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