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 */ 71 #if !defined(CONFIG_ARCH_SUPPORTS_OPTIMIZED_INLINING) || \ 72 !defined(CONFIG_OPTIMIZE_INLINING) || (__GNUC__ < 4) 73 #define inline inline __attribute__((always_inline)) notrace 74 #define __inline__ __inline__ __attribute__((always_inline)) notrace 75 #define __inline __inline __attribute__((always_inline)) notrace 76 #else 77 /* A lot of inline functions can cause havoc with function tracing */ 78 #define inline inline notrace 79 #define __inline__ __inline__ notrace 80 #define __inline __inline notrace 81 #endif 82 83 #define __always_inline inline __attribute__((always_inline)) 84 #define noinline __attribute__((noinline)) 85 86 #define __deprecated __attribute__((deprecated)) 87 #define __packed __attribute__((packed)) 88 #define __weak __attribute__((weak)) 89 #define __alias(symbol) __attribute__((alias(#symbol))) 90 91 /* 92 * it doesn't make sense on ARM (currently the only user of __naked) 93 * to trace naked functions because then mcount is called without 94 * stack and frame pointer being set up and there is no chance to 95 * restore the lr register to the value before mcount was called. 96 * 97 * The asm() bodies of naked functions often depend on standard calling 98 * conventions, therefore they must be noinline and noclone. 99 * 100 * GCC 4.[56] currently fail to enforce this, so we must do so ourselves. 101 * See GCC PR44290. 102 */ 103 #define __naked __attribute__((naked)) noinline __noclone notrace 104 105 #define __noreturn __attribute__((noreturn)) 106 107 /* 108 * From the GCC manual: 109 * 110 * Many functions have no effects except the return value and their 111 * return value depends only on the parameters and/or global 112 * variables. Such a function can be subject to common subexpression 113 * elimination and loop optimization just as an arithmetic operator 114 * would be. 115 * [...] 116 */ 117 #define __pure __attribute__((pure)) 118 #define __aligned(x) __attribute__((aligned(x))) 119 #define __printf(a, b) __attribute__((format(printf, a, b))) 120 #define __scanf(a, b) __attribute__((format(scanf, a, b))) 121 #define __attribute_const__ __attribute__((__const__)) 122 #define __maybe_unused __attribute__((unused)) 123 #define __always_unused __attribute__((unused)) 124 125 /* gcc version specific checks */ 126 127 #if GCC_VERSION < 30200 128 # error Sorry, your compiler is too old - please upgrade it. 129 #endif 130 131 #if GCC_VERSION < 30300 132 # define __used __attribute__((__unused__)) 133 #else 134 # define __used __attribute__((__used__)) 135 #endif 136 137 #ifdef CONFIG_GCOV_KERNEL 138 # if GCC_VERSION < 30400 139 # error "GCOV profiling support for gcc versions below 3.4 not included" 140 # endif /* __GNUC_MINOR__ */ 141 #endif /* CONFIG_GCOV_KERNEL */ 142 143 #if GCC_VERSION >= 30400 144 #define __must_check __attribute__((warn_unused_result)) 145 #endif 146 147 #if GCC_VERSION >= 40000 148 149 /* GCC 4.1.[01] miscompiles __weak */ 150 #ifdef __KERNEL__ 151 # if GCC_VERSION >= 40100 && GCC_VERSION <= 40101 152 # error Your version of gcc miscompiles the __weak directive 153 # endif 154 #endif 155 156 #define __used __attribute__((__used__)) 157 #define __compiler_offsetof(a, b) \ 158 __builtin_offsetof(a, b) 159 160 #if GCC_VERSION >= 40100 && GCC_VERSION < 40600 161 # define __compiletime_object_size(obj) __builtin_object_size(obj, 0) 162 #endif 163 164 #if GCC_VERSION >= 40300 165 /* Mark functions as cold. gcc will assume any path leading to a call 166 * to them will be unlikely. This means a lot of manual unlikely()s 167 * are unnecessary now for any paths leading to the usual suspects 168 * like BUG(), printk(), panic() etc. [but let's keep them for now for 169 * older compilers] 170 * 171 * Early snapshots of gcc 4.3 don't support this and we can't detect this 172 * in the preprocessor, but we can live with this because they're unreleased. 