1 /* SPDX-License-Identifier: GPL-2.0 */
2 #ifndef __LINUX_COMPILER_H
3 #define __LINUX_COMPILER_H
5 #include <linux/compiler_types.h>
12 * Note: DISABLE_BRANCH_PROFILING can be used by special lowlevel code
13 * to disable branch tracing on a per file basis.
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);
20 #define likely_notrace(x) __builtin_expect(!!(x), 1)
21 #define unlikely_notrace(x) __builtin_expect(!!(x), 0)
23 #define __branch_check__(x, expect, is_constant) ({ \
25 static struct ftrace_likely_data \
27 __section(_ftrace_annotated_branch) \
29 .data.func = __func__, \
30 .data.file = __FILE__, \
31 .data.line = __LINE__, \
33 ______r = __builtin_expect(!!(x), expect); \
34 ftrace_likely_update(&______f, ______r, \
35 expect, is_constant); \
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.
45 # define likely(x) (__branch_check__(x, 1, __builtin_constant_p(x)))
48 # define unlikely(x) (__branch_check__(x, 0, __builtin_constant_p(x)))
51 #ifdef CONFIG_PROFILE_ALL_BRANCHES
53 * "Define 'is'", Bill Clinton
54 * "Define 'if'", Steven Rostedt
56 #define if(cond, ...) if ( __trace_if_var( !!(cond , ## __VA_ARGS__) ) )
58 #define __trace_if_var(cond) (__builtin_constant_p(cond) ? (cond) : __trace_if_value(cond))
60 #define __trace_if_value(cond) ({ \
61 static struct ftrace_branch_data \
63 __section(_ftrace_branch) \
70 (__if_trace.miss_hit[1]++,1) : \
71 (__if_trace.miss_hit[0]++,0); \
74 #endif /* CONFIG_PROFILE_ALL_BRANCHES */
77 # define likely(x) __builtin_expect(!!(x), 1)
78 # define unlikely(x) __builtin_expect(!!(x), 0)
81 /* Optimization barrier */
83 # define barrier() __memory_barrier()
87 # define barrier_data(ptr) barrier()
90 /* workaround for GCC PR82365 if needed */
91 #ifndef barrier_before_unreachable
92 # define barrier_before_unreachable() do { } while (0)
95 /* Unreachable code */
96 #ifdef CONFIG_STACK_VALIDATION
98 * These macros help objtool understand GCC code flow for unreachable code.
99 * The __COUNTER__ based labels are a hack to make each instance of the macros
100 * unique, to convince GCC not to merge duplicate inline asm statements.
102 #define annotate_reachable() ({ \
103 asm volatile("%c0:\n\t" \
104 ".pushsection .discard.reachable\n\t" \
105 ".long %c0b - .\n\t" \
106 ".popsection\n\t" : : "i" (__COUNTER__)); \
108 #define annotate_unreachable() ({ \
109 asm volatile("%c0:\n\t" \
110 ".pushsection .discard.unreachable\n\t" \
111 ".long %c0b - .\n\t" \
112 ".popsection\n\t" : : "i" (__COUNTER__)); \
114 #define ASM_UNREACHABLE \
116 ".pushsection .discard.unreachable\n\t" \
117 ".long 999b - .\n\t" \
120 /* Annotate a C jump table to allow objtool to follow the code flow */
121 #define __annotate_jump_table __section(.rodata..c_jump_table)
124 #define annotate_reachable()
125 #define annotate_unreachable()
126 #define __annotate_jump_table
129 #ifndef ASM_UNREACHABLE
130 # define ASM_UNREACHABLE
133 # define unreachable() do { \
134 annotate_unreachable(); \
135 __builtin_unreachable(); \
140 * KENTRY - kernel entry point
141 * This can be used to annotate symbols (functions or data) that are used
142 * without their linker symbol being referenced explicitly. For example,
143 * interrupt vector handlers, or functions in the kernel image that are found
146 * Not required for symbols exported with EXPORT_SYMBOL, or initcalls. Those
147 * are handled in their own way (with KEEP() in linker scripts).
149 * KENTRY can be avoided if the symbols in question are marked as KEEP() in the
150 * linker script. For example an architecture could KEEP() its entire
151 * boot/exception vector code rather than annotate each function and data.
