1 /* SPDX-License-Identifier: GPL-2.0 */
2 #ifndef __LINUX_COMPILER_H
3 #define __LINUX_COMPILER_H
4
5 #include <linux/compiler_types.h>
6
7 #ifndef __ASSEMBLY__
8
9 #ifdef __KERNEL__
10
11 /*
12 * Note: DISABLE_BRANCH_PROFILING can be used by special lowlevel code
13 * to disable branch tracing on a per file basis.
14 */
15 #if defined(CONFIG_TRACE_BRANCH_PROFILING) \
16 && !defined(DISABLE_BRANCH_PROFILING) && !defined(__CHECKER__)
17 void ftrace_likely_update(struct ftrace_likely_data *f, int val,
18 int expect, int is_constant);
19
20 #define likely_notrace(x) __builtin_expect(!!(x), 1)
21 #define unlikely_notrace(x) __builtin_expect(!!(x), 0)
22
23 #define __branch_check__(x, expect, is_constant) ({ \
24 long ______r; \
25 static struct ftrace_likely_data \
26 __attribute__((__aligned__(4))) \
27 __attribute__((section("_ftrace_annotated_branch"))) \
28 ______f = { \
29 .data.func = __func__, \
30 .data.file = __FILE__, \
31 .data.line = __LINE__, \
32 }; \
33 ______r = __builtin_expect(!!(x), expect); \
34 ftrace_likely_update(&______f, ______r, \
35 expect, is_constant); \
36 ______r; \
37 })
38
39 /*
40 * Using __builtin_constant_p(x) to ignore cases where the return
41 * value is always the same. This idea is taken from a similar patch
42 * written by Daniel Walker.
43 */
44 # ifndef likely
45 # define likely(x) (__branch_check__(x, 1, __builtin_constant_p(x)))
46 # endif
47 # ifndef unlikely
48 # define unlikely(x) (__branch_check__(x, 0, __builtin_constant_p(x)))
49 # endif
50
51 #ifdef CONFIG_PROFILE_ALL_BRANCHES
52 /*
53 * "Define 'is'", Bill Clinton
54 * "Define 'if'", Steven Rostedt
55 */
56 #define if(cond, ...) __trace_if( (cond , ## __VA_ARGS__) )
57 #define __trace_if(cond) \
58 if (__builtin_constant_p(!!(cond)) ? !!(cond) : \
59 ({ \
60 int ______r; \
61 static struct ftrace_branch_data \
62 __attribute__((__aligned__(4))) \
63 __attribute__((section("_ftrace_branch"))) \
64 ______f = { \
65 .func = __func__, \
66 .file = __FILE__, \
67 .line = __LINE__, \
68 }; \
69 ______r = !!(cond); \
70 ______f.miss_hit[______r]++; \
71 ______r; \
72 }))
73 #endif /* CONFIG_PROFILE_ALL_BRANCHES */
74
75 #else
76 # define likely(x) __builtin_expect(!!(x), 1)
77 # define unlikely(x) __builtin_expect(!!(x), 0)
78 #endif
79
80 /* Optimization barrier */
81 #ifndef barrier
82 # define barrier() __memory_barrier()
83 #endif
84
85 #ifndef barrier_data
86 # define barrier_data(ptr) barrier()
87 #endif
88
89 /* workaround for GCC PR82365 if needed */
90 #ifndef barrier_before_unreachable
91 # define barrier_before_unreachable() do { } while (0)
92 #endif
93
94 /* Unreachable code */
95 #ifdef CONFIG_STACK_VALIDATION
96 #define annotate_reachable() ({ \
97 asm("%c0:\n\t" \
98 ".pushsection .discard.reachable\n\t" \
99 ".long %c0b - .\n\t" \
100 ".popsection\n\t" : : "i" (__COUNTER__)); \
101 })
102 #define annotate_unreachable() ({ \
103 asm("%c0:\n\t" \
104 ".pushsection .discard.unreachable\n\t" \
105 ".long %c0b - .\n\t" \
106 ".popsection\n\t" : : "i" (__COUNTER__)); \
107 })
108 #define ASM_UNREACHABLE \
109 "999:\n\t" \
110 ".pushsection .discard.unreachable\n\t" \
111 ".long 999b - .\n\t" \
112 ".popsection\n\t"
113 #else
114 #define annotate_reachable()
115 #define annotate_unreachable()
116 #endif
117
118 #ifndef ASM_UNREACHABLE
119 # define ASM_UNREACHABLE
120 #endif
121 #ifndef unreachable
122 # define unreachable() do { annotate_reachable(); do { } while (1); } while (0)
123 #endif
124
125 /*
126 * KENTRY - kernel entry point
127 * This can be used to annotate symbols (functions or data) that are used
128 * without their linker symbol being referenced explicitly. For example,
129 * interrupt vector handlers, or functions in the kernel image that are found
130 * programatically.
