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 void ftrace_likely_update(struct ftrace_likely_data *f, int val, 16 int expect, int is_constant); 17 #if defined(CONFIG_TRACE_BRANCH_PROFILING) \ 18 && !defined(DISABLE_BRANCH_PROFILING) && !defined(__CHECKER__) 19 #define likely_notrace(x) __builtin_expect(!!(x), 1) 20 #define unlikely_notrace(x) __builtin_expect(!!(x), 0) 21 22 #define __branch_check__(x, expect, is_constant) ({ \ 23 long ______r; \ 24 static struct ftrace_likely_data \ 25 __aligned(4) \ 26 __section("_ftrace_annotated_branch") \ 27 ______f = { \ 28 .data.func = __func__, \ 29 .data.file = __FILE__, \ 30 .data.line = __LINE__, \ 31 }; \ 32 ______r = __builtin_expect(!!(x), expect); \ 33 ftrace_likely_update(&______f, ______r, \ 34 expect, is_constant); \ 35 ______r; \ 36 }) 37 38 /* 39 * Using __builtin_constant_p(x) to ignore cases where the return 40 * value is always the same. This idea is taken from a similar patch 41 * written by Daniel Walker. 42 */ 43 # ifndef likely 44 # define likely(x) (__branch_check__(x, 1, __builtin_constant_p(x))) 45 # endif 46 # ifndef unlikely 47 # define unlikely(x) (__branch_check__(x, 0, __builtin_constant_p(x))) 48 # endif 49 50 #ifdef CONFIG_PROFILE_ALL_BRANCHES 51 /* 52 * "Define 'is'", Bill Clinton 53 * "Define 'if'", Steven Rostedt 54 */ 55 #define if(cond, ...) if ( __trace_if_var( !!(cond , ## __VA_ARGS__) ) ) 56 57 #define __trace_if_var(cond) (__builtin_constant_p(cond) ? (cond) : __trace_if_value(cond)) 58 59 #define __trace_if_value(cond) ({ \ 60 static struct ftrace_branch_data \ 61 __aligned(4) \ 62 __section("_ftrace_branch") \ 63 __if_trace = { \ 64 .func = __func__, \ 65 .file = __FILE__, \ 66 .line = __LINE__, \ 67 }; \ 68 (cond) ? \ 69 (__if_trace.miss_hit[1]++,1) : \ 70 (__if_trace.miss_hit[0]++,0); \ 71 }) 72 73 #endif /* CONFIG_PROFILE_ALL_BRANCHES */ 74 75 #else 76 # define likely(x) __builtin_expect(!!(x), 1) 77 # define unlikely(x) __builtin_expect(!!(x), 0) 78 # define likely_notrace(x) likely(x) 79 # define unlikely_notrace(x) unlikely(x) 80 #endif 81 82 /* Optimization barrier */ 83 #ifndef barrier 84 /* The "volatile" is due to gcc bugs */ 85 # define barrier() __asm__ __volatile__("": : :"memory") 86 #endif 87 88 #ifndef barrier_data 89 /* 90 * This version is i.e. to prevent dead stores elimination on @ptr 91 * where gcc and llvm may behave differently when otherwise using 92 * normal barrier(): while gcc behavior gets along with a normal 93 * barrier(), llvm needs an explicit input variable to be assumed 94 * clobbered. The issue is as follows: while the inline asm might 95 * access any memory it wants, the compiler could have fit all of 96 * @ptr into memory registers instead, and since @ptr never escaped 97 * from that, it proved that the inline asm wasn't touching any of 98 * it. This version works well with both compilers, i.e. we're telling 99 * the compiler that the inline asm absolutely may see the contents 100 * of @ptr. See also: https://llvm.org/bugs/show_bug.cgi?id=15495 101 */ 102 # define barrier_data(ptr) __asm__ __volatile__("": :"r"(ptr) :"memory") 103 #endif 104 105 /* workaround for GCC PR82365 if needed */ 106 #ifndef barrier_before_unreachable 107 # define barrier_before_unreachable() do { } while (0) 108 #endif 109 110 /* Unreachable code */ 111 #ifdef CONFIG_OBJTOOL 112 /* 113 * These macros help objtool understand GCC code flow for unreachable code. 114 * The __COUNTER__ based labels are a hack to make each instance of the macros 115 * unique, to convince GCC not to merge duplicate inline asm statements. 116 */ 117 #define __stringify_label(n) #n 118 119 #define __annotate_unreachable(c) ({ \ 120 asm volatile(__stringify_label(c) ":\n\t" \ 121 ".pushsection .discard.unreachable\n\t" \ 122 ".long " __stringify_label(c) "b - .\n\t" \ 123 ".popsection\n\t" : : "i" (c)); \ 124 }) 125 #define annotate_unreachable() __annotate_unreachable(__COUNTER__) 126 127 /* Annotate a C jump table to allow objtool to follow the code flow */ 128 #define __annotate_jump_table __section(".rodata..c_jump_table") 129 130 #else /* !CONFIG_OBJTOOL */ 131 #define annotate_unreachable() 132 #define __annotate_jump_table 133 #endif /* CONFIG_OBJTOOL */ 134 135 #ifndef unreachable 136 # define unreachable() do { \ 137 annotate_unreachable(); \ 138 __builtin_unreachable(); \ 139 } while (0) 140 #endif 141 142 /* 143 * KENTRY - kernel entry point 144 * This can be used to annotate symbols (functions or data) that are used 145 * without their linker symbol being referenced explicitly. For example, 146 * interrupt vector handlers, or functions in the kernel image that are found 147 * programatically. 148 * 149 * Not required for symbols exported with EXPORT_SYMBOL, or initcalls. Those 150 * are handled in their own way (with KEEP() in linker scripts). 