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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> | |
8 | * Copyright (C) 2011-2012 Peter Zijlstra <pzijlstr@redhat.com> | |
9 | * | |
10 | * Jump labels provide an interface to generate dynamic branches using | |
11 | * self-modifying code. Assuming toolchain and architecture support the result | |
c5905afb | 12 | * of a "if (static_key_false(&key))" statement is a unconditional branch (which |
efb3040d PZ |
13 | * defaults to false - and the true block is placed out of line). |
14 | * | |
c5905afb IM |
15 | * However at runtime we can change the branch target using |
16 | * static_key_slow_{inc,dec}(). These function as a 'reference' count on the key | |
efb3040d PZ |
17 | * object and for as long as there are references all branches referring to |
18 | * that particular key will point to the (out of line) true block. | |
19 | * | |
c5905afb | 20 | * Since this relies on modifying code the static_key_slow_{inc,dec}() functions |
efb3040d PZ |
21 | * must be considered absolute slow paths (machine wide synchronization etc.). |
22 | * OTOH, since the affected branches are unconditional their runtime overhead | |
23 | * will be absolutely minimal, esp. in the default (off) case where the total | |
24 | * effect is a single NOP of appropriate size. The on case will patch in a jump | |
25 | * to the out-of-line block. | |
26 | * | |
27 | * When the control is directly exposed to userspace it is prudent to delay the | |
28 | * decrement to avoid high frequency code modifications which can (and do) | |
c5905afb IM |
29 | * cause significant performance degradation. Struct static_key_deferred and |
30 | * static_key_slow_dec_deferred() provide for this. | |
efb3040d PZ |
31 | * |
32 | * Lacking toolchain and or architecture support, it falls back to a simple | |
33 | * conditional branch. | |
c5905afb IM |
34 | * |
35 | * struct static_key my_key = STATIC_KEY_INIT_TRUE; | |
36 | * | |
37 | * if (static_key_true(&my_key)) { | |
38 | * } | |
39 | * | |
40 | * will result in the true case being in-line and starts the key with a single | |
41 | * reference. Mixing static_key_true() and static_key_false() on the same key is not | |
42 | * allowed. | |
43 | * | |
44 | * Not initializing the key (static data is initialized to 0s anyway) is the | |
45 | * same as using STATIC_KEY_INIT_FALSE and static_key_false() is | |
46 | * equivalent with static_branch(). | |
47 | * | |
48 | */ | |
efb3040d | 49 | |
d430d3d7 JB |
50 | #include <linux/types.h> |
51 | #include <linux/compiler.h> | |
b2029520 | 52 | #include <linux/workqueue.h> |
d430d3d7 | 53 | |
45f81b1c | 54 | #if defined(CC_HAVE_ASM_GOTO) && defined(CONFIG_JUMP_LABEL) |
d430d3d7 | 55 | |
c5905afb | 56 | struct static_key { |
d430d3d7 | 57 | atomic_t enabled; |
c5905afb | 58 | /* Set lsb bit to 1 if branch is default true, 0 ot */ |
d430d3d7 JB |
59 | struct jump_entry *entries; |
60 | #ifdef CONFIG_MODULES | |
c5905afb | 61 | struct static_key_mod *next; |
d430d3d7 JB |
62 | #endif |
63 | }; | |
64 | ||
c5905afb IM |
65 | struct static_key_deferred { |
66 | struct static_key key; | |
b2029520 GN |
67 | unsigned long timeout; |
68 | struct delayed_work work; | |
69 | }; | |
70 | ||
bf5438fc JB |
71 | # include <asm/jump_label.h> |
72 | # define HAVE_JUMP_LABEL | |
97ce2c88 | 73 | #endif /* CC_HAVE_ASM_GOTO && CONFIG_JUMP_LABEL */ |
bf5438fc JB |
74 | |
75 | enum jump_label_type { | |
d430d3d7 | 76 | JUMP_LABEL_DISABLE = 0, |
bf5438fc | 77 | JUMP_LABEL_ENABLE, |
bf5438fc JB |
78 | }; |
79 | ||
80 | struct module; | |
81 | ||
82 | #ifdef HAVE_JUMP_LABEL | |
83 | ||
c5905afb IM |
84 | #define JUMP_LABEL_TRUE_BRANCH 1UL |
85 | ||
86 | static | |
87 | inline struct jump_entry *jump_label_get_entries(struct static_key *key) | |
88 | { | |
89 | return (struct jump_entry *)((unsigned long)key->entries | |
90 | & ~JUMP_LABEL_TRUE_BRANCH); | |
91 | } | |
92 | ||
93 | static inline bool jump_label_get_branch_default(struct static_key *key) | |
94 | { | |
95 | if ((unsigned long)key->entries & JUMP_LABEL_TRUE_BRANCH) | |
96 | return true; | |
97 | return false; | |
98 | } | |
99 | ||
100 | static __always_inline bool static_key_false(struct static_key *key) | |
101 | { | |
102 | return arch_static_branch(key); | |
103 | } | |
d430d3d7 | 104 | |
c5905afb IM |
105 | static __always_inline bool static_key_true(struct static_key *key) |
106 | { | |
107 | return !static_key_false(key); | |
108 | } | |
109 | ||
110 | /* Deprecated. Please use 'static_key_false() instead. */ | |