131 *
132 * Not required for symbols exported with EXPORT_SYMBOL, or initcalls. Those
133 * are handled in their own way (with KEEP() in linker scripts).
134 *
135 * KENTRY can be avoided if the symbols in question are marked as KEEP() in the
136 * linker script. For example an architecture could KEEP() its entire
137 * boot/exception vector code rather than annotate each function and data.
138 */
139 #ifndef KENTRY
140 # define KENTRY(sym) \
141 extern typeof(sym) sym; \
142 static const unsigned long __kentry_##sym \
143 __used \
144 __attribute__((section("___kentry" "+" #sym ), used)) \
145 = (unsigned long)&sym;
146 #endif
147
148 #ifndef RELOC_HIDE
149 # define RELOC_HIDE(ptr, off) \
150 ({ unsigned long __ptr; \
151 __ptr = (unsigned long) (ptr); \
152 (typeof(ptr)) (__ptr + (off)); })
153 #endif
154
155 #ifndef OPTIMIZER_HIDE_VAR
156 #define OPTIMIZER_HIDE_VAR(var) barrier()
157 #endif
158
159 /* Not-quite-unique ID. */
160 #ifndef __UNIQUE_ID
161 # define __UNIQUE_ID(prefix) __PASTE(__PASTE(__UNIQUE_ID_, prefix), __LINE__)
162 #endif
163
164 #include <uapi/linux/types.h>
165
166 #define __READ_ONCE_SIZE \
167 ({ \
168 switch (size) { \
169 case 1: *(__u8 *)res = *(volatile __u8 *)p; break; \
170 case 2: *(__u16 *)res = *(volatile __u16 *)p; break; \
171 case 4: *(__u32 *)res = *(volatile __u32 *)p; break; \
172 case 8: *(__u64 *)res = *(volatile __u64 *)p; break; \
173 default: \
174 barrier(); \
175 __builtin_memcpy((void *)res, (const void *)p, size); \
176 barrier(); \
177 } \
178 })
179
180 static __always_inline
__read_once_size(const volatile void * p,void * res,int size)181 void __read_once_size(const volatile void *p, void *res, int size)
182 {
183 __READ_ONCE_SIZE;
184 }
185
186 #ifdef CONFIG_KASAN
187 /*
188 * We can't declare function 'inline' because __no_sanitize_address confilcts
189 * with inlining. Attempt to inline it may cause a build failure.
190 * https://gcc.gnu.org/bugzilla/show_bug.cgi?id=67368
191 * '__maybe_unused' allows us to avoid defined-but-not-used warnings.
