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 int ______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 /* Unreachable code */ 90 #ifdef CONFIG_STACK_VALIDATION 91 #define annotate_reachable() ({ \ 92 asm("%c0:\n\t" \ 93 ".pushsection .discard.reachable\n\t" \ 94 ".long %c0b - .\n\t" \ 95 ".popsection\n\t" : : "i" (__COUNTER__)); \ 96 }) 97 #define annotate_unreachable() ({ \ 98 asm("%c0:\n\t" \ 99 ".pushsection .discard.unreachable\n\t" \ 100 ".long %c0b - .\n\t" \ 101 ".popsection\n\t" : : "i" (__COUNTER__)); \ 102 }) 103 #define ASM_UNREACHABLE \ 104 "999:\n\t" \ 105 ".pushsection .discard.unreachable\n\t" \ 106 ".long 999b - .\n\t" \ 107 ".popsection\n\t" 108 #else 109 #define annotate_reachable() 110 #define annotate_unreachable() 111 #endif 112 113 #ifndef ASM_UNREACHABLE 114 # define ASM_UNREACHABLE 115 #endif 116 #ifndef unreachable 117 # define unreachable() do { annotate_reachable(); do { } while (1); } while (0) 118 #endif 119 120 /* 121 * KENTRY - kernel entry point 122 * This can be used to annotate symbols (functions or data) that are used 123 * without their linker symbol being referenced explicitly. For example, 124 * interrupt vector handlers, or functions in the kernel image that are found 125 * programatically. 126 * 127 * Not required for symbols exported with EXPORT_SYMBOL, or initcalls. Those 128 * are handled in their own way (with KEEP() in linker scripts). 129 * 130 * KENTRY can be avoided if the symbols in question are marked as KEEP() in the 131 * linker script. For example an architecture could KEEP() its entire 132 * boot/exception vector code rather than annotate each function and data. 133 */ 134 #ifndef KENTRY 135 # define KENTRY(sym) \ 136 extern typeof(sym) sym; \ 137 static const unsigned long __kentry_##sym \ 138 __used \ 139 __attribute__((section("___kentry" "+" #sym ), used)) \ 140 = (unsigned long)&sym; 141 #endif 142 143 #ifndef RELOC_HIDE 144 # define RELOC_HIDE(ptr, off) \ 145 ({ unsigned long __ptr; \ 146 __ptr = (unsigned long) (ptr); \ 147 (typeof(ptr)) (__ptr + (off)); }) 148 #endif 149 150 #ifndef OPTIMIZER_HIDE_VAR 151 #define OPTIMIZER_HIDE_VAR(var) barrier() 152 #endif 153 154 /* Not-quite-unique ID. */ 155 #ifndef __UNIQUE_ID 156 # define __UNIQUE_ID(prefix) __PASTE(__PASTE(__UNIQUE_ID_, prefix), __LINE__) 157 #endif 158 159 #include <uapi/linux/types.h> 160 161 #define __READ_ONCE_SIZE \ 162 ({ \ 163 switch (size) { \ 164 case 1: *(__u8 *)res = *(volatile __u8 *)p; break; \ 165 case 2: *(__u16 *)res = *(volatile __u16 *)p; break; \ 166 case 4: *(__u32 *)res = *(volatile __u32 *)p; break; \ 167 case 8: *(__u64 *)res = *(volatile __u64 *)p; break; \ 168 default: \ 169 barrier(); \ 170 __builtin_memcpy((void *)res, (const void *)p, size); \ 171 barrier(); \ 172 } \ 173 }) 174 175 static __always_inline 176 void __read_once_size(const volatile void *p, void *res, int size) 177 { 178 __READ_ONCE_SIZE; 179 } 180 181 #ifdef CONFIG_KASAN 182 /* 183 * This function is not 'inline' because __no_sanitize_address confilcts 184 * with inlining. Attempt to inline it may cause a build failure. 185 * https://gcc.gnu.org/bugzilla/show_bug.cgi?id=67368 186 * '__maybe_unused' allows us to avoid defined-but-not-used warnings. 187 */ 188 static __no_sanitize_address __maybe_unused 189 void __read_once_size_nocheck(const volatile void *p, void *res, int size) 190 { 191 __READ_ONCE_SIZE; 192 } 193 #else 194 static __always_inline 195 void __read_once_size_nocheck(const volatile void *p, void *res, int size) 196 { 197 __READ_ONCE_SIZE; 198 } 199 #endif 200 201 static __always_inline void __write_once_size(volatile void *p, void *res, int size) 202 { 203 switch (size) { 204 case 1: *(volatile __u8 *)p = *(__u8 *)res; break; 205 case 2: *(volatile __u16 *)p = *(__u16 *)res; break; 206 case 4: *(volatile __u32 *)p = *(__u32 *)res; break; 207 case 8: *(volatile __u64 *)p = *(__u64 *)res; break; 208 default: 209 barrier(); 210 __builtin_memcpy((void *)p, (const void *)res, size); 211 barrier(); 212 } 213 } 214 215 /* 216 * Prevent the compiler from merging or refetching reads or writes. The 217 * compiler is also forbidden from reordering successive instances of 218 * READ_ONCE, WRITE_ONCE and ACCESS_ONCE (see below), but only when the 219 * compiler is aware of some particular ordering. One way to make the 220 * compiler aware of ordering is to put the two invocations of READ_ONCE, 221 * WRITE_ONCE or ACCESS_ONCE() in different C statements. 222 * 223 * In contrast to ACCESS_ONCE these two macros will also work on aggregate 224 * data types like structs or unions. If the size of the accessed data 225 * type exceeds the word size of the machine (e.g., 32 bits or 64 bits) 226 * READ_ONCE() and WRITE_ONCE() will fall back to memcpy(). There's at 227 * least two memcpy()s: one for the __builtin_memcpy() and then one for 228 * the macro doing the copy of variable - '__u' allocated on the stack. 