, IS_ENABLED(cfg))(name) |
| |
| #define _DEFINE_STATIC_KEY_RO_1(name) DEFINE_STATIC_KEY_TRUE_RO(name) |
| #define _DEFINE_STATIC_KEY_RO_0(name) DEFINE_STATIC_KEY_FALSE_RO(name) |
| #define DEFINE_STATIC_KEY_MAYBE_RO(cfg, name) \ |
| __PASTE(_DEFINE_STATIC_KEY_RO_, IS_ENABLED(cfg))(name) |
| |
| #define _DECLARE_STATIC_KEY_1(name) DECLARE_STATIC_KEY_TRUE(name) |
| #define _DECLARE_STATIC_KEY_0(name) DECLARE_STATIC_KEY_FALSE(name) |
| #define DECLARE_STATIC_KEY_MAYBE(cfg, name) \ |
| __PASTE(_DECLARE_STATIC_KEY_, IS_ENABLED(cfg))(name) |
| |
| 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_notrace(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_notrace(branch); \ |
| }) |
| |
| #else /* !CONFIG_JUMP_LABEL */ |
| |
| #define static_branch_likely(x) likely_notrace(static_key_enabled(&(x)->key)) |
| #define static_branch_unlikely(x) unlikely_notrace(static_key_enabled(&(x)->key)) |
| |
| #endif /* CONFIG_JUMP_LABEL */ |
| |
| #define static_branch_maybe(config, x) \ |
| (IS_ENABLED(config) ? static_branch_likely(x) \ |
| : static_branch_unlikely(x)) |
| |
| /* |
| * 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 */ |