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 13 /* Optimization barrier */ 14 /* The "volatile" is due to gcc bugs */ 15 #define barrier() __asm__ __volatile__("": : :"memory") 16 17 /* 18 * This macro obfuscates arithmetic on a variable address so that gcc 19 * shouldn't recognize the original var, and make assumptions about it. 20 * 21 * This is needed because the C standard makes it undefined to do 22 * pointer arithmetic on "objects" outside their boundaries and the 23 * gcc optimizers assume this is the case. In particular they 24 * assume such arithmetic does not wrap. 25 * 26 * A miscompilation has been observed because of this on PPC. 27 * To work around it we hide the relationship of the pointer and the object 28 * using this macro. 29 * 30 * Versions of the ppc64 compiler before 4.1 had a bug where use of 31 * RELOC_HIDE could trash r30. The bug can be worked around by changing 32 * the inline assembly constraint from =g to =r, in this particular 33 * case either is valid. 34 */ 35 #define RELOC_HIDE(ptr, off) \ 36 ({ unsigned long __ptr; \ 37 __asm__ ("" : "=r"(__ptr) : "0"(ptr)); \ 38 (typeof(ptr)) (__ptr + (off)); }) 39 40 /* Make the optimizer believe the variable can be manipulated arbitrarily. */ 41 #define OPTIMIZER_HIDE_VAR(var) __asm__ ("" : "=r" (var) : "0" (var)) 42 43 #ifdef __CHECKER__ 44 #define __must_be_array(arr) 0 45 #else 46 /* &a[0] degrades to a pointer: a different type from an array */ 47 #define __must_be_array(a) BUILD_BUG_ON_ZERO(__same_type((a), &(a)[0])) 48 #endif 49 50 /* 51 * Force always-inline if the user requests it so via the .config, 52 * or if gcc is too old: 53 */ 54 #if !defined(CONFIG_ARCH_SUPPORTS_OPTIMIZED_INLINING) || \ 55 !defined(CONFIG_OPTIMIZE_INLINING) || (__GNUC__ < 4) 56 # define inline inline __attribute__((always_inline)) notrace 57 # define __inline__ __inline__ __attribute__((always_inline)) notrace 58 # define __inline __inline __attribute__((always_inline)) notrace 59 #else 60 /* A lot of inline functions can cause havoc with function tracing */ 61 # define inline inline notrace 62 # define __inline__ __inline__ notrace 63 # define __inline __inline notrace 64 #endif 65 66 #define __deprecated __attribute__((deprecated)) 67 #define __packed __attribute__((packed)) 68 #define __weak __attribute__((weak)) 69 70 /* 71 * it doesn't make sense on ARM (currently the only user of __naked) to trace 72 * naked functions because then mcount is called without stack and frame pointer 73 * being set up and there is no chance to restore the lr register to the value 74 * before mcount was called. 75 * 76 * The asm() bodies of naked functions often depend on standard calling conventions, 77 * therefore they must be noinline and noclone. GCC 4.[56] currently fail to enforce 78 * this, so we must do so ourselves. See GCC PR44290. 79 */ 80 #define __naked __attribute__((naked)) noinline __noclone notrace 81 82 #define __noreturn __attribute__((noreturn)) 83 84 /* 85 * From the GCC manual: 86 * 87 * Many functions have no effects except the return value and their 88 * return value depends only on the parameters and/or global 89 * variables. Such a function can be subject to common subexpression 90 * elimination and loop optimization just as an arithmetic operator 91 * would be. 92 * [...] 93 */ 94 #define __pure __attribute__((pure)) 95 #define __aligned(x) __attribute__((aligned(x))) 96 #define __printf(a, b) __attribute__((format(printf, a, b))) 97 #define __scanf(a, b) __attribute__((format(scanf, a, b))) 98 #define noinline __attribute__((noinline)) 99 #define __attribute_const__ __attribute__((__const__)) 100 #define __maybe_unused __attribute__((unused)) 101 #define __always_unused __attribute__((unused)) 102 103 /* gcc version specific checks */ 104 105 #if GCC_VERSION < 30200 106 # error Sorry, your compiler is too old - please upgrade it. 107 #endif 108 109 #if GCC_VERSION < 30300 110 # define __used __attribute__((__unused__)) 111 #else 112 # define __used __attribute__((__used__)) 113 #endif 114 115 #ifdef CONFIG_GCOV_KERNEL 116 # if GCC_VERSION < 30400 117 # error "GCOV profiling support for gcc versions below 3.4 not included" 118 # endif /* __GNUC_MINOR__ */ 119 #endif /* CONFIG_GCOV_KERNEL */ 120 121 #if GCC_VERSION >= 30400 122 #define __must_check __attribute__((warn_unused_result)) 123 #endif 124 125 #if GCC_VERSION >= 40000 126 127 /* GCC 4.1.