229 * 230 * Their two major use cases are: (1) Mediating communication between 231 * process-level code and irq/NMI handlers, all running on the same CPU, 232 * and (2) Ensuring that the compiler does not fold, spindle, or otherwise 233 * mutilate accesses that either do not require ordering or that interact 234 * with an explicit memory barrier or atomic instruction that provides the 235 * required ordering. 236 */ 237 #include <asm/barrier.h> 238 239 #define __READ_ONCE(x, check) \ 240 ({ \ 241 union { typeof(x) __val; char __c[1]; } __u; \ 242 if (check) \ 243 __read_once_size(&(x), __u.__c, sizeof(x)); \ 244 else \ 245 __read_once_size_nocheck(&(x), __u.__c, sizeof(x)); \ 246 smp_read_barrier_depends(); /* Enforce dependency ordering from x */ \ 247 __u.__val; \ 248 }) 249 #define READ_ONCE(x) __READ_ONCE(x, 1) 250 251 /* 252 * Use READ_ONCE_NOCHECK() instead of READ_ONCE() if you need 253 * to hide memory access from KASAN. 254 */ 255 #define READ_ONCE_NOCHECK(x) __READ_ONCE(x, 0) 256 257 #define WRITE_ONCE(x, val) \ 258 ({ \ 259 union { typeof(x) __val; char __c[1]; } __u = \ 260 { .__val = (__force typeof(x)) (val) }; \ 261 __write_once_size(&(x), __u.__c, sizeof(x)); \ 262 __u.__val; \ 263 }) 264 265 #endif /* __KERNEL__ */ 266 267 #endif /* __ASSEMBLY__ */ 268 269 /* Compile time object size, -1 for unknown */ 270 #ifndef __compiletime_object_size 271 # define __compiletime_object_size(obj) -1 272 #endif 273 #ifndef __compiletime_warning 274 # define __compiletime_warning(message) 275 #endif 276 #ifndef __compiletime_error 277 # define __compiletime_error(message) 278 /* 279 * Sparse complains of variable sized arrays due to the temporary variable in 280 * __compiletime_assert. Unfortunately we can't just expand it out to make 281 * sparse see a constant array size without breaking compiletime_assert on old 282 * versions of GCC (e.g. 4.2.4), so hide the array from sparse altogether. 283 */ 284 # ifndef __CHECKER__ 285 # define __compiletime_error_fallback(condition) \ 286 do { ((void)sizeof(char[1 - 2 * condition])); } while (0) 287 # endif 288 #endif 289 #ifndef __compiletime_error_fallback 290 # define __compiletime_error_fallback(condition) do { } while (0) 291 #endif 292 293 #ifdef __OPTIMIZE__ 294 # define __compiletime_assert(condition, msg, prefix, suffix) \ 295 do { \ 296 bool __cond = !(condition); \ 297 extern void prefix ## suffix(void) __compiletime_error(msg); \ 298 if (__cond) \ 299 prefix ## suffix(); \ 300 __compiletime_error_fallback(__cond); \ 301 } while (0) 302 #else 303 # define __compiletime_assert(condition, msg, prefix, suffix) do { } while (0) 304 #endif 305 306 #define _compiletime_assert(condition, msg, prefix, suffix) \ 307 __compiletime_assert(condition, msg, prefix, suffix) 308 309 /** 310 * compiletime_assert - break build and emit msg if condition is false 311 * @condition: a compile-time constant condition to check 312 * @msg: a message to emit if condition is false 313 * 314 * In tradition of POSIX assert, this macro will break the build if the 315 * supplied condition is *false*, emitting the supplied error message if the 316 * compiler has support to do so. 317 */ 318 #define compiletime_assert(condition, msg) \ 319 _compiletime_assert(condition, msg, __compiletime_assert_, __LINE__) 320 321 #define compiletime_assert_atomic_type(t) \ 322 compiletime_assert(__native_word(t), \ 323 "Need native word sized stores/loads for atomicity.") 324 325 /* 326 * Prevent the compiler from merging or refetching accesses. The compiler 327 * is also forbidden from reordering successive instances of ACCESS_ONCE(), 328 * but only when the compiler is aware of some particular ordering. One way 329 * to make the compiler aware of ordering is to put the two invocations of 330 * ACCESS_ONCE() in different C statements. 331 * 332 * ACCESS_ONCE will only work on scalar types. For union types, ACCESS_ONCE 333 * on a union member will work as long as the size of the member matches the 334 * size of the union and the size is smaller than word size. 335 * 336 * The major use cases of ACCESS_ONCE used to be (1) Mediating communication 337 * between process-level code and irq/NMI handlers, all running on the same CPU, 338 * and (2) Ensuring that the compiler does not fold, spindle, or otherwise 339 * mutilate accesses that either do not require ordering or that interact 340 * with an explicit memory barrier or atomic instruction that provides the 341 * required ordering. 342 * 343 * If possible use READ_ONCE()/WRITE_ONCE() instead. 344 */ 345 #define __ACCESS_ONCE(x) ({ \ 346 __maybe_unused typeof(x) __var = (__force typeof(x)) 0; \ 347 (volatile typeof(x) *)&(x); }) 348 #define ACCESS_ONCE(x) (*__ACCESS_ONCE(x)) 349 350 #endif /* __LINUX_COMPILER_H */ 351