1 /* SPDX-License-Identifier: GPL-2.0 */ 2 #ifndef __LINUX_COMPILER_H 3 #define __LINUX_COMPILER_H 4 5 #include <linux/compiler_types.h> 6 7 #ifndef __ASSEMBLY__ 8 9 #ifdef __KERNEL__ 10 11 /* 12 * Note: DISABLE_BRANCH_PROFILING can be used by special lowlevel code 13 * to disable branch tracing on a per file basis. 14 */ 15 #if defined(CONFIG_TRACE_BRANCH_PROFILING) \ 16 && !defined(DISABLE_BRANCH_PROFILING) && !defined(__CHECKER__) 17 void ftrace_likely_update(struct ftrace_likely_data *f, int val, 18 int expect, int is_constant); 19 20 #define likely_notrace(x) __builtin_expect(!!(x), 1) 21 #define unlikely_notrace(x) __builtin_expect(!!(x), 0) 22 23 #define __branch_check__(x, expect, is_constant) ({ \ 24 long ______r; \ 25 static struct ftrace_likely_data \ 26 __aligned(4) \ 27 __section("_ftrace_annotated_branch") \ 28 ______f = { \ 29 .data.func = __func__, \ 30 .data.file = __FILE__, \ 31 .data.line = __LINE__, \ 32 }; \ 33 ______r = __builtin_expect(!!(x), expect); \ 34 ftrace_likely_update(&______f, ______r, \ 35 expect, is_constant); \ 36 ______r; \ 37 }) 38 39 /* 40 * Using __builtin_constant_p(x) to ignore cases where the return 41 * value is always the same. This idea is taken from a similar patch 42 * written by Daniel Walker. 43 */ 44 # ifndef likely 45 # define likely(x) (__branch_check__(x, 1, __builtin_constant_p(x))) 46 # endif 47 # ifndef unlikely 48 # define unlikely(x) (__branch_check__(x, 0, __builtin_constant_p(x))) 49 # endif 50 51 #ifdef CONFIG_PROFILE_ALL_BRANCHES 52 /* 53 * "Define 'is'", Bill Clinton 54 * "Define 'if'", Steven Rostedt 55 */ 56 #define if(cond, ...) if ( __trace_if_var( !!(cond , ## __VA_ARGS__) ) ) 57 58 #define __trace_if_var(cond) (__builtin_constant_p(cond) ? (cond) : __trace_if_value(cond)) 59 60 #define __trace_if_value(cond) ({ \ 61 static struct ftrace_branch_data \ 62 __aligned(4) \ 63 __section("_ftrace_branch") \ 64 __if_trace = { \ 65 .func = __func__, \ 66 .file = __FILE__, \ 67 .line = __LINE__, \ 68 }; \ 69 (cond) ? \ 70 (__if_trace.miss_hit[1]++,1) : \ 71 (__if_trace.miss_hit[0]++,0); \ 72 }) 73 74 #endif /* CONFIG_PROFILE_ALL_BRANCHES */ 75 76 #else 77 # define likely(x) __builtin_expect(!!(x), 1) 78 # define unlikely(x) __builtin_expect(!!(x), 0) 79 # define likely_notrace(x) likely(x) 80 # define unlikely_notrace(x) unlikely(x) 81 #endif 82 83 /* Optimization barrier */ 84 #ifndef barrier 85 /* The "volatile" is due to gcc bugs */ 86 # define barrier() __asm__ __volatile__("": : :"memory") 87 #endif 88 89 #ifndef barrier_data 90 /* 91 * This version is i.e. to prevent dead stores elimination on @ptr 92 * where gcc and llvm may behave differently when otherwise using 93 * normal barrier(): while gcc behavior gets along with a normal 94 * barrier(), llvm needs an explicit input variable to be assumed 95 * clobbered. The issue is as follows: while the inline asm might 96 * access any memory it wants, the compiler could have fit all of 97 * @ptr into memory registers instead, and since @ptr never escaped 98 * from that, it proved that the inline asm wasn't touching any of 99 * it. This version works well with both compilers, i.e. we're telling 100 * the compiler that the inline asm absolutely may see the contents 101 * of @ptr. See also: https://llvm.org/bugs/show_bug.cgi?id=15495 102 */ 103 # define barrier_data(ptr) __asm__ __volatile__("": :"r"(ptr) :"memory") 104 #endif 105 106 /* workaround for GCC PR82365 if needed */ 107 #ifndef barrier_before_unreachable 108 # define barrier_before_unreachable() do { } while (0) 109 #endif 110 111 /* Unreachable code */ 112 #ifdef CONFIG_OBJTOOL 113 /* 114 * These macros help objtool understand GCC code flow for unreachable code. 115 * The __COUNTER__ based labels are a hack to make each instance of the macros 116 * unique, to convince GCC not to merge duplicate inline asm statements. 117 */ 118 #define __stringify_label(n) #n 119 120 #define __annotate_unreachable(c) ({ \ 121 asm volatile(__stringify_label(c) ":\n\t" \ 122 ".pushsection .discard.unreachable\n\t" \ 123 ".long " __stringify_label(c) "b - .