[01] miscompiles __weak */ 128 #ifdef __KERNEL__ 129 # if GCC_VERSION >= 40100 && GCC_VERSION <= 40101 130 # error Your version of gcc miscompiles the __weak directive 131 # endif 132 #endif 133 134 #define __used __attribute__((__used__)) 135 #define __compiler_offsetof(a, b) \ 136 __builtin_offsetof(a, b) 137 138 #if GCC_VERSION >= 40100 && GCC_VERSION < 40600 139 # define __compiletime_object_size(obj) __builtin_object_size(obj, 0) 140 #endif 141 142 #if GCC_VERSION >= 40300 143 /* Mark functions as cold. gcc will assume any path leading to a call 144 * to them will be unlikely. This means a lot of manual unlikely()s 145 * are unnecessary now for any paths leading to the usual suspects 146 * like BUG(), printk(), panic() etc. [but let's keep them for now for 147 * older compilers] 148 * 149 * Early snapshots of gcc 4.3 don't support this and we can't detect this 150 * in the preprocessor, but we can live with this because they're unreleased. 151 * Maketime probing would be overkill here. 152 * 153 * gcc also has a __attribute__((__hot__)) to move hot functions into 154 * a special section, but I don't see any sense in this right now in 155 * the kernel context 156 */ 157 #define __cold __attribute__((__cold__)) 158 159 #define __UNIQUE_ID(prefix) __PASTE(__PASTE(__UNIQUE_ID_, prefix), __COUNTER__) 160 161 #ifndef __CHECKER__ 162 # define __compiletime_warning(message) __attribute__((warning(message))) 163 # define __compiletime_error(message) __attribute__((error(message))) 164 #endif /* __CHECKER__ */ 165 #endif /* GCC_VERSION >= 40300 */ 166 167 #if GCC_VERSION >= 40500 168 /* 169 * Mark a position in code as unreachable. This can be used to 170 * suppress control flow warnings after asm blocks that transfer 171 * control elsewhere. 172 * 173 * Early snapshots of gcc 4.5 don't support this and we can't detect 174 * this in the preprocessor, but we can live with this because they're 175 * unreleased. Really, we need to have autoconf for the kernel. 176 */ 177 #define unreachable() __builtin_unreachable() 178 179 /* Mark a function definition as prohibited from being cloned. */ 180 #define __noclone __attribute__((__noclone__, __optimize__("no-tracer"))) 181 182 #endif /* GCC_VERSION >= 40500 */ 183 184 #if GCC_VERSION >= 40600 185 /* 186 * Tell the optimizer that something else uses this function or variable. 187 */ 188 #define __visible __attribute__((externally_visible)) 189 #endif 190 191 /* 192 * GCC 'asm goto' miscompiles certain code sequences: 193 * 194 * http://gcc.gnu.org/bugzilla/show_bug.cgi?id=58670 195 * 196 * Work it around via a compiler barrier quirk suggested by Jakub Jelinek. 197 * 198 * (asm goto is automatically volatile - the naming reflects this.) 199 */ 200 #define asm_volatile_goto(x...) do { asm goto(x); asm (""); } while (0) 201 202 #ifdef CONFIG_ARCH_USE_BUILTIN_BSWAP 203 #if GCC_VERSION >= 40400 204 #define __HAVE_BUILTIN_BSWAP32__ 205 #define __HAVE_BUILTIN_BSWAP64__ 206 #endif 207 #if GCC_VERSION >= 40800 || (defined(__powerpc__) && GCC_VERSION >= 40600) 208 #define __HAVE_BUILTIN_BSWAP16__ 209 #endif 210 #endif /* CONFIG_ARCH_USE_BUILTIN_BSWAP */ 211 212 #if GCC_VERSION >= 50000 213 #define KASAN_ABI_VERSION 4 214 #elif GCC_VERSION >= 40902 215 #define KASAN_ABI_VERSION 3 216 #endif 217 218 #endif /* gcc version >= 40000 specific checks */ 219 220 #if !defined(__noclone) 221 #define __noclone /* not needed */ 222 #endif 223 224 /* 225 * A trick to suppress uninitialized variable warning without generating any 226 * code 227 */ 228 #define uninitialized_var(x) x = x 229 230 #define __always_inline inline __attribute__((always_inline)) 231