173 * Maketime probing would be overkill here. 174 * 175 * gcc also has a __attribute__((__hot__)) to move hot functions into 176 * a special section, but I don't see any sense in this right now in 177 * the kernel context 178 */ 179 #define __cold __attribute__((__cold__)) 180 181 #define __UNIQUE_ID(prefix) __PASTE(__PASTE(__UNIQUE_ID_, prefix), __COUNTER__) 182 183 #ifndef __CHECKER__ 184 # define __compiletime_warning(message) __attribute__((warning(message))) 185 # define __compiletime_error(message) __attribute__((error(message))) 186 #endif /* __CHECKER__ */ 187 #endif /* GCC_VERSION >= 40300 */ 188 189 #if GCC_VERSION >= 40500 190 /* 191 * Mark a position in code as unreachable. This can be used to 192 * suppress control flow warnings after asm blocks that transfer 193 * control elsewhere. 194 * 195 * Early snapshots of gcc 4.5 don't support this and we can't detect 196 * this in the preprocessor, but we can live with this because they're 197 * unreleased. Really, we need to have autoconf for the kernel. 198 */ 199 #define unreachable() __builtin_unreachable() 200 201 /* Mark a function definition as prohibited from being cloned. */ 202 #define __noclone __attribute__((__noclone__)) 203 204 #endif /* GCC_VERSION >= 40500 */ 205 206 #if GCC_VERSION >= 40600 207 /* 208 * When used with Link Time Optimization, gcc can optimize away C functions or 209 * variables which are referenced only from assembly code. __visible tells the 210 * optimizer that something else uses this function or variable, thus preventing 211 * this. 212 */ 213 #define __visible __attribute__((externally_visible)) 214 #endif 215 216 217 #if GCC_VERSION >= 40900 && !defined(__CHECKER__) 218 /* 219 * __assume_aligned(n, k): Tell the optimizer that the returned 220 * pointer can be assumed to be k modulo n. The second argument is 221 * optional (default 0), so we use a variadic macro to make the 222 * shorthand. 223 * 224 * Beware: Do not apply this to functions which may return 225 * ERR_PTRs. Also, it is probably unwise to apply it to functions 226 * returning extra information in the low bits (but in that case the 227 * compiler should see some alignment anyway, when the return value is 228 * massaged by 'flags = ptr & 3; ptr &= ~3;'). 229 */ 230 #define __assume_aligned(a, ...) __attribute__((__assume_aligned__(a, ## __VA_ARGS__))) 231 #endif 232 233 /* 234 * GCC 'asm goto' miscompiles certain code sequences: 235 * 236 * http://gcc.gnu.org/bugzilla/show_bug.cgi?id=58670 237 * 238 * Work it around via a compiler barrier quirk suggested by Jakub Jelinek. 239 * 240 * (asm goto is automatically volatile - the naming reflects this.) 241 */ 242 #define asm_volatile_goto(x...) do { asm goto(x); asm (""); } while (0) 243 244 #ifdef CONFIG_ARCH_USE_BUILTIN_BSWAP 245 #if GCC_VERSION >= 40400 246 #define __HAVE_BUILTIN_BSWAP32__ 247 #define __HAVE_BUILTIN_BSWAP64__ 248 #endif 249 #if GCC_VERSION >= 40800 || (defined(__powerpc__) && GCC_VERSION >= 40600) 250 #define __HAVE_BUILTIN_BSWAP16__ 251 #endif 252 #endif /* CONFIG_ARCH_USE_BUILTIN_BSWAP */ 253 254 #if GCC_VERSION >= 50000 255 #define KASAN_ABI_VERSION 4 256 #elif GCC_VERSION >= 40902 257 #define KASAN_ABI_VERSION 3 258 #endif 259 260 #if GCC_VERSION >= 40902 261 /* 262 * Tell the compiler that address safety instrumentation (KASAN) 263 * should not be applied to that function. 264 * Conflicts with inlining: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=67368 265 */ 266 #define __no_sanitize_address __attribute__((no_sanitize_address)) 267 #endif 268 269 #endif /* gcc version >= 40000 specific checks */ 270 271 #if !defined(__noclone) 272 #define __noclone /* not needed */ 273 #endif 274 275 #if !defined(__no_sanitize_address) 276 #define __no_sanitize_address 277 #endif 278 279 /* 280 * A trick to suppress uninitialized variable warning without generating any 281 * code 282 */ 283 #define uninitialized_var(x) x = x 284
