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__)
181 * Prevent the compiler from merging or refetching reads or writes. The
182 * compiler is also forbidden from reordering successive instances of
183 * READ_ONCE and WRITE_ONCE, but only when the compiler is aware of some
184 * particular ordering. One way to make the compiler aware of ordering is to
185 * put the two invocations of READ_ONCE or WRITE_ONCE in different C
188 * These two macros will also work on aggregate data types like structs or
191 * Their two major use cases are: (1) Mediating communication between
192 * process-level code and irq/NMI handlers, all running on the same CPU,
193 * and (2) Ensuring that the compiler does not fold, spindle, or otherwise
194 * mutilate accesses that either do not require ordering or that interact
195 * with an explicit memory barrier or atomic instruction that provides the
198 #include <asm/barrier.h>
199 #include <linux/kasan-checks.h>
202 * Use __READ_ONCE() instead of READ_ONCE() if you do not require any
203 * atomicity or dependency ordering guarantees. Note that this may result
206 #define __READ_ONCE(x) (*(const volatile typeof(x) *)&(x))
208 #define __READ_ONCE_SCALAR(x) \
210 typeof(x) __x = __READ_ONCE(x); \
211 smp_read_barrier_depends(); \
215 #define READ_ONCE(x) \
217 compiletime_assert_rwonce_type(x); \
218 __READ_ONCE_SCALAR(x); \
221 #define __WRITE_ONCE(x, val) \
223 *(volatile typeof(x) *)&(x) = (val); \
226 #define WRITE_ONCE(x, val) \
228 compiletime_assert_rwonce_type(x); \
229 __WRITE_ONCE(x, val); \
234 * We can't declare function 'inline' because __no_sanitize_address conflicts
235 * with inlining. Attempt to inline it may cause a build failure.
236 * https://gcc.gnu.org/bugzilla/show_bug.cgi?id=67368
237 * '__maybe_unused' allows us to avoid defined-but-not-used warnings.
239 # define __no_kasan_or_inline __no_sanitize_address notrace __maybe_unused
241 # define __no_kasan_or_inline __always_inline
244 static __no_kasan_or_inline
245 unsigned long __read_once_word_nocheck(const void *addr)
247 return __READ_ONCE(*(unsigned long *)addr);
251 * Use READ_ONCE_NOCHECK() instead of READ_ONCE() if you need to load a
252 * word from memory atomically but without telling KASAN. This is usually
253 * used by unwinding code when walking the stack of a running process.
255 #define READ_ONCE_NOCHECK(x) \
257 unsigned long __x = __read_once_word_nocheck(&(x)); \
258 smp_read_barrier_depends(); \
262 static __no_kasan_or_inline
263 unsigned long read_word_at_a_time(const void *addr)
265 kasan_check_read(addr, 1);
266 return *(unsigned long *)addr;
269 #endif /* __KERNEL__ */
272 * Force the compiler to emit 'sym' as a symbol, so that we can reference
273 * it from inline assembler. Necessary in case 'sym' could be inlined
274 * otherwise, or eliminated entirely due to lack of references that are
275 * visible to the compiler.
277 #define __ADDRESSABLE(sym) \
278 static void * __section(.discard.addressable) __used \
279 __PASTE(__addressable_##sym, __LINE__) = (void *)&sym;
282 * offset_to_ptr - convert a relative memory offset to an absolute pointer
283 * @off: the address of the 32-bit offset value
285 static inline void *offset_to_ptr(const int *off)
287 return (void *)((unsigned long)off + *off);
290 #endif /* __ASSEMBLY__ */
292 /* Compile time object size, -1 for unknown */
293 #ifndef __compiletime_object_size
294 # define __compiletime_object_size(obj) -1
296 #ifndef __compiletime_warning
297 # define __compiletime_warning(message)
299 #ifndef __compiletime_error
300 # define __compiletime_error(message)
304 # define __compiletime_assert(condition, msg, prefix, suffix) \
306 extern void prefix ## suffix(void) __compiletime_error(msg); \
308 prefix ## suffix(); \
311 # define __compiletime_assert(condition, msg, prefix, suffix) do { } while (0)
314 #define _compiletime_assert(condition, msg, prefix, suffix) \
315 __compiletime_assert(condition, msg, prefix, suffix)
318 * compiletime_assert - break build and emit msg if condition is false
319 * @condition: a compile-time constant condition to check
320 * @msg: a message to emit if condition is false
322 * In tradition of POSIX assert, this macro will break the build if the
323 * supplied condition is *false*, emitting the supplied error message if the
324 * compiler has support to do so.
326 #define compiletime_assert(condition, msg) \
327 _compiletime_assert(condition, msg, __compiletime_assert_, __COUNTER__)
329 #define compiletime_assert_atomic_type(t) \
330 compiletime_assert(__native_word(t), \
331 "Need native word sized stores/loads for atomicity.")
334 * Yes, this permits 64-bit accesses on 32-bit architectures. These will
335 * actually be atomic in many cases (namely x86), but for others we rely on
336 * the access being split into 2x32-bit accesses for a 32-bit quantity (e.g.
337 * a virtual address) and a strong prevailing wind.
339 #define compiletime_assert_rwonce_type(t) \
340 compiletime_assert(__native_word(t) || sizeof(t) == sizeof(long long), \
341 "Unsupported access size for {READ,WRITE}_ONCE().")
343 /* &a[0] degrades to a pointer: a different type from an array */
344 #define __must_be_array(a) BUILD_BUG_ON_ZERO(__same_type((a), &(a)[0]))
346 #endif /* __LINUX_COMPILER_H */