192 */
193 # define __no_kasan_or_inline __no_sanitize_address __maybe_unused
194 #else
195 # define __no_kasan_or_inline __always_inline
196 #endif
197
198 static __no_kasan_or_inline
__read_once_size_nocheck(const volatile void * p,void * res,int size)199 void __read_once_size_nocheck(const volatile void *p, void *res, int size)
200 {
201 __READ_ONCE_SIZE;
202 }
203
__write_once_size(volatile void * p,void * res,int size)204 static __always_inline void __write_once_size(volatile void *p, void *res, int size)
205 {
206 switch (size) {
207 case 1: *(volatile __u8 *)p = *(__u8 *)res; break;
208 case 2: *(volatile __u16 *)p = *(__u16 *)res; break;
209 case 4: *(volatile __u32 *)p = *(__u32 *)res; break;
210 case 8: *(volatile __u64 *)p = *(__u64 *)res; break;
211 default:
212 barrier();
213 __builtin_memcpy((void *)p, (const void *)res, size);
214 barrier();
215 }
216 }
217
218 /*
219 * Prevent the compiler from merging or refetching reads or writes. The
220 * compiler is also forbidden from reordering successive instances of
221 * READ_ONCE, WRITE_ONCE and ACCESS_ONCE (see below), but only when the
222 * compiler is aware of some particular ordering. One way to make the
223 * compiler aware of ordering is to put the two invocations of READ_ONCE,
224 * WRITE_ONCE or ACCESS_ONCE() in different C statements.
225 *
226 * In contrast to ACCESS_ONCE these two macros will also work on aggregate
227 * data types like structs or unions. If the size of the accessed data
228 * type exceeds the word size of the machine (e.g., 32 bits or 64 bits)
229 * READ_ONCE() and WRITE_ONCE() will fall back to memcpy(). There's at
230 * least two memcpy()s: one for the __builtin_memcpy() and then one for
231 * the macro doing the copy of variable - '__u' allocated on the stack.
232 *
233 * Their two major use cases are: (1) Mediating communication between
234 * process-level code and irq/NMI handlers, all running on the same CPU,
235 * and (2) Ensuring that the compiler does not fold, spindle, or otherwise
236 * mutilate accesses that either do not require ordering or that interact
237 * with an explicit memory barrier or atomic instruction that provides the
238 * required ordering.
239 */
240 #include <asm/barrier.h>
241 #include <linux/kasan-checks.h>
242
243 #define __READ_ONCE(x, check) \
244 ({ \
245 union { typeof(x) __val; char __c[1]; } __u; \
246 if (check) \
247 __read_once_size(&(x), __u.__c, sizeof(x)); \
248 else \
249 __read_once_size_nocheck(&(x), __u.__c, sizeof(x)); \
250 smp_read_barrier_depends(); /* Enforce dependency ordering from x */ \
251 __u.__val; \
252 })
253 #define READ_ONCE(x) __READ_ONCE(x, 1)
254
255 /*
256 * Use READ_ONCE_NOCHECK() instead of READ_ONCE() if you need
257 * to hide memory access from KASAN.
258 */
259 #define READ_ONCE_NOCHECK(x) __READ_ONCE(x, 0)
260
261 static __no_kasan_or_inline
read_word_at_a_time(const void * addr)262 unsigned long read_word_at_a_time(const void *addr)
263 {
264 kasan_check_read(addr, 1);
265 return *(unsigned long *)addr;
266 }
267
268 #define WRITE_ONCE(x, val) \
269 ({ \
270 union { typeof(x) __val; char __c[1]; } __u = \
271 { .__val = (__force typeof(x)) (val) }; \
272 __write_once_size(&(x), __u.__c, sizeof(x)); \
273 __u.__val; \
274 })
275
276 #endif /* __KERNEL__ */
277
278 #endif /* __ASSEMBLY__ */
279
280 #ifndef __optimize
281 # define __optimize(level)
282 #endif
283
284 /* Compile time object size, -1 for unknown */
285 #ifndef __compiletime_object_size
286 # define __compiletime_object_size(obj) -1
287 #endif
288 #ifndef __compiletime_warning
289 # define __compiletime_warning(message)
290 #endif
291 #ifndef __compiletime_error
292 # define __compiletime_error(message)
293 /*
294 * Sparse complains of variable sized arrays due to the temporary variable in
295 * __compiletime_assert. Unfortunately we can't just expand it out to make
296 * sparse see a constant array size without breaking compiletime_assert on old
297 * versions of GCC (e.g. 4.2.4), so hide the array from sparse altogether.
