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 ({ unsigned long __ptr; \ 51 __asm__ ("" : "=r"(__ptr) : "0"(ptr)); \ 52 (typeof(ptr)) (__ptr + (off)); }) 53 54 /* Make the optimizer believe the variable can be manipulated arbitrarily. */ 55 #define OPTIMIZER_HIDE_VAR(var) __asm__ ("" : "=r" (var) : "0" (var)) 56 57 #ifdef __CHECKER__ 58 #define __must_be_array(arr) 0 59 #else 60 /* &a[0] degrades to a pointer: a different type from an array */ 61 #define __must_be_array(a) BUILD_BUG_ON_ZERO(__same_type((a), &(a)[0])) 62 #endif 63 64 /* 65 * Force always-inline if the user requests it so via the .config, 66 * or if gcc is too old: 67 */ 68 #if !defined(CONFIG_ARCH_SUPPORTS_OPTIMIZED_INLINING) || \ 69 !defined(CONFIG_OPTIMIZE_INLINING) || (__GNUC__ < 4) 70 # define inline inline __attribute__((always_inline)) notrace 71 # define __inline__ __inline__ __attribute__((always_inline)) notrace 72 # define __inline __inline __attribute__((always_inline)) notrace 73 #else 74 /* A lot of inline functions can cause havoc with function tracing */ 75 # define inline inline notrace 76 # define __inline__ __inline__ notrace 77 # define __inline __inline notrace 78 #endif 79 80 #define __deprecated __attribute__((deprecated)) 81 #define __packed __attribute__((packed)) 82 #define __weak __attribute__((weak)) 83 #define __alias(symbol) __attribute__((alias(#symbol))) 84 85 /* 86 * it doesn't make sense on ARM (currently the only user of __naked) to trace 87 * naked functions because then mcount is called without stack and frame pointer 88 * being set up and there is no chance to restore the lr register to the value 89 * before mcount was called. 90 * 91 * The asm() bodies of naked functions often depend on standard calling conventions, 92 * therefore they must be noinline and noclone. GCC 4.[56] currently fail to enforce 93 * this, so we must do so ourselves. See GCC PR44290. 94 */ 95 #define __naked __attribute__((naked)) noinline __noclone notrace 96 97 #define __noreturn __attribute__((noreturn)) 98 99 /* 100 * From the GCC manual: 101 * 102 * Many functions have no effects except the return value and their 103 * return value depends only on the parameters and/or global 104 * variables. Such a function can be subject to common subexpression 105 * elimination and loop optimization just as an arithmetic operator 106 * would be. 107 * [...] 108 */ 109 #define __pure __attribute__((pure)) 110 #define __aligned(x) __attribute__((aligned(x))) 111 #define __printf(a, b) __attribute__((format(printf, a, b))) 112 #define __scanf(a, b) __attribute__((format(scanf, a, b))) 113 #define noinline __attribute__((noinline)) 114 #define __attribute_const__ __attribute__((__const__)) 115 #define __maybe_unused __attribute__((unused)) 116 #define __always_unused __attribute__((unused)) 117 118 /* gcc version specific checks */ 119 120 #if GCC_VERSION < 30200 121 # error Sorry, your compiler is too old - please upgrade it. 122 #endif 123 124 #if GCC_VERSION < 30300 125 # define __used __attribute__((__unused__)) 126 #else 127 # define __used __attribute__((__used__)) 128 #endif 129 130 #ifdef CONFIG_GCOV_KERNEL 131 # if GCC_VERSION < 30400 132 # error "GCOV profiling support for gcc versions below 3.4 not included" 133 # endif /* __GNUC_MINOR__ */ 134 #endif /* CONFIG_GCOV_KERNEL */ 135 136 #if GCC_VERSION >= 30400 137 #define __must_check __attribute__((warn_unused_result)) 138 #endif 139 140 #if GCC_VERSION >= 40000 141 142 /* GCC 4.1.