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 __aligned(4) \ 27 __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 __aligned(4) \ 63 __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 { \ 128 annotate_unreachable(); \ 129 __builtin_unreachable(); \ 130 } while (0) 131 #endif 132 133 /* 134 * KENTRY - kernel entry point 135 * This can be used to annotate symbols (functions or data) that are used 136 * without their linker symbol being referenced explicitly. For example, 137 * interrupt vector handlers, or functions in the kernel image that are found 138 * programatically. 139 * 140 * Not required for symbols exported with EXPORT_SYMBOL, or initcalls. Those 141 * are handled in their own way (with KEEP() in linker scripts). 142 * 143 * KENTRY can be avoided if the symbols in question are marked as KEEP() in the 144 * linker script. For example an architecture could KEEP() its entire 145 * boot/exception vector code rather than annotate each function and data. 146 */ 147 #ifndef KENTRY 148 # define KENTRY(sym) \ 149 extern typeof(sym) sym; \ 150 static const unsigned long __kentry_##sym \ 151 __used \ 152 __section("___kentry" "+" #sym ) \ 153 = (unsigned long)&sym; 154 #endif 155 156 #ifndef RELOC_HIDE 157 # define RELOC_HIDE(ptr, off) \ 158 ({ unsigned long __ptr; \ 159 __ptr = (unsigned long) (ptr); \ 160 (typeof(ptr)) (__ptr + (off)); }) 161 #endif 162 163 #ifndef OPTIMIZER_HIDE_VAR 164 #define OPTIMIZER_HIDE_VAR(var) barrier() 165 #endif 166 167 /* Not-quite-unique ID. */ 168 #ifndef __UNIQUE_ID 169 # define __UNIQUE_ID(prefix) __PASTE(__PASTE(__UNIQUE_ID_, prefix), __LINE__) 170 #endif 171 172 #include <uapi/linux/types.h> 173 174 #define __READ_ONCE_SIZE \ 175 ({ \ 176 switch (size) { \ 177 case 1: *(__u8 *)res = *(volatile __u8 *)p; break; \ 178 case 2: *(__u16 *)res = *(volatile __u16 *)p; break; \ 179 case 4: *(__u32 *)res = *(volatile __u32 *)p; break; \ 180 case 8: *(__u64 *)res = *(volatile __u64 *)p; break; \ 181 default: \ 182 barrier(); \ 183 __builtin_memcpy((void *)res, (const void *)p, size); \ 184 barrier(); \ 185 } \ 186 }) 187 188 static __always_inline 189 void __read_once_size(const volatile void *p, void *res, int size) 190 { 191 __READ_ONCE_SIZE; 192 } 193 194 #ifdef CONFIG_KASAN 195 /* 196 * We can't declare function 'inline' because __no_sanitize_address confilcts 197 * with inlining. Attempt to inline it may cause a build failure. 198 * https://gcc.gnu.org/bugzilla/show_bug.cgi?id=67368 199 * '__maybe_unused' allows us to avoid defined-but-not-used warnings. 200 */ 201 # define __no_kasan_or_inline __no_sanitize_address notrace __maybe_unused 202 #else 203 # define __no_kasan_or_inline __always_inline 204 #endif 205 206 static __no_kasan_or_inline 207 void __read_once_size_nocheck(const volatile void *p, void *res, int size) 208 { 209 __READ_ONCE_SIZE; 210 } 211 212 static __always_inline void __write_once_size(volatile void *p, void *res, int size) 213 { 214 switch (size) { 215 case 1: *(volatile __u8 *)p = *(__u8 *)res; break; 216 case 2: *(volatile __u16 *)p = *(__u16 *)res; break; 217 case 4: *(volatile __u32 *)p = *(__u32 *)res; break; 218 case 8: *(volatile __u64 *)p = *(__u64 *)res; break; 219 default: 220 barrier(); 221 __builtin_memcpy((void *)p, (const void *)res, size); 222 barrier(); 223 } 224 } 225 226 /* 227 * Prevent the compiler from merging or refetching reads or writes. The 228 * compiler is also forbidden from reordering successive instances of 229 * READ_ONCE and WRITE_ONCE, but only when the compiler is aware of some 230 * particular ordering. One way to make the compiler aware of ordering is to 231 * put the two invocations of READ_ONCE or WRITE_ONCE in different C 232 * statements. 233 * 234 * These two macros will also work on aggregate data types like structs or 235 * unions. If the size of the accessed data type exceeds the word size of 236 * the machine (e.g., 32 bits or 64 bits) READ_ONCE() and WRITE_ONCE() will 237 * fall back to memcpy(). There's at least two memcpy()s: one for the 238 * __builtin_memcpy() and then one for the macro doing the copy of variable 239 * - '__u' allocated on the stack. 