1 #ifndef __LINUX_COMPILER_H 2 #error "Please don't include <linux/compiler-gcc.h> directly, include <linux/compiler.h> instead." 3 #endif 4 5 /* 6 * Common definitions for all gcc versions go here. 7 */ 8 #define GCC_VERSION (__GNUC__ * 10000 \ 9 + __GNUC_MINOR__ * 100 \ 10 + __GNUC_PATCHLEVEL__) 11 12 /* Optimization barrier */ 13 14 /* The "volatile" is due to gcc bugs */ 15 #define barrier() __asm__ __volatile__("": : :"memory") 16 /* 17 * This version is i.e. to prevent dead stores elimination on @ptr 18 * where gcc and llvm may behave differently when otherwise using 19 * normal barrier(): while gcc behavior gets along with a normal 20 * barrier(), llvm needs an explicit input variable to be assumed 21 * clobbered. The issue is as follows: while the inline asm might 22 * access any memory it wants, the compiler could have fit all of 23 * @ptr into memory registers instead, and since @ptr never escaped 24 * from that, it proved that the inline asm wasn't touching any of 25 * it. This version works well with both compilers, i.e. we're telling 26 * the compiler that the inline asm absolutely may see the contents 27 * of @ptr. See also: https://llvm.org/bugs/show_bug.cgi?id=15495 28 */ 29 #define barrier_data(ptr) __asm__ __volatile__("": :"r"(ptr) :"memory") 30 31 /* 32 * This macro obfuscates arithmetic on a variable address so that gcc 33 * shouldn't recognize the original var, and make assumptions about it. 34 * 35 * This is needed because the C standard makes it undefined to do 36 * pointer arithmetic on "objects" outside their boundaries and the 37 * gcc optimizers assume this is the case. In particular they 38 * assume such arithmetic does not wrap. 39 * 40 * A miscompilation has been observed because of this on PPC. 41 * To work around it we hide the relationship of the pointer and the object 42 * using this macro. 43 * 44 * Versions of the ppc64 compiler before 4.1 had a bug where use of 45 * RELOC_HIDE could trash r30. The bug can be worked around by changing 46 * the inline assembly constraint from =g to =r, in this particular 47 * case either is valid. 48 */ 49 #define RELOC_HIDE(ptr, off) \ 50 ({ \ 51 unsigned long __ptr; \ 52 __asm__ ("" : "=r"(__ptr) : "0"(ptr)); \ 53 (typeof(ptr)) (__ptr + (off)); \ 54 }) 55 56 /* Make the optimizer believe the variable can be manipulated arbitrarily. */ 57 #define OPTIMIZER_HIDE_VAR(var) \ 58 __asm__ ("" : "=r" (var) : "0" (var)) 59 60 #ifdef __CHECKER__ 61 #define __must_be_array(a) 0 62 #else 63 /* &a[0] degrades to a pointer: a different type from an array */ 64 #define __must_be_array(a) BUILD_BUG_ON_ZERO(__same_type((a), &(a)[0])) 65 #endif 66 67 /* 68 * Force always-inline if the user requests it so via the .config, 69 * or if gcc is too old. 70 * GCC does not warn about unused static inline functions for 71 * -Wunused-function. This turns out to avoid the need for complex #ifdef 72 * directives. Suppress the warning in clang as well by using "unused" 73 * function attribute, which is redundant but not harmful for gcc. 74 */ 75 #if !defined(CONFIG_ARCH_SUPPORTS_OPTIMIZED_INLINING) || \ 76 !defined(CONFIG_OPTIMIZE_INLINING) || (__GNUC__ < 4) 77 #define inline inline __attribute__((always_inline,unused)) notrace 78 #define __inline__ __inline__ __attribute__((always_inline,unused)) notrace 79 #define __inline __inline __attribute__((always_inline,unused)) notrace 80 #else 81 /* A lot of inline functions can cause havoc with function tracing */ 82 #define inline inline __attribute__((unused)) notrace 83 #define __inline__ __inline__ __attribute__((unused)) notrace 84 #define __inline __inline __attribute__((unused)) notrace 85 #endif 86 87 #define __always_inline inline __attribute__((always_inline)) 88 #define noinline __attribute__((noinline)) 89 90 #define __deprecated __attribute__((deprecated)) 91 #define __packed __attribute__((packed)) 92 #define __weak __attribute__((weak)) 93 #define __alias(symbol) __attribute__((alias(#symbol))) 94 95 /* 96 * it doesn't make sense on ARM (currently the only user of __naked) 97 * to trace naked functions because then mcount is called without 98 * stack and frame pointer being set up and there is no chance to 99 * restore the lr register to the value before mcount was called. 