298 */
299 # ifndef __CHECKER__
300 # define __compiletime_error_fallback(condition) \
301 do { ((void)sizeof(char[1 - 2 * condition])); } while (0)
302 # endif
303 #endif
304 #ifndef __compiletime_error_fallback
305 # define __compiletime_error_fallback(condition) do { } while (0)
306 #endif
307
308 #ifdef __OPTIMIZE__
309 # define __compiletime_assert(condition, msg, prefix, suffix) \
310 do { \
311 bool __cond = !(condition); \
312 extern void prefix ## suffix(void) __compiletime_error(msg); \
313 if (__cond) \
314 prefix ## suffix(); \
315 __compiletime_error_fallback(__cond); \
316 } while (0)
317 #else
318 # define __compiletime_assert(condition, msg, prefix, suffix) do { } while (0)
319 #endif
320
321 #define _compiletime_assert(condition, msg, prefix, suffix) \
322 __compiletime_assert(condition, msg, prefix, suffix)
323
324 /**
325 * compiletime_assert - break build and emit msg if condition is false
326 * @condition: a compile-time constant condition to check
327 * @msg: a message to emit if condition is false
328 *
329 * In tradition of POSIX assert, this macro will break the build if the
330 * supplied condition is *false*, emitting the supplied error message if the
331 * compiler has support to do so.
332 */
333 #define compiletime_assert(condition, msg) \
334 _compiletime_assert(condition, msg, __compiletime_assert_, __LINE__)
335
336 #define compiletime_assert_atomic_type(t) \
337 compiletime_assert(__native_word(t), \
338 "Need native word sized stores/loads for atomicity.")
339
340 /*
341 * Prevent the compiler from merging or refetching accesses. The compiler
342 * is also forbidden from reordering successive instances of ACCESS_ONCE(),
343 * but only when the compiler is aware of some particular ordering. One way
344 * to make the compiler aware of ordering is to put the two invocations of
345 * ACCESS_ONCE() in different C statements.
346 *
347 * ACCESS_ONCE will only work on scalar types. For union types, ACCESS_ONCE
348 * on a union member will work as long as the size of the member matches the
349 * size of the union and the size is smaller than word size.
350 *
351 * The major use cases of ACCESS_ONCE used to be (1) Mediating communication
352 * between process-level code and irq/NMI handlers, all running on the same CPU,
353 * and (2) Ensuring that the compiler does not fold, spindle, or otherwise
354 * mutilate accesses that either do not require ordering or that interact
355 * with an explicit memory barrier or atomic instruction that provides the
356 * required ordering.
357 *
358 * If possible use READ_ONCE()/WRITE_ONCE() instead.
359 */
360 #define __ACCESS_ONCE(x) ({ \
361 __maybe_unused typeof(x) __var = (__force typeof(x)) 0; \
362 (volatile typeof(x) *)&(x); })
363 #define ACCESS_ONCE(x) (*__ACCESS_ONCE(x))
364
365 /**
366 * lockless_dereference() - safely load a pointer for later dereference
367 * @p: The pointer to load
368 *
369 * Similar to rcu_dereference(), but for situations where the pointed-to
370 * object's lifetime is managed by something other than RCU. That
371 * "something other" might be reference counting or simple immortality.
372 *
373 * The seemingly unused variable ___typecheck_p validates that @p is
374 * indeed a pointer type by using a pointer to typeof(*p) as the type.
375 * Taking a pointer to typeof(*p) again is needed in case p is void *.
376 */
377 #define lockless_dereference(p) \
378 ({ \
379 typeof(p) _________p1 = READ_ONCE(p); \
380 typeof(*(p)) *___typecheck_p __maybe_unused; \
381 smp_read_barrier_depends(); /* Dependency order vs. p above. */ \
382 (_________p1); \
383 })
384
385 #endif /* __LINUX_COMPILER_H */
386