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