| 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 |