154 # define KENTRY(sym) \
155 extern typeof(sym) sym; \
156 static const unsigned long __kentry_##sym \
158 __section("___kentry" "+" #sym ) \
159 = (unsigned long)&sym;
163 # define RELOC_HIDE(ptr, off) \
164 ({ unsigned long __ptr; \
165 __ptr = (unsigned long) (ptr); \
166 (typeof(ptr)) (__ptr + (off)); })
169 #ifndef OPTIMIZER_HIDE_VAR
170 /* Make the optimizer believe the variable can be manipulated arbitrarily. */
171 #define OPTIMIZER_HIDE_VAR(var) \
172 __asm__ ("" : "=r" (var) : "0" (var))
175 /* Not-quite-unique ID. */
177 # define __UNIQUE_ID(prefix) __PASTE(__PASTE(__UNIQUE_ID_, prefix), __LINE__)
180 #include <uapi/linux/types.h>
181 #include <linux/kcsan-checks.h>
183 #define __READ_ONCE_SIZE \
186 case 1: *(__u8 *)res = *(volatile __u8 *)p; break; \
187 case 2: *(__u16 *)res = *(volatile __u16 *)p; break; \
188 case 4: *(__u32 *)res = *(volatile __u32 *)p; break; \
189 case 8: *(__u64 *)res = *(volatile __u64 *)p; break; \
192 __builtin_memcpy((void *)res, (const void *)p, size); \
199 * We can't declare function 'inline' because __no_sanitize_address confilcts
200 * with inlining. Attempt to inline it may cause a build failure.
201 * https://gcc.gnu.org/bugzilla/show_bug.cgi?id=67368
202 * '__maybe_unused' allows us to avoid defined-but-not-used warnings.
204 # define __no_kasan_or_inline __no_sanitize_address notrace __maybe_unused
205 # define __no_sanitize_or_inline __no_kasan_or_inline
207 # define __no_kasan_or_inline __always_inline
210 #define __no_kcsan __no_sanitize_thread
211 #ifdef __SANITIZE_THREAD__
213 * Rely on __SANITIZE_THREAD__ instead of CONFIG_KCSAN, to avoid not inlining in
214 * compilation units where instrumentation is disabled. The attribute 'noinline'
215 * is required for older compilers, where implicit inlining of very small
216 * functions renders __no_sanitize_thread ineffective.
218 # define __no_kcsan_or_inline __no_kcsan noinline notrace __maybe_unused
219 # define __no_sanitize_or_inline __no_kcsan_or_inline
221 # define __no_kcsan_or_inline __always_inline
224 #ifndef __no_sanitize_or_inline
225 #define __no_sanitize_or_inline __always_inline
228 static __no_kcsan_or_inline
229 void __read_once_size(const volatile void *p, void *res, int size)
231 kcsan_check_atomic_read(p, size);
235 static __no_sanitize_or_inline
236 void __read_once_size_nocheck(const volatile void *p, void *res, int size)
241 static __no_kcsan_or_inline
242 void __write_once_size(volatile void *p, void *res, int size)
244 kcsan_check_atomic_write(p, size);
247 case 1: *(volatile __u8 *)p = *(__u8 *)res; break;
248 case 2: *(volatile __u16 *)p = *(__u16 *)res; break;
249 case 4: *(volatile __u32 *)p = *(__u32 *)res; break;
250 case 8: *(volatile __u64 *)p = *(__u64 *)res; break;
253 __builtin_memcpy((void *)p, (const void *)res, size);
259 * Prevent the compiler from merging or refetching reads or writes. The
260 * compiler is also forbidden from reordering successive instances of
261 * READ_ONCE and WRITE_ONCE, but only when the compiler is aware of some
262 * particular ordering. One way to make the compiler aware of ordering is to
263 * put the two invocations of READ_ONCE or WRITE_ONCE in different C
266 * These two macros will also work on aggregate data types like structs or
267 * unions. If the size of the accessed data type exceeds the word size of
268 * the machine (e.g., 32 bits or 64 bits) READ_ONCE() and WRITE_ONCE() will
269 * fall back to memcpy(). There's at least two memcpy()s: one for the
270 * __builtin_memcpy() and then one for the macro doing the copy of variable
271 * - '__u' allocated on the stack.