100 * 101 * The asm() bodies of naked functions often depend on standard calling 102 * conventions, therefore they must be noinline and noclone. 103 * 104 * GCC 4.[56] currently fail to enforce this, so we must do so ourselves. 105 * See GCC PR44290. 106 */ 107 #define __naked __attribute__((naked)) noinline __noclone notrace 108 109 #define __noreturn __attribute__((noreturn)) 110 111 /* 112 * From the GCC manual: 113 * 114 * Many functions have no effects except the return value and their 115 * return value depends only on the parameters and/or global 116 * variables. Such a function can be subject to common subexpression 117 * elimination and loop optimization just as an arithmetic operator 118 * would be. 119 * [...] 120 */ 121 #define __pure __attribute__((pure)) 122 #define __aligned(x) __attribute__((aligned(x))) 123 #define __aligned_largest __attribute__((aligned)) 124 #define __printf(a, b) __attribute__((format(printf, a, b))) 125 #define __scanf(a, b) __attribute__((format(scanf, a, b))) 126 #define __attribute_const__ __attribute__((__const__)) 127 #define __maybe_unused __attribute__((unused)) 128 #define __always_unused __attribute__((unused)) 129 #define __mode(x) __attribute__((mode(x))) 130 131 /* gcc version specific checks */ 132 133 #if GCC_VERSION < 30200 134 # error Sorry, your compiler is too old - please upgrade it. 135 #endif 136 137 #if GCC_VERSION < 30300 138 # define __used __attribute__((__unused__)) 139 #else 140 # define __used __attribute__((__used__)) 141 #endif 142 143 #ifdef CONFIG_GCOV_KERNEL 144 # if GCC_VERSION < 30400 145 # error "GCOV profiling support for gcc versions below 3.4 not included" 146 # endif /* __GNUC_MINOR__ */ 147 #endif /* CONFIG_GCOV_KERNEL */ 148 149 #if GCC_VERSION >= 30400 150 #define __must_check __attribute__((warn_unused_result)) 151 #define __malloc __attribute__((__malloc__)) 152 #endif 153 154 #if GCC_VERSION >= 40000 155 156 /* GCC 4.1.[01] miscompiles __weak */ 157 #ifdef __KERNEL__ 158 # if GCC_VERSION >= 40100 && GCC_VERSION <= 40101 159 # error Your version of gcc miscompiles the __weak directive 160 # endif 161 #endif 162 163 #define __used __attribute__((__used__)) 164 #define __compiler_offsetof(a, b) \ 165 __builtin_offsetof(a, b) 166 167 #if GCC_VERSION >= 40100 168 # define __compiletime_object_size(obj) __builtin_object_size(obj, 0) 169 170 #define __nostackprotector __attribute__((__optimize__("no-stack-protector"))) 171 #endif 172 173 #if GCC_VERSION >= 40300 174 /* Mark functions as cold. gcc will assume any path leading to a call 175 * to them will be unlikely. This means a lot of manual unlikely()s 176 * are unnecessary now for any paths leading to the usual suspects 177 * like BUG(), printk(), panic() etc. [but let's keep them for now for 178 * older compilers] 179 * 180 * Early snapshots of gcc 4.3 don't support this and we can't detect this 181 * in the preprocessor, but we can live with this because they're unreleased. 182 * Maketime probing would be overkill here. 183 * 184 * gcc also has a __attribute__((__hot__)) to move hot functions into 185 * a special section, but I don't see any sense in this right now in 186 * the kernel context 187 */ 188 #define __cold __attribute__((__cold__)) 189 190 #define __UNIQUE_ID(prefix) __PASTE(__PASTE(__UNIQUE_ID_, prefix), __COUNTER__) 191 192 #ifndef __CHECKER__ 193 # define __compiletime_warning(message) __attribute__((warning(message))) 194 # define __compiletime_error(message) __attribute__((error(message))) 195 #endif /* __CHECKER__ */ 196 #endif /* GCC_VERSION >= 40300 */ 197 198 #if GCC_VERSION >= 40500 199 200 #ifndef __CHECKER__ 201 #ifdef LATENT_ENTROPY_PLUGIN 202 #define __latent_entropy __attribute__((latent_entropy)) 203 #endif 204 #endif 205 206 /* 207 * Mark a position in code as unreachable. This can be used to 208 * suppress control flow warnings after asm blocks that transfer 209 * control elsewhere. 