111 | static __always_inline bool static_branch(struct static_key *key) | |
d430d3d7 JB |
112 | { |
113 | return arch_static_branch(key); | |
114 | } | |
115 | ||
bf5438fc JB |
116 | extern struct jump_entry __start___jump_table[]; |
117 | extern struct jump_entry __stop___jump_table[]; | |
118 | ||
97ce2c88 | 119 | extern void jump_label_init(void); |
91bad2f8 JB |
120 | extern void jump_label_lock(void); |
121 | extern void jump_label_unlock(void); | |
bf5438fc | 122 | extern void arch_jump_label_transform(struct jump_entry *entry, |
37348804 | 123 | enum jump_label_type type); |
20284aa7 JF |
124 | extern void arch_jump_label_transform_static(struct jump_entry *entry, |
125 | enum jump_label_type type); | |
4c3ef6d7 | 126 | extern int jump_label_text_reserved(void *start, void *end); |
c5905afb IM |
127 | extern void static_key_slow_inc(struct static_key *key); |
128 | extern void static_key_slow_dec(struct static_key *key); | |
129 | extern void static_key_slow_dec_deferred(struct static_key_deferred *key); | |
d430d3d7 | 130 | extern void jump_label_apply_nops(struct module *mod); |
c5905afb IM |
131 | extern void |
132 | jump_label_rate_limit(struct static_key_deferred *key, unsigned long rl); | |
133 | ||
134 | #define STATIC_KEY_INIT_TRUE ((struct static_key) \ | |
135 | { .enabled = ATOMIC_INIT(1), .entries = (void *)1 }) | |
136 | #define STATIC_KEY_INIT_FALSE ((struct static_key) \ | |
137 | { .enabled = ATOMIC_INIT(0), .entries = (void *)0 }) | |
bf5438fc | 138 | |
97ce2c88 | 139 | #else /* !HAVE_JUMP_LABEL */ |
bf5438fc | 140 | |
60063497 | 141 | #include <linux/atomic.h> |
bf5438fc | 142 | |
c5905afb | 143 | struct static_key { |
d430d3d7 JB |
144 | atomic_t enabled; |
145 | }; | |
bf5438fc | 146 | |
97ce2c88 JF |
147 | static __always_inline void jump_label_init(void) |
148 | { | |
149 | } | |
150 | ||
c5905afb IM |
151 | struct static_key_deferred { |
152 | struct static_key key; | |
b2029520 GN |
153 | }; |
154 | ||
c5905afb IM |
155 | static __always_inline bool static_key_false(struct static_key *key) |
156 | { | |
157 | if (unlikely(atomic_read(&key->enabled)) > 0) | |
158 | return true; | |
159 | return false; | |
160 | } | |
161 | ||
162 | static __always_inline bool static_key_true(struct static_key *key) | |
d430d3d7 | 163 | { |
c5905afb | 164 | if (likely(atomic_read(&key->enabled)) > 0) |
d430d3d7 JB |
165 | return true; |
166 | return false; | |
167 | } | |
bf5438fc | 168 | |
c5905afb IM |
169 | /* Deprecated. Please use 'static_key_false() instead. */ |
170 | static __always_inline bool static_branch(struct static_key *key) | |
171 | { | |
172 | if (unlikely(atomic_read(&key->enabled)) > 0) | |
173 | return true; | |
174 | return false; | |
175 | } | |
176 | ||
177 | static inline void static_key_slow_inc(struct static_key *key) | |
d430d3d7 JB |
178 | { |
179 | atomic_inc(&key->enabled); | |
180 | } | |
bf5438fc | 181 | |
c5905afb | 182 | static inline void static_key_slow_dec(struct static_key *key) |
bf5438fc | 183 | { |
d430d3d7 | 184 | atomic_dec(&key->enabled); |
bf5438fc JB |
185 | } |
186 | ||
c5905afb | 187 | static inline void static_key_slow_dec_deferred(struct static_key_deferred *key) |
b2029520 | 188 | { |
c5905afb | 189 | static_key_slow_dec(&key->key); |
b2029520 GN |
190 | } |
191 | ||
4c3ef6d7 JB |
192 | static inline int jump_label_text_reserved(void *start, void *end) |
193 | { | |
194 | return 0; | |
195 | } | |
196 | ||
91bad2f8 JB |
197 | static inline void jump_label_lock(void) {} |
198 | static inline void jump_label_unlock(void) {} | |
199 | ||
d430d3d7 JB |
200 | static inline int jump_label_apply_nops(struct module *mod) |
201 | { | |
202 | return 0; | |
203 | } | |
b2029520 | 204 | |
c5905afb IM |
205 | static inline void |
206 | jump_label_rate_limit(struct static_key_deferred *key, | |
b2029520 GN |
207 | unsigned long rl) |
208 | { | |
209 | } | |
c5905afb IM |
210 | |
211 | #define STATIC_KEY_INIT_TRUE ((struct static_key) \ | |
212 | { .enabled = ATOMIC_INIT(1) }) | |
213 | #define STATIC_KEY_INIT_FALSE ((struct static_key) \ | |
214 | { .enabled = ATOMIC_INIT(0) }) | |
215 | ||
97ce2c88 | 216 | #endif /* HAVE_JUMP_LABEL */ |
d430d3d7 | 217 | |
c5905afb IM |
218 | #define STATIC_KEY_INIT STATIC_KEY_INIT_FALSE |
219 | #define jump_label_enabled static_key_enabled | |
ac99b862 | 220 | |
8eedce99 JB |
221 | static inline bool static_key_enabled(struct static_key *key) |
222 | { | |
223 | return (atomic_read(&key->enabled) > 0); | |
224 | } | |
225 | ||
97ce2c88 | 226 | #endif /* _LINUX_JUMP_LABEL_H */ |