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 long ______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 /* workaround for GCC PR82365 if needed */ 90 #ifndef barrier_before_unreachable 91 # define barrier_before_unreachable() do { } while (0) 92 #endif 93 94 /* Unreachable code */ 95 #ifdef CONFIG_STACK_VALIDATION 96 /* 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. 100 */ 101 #define annotate_reachable() ({ \ 102 asm volatile("%c0:\n\t" \ 103 ".pushsection .discard.reachable\n\t" \ 104 ".long %c0b - .\n\t" \ 105 ".popsection\n\t" : : "i" (__COUNTER__)); \ 106 }) 107 #define annotate_unreachable() ({ \ 108 asm volatile("%c0:\n\t" \ 109 ".pushsection .discard.unreachable\n\t" \ 110 ".long %c0b - .\n\t" \ 111 ".popsection\n\t" : : "i" (__COUNTER__)); \ 112 }) 113 #define ASM_UNREACHABLE \ 114 "999:\n\t" \ 115 ".pushsection .discard.unreachable\n\t" \ 116 ".long 999b - .\n\t" \ 117 ".popsection\n\t" 118 #else 119 #define annotate_reachable() 120 #define annotate_unreachable() 121 #endif 122 123 #ifndef ASM_UNREACHABLE 124 # define ASM_UNREACHABLE 125 #endif 126 #ifndef unreachable 127 # define unreachable() do { annotate_reachable(); do { } while (1); } while (0) 128 #endif 129 130 /* 131 * KENTRY - kernel entry point 132 * This can be used to annotate symbols (functions or data) that are used 133 * without their linker symbol being referenced explicitly. For example, 134 * interrupt vector handlers, or functions in the kernel image that are found 135 * programatically. 136 * 137 * Not required for symbols exported with EXPORT_SYMBOL, or initcalls. Those 138 * are handled in their own way (with KEEP() in linker scripts). 139 * 140 * KENTRY can be avoided if the symbols in question are marked as KEEP() in the 141 * linker script. For example an architecture could KEEP() its entire 142 * boot/exception vector code rather than annotate each function and data. 143 */ 144 #ifndef KENTRY 145 # define KENTRY(sym) \ 146 extern typeof(sym) sym; \ 147 static const unsigned long __kentry_##sym \ 148 __used \ 149 __attribute__((section("___kentry" "+" #sym ), used)) \ 150 = (unsigned long)&sym; 151 #endif 152 153 #ifndef RELOC_HIDE 154 # define RELOC_HIDE(ptr, off) \ 155 ({ unsigned long __ptr; \ 156 __ptr = (unsigned long) (ptr); \ 157 (typeof(ptr)) (__ptr + (off)); }) 158 #endif 159 160 #ifndef OPTIMIZER_HIDE_VAR 161 #define OPTIMIZER_HIDE_VAR(var) barrier() 162 #endif 163 164 /* Not-quite-unique ID. */ 165 #ifndef __UNIQUE_ID 166 # define __UNIQUE_ID(prefix) __PASTE(__PASTE(__UNIQUE_ID_, prefix), __LINE__) 167 #endif 168 169 #include <uapi/linux/types.h> 170 171 #define __READ_ONCE_SIZE \ 172 ({ \ 173 switch (size) { \ 174 case 1: *(__u8 *)res = *(volatile __u8 *)p; break; \ 175 case 2: *(__u16 *)res = *(volatile __u16 *)p; break; \ 176 case 4: *(__u32 *)res = *(volatile __u32 *)p; break; \ 177 case 8: *(__u64 *)res = *(volatile __u64 *)p; break; \ 178 default: \ 179 barrier(); \ 180 __builtin_memcpy((void *)res, (const void *)p, size); \ 181 barrier(); \ 182 } \ 183 }) 184 185 static __always_inline 186 void __read_once_size(const volatile void *p, void *res, int size) 187 { 188 __READ_ONCE_SIZE; 189 } 190 191 #ifdef CONFIG_KASAN 192 /* 193 * We can't declare function 'inline' because __no_sanitize_address confilcts 194 * with inlining. Attempt to inline it may cause a build failure. 195 * https://gcc.gnu.org/bugzilla/show_bug.cgi?id=67368 196 * '__maybe_unused' allows us to avoid defined-but-not-used warnings. 197 */ 198 # define __no_kasan_or_inline __no_sanitize_address __maybe_unused 199 #else 200 # define __no_kasan_or_inline __always_inline 201 #endif 202 203 static __no_kasan_or_inline 204 void __read_once_size_nocheck(const volatile void *p, void *res, int size) 205 { 206 __READ_ONCE_SIZE; 207 } 208 209 static __always_inline void __write_once_size(volatile void *p, void *res, int size) 210 { 211 switch (size) { 212 case 1: *(volatile __u8 *)p = *(__u8 *)res; break; 213 case 2: *(volatile __u16 *)p = *(__u16 *)res; break; 214 case 4: *(volatile __u32 *)p = *(__u32 *)res; break; 215 case 8: *(volatile __u64 *)p = *(__u64 *)res; break; 216 default: 217 barrier(); 218 __builtin_memcpy((void *)p, (const void *)res, size); 219 barrier(); 220 } 221 } 222 223 /* 224 * Prevent the compiler from merging or refetching reads or writes. The 225 * compiler is also forbidden from reordering successive instances of 226 * READ_ONCE and WRITE_ONCE, but only when the compiler is aware of some 227 * particular ordering. One way to make the compiler aware of ordering is to 228 * put the two invocations of READ_ONCE or WRITE_ONCE in different C 229 * statements. 