240 * 241 * Their two major use cases are: (1) Mediating communication between 242 * process-level code and irq/NMI handlers, all running on the same CPU, 243 * and (2) Ensuring that the compiler does not fold, spindle, or otherwise 244 * mutilate accesses that either do not require ordering or that interact 245 * with an explicit memory barrier or atomic instruction that provides the 246 * required ordering. 247 */ 248 #include <asm/barrier.h> 249 #include <linux/kasan-checks.h> 250 251 #define __READ_ONCE(x, check) \ 252 ({ \ 253 union { typeof(x) __val; char __c[1]; } __u; \ 254 if (check) \ 255 __read_once_size(&(x), __u.__c, sizeof(x)); \ 256 else \ 257 __read_once_size_nocheck(&(x), __u.__c, sizeof(x)); \ 258 smp_read_barrier_depends(); /* Enforce dependency ordering from x */ \ 259 __u.__val; \ 260 }) 261 #define READ_ONCE(x) __READ_ONCE(x, 1) 262 263 /* 264 * Use READ_ONCE_NOCHECK() instead of READ_ONCE() if you need 265 * to hide memory access from KASAN. 266 */ 267 #define READ_ONCE_NOCHECK(x) __READ_ONCE(x, 0) 268 269 static __no_kasan_or_inline 270 unsigned long read_word_at_a_time(const void *addr) 271 { 272 kasan_check_read(addr, 1); 273 return *(unsigned long *)addr; 274 } 275 276 #define WRITE_ONCE(x, val) \ 277 ({ \ 278 union { typeof(x) __val; char __c[1]; } __u = \ 279 { .__val = (__force typeof(x)) (val) }; \ 280 __write_once_size(&(x), __u.__c, sizeof(x)); \ 281 __u.__val; \ 282 }) 283 284 #endif /* __KERNEL__ */ 285 286 /* 287 * Force the compiler to emit 'sym' as a symbol, so that we can reference 288 * it from inline assembler. Necessary in case 'sym' could be inlined 289 * otherwise, or eliminated entirely due to lack of references that are 290 * visible to the compiler. 291 */ 292 #define __ADDRESSABLE(sym) \ 293 static void * __section(".discard.addressable") __used \ 294 __PASTE(__addressable_##sym, __LINE__) = (void *)&sym; 295 296 /** 297 * offset_to_ptr - convert a relative memory offset to an absolute pointer 298 * @off: the address of the 32-bit offset value 299 */ 300 static inline void *offset_to_ptr(const int *off) 301 { 302 return (void *)((unsigned long)off + *off); 303 } 304 305 #endif /* __ASSEMBLY__ */ 306 307 /* Compile time object size, -1 for unknown */ 308 #ifndef __compiletime_object_size 309 # define __compiletime_object_size(obj) -1 310 #endif 311 #ifndef __compiletime_warning 312 # define __compiletime_warning(message) 313 #endif 314 #ifndef __compiletime_error 315 # define __compiletime_error(message) 316 #endif 317 318 #ifdef __OPTIMIZE__ 319 # define __compiletime_assert(condition, msg, prefix, suffix) \ 320 do { \ 321 extern void prefix ## suffix(void) __compiletime_error(msg); \ 322 if (!(condition)) \ 323 prefix ## suffix(); \ 324 } while (0) 325 #else 326 # define __compiletime_assert(condition, msg, prefix, suffix) do { } while (0) 327 #endif 328 329 #define _compiletime_assert(condition, msg, prefix, suffix) \ 330 __compiletime_assert(condition, msg, prefix, suffix) 331 332 /** 333 * compiletime_assert - break build and emit msg if condition is false 334 * @condition: a compile-time constant condition to check 335 * @msg: a message to emit if condition is false 336 * 337 * In tradition of POSIX assert, this macro will break the build if the 338 * supplied condition is *false*, emitting the supplied error message if the 339 * compiler has support to do so. 340 */ 341 #define compiletime_assert(condition, msg) \ 342 _compiletime_assert(condition, msg, __compiletime_assert_, __LINE__) 343 344 #define compiletime_assert_atomic_type(t) \ 345 compiletime_assert(__native_word(t), \ 346 "Need native word sized stores/loads for atomicity.") 347 348 /* &a[0] degrades to a pointer: a different type from an array */ 349 #define __must_be_array(a) BUILD_BUG_ON_ZERO(__same_type((a), &(a)[0])) 350 351 #endif /* __LINUX_COMPILER_H */ 352