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 #define __gcc_header(x) #x 119 #define _gcc_header(x) __gcc_header(linux/compiler-gcc##x.h) 120 #define gcc_header(x) _gcc_header(x) 121 #include gcc_header(__GNUC__) 122 123 #if !defined(__noclone) 124 #define __noclone /* not needed */ 125 #endif 126 127 /* 128 * A trick to suppress uninitialized variable warning without generating any 129 * code 130 */ 131 #define uninitialized_var(x) x = x 132 133 #define __always_inline inline __attribute__((always_inline)) 134