230 * 231 * These two macros will also work on aggregate data types like structs or 232 * unions. If the size of the accessed data type exceeds the word size of 233 * the machine (e.g., 32 bits or 64 bits) READ_ONCE() and WRITE_ONCE() will 234 * fall back to memcpy(). There's at least two memcpy()s: one for the 235 * __builtin_memcpy() and then one for the macro doing the copy of variable 236 * - '__u' allocated on the stack. 237 * 238 * Their two major use cases are: (1) Mediating communication between 239 * process-level code and irq/NMI handlers, all running on the same CPU, 240 * and (2) Ensuring that the compiler does not fold, spindle, or otherwise 241 * mutilate accesses that either do not require ordering or that interact 242 * with an explicit memory barrier or atomic instruction that provides the 243 * required ordering. 244 */ 245 #include <asm/barrier.h> 246 #include <linux/kasan-checks.h> 247 248 #define __READ_ONCE(x, check) \ 249 ({ \ 250 union { typeof(x) __val; char __c[1]; } __u; \ 251 if (check) \ 252 __read_once_size(&(x), __u.__c, sizeof(x)); \ 253 else \ 254 __read_once_size_nocheck(&(x), __u.__c, sizeof(x)); \ 255 smp_read_barrier_depends(); /* Enforce dependency ordering from x */ \ 256 __u.__val; \ 257 }) 258 #define READ_ONCE(x) __READ_ONCE(x, 1) 259 260 /* 261 * Use READ_ONCE_NOCHECK() instead of READ_ONCE() if you need 262 * to hide memory access from KASAN. 263 */ 264 #define READ_ONCE_NOCHECK(x) __READ_ONCE(x, 0) 265 266 static __no_kasan_or_inline 267 unsigned long read_word_at_a_time(const void *addr) 268 { 269 kasan_check_read(addr, 1); 270 return *(unsigned long *)addr; 271 } 272 273 #define WRITE_ONCE(x, val) \ 274 ({ \ 275 union { typeof(x) __val; char __c[1]; } __u = \ 276 { .__val = (__force typeof(x)) (val) }; \ 277 __write_once_size(&(x), __u.__c, sizeof(x)); \ 278 __u.__val; \ 279 }) 280 281 #endif /* __KERNEL__ */ 282 283 #endif /* __ASSEMBLY__ */ 284 285 #ifndef __optimize 286 # define __optimize(level) 287 #endif 288 289 /* Compile time object size, -1 for unknown */ 290 #ifndef __compiletime_object_size 291 # define __compiletime_object_size(obj) -1 292 #endif 293 #ifndef __compiletime_warning 294 # define __compiletime_warning(message) 295 #endif 296 #ifndef __compiletime_error 297 # define __compiletime_error(message) 298 /* 299 * Sparse complains of variable sized arrays due to the temporary variable in 300 * __compiletime_assert. Unfortunately we can't just expand it out to make 301 * sparse see a constant array size without breaking compiletime_assert on old 302 * versions of GCC (e.g. 4.2.4), so hide the array from sparse altogether. 303 */ 304 # ifndef __CHECKER__ 305 # define __compiletime_error_fallback(condition) \ 306 do { ((void)sizeof(char[1 - 2 * condition])); } while (0) 307 # endif 308 #endif 309 #ifndef __compiletime_error_fallback 310 # define __compiletime_error_fallback(condition) do { } while (0) 311 #endif 312 313 #ifdef __OPTIMIZE__ 314 # define __compiletime_assert(condition, msg, prefix, suffix) \ 315 do { \ 316 bool __cond = !(condition); \ 317 extern void prefix ## suffix(void) __compiletime_error(msg); \ 318 if (__cond) \ 319 prefix ## suffix(); \ 320 __compiletime_error_fallback(__cond); \ 321 } while (0) 322 #else 323 # define __compiletime_assert(condition, msg, prefix, suffix) do { } while (0) 324 #endif 325 326 #define _compiletime_assert(condition, msg, prefix, suffix) \ 327 __compiletime_assert(condition, msg, prefix, suffix) 328 329 /** 330 * compiletime_assert - break build and emit msg if condition is false 331 * @condition: a compile-time constant condition to check 332 * @msg: a message to emit if condition is false 333 * 334 * In tradition of POSIX assert, this macro will break the build if the 335 * supplied condition is *false*, emitting the supplied error message if the 336 * compiler has support to do so. 337 */ 338 #define compiletime_assert(condition, msg) \ 339 _compiletime_assert(condition, msg, __compiletime_assert_, __LINE__) 340 341 #define compiletime_assert_atomic_type(t) \ 342 compiletime_assert(__native_word(t), \ 343 "Need native word sized stores/loads for atomicity.") 344 345 #endif /* __LINUX_COMPILER_H */ 346