210 * 211 * Early snapshots of gcc 4.5 don't support this and we can't detect 212 * this in the preprocessor, but we can live with this because they're 213 * unreleased. Really, we need to have autoconf for the kernel. 214 */ 215 #define unreachable() \ 216 do { annotate_unreachable(); __builtin_unreachable(); } while (0) 217 218 /* Mark a function definition as prohibited from being cloned. */ 219 #define __noclone __attribute__((__noclone__, __optimize__("no-tracer"))) 220 221 #ifdef RANDSTRUCT_PLUGIN 222 #define __randomize_layout __attribute__((randomize_layout)) 223 #define __no_randomize_layout __attribute__((no_randomize_layout)) 224 #endif 225 226 #endif /* GCC_VERSION >= 40500 */ 227 228 #if GCC_VERSION >= 40600 229 230 /* 231 * When used with Link Time Optimization, gcc can optimize away C functions or 232 * variables which are referenced only from assembly code. __visible tells the 233 * optimizer that something else uses this function or variable, thus preventing 234 * this. 235 */ 236 #define __visible __attribute__((externally_visible)) 237 238 /* 239 * RANDSTRUCT_PLUGIN wants to use an anonymous struct, but it is only 240 * possible since GCC 4.6. To provide as much build testing coverage 241 * as possible, this is used for all GCC 4.6+ builds, and not just on 242 * RANDSTRUCT_PLUGIN builds. 243 */ 244 #define randomized_struct_fields_start struct { 245 #define randomized_struct_fields_end } __randomize_layout; 246 247 #endif /* GCC_VERSION >= 40600 */ 248 249 250 #if GCC_VERSION >= 40900 && !defined(__CHECKER__) 251 /* 252 * __assume_aligned(n, k): Tell the optimizer that the returned 253 * pointer can be assumed to be k modulo n. The second argument is 254 * optional (default 0), so we use a variadic macro to make the 255 * shorthand. 256 * 257 * Beware: Do not apply this to functions which may return 258 * ERR_PTRs. Also, it is probably unwise to apply it to functions 259 * returning extra information in the low bits (but in that case the 260 * compiler should see some alignment anyway, when the return value is 261 * massaged by 'flags = ptr & 3; ptr &= ~3;'). 262 */ 263 #define __assume_aligned(a, ...) __attribute__((__assume_aligned__(a, ## __VA_ARGS__))) 264 #endif 265 266 /* 267 * GCC 'asm goto' miscompiles certain code sequences: 268 * 269 * http://gcc.gnu.org/bugzilla/show_bug.cgi?id=58670 270 * 271 * Work it around via a compiler barrier quirk suggested by Jakub Jelinek. 272 * 273 * (asm goto is automatically volatile - the naming reflects this.) 274 */ 275 #define asm_volatile_goto(x...) do { asm goto(x); asm (""); } while (0) 276 277 /* 278 * sparse (__CHECKER__) pretends to be gcc, but can't do constant 279 * folding in __builtin_bswap*() (yet), so don't set these for it. 280 */ 281 #if defined(CONFIG_ARCH_USE_BUILTIN_BSWAP) && !defined(__CHECKER__) 282 #if GCC_VERSION >= 40400 283 #define __HAVE_BUILTIN_BSWAP32__ 284 #define __HAVE_BUILTIN_BSWAP64__ 285 #endif 286 #if GCC_VERSION >= 40800 287 #define __HAVE_BUILTIN_BSWAP16__ 288 #endif 289 #endif /* CONFIG_ARCH_USE_BUILTIN_BSWAP && !__CHECKER__ */ 290 291 #if GCC_VERSION >= 70000 292 #define KASAN_ABI_VERSION 5 293 #elif GCC_VERSION >= 50000 294 #define KASAN_ABI_VERSION 4 295 #elif GCC_VERSION >= 40902 296 #define KASAN_ABI_VERSION 3 297 #endif 298 299 #if GCC_VERSION >= 40902 300 /* 301 * Tell the compiler that address safety instrumentation (KASAN) 302 * should not be applied to that function. 303 * Conflicts with inlining: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=67368 304 */ 305 #define __no_sanitize_address __attribute__((no_sanitize_address)) 306 #endif 307 308 #if GCC_VERSION >= 50100 309 /* 310 * Mark structures as requiring designated initializers. 311 * https://gcc.gnu.org/onlinedocs/gcc/Designated-Inits.html 312 */ 313 #define __designated_init __attribute__((designated_init)) 314 #endif 315 316 #endif /* gcc version >= 40000 specific checks */ 317 318 #if !defined(__noclone) 319 #define __noclone /* not needed */ 320 #endif 321 322 #if !defined(__no_sanitize_address) 323 #define __no_sanitize_address 324 #endif 325 326 /* 327 * A trick to suppress uninitialized variable warning without generating any 328 * code 329 */ 330 #define uninitialized_var(x) x = x 331