[01] miscompiles __weak */ 143 #ifdef __KERNEL__ 144 # if GCC_VERSION >= 40100 && GCC_VERSION <= 40101 145 # error Your version of gcc miscompiles the __weak directive 146 # endif 147 #endif 148 149 #define __used __attribute__((__used__)) 150 #define __compiler_offsetof(a, b) \ 151 __builtin_offsetof(a, b) 152 153 #if GCC_VERSION >= 40100 && GCC_VERSION < 40600 154 # define __compiletime_object_size(obj) __builtin_object_size(obj, 0) 155 #endif 156 157 #if GCC_VERSION >= 40300 158 /* Mark functions as cold. gcc will assume any path leading to a call 159 * to them will be unlikely. This means a lot of manual unlikely()s 160 * are unnecessary now for any paths leading to the usual suspects 161 * like BUG(), printk(), panic() etc. [but let's keep them for now for 162 * older compilers] 163 * 164 * Early snapshots of gcc 4.3 don't support this and we can't detect this 165 * in the preprocessor, but we can live with this because they're unreleased. 166 * Maketime probing would be overkill here. 167 * 168 * gcc also has a __attribute__((__hot__)) to move hot functions into 169 * a special section, but I don't see any sense in this right now in 170 * the kernel context 171 */ 172 #define __cold __attribute__((__cold__)) 173 174 #define __UNIQUE_ID(prefix) __PASTE(__PASTE(__UNIQUE_ID_, prefix), __COUNTER__) 175 176 #ifndef __CHECKER__ 177 # define __compiletime_warning(message) __attribute__((warning(message))) 178 # define __compiletime_error(message) __attribute__((error(message))) 179 #endif /* __CHECKER__ */ 180 #endif /* GCC_VERSION >= 40300 */ 181 182 #if GCC_VERSION >= 40500 183 /* 184 * Mark a position in code as unreachable. This can be used to 185 * suppress control flow warnings after asm blocks that transfer 186 * control elsewhere. 187 * 188 * Early snapshots of gcc 4.5 don't support this and we can't detect 189 * this in the preprocessor, but we can live with this because they're 190 * unreleased. Really, we need to have autoconf for the kernel. 191 */ 192 #define unreachable() __builtin_unreachable() 193 194 /* Mark a function definition as prohibited from being cloned. */ 195 #define __noclone __attribute__((__noclone__, __optimize__("no-tracer"))) 196 197 #endif /* GCC_VERSION >= 40500 */ 198 199 #if GCC_VERSION >= 40600 200 /* 201 * Tell the optimizer that something else uses this function or variable. 202 */ 203 #define __visible __attribute__((externally_visible)) 204 #endif 205 206 /* 207 * GCC 'asm goto' miscompiles certain code sequences: 208 * 209 * http://gcc.gnu.org/bugzilla/show_bug.cgi?id=58670 210 * 211 * Work it around via a compiler barrier quirk suggested by Jakub Jelinek. 212 * 213 * (asm goto is automatically volatile - the naming reflects this.) 214 */ 215 #define asm_volatile_goto(x...) do { asm goto(x); asm (""); } while (0) 216 217 #ifdef CONFIG_ARCH_USE_BUILTIN_BSWAP 218 #if GCC_VERSION >= 40400 219 #define __HAVE_BUILTIN_BSWAP32__ 220 #define __HAVE_BUILTIN_BSWAP64__ 221 #endif 222 #if GCC_VERSION >= 40800 || (defined(__powerpc__) && GCC_VERSION >= 40600) 223 #define __HAVE_BUILTIN_BSWAP16__ 224 #endif 225 #endif /* CONFIG_ARCH_USE_BUILTIN_BSWAP */ 226 227 #if GCC_VERSION >= 50000 228 #define KASAN_ABI_VERSION 4 229 #elif GCC_VERSION >= 40902 230 #define KASAN_ABI_VERSION 3 231 #endif 232 233 #endif /* gcc version >= 40000 specific checks */ 234 235 #if !defined(__noclone) 236 #define __noclone /* not needed */ 237 #endif 238 239 /* 240 * A trick to suppress uninitialized variable warning without generating any 241 * code 242 */ 243 #define uninitialized_var(x) x = x 244 245 #define __always_inline inline __attribute__((always_inline)) 246