273 * Their two major use cases are: (1) Mediating communication between
274 * process-level code and irq/NMI handlers, all running on the same CPU,
275 * and (2) Ensuring that the compiler does not fold, spindle, or otherwise
276 * mutilate accesses that either do not require ordering or that interact
277 * with an explicit memory barrier or atomic instruction that provides the
280 #include <asm/barrier.h>
281 #include <linux/kasan-checks.h>
283 #define __READ_ONCE(x, check) \
285 union { typeof(x) __val; char __c[1]; } __u; \
287 __read_once_size(&(x), __u.__c, sizeof(x)); \
289 __read_once_size_nocheck(&(x), __u.__c, sizeof(x)); \
290 smp_read_barrier_depends(); /* Enforce dependency ordering from x */ \
293 #define READ_ONCE(x) __READ_ONCE(x, 1)
296 * Use READ_ONCE_NOCHECK() instead of READ_ONCE() if you need
297 * to hide memory access from KASAN.
299 #define READ_ONCE_NOCHECK(x) __READ_ONCE(x, 0)
301 static __no_kasan_or_inline
302 unsigned long read_word_at_a_time(const void *addr)
304 kasan_check_read(addr, 1);
305 return *(unsigned long *)addr;
308 #define WRITE_ONCE(x, val) \
310 union { typeof(x) __val; char __c[1]; } __u = \
311 { .__val = (__force typeof(x)) (val) }; \
312 __write_once_size(&(x), __u.__c, sizeof(x)); \
317 * data_race - mark an expression as containing intentional data races
319 * This data_race() macro is useful for situations in which data races
320 * should be forgiven. One example is diagnostic code that accesses
321 * shared variables but is not a part of the core synchronization design.
323 * This macro *does not* affect normal code generation, but is a hint
324 * to tooling that data races here are to be ignored.
326 #define data_race(expr) \
328 typeof(({ expr; })) __val; \
329 kcsan_nestable_atomic_begin(); \
330 __val = ({ expr; }); \
331 kcsan_nestable_atomic_end(); \
336 #endif /* __KERNEL__ */
339 * Force the compiler to emit 'sym' as a symbol, so that we can reference
340 * it from inline assembler. Necessary in case 'sym' could be inlined
341 * otherwise, or eliminated entirely due to lack of references that are
342 * visible to the compiler.
344 #define __ADDRESSABLE(sym) \
345 static void * __section(.discard.addressable) __used \
346 __PASTE(__addressable_##sym, __LINE__) = (void *)&sym;
349 * offset_to_ptr - convert a relative memory offset to an absolute pointer
350 * @off: the address of the 32-bit offset value
352 static inline void *offset_to_ptr(const int *off)
354 return (void *)((unsigned long)off + *off);
357 #endif /* __ASSEMBLY__ */
359 /* Compile time object size, -1 for unknown */
360 #ifndef __compiletime_object_size
361 # define __compiletime_object_size(obj) -1
363 #ifndef __compiletime_warning
364 # define __compiletime_warning(message)
366 #ifndef __compiletime_error
367 # define __compiletime_error(message)
371 # define __compiletime_assert(condition, msg, prefix, suffix) \
373 extern void prefix ## suffix(void) __compiletime_error(msg); \
375 prefix ## suffix(); \
378 # define __compiletime_assert(condition, msg, prefix, suffix) do { } while (0)
381 #define _compiletime_assert(condition, msg, prefix, suffix) \
382 __compiletime_assert(condition, msg, prefix, suffix)
385 * compiletime_assert - break build and emit msg if condition is false
386 * @condition: a compile-time constant condition to check
387 * @msg: a message to emit if condition is false
389 * In tradition of POSIX assert, this macro will break the build if the
390 * supplied condition is *false*, emitting the supplied error message if the
391 * compiler has support to do so.
393 #define compiletime_assert(condition, msg) \
394 _compiletime_assert(condition, msg, __compiletime_assert_, __COUNTER__)
396 #define compiletime_assert_atomic_type(t) \
397 compiletime_assert(__native_word(t), \
398 "Need native word sized stores/loads for atomicity.")
400 /* &a[0] degrades to a pointer: a different type from an array */
401 #define __must_be_array(a) BUILD_BUG_ON_ZERO(__same_type((a), &(a)[0]))
403 #endif /* __LINUX_COMPILER_H */