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 \
26 __attribute__((__aligned__(4))) \
27 __attribute__((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, ...) __trace_if( (cond , ## __VA_ARGS__) )
57 #define __trace_if(cond) \
58 if (__builtin_constant_p(!!(cond)) ? !!(cond) : \
61 static struct ftrace_branch_data \
62 __attribute__((__aligned__(4))) \
63 __attribute__((section("_ftrace_branch"))) \
70 ______f.miss_hit[______r]++; \
73 #endif /* CONFIG_PROFILE_ALL_BRANCHES */
76 # define likely(x) __builtin_expect(!!(x), 1)
77 # define unlikely(x) __builtin_expect(!!(x), 0)
80 /* Optimization barrier */
82 # define barrier() __memory_barrier()
86 # define barrier_data(ptr) barrier()
89 /* workaround for GCC PR82365 if needed */
90 #ifndef barrier_before_unreachable
91 # define barrier_before_unreachable() do { } while (0)
94 /* Unreachable code */
95 #ifdef CONFIG_STACK_VALIDATION
97 * These macros help objtool understand GCC code flow for unreachable code.
98 * The __COUNTER__ based labels are a hack to make each instance of the macros
99 * unique, to convince GCC not to merge duplicate inline asm statements.
101 #define annotate_reachable() ({ \
102 asm volatile("ANNOTATE_REACHABLE counter=%c0" \
103 : : "i" (__COUNTER__)); \
105 #define annotate_unreachable() ({ \
106 asm volatile("ANNOTATE_UNREACHABLE counter=%c0" \
107 : : "i" (__COUNTER__)); \
110 #define annotate_reachable()
111 #define annotate_unreachable()
114 #ifndef ASM_UNREACHABLE
115 # define ASM_UNREACHABLE
118 # define unreachable() do { annotate_reachable(); do { } while (1); } while (0)
122 * KENTRY - kernel entry point
123 * This can be used to annotate symbols (functions or data) that are used
124 * without their linker symbol being referenced explicitly. For example,
125 * interrupt vector handlers, or functions in the kernel image that are found
128 * Not required for symbols exported with EXPORT_SYMBOL, or initcalls. Those
129 * are handled in their own way (with KEEP() in linker scripts).
131 * KENTRY can be avoided if the symbols in question are marked as KEEP() in the
132 * linker script. For example an architecture could KEEP() its entire
133 * boot/exception vector code rather than annotate each function and data.
136 # define KENTRY(sym) \
137 extern typeof(sym) sym; \
138 static const unsigned long __kentry_##sym \
140 __attribute__((section("___kentry" "+" #sym ), used)) \
141 = (unsigned long)&sym;
145 # define RELOC_HIDE(ptr, off) \
146 ({ unsigned long __ptr; \
147 __ptr = (unsigned long) (ptr); \
148 (typeof(ptr)) (__ptr + (off)); })
151 #ifndef OPTIMIZER_HIDE_VAR
152 #define OPTIMIZER_HIDE_VAR(var) barrier()
155 /* Not-quite-unique ID. */
157 # define __UNIQUE_ID(prefix) __PASTE(__PASTE(__UNIQUE_ID_, prefix), __LINE__)
160 #include <uapi/linux/types.h>
162 #define __READ_ONCE_SIZE \
165 case 1: *(__u8 *)res = *(volatile __u8 *)p; break; \
166 case 2: *(__u16 *)res = *(volatile __u16 *)p; break; \
167 case 4: *(__u32 *)res = *(volatile __u32 *)p; break; \
168 case 8: *(__u64 *)res = *(volatile __u64 *)p; break; \
171 __builtin_memcpy((void *)res, (const void *)p, size); \
176 static __always_inline
177 void __read_once_size(const volatile void *p, void *res, int size)
184 * We can't declare function 'inline' because __no_sanitize_address confilcts
185 * with inlining. Attempt to inline it may cause a build failure.
186 * https://gcc.gnu.org/bugzilla/show_bug.cgi?id=67368
187 * '__maybe_unused' allows us to avoid defined-but-not-used warnings.
189 # define __no_kasan_or_inline __no_sanitize_address __maybe_unused
191 # define __no_kasan_or_inline __always_inline
194 static __no_kasan_or_inline
195 void __read_once_size_nocheck(const volatile void *p, void *res, int size)
200 static __always_inline void __write_once_size(volatile void *p, void *res, int size)
203 case 1: *(volatile __u8 *)p = *(__u8 *)res; break;
204 case 2: *(volatile __u16 *)p = *(__u16 *)res; break;
205 case 4: *(volatile __u32 *)p = *(__u32 *)res; break;
206 case 8: *(volatile __u64 *)p = *(__u64 *)res; break;
209 __builtin_memcpy((void *)p, (const void *)res, size);
215 * Prevent the compiler from merging or refetching reads or writes. The
216 * compiler is also forbidden from reordering successive instances of
217 * READ_ONCE and WRITE_ONCE, but only when the compiler is aware of some
218 * particular ordering. One way to make the compiler aware of ordering is to
219 * put the two invocations of READ_ONCE or WRITE_ONCE in different C
222 * These two macros will also work on aggregate data types like structs or
223 * unions. If the size of the accessed data type exceeds the word size of
224 * the machine (e.g., 32 bits or 64 bits) READ_ONCE() and WRITE_ONCE() will
225 * fall back to memcpy(). There's at least two memcpy()s: one for the
226 * __builtin_memcpy() and then one for the macro doing the copy of variable
227 * - '__u' allocated on the stack.