\n\t" \ 124 ".popsection\n\t" : : "i" (c)); \ 125 }) 126 #define annotate_unreachable() __annotate_unreachable(__COUNTER__) 127 128 /* Annotate a C jump table to allow objtool to follow the code flow */ 129 #define __annotate_jump_table __section(".rodata..c_jump_table") 130 131 #else /* !CONFIG_OBJTOOL */ 132 #define annotate_unreachable() 133 #define __annotate_jump_table 134 #endif /* CONFIG_OBJTOOL */ 135 136 #ifndef unreachable 137 # define unreachable() do { \ 138 annotate_unreachable(); \ 139 __builtin_unreachable(); \ 140 } while (0) 141 #endif 142 143 /* 144 * KENTRY - kernel entry point 145 * This can be used to annotate symbols (functions or data) that are used 146 * without their linker symbol being referenced explicitly. For example, 147 * interrupt vector handlers, or functions in the kernel image that are found 148 * programatically. 149 * 150 * Not required for symbols exported with EXPORT_SYMBOL, or initcalls. Those 151 * are handled in their own way (with KEEP() in linker scripts). 152 * 153 * KENTRY can be avoided if the symbols in question are marked as KEEP() in the 154 * linker script. For example an architecture could KEEP() its entire 155 * boot/exception vector code rather than annotate each function and data. 156 */ 157 #ifndef KENTRY 158 # define KENTRY(sym) \ 159 extern typeof(sym) sym; \ 160 static const unsigned long __kentry_##sym \ 161 __used \ 162 __attribute__((__section__("___kentry+" #sym))) \ 163 = (unsigned long)&sym; 164 #endif 165 166 #ifndef RELOC_HIDE 167 # define RELOC_HIDE(ptr, off) \ 168 ({ unsigned long __ptr; \ 169 __ptr = (unsigned long) (ptr); \ 170 (typeof(ptr)) (__ptr + (off)); }) 171 #endif 172 173 #define absolute_pointer(val) RELOC_HIDE((void *)(val), 0) 174 175 #ifndef OPTIMIZER_HIDE_VAR 176 /* Make the optimizer believe the variable can be manipulated arbitrarily. */ 177 #define OPTIMIZER_HIDE_VAR(var) \ 178 __asm__ ("" : "=r" (var) : "0" (var)) 179 #endif 180 181 /* Not-quite-unique ID. */ 182 #ifndef __UNIQUE_ID 183 # define __UNIQUE_ID(prefix) __PASTE(__PASTE(__UNIQUE_ID_, prefix), __LINE__) 184 #endif 185 186 /** 187 * data_race - mark an expression as containing intentional data races 188 * 189 * This data_race() macro is useful for situations in which data races 190 * should be forgiven. One example is diagnostic code that accesses 191 * shared variables but is not a part of the core synchronization design. 192 * 193 * This macro *does not* affect normal code generation, but is a hint 194 * to tooling that data races here are to be ignored. 195 */ 196 #define data_race(expr) \ 197 ({ \ 198 __unqual_scalar_typeof(({ expr; })) __v = ({ \ 199 __kcsan_disable_current(); \ 200 expr; \ 201 }); \ 202 __kcsan_enable_current(); \ 203 __v; \ 204 }) 205 206 /* 207 * With CONFIG_CFI_CLANG, the compiler replaces function addresses in 208 * instrumented C code with jump table addresses. Architectures that 209 * support CFI can define this macro to return the actual function address 210 * when needed. 211 */ 212 #ifndef function_nocfi 213 #define function_nocfi(x) (x) 214 #endif 215 216 #endif /* __KERNEL__ */ 217 218 /* 219 * Force the compiler to emit 'sym' as a symbol, so that we can reference 220 * it from inline assembler. Necessary in case 'sym' could be inlined 221 * otherwise, or eliminated entirely due to lack of references that are 222 * visible to the compiler. 223 */ 224 #define __ADDRESSABLE(sym) \ 225 static void * __section(".discard.addressable") __used \ 226 __UNIQUE_ID(__PASTE(__addressable_,sym)) = (void *)&sym; 227 228 /** 229 * offset_to_ptr - convert a relative memory offset to an absolute pointer 230 * @off: the address of the 32-bit offset value 231 */ 232 static inline void *offset_to_ptr(const int *off) 233 { 234 return (void *)((unsigned long)off + *off); 235 } 236 237 #endif /* __ASSEMBLY__ */ 238 239 /* &a[0] degrades to a pointer: a different type from an array */ 240 #define __must_be_array(a) BUILD_BUG_ON_ZERO(__same_type((a), &(a)[0])) 241 242 /* 243 * This is needed in functions which generate the stack canary, see 244 * arch/x86/kernel/smpboot.c::start_secondary() for an example. 245 */ 246 #define prevent_tail_call_optimization() mb() 247 248 #include <asm/rwonce.h> 249 250 #endif /* __LINUX_COMPILER_H */ 251