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 proofed 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 #ifdef RETPOLINE 96 #define __noretpoline __attribute__((indirect_branch("keep"))) 97 #endif 98 99 /* 100 * it doesn't make sense on ARM (currently the only user of __naked) 101 * to trace naked functions because then mcount is called without 102 * stack and frame pointer being set up and there is no chance to 103 * restore the lr register to the value before mcount was called. 104 * 105 * The asm() bodies of naked functions often depend on standard calling 106 * conventions, therefore they must be noinline and noclone. 107 * 108 * GCC 4.[56] currently fail to enforce this, so we must do so ourselves. 109 * See GCC PR44290. 110 */ 111 #define __naked __attribute__((naked)) noinline __noclone notrace 112 113 #define __noreturn __attribute__((noreturn)) 114 115 /* 116 * From the GCC manual: 117 * 118 * Many functions have no effects except the return value and their 119 * return value depends only on the parameters and/or global 120 * variables. Such a function can be subject to common subexpression 121 * elimination and loop optimization just as an arithmetic operator 122 * would be. 123 * [...] 124 */ 125 #define __pure __attribute__((pure)) 126 #define __aligned(x) __attribute__((aligned(x))) 127 #define __printf(a, b) __attribute__((format(printf, a, b))) 128 #define __scanf(a, b) __attribute__((format(scanf, a, b))) 129 #define __attribute_const__ __attribute__((__const__)) 130 #define __maybe_unused __attribute__((unused)) 131 #define __always_unused __attribute__((unused)) 132 133 /* gcc version specific checks */ 134 135 #if GCC_VERSION < 30200 136 # error Sorry, your compiler is too old - please upgrade it. 137 #endif 138 139 #if GCC_VERSION < 30300 140 # define __used __attribute__((__unused__)) 141 #else 142 # define __used __attribute__((__used__)) 143 #endif 144 145 #ifdef CONFIG_GCOV_KERNEL 146 # if GCC_VERSION < 30400 147 # error "GCOV profiling support for gcc versions below 3.4 not included" 148 # endif /* __GNUC_MINOR__ */ 149 #endif /* CONFIG_GCOV_KERNEL */ 150 151 #if GCC_VERSION >= 30400 152 #define __must_check __attribute__((warn_unused_result)) 153 #define __malloc __attribute__((__malloc__)) 154 #endif 155 156 #if GCC_VERSION >= 40000 157 158 /* GCC 4.1.[01] miscompiles __weak */ 159 #ifdef __KERNEL__ 160 # if GCC_VERSION >= 40100 && GCC_VERSION <= 40101 161 # error Your version of gcc miscompiles the __weak directive 162 # endif 163 #endif 164 165 #define __used __attribute__((__used__)) 166 #define __compiler_offsetof(a, b) \ 167 __builtin_offsetof(a, b) 168 169 #if GCC_VERSION >= 40100 170 # define __compiletime_object_size(obj) __builtin_object_size(obj, 0) 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 >= 40400 199 #define __optimize(level) __attribute__((__optimize__(level))) 200 #endif /* GCC_VERSION >= 40400 */ 201 202 #if GCC_VERSION >= 40500 203 204 #ifndef __CHECKER__ 205 #ifdef LATENT_ENTROPY_PLUGIN 206 #define __latent_entropy __attribute__((latent_entropy)) 207 #endif 208 #endif 209 210 /* 211 * Mark a position in code as unreachable. This can be used to 212 * suppress control flow warnings after asm blocks that transfer 213 * control elsewhere. 214 * 215 * Early snapshots of gcc 4.5 don't support this and we can't detect 216 * this in the preprocessor, but we can live with this because they're 217 * unreleased. Really, we need to have autoconf for the kernel. 218 */ 219 #define unreachable() __builtin_unreachable() 220 221 /* Mark a function definition as prohibited from being cloned. */ 222 #define __noclone __attribute__((__noclone__, __optimize__("no-tracer"))) 223 224 #endif /* GCC_VERSION >= 40500 */ 225 226 #if GCC_VERSION >= 40600 227 /* 228 * When used with Link Time Optimization, gcc can optimize away C functions or 229 * variables which are referenced only from assembly code. __visible tells the 230 * optimizer that something else uses this function or variable, thus preventing 231 * this. 232 */ 233 #define __visible __attribute__((externally_visible)) 234 #endif 235 236 237 #if GCC_VERSION >= 40900 && !defined(__CHECKER__) 238 /* 239 * __assume_aligned(n, k): Tell the optimizer that the returned 240 * pointer can be assumed to be k modulo n. The second argument is 241 * optional (default 0), so we use a variadic macro to make the 242 * shorthand. 243 * 244 * Beware: Do not apply this to functions which may return 245 * ERR_PTRs. Also, it is probably unwise to apply it to functions 246 * returning extra information in the low bits (but in that case the 247 * compiler should see some alignment anyway, when the return value is 248 * massaged by 'flags = ptr & 3; ptr &= ~3;'). 249 */ 250 #define __assume_aligned(a, ...) __attribute__((__assume_aligned__(a, ## __VA_ARGS__))) 251 #endif 252 253 /* 254 * GCC 'asm goto' miscompiles certain code sequences: 255 * 256 * http://gcc.gnu.org/bugzilla/show_bug.cgi?id=58670 257 * 258 * Work it around via a compiler barrier quirk suggested by Jakub Jelinek. 259 * 260 * (asm goto is automatically volatile - the naming reflects this.) 261 */ 262 #define asm_volatile_goto(x...) do { asm goto(x); asm (""); } while (0) 263 264 /* 265 * sparse (__CHECKER__) pretends to be gcc, but can't do constant 266 * folding in __builtin_bswap*() (yet), so don't set these for it. 267 */ 268 #if defined(CONFIG_ARCH_USE_BUILTIN_BSWAP) && !defined(__CHECKER__) 269 #if GCC_VERSION >= 40400 270 #define __HAVE_BUILTIN_BSWAP32__ 271 #define __HAVE_BUILTIN_BSWAP64__ 272 #endif 273 #if GCC_VERSION >= 40800 274 #define __HAVE_BUILTIN_BSWAP16__ 275 #endif 276 #endif /* CONFIG_ARCH_USE_BUILTIN_BSWAP && !__CHECKER__ */ 277 278 #if GCC_VERSION >= 70000 279 #define KASAN_ABI_VERSION 5 280 #elif GCC_VERSION >= 50000 281 #define KASAN_ABI_VERSION 4 282 #elif GCC_VERSION >= 40902 283 #define KASAN_ABI_VERSION 3 284 #endif 285 286 #if GCC_VERSION >= 40902 287 /* 288 * Tell the compiler that address safety instrumentation (KASAN) 289 * should not be applied to that function. 290 * Conflicts with inlining: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=67368 291 */ 292 #define __no_sanitize_address __attribute__((no_sanitize_address)) 293 #endif 294 295 #endif /* gcc version >= 40000 specific checks */ 296 297 #if !defined(__noclone) 298 #define __noclone /* not needed */ 299 #endif 300 301 #if !defined(__no_sanitize_address) 302 #define __no_sanitize_address 303 #endif 304 305 /* 306 * A trick to suppress uninitialized variable warning without generating any 307 * code 308 */ 309 #define uninitialized_var(x) x = x 310