229 * Their two major use cases are: (1) Mediating communication between
230 * process-level code and irq/NMI handlers, all running on the same CPU,
231 * and (2) Ensuring that the compiler does not fold, spindle, or otherwise
232 * mutilate accesses that either do not require ordering or that interact
233 * with an explicit memory barrier or atomic instruction that provides the
236 #include <asm/barrier.h>
237 #include <linux/kasan-checks.h>
239 #define __READ_ONCE(x, check) \
241 union { typeof(x) __val; char __c[1]; } __u; \
243 __read_once_size(&(x), __u.__c, sizeof(x)); \
245 __read_once_size_nocheck(&(x), __u.__c, sizeof(x)); \
246 smp_read_barrier_depends(); /* Enforce dependency ordering from x */ \
249 #define READ_ONCE(x) __READ_ONCE(x, 1)
252 * Use READ_ONCE_NOCHECK() instead of READ_ONCE() if you need
253 * to hide memory access from KASAN.
255 #define READ_ONCE_NOCHECK(x) __READ_ONCE(x, 0)
257 static __no_kasan_or_inline
258 unsigned long read_word_at_a_time(const void *addr)
260 kasan_check_read(addr, 1);
261 return *(unsigned long *)addr;
264 #define WRITE_ONCE(x, val) \
266 union { typeof(x) __val; char __c[1]; } __u = \
267 { .__val = (__force typeof(x)) (val) }; \
268 __write_once_size(&(x), __u.__c, sizeof(x)); \
272 #endif /* __KERNEL__ */
275 * Force the compiler to emit 'sym' as a symbol, so that we can reference
276 * it from inline assembler. Necessary in case 'sym' could be inlined
277 * otherwise, or eliminated entirely due to lack of references that are
278 * visible to the compiler.
280 #define __ADDRESSABLE(sym) \
281 static void * __attribute__((section(".discard.addressable"), used)) \
282 __PASTE(__addressable_##sym, __LINE__) = (void *)&sym;
285 * offset_to_ptr - convert a relative memory offset to an absolute pointer
286 * @off: the address of the 32-bit offset value
288 static inline void *offset_to_ptr(const int *off)
290 return (void *)((unsigned long)off + *off);
293 #else /* __ASSEMBLY__ */
296 #ifndef LINKER_SCRIPT
298 #ifdef CONFIG_STACK_VALIDATION
299 .macro ANNOTATE_UNREACHABLE counter:req
301 .pushsection .discard.unreachable
302 .long \counter\()b -.
306 .macro ANNOTATE_REACHABLE counter:req
308 .pushsection .discard.reachable
309 .long \counter\()b -.
313 .macro ASM_UNREACHABLE
315 .pushsection .discard.unreachable
319 #else /* CONFIG_STACK_VALIDATION */
320 .macro ANNOTATE_UNREACHABLE counter:req
323 .macro ANNOTATE_REACHABLE counter:req
326 .macro ASM_UNREACHABLE
328 #endif /* CONFIG_STACK_VALIDATION */
330 #endif /* LINKER_SCRIPT */
331 #endif /* __KERNEL__ */
332 #endif /* __ASSEMBLY__ */
335 # define __optimize(level)
338 /* Compile time object size, -1 for unknown */
339 #ifndef __compiletime_object_size
340 # define __compiletime_object_size(obj) -1
342 #ifndef __compiletime_warning
343 # define __compiletime_warning(message)
345 #ifndef __compiletime_error
346 # define __compiletime_error(message)
348 * Sparse complains of variable sized arrays due to the temporary variable in
349 * __compiletime_assert. Unfortunately we can't just expand it out to make
350 * sparse see a constant array size without breaking compiletime_assert on old
351 * versions of GCC (e.g. 4.2.4), so hide the array from sparse altogether.
354 # define __compiletime_error_fallback(condition) \
355 do { ((void)sizeof(char[1 - 2 * condition])); } while (0)
358 #ifndef __compiletime_error_fallback
359 # define __compiletime_error_fallback(condition) do { } while (0)
363 # define __compiletime_assert(condition, msg, prefix, suffix) \
365 int __cond = !(condition); \
366 extern void prefix ## suffix(void) __compiletime_error(msg); \
368 prefix ## suffix(); \
369 __compiletime_error_fallback(__cond); \
372 # define __compiletime_assert(condition, msg, prefix, suffix) do { } while (0)
375 #define _compiletime_assert(condition, msg, prefix, suffix) \
376 __compiletime_assert(condition, msg, prefix, suffix)
379 * compiletime_assert - break build and emit msg if condition is false
380 * @condition: a compile-time constant condition to check
381 * @msg: a message to emit if condition is false
383 * In tradition of POSIX assert, this macro will break the build if the
384 * supplied condition is *false*, emitting the supplied error message if the
385 * compiler has support to do so.
387 #define compiletime_assert(condition, msg) \
388 _compiletime_assert(condition, msg, __compiletime_assert_, __LINE__)
390 #define compiletime_assert_atomic_type(t) \
391 compiletime_assert(__native_word(t), \
392 "Need native word sized stores/loads for atomicity.")
394 #endif /* __LINUX_COMPILER_H */