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 /* 92 * These macros help objtool understand GCC code flow for unreachable code. 93 * The __COUNTER__ based labels are a hack to make each instance of the macros 94 * unique, to convince GCC not to merge duplicate inline asm statements. 95 */ 96 #define annotate_reachable() ({ \ 97 asm volatile("%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 volatile("%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 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 * This function is not '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 static __no_sanitize_address __maybe_unused 194 void __read_once_size_nocheck(const volatile void *p, void *res, int size) 195 { 196 __READ_ONCE_SIZE; 197 } 198 #else 199 static __always_inline 200 void __read_once_size_nocheck(const volatile void *p, void *res, int size) 201 { 202 __READ_ONCE_SIZE; 203 } 204 #endif 205 206 static __always_inline void __write_once_size(volatile void *p, void *res, int size) 207 { 208 switch (size) { 209 case 1: *(volatile __u8 *)p = *(__u8 *)res; break; 210 case 2: *(volatile __u16 *)p = *(__u16 *)res; break; 211 case 4: *(volatile __u32 *)p = *(__u32 *)res; break; 212 case 8: *(volatile __u64 *)p = *(__u64 *)res; break; 213 default: 214 barrier(); 215 __builtin_memcpy((void *)p, (const void *)res, size); 216 barrier(); 217 } 218 } 219 220 /* 221 * Prevent the compiler from merging or refetching reads or writes. The 222 * compiler is also forbidden from reordering successive instances of 223 * READ_ONCE, WRITE_ONCE and ACCESS_ONCE (see below), but only when the 224 * compiler is aware of some particular ordering. One way to make the 225 * compiler aware of ordering is to put the two invocations of READ_ONCE, 226 * WRITE_ONCE or ACCESS_ONCE() in different C statements. 227 * 228 * In contrast to ACCESS_ONCE these two macros will also work on aggregate 229 * data types like structs or unions. If the size of the accessed data 230 * type exceeds the word size of the machine (e.g., 32 bits or 64 bits) 231 * READ_ONCE() and WRITE_ONCE() will fall back to memcpy(). There's at 232 * least two memcpy()s: one for the __builtin_memcpy() and then one for 233 * the macro doing the copy of variable - '__u' allocated on the stack. 234 * 235 * Their two major use cases are: (1) Mediating communication between 236 * process-level code and irq/NMI handlers, all running on the same CPU, 237 * and (2) Ensuring that the compiler does not fold, spindle, or otherwise 238 * mutilate accesses that either do not require ordering or that interact 239 * with an explicit memory barrier or atomic instruction that provides the 240 * required ordering. 241 */ 242 #include <asm/barrier.h> 243 244 #define __READ_ONCE(x, check) \ 245 ({ \ 246 union { typeof(x) __val; char __c[1]; } __u; \ 247 if (check) \ 248 __read_once_size(&(x), __u.__c, sizeof(x)); \ 249 else \ 250 __read_once_size_nocheck(&(x), __u.__c, sizeof(x)); \ 251 smp_read_barrier_depends(); /* Enforce dependency ordering from x */ \ 252 __u.__val; \ 253 }) 254 #define READ_ONCE(x) __READ_ONCE(x, 1) 255 256 /* 257 * Use READ_ONCE_NOCHECK() instead of READ_ONCE() if you need 258 * to hide memory access from KASAN. 259 */ 260 #define READ_ONCE_NOCHECK(x) __READ_ONCE(x, 0) 261 262 #define WRITE_ONCE(x, val) \ 263 ({ \ 264 union { typeof(x) __val; char __c[1]; } __u = \ 265 { .__val = (__force typeof(x)) (val) }; \ 266 __write_once_size(&(x), __u.__c, sizeof(x)); \ 267 __u.__val; \ 268 }) 269 270 #endif /* __KERNEL__ */ 271 272 #endif /* __ASSEMBLY__ */ 273 274 /* Compile time object size, -1 for unknown */ 275 #ifndef __compiletime_object_size 276 # define __compiletime_object_size(obj) -1 277 #endif 278 #ifndef __compiletime_warning 279 # define __compiletime_warning(message) 280 #endif 281 #ifndef __compiletime_error 282 # define __compiletime_error(message) 283 /* 284 * Sparse complains of variable sized arrays due to the temporary variable in 285 * __compiletime_assert. Unfortunately we can't just expand it out to make 286 * sparse see a constant array size without breaking compiletime_assert on old 287 * versions of GCC (e.g. 4.2.4), so hide the array from sparse altogether. 288 */ 289 # ifndef __CHECKER__ 290 # define __compiletime_error_fallback(condition) \ 291 do { ((void)sizeof(char[1 - 2 * condition])); } while (0) 292 # endif 293 #endif 294 #ifndef __compiletime_error_fallback 295 # define __compiletime_error_fallback(condition) do { } while (0) 296 #endif 297 298 #ifdef __OPTIMIZE__ 299 # define __compiletime_assert(condition, msg, prefix, suffix) \ 300 do { \ 301 bool __cond = !(condition); \ 302 extern void prefix ## suffix(void) __compiletime_error(msg); \ 303 if (__cond) \ 304 prefix ## suffix(); \ 305 __compiletime_error_fallback(__cond); \ 306 } while (0) 307 #else 308 # define __compiletime_assert(condition, msg, prefix, suffix) do { } while (0) 309 #endif 310 311 #define _compiletime_assert(condition, msg, prefix, suffix) \ 312 __compiletime_assert(condition, msg, prefix, suffix) 313 314 /** 315 * compiletime_assert - break build and emit msg if condition is false 316 * @condition: a compile-time constant condition to check 317 * @msg: a message to emit if condition is false 318 * 319 * In tradition of POSIX assert, this macro will break the build if the 320 * supplied condition is *false*, emitting the supplied error message if the 321 * compiler has support to do so. 322 */ 323 #define compiletime_assert(condition, msg) \ 324 _compiletime_assert(condition, msg, __compiletime_assert_, __LINE__) 325 326 #define compiletime_assert_atomic_type(t) \ 327 compiletime_assert(__native_word(t), \ 328 "Need native word sized stores/loads for atomicity.") 329 330 /* 331 * Prevent the compiler from merging or refetching accesses. The compiler 332 * is also forbidden from reordering successive instances of ACCESS_ONCE(), 333 * but only when the compiler is aware of some particular ordering. One way 334 * to make the compiler aware of ordering is to put the two invocations of 335 * ACCESS_ONCE() in different C statements. 336 * 337 * ACCESS_ONCE will only work on scalar types. For union types, ACCESS_ONCE 338 * on a union member will work as long as the size of the member matches the 339 * size of the union and the size is smaller than word size. 340 * 341 * The major use cases of ACCESS_ONCE used to be (1) Mediating communication 342 * between process-level code and irq/NMI handlers, all running on the same CPU, 343 * and (2) Ensuring that the compiler does not fold, spindle, or otherwise 344 * mutilate accesses that either do not require ordering or that interact 345 * with an explicit memory barrier or atomic instruction that provides the 346 * required ordering. 347 * 348 * If possible use READ_ONCE()/WRITE_ONCE() instead. 349 */ 350 #define __ACCESS_ONCE(x) ({ \ 351 __maybe_unused typeof(x) __var = (__force typeof(x)) 0; \ 352 (volatile typeof(x) *)&(x); }) 353 #define ACCESS_ONCE(x) (*__ACCESS_ONCE(x)) 354 355 #endif /* __LINUX_COMPILER_H */ 356