151 * 152 * KENTRY can be avoided if the symbols in question are marked as KEEP() in the 153 * linker script. For example an architecture could KEEP() its entire 154 * boot/exception vector code rather than annotate each function and data. 155 */ 156 #ifndef KENTRY 157 # define KENTRY(sym) \ 158 extern typeof(sym) sym; \ 159 static const unsigned long __kentry_##sym \ 160 __used \ 161 __attribute__((__section__("___kentry+" #sym))) \ 162 = (unsigned long)&sym; 163 #endif 164 165 #ifndef RELOC_HIDE 166 # define RELOC_HIDE(ptr, off) \ 167 ({ unsigned long __ptr; \ 168 __ptr = (unsigned long) (ptr); \ 169 (typeof(ptr)) (__ptr + (off)); }) 170 #endif 171 172 #define absolute_pointer(val) RELOC_HIDE((void *)(val), 0) 173 174 #ifndef OPTIMIZER_HIDE_VAR 175 /* Make the optimizer believe the variable can be manipulated arbitrarily. */ 176 #define OPTIMIZER_HIDE_VAR(var) \ 177 __asm__ ("" : "=r" (var) : "0" (var)) 178 #endif 179 180 #define __UNIQUE_ID(prefix) __PASTE(__PASTE(__UNIQUE_ID_, prefix), __COUNTER__) 181 182 /** 183 * data_race - mark an expression as containing intentional data races 184 * 185 * This data_race() macro is useful for situations in which data races 186 * should be forgiven. One example is diagnostic code that accesses 187 * shared variables but is not a part of the core synchronization design. 188 * 189 * This macro *does not* affect normal code generation, but is a hint 190 * to tooling that data races here are to be ignored. 191 */ 192 #define data_race(expr) \ 193 ({ \ 194 __unqual_scalar_typeof(({ expr; })) __v = ({ \ 195 __kcsan_disable_current(); \ 196 expr; \ 197 }); \ 198 __kcsan_enable_current(); \ 199 __v; \ 200 }) 201 202 #endif /* __KERNEL__ */ 203 204 /* 205 * Force the compiler to emit 'sym' as a symbol, so that we can reference 206 * it from inline assembler. Necessary in case 'sym' could be inlined 207 * otherwise, or eliminated entirely due to lack of references that are 208 * visible to the compiler. 209 */ 210 #define ___ADDRESSABLE(sym, __attrs) \ 211 static void * __used __attrs \ 212 __UNIQUE_ID(__PASTE(__addressable_,sym)) = (void *)(uintptr_t)&sym; 213 #define __ADDRESSABLE(sym) \ 214 ___ADDRESSABLE(sym, __section(".discard.addressable")) 215 216 /** 217 * offset_to_ptr - convert a relative memory offset to an absolute pointer 218 * @off: the address of the 32-bit offset value 219 */ 220 static inline void *offset_to_ptr(const int *off) 221 { 222 return (void *)((unsigned long)off + *off); 223 } 224 225 #endif /* __ASSEMBLY__ */ 226 227 /* &a[0] degrades to a pointer: a different type from an array */ 228 #define __must_be_array(a) BUILD_BUG_ON_ZERO(__same_type((a), &(a)[0])) 229 230 /* 231 * This returns a constant expression while determining if an argument is 232 * a constant expression, most importantly without evaluating the argument. 233 * Glory to Martin Uecker <Martin.Uecker@med.uni-goettingen.de> 234 * 235 * Details: 236 * - sizeof() return an integer constant expression, and does not evaluate 237 * the value of its operand; it only examines the type of its operand. 238 * - The results of comparing two integer constant expressions is also 239 * an integer constant expression. 240 * - The first literal "8" isn't important. It could be any literal value. 241 * - The second literal "8" is to avoid warnings about unaligned pointers; 242 * this could otherwise just be "1". 243 * - (long)(x) is used to avoid warnings about 64-bit types on 32-bit 244 * architectures. 245 * - The C Standard defines "null pointer constant", "(void *)0", as 246 * distinct from other void pointers. 247 * - If (x) is an integer constant expression, then the "* 0l" resolves 248 * it into an integer constant expression of value 0. Since it is cast to 249 * "void *", this makes the second operand a null pointer constant. 250 * - If (x) is not an integer constant expression, then the second operand 251 * resolves to a void pointer (but not a null pointer constant: the value 252 * is not an integer constant 0). 253 * - The conditional operator's third operand, "(int *)8", is an object 254 * pointer (to type "int"). 255 * - The behavior (including the return type) of the conditional operator 256 * ("operand1 ? operand2 : operand3") depends on the kind of expressions 257 * given for the second and third operands. This is the central mechanism 258 * of the macro: 259 * - When one operand is a null pointer constant (i.e. when x is an integer 260 * constant expression) and the other is an object pointer (i.e. our 261 * third operand), the conditional operator returns the type of the 262 * object pointer operand (i.e. "int *). Here, within the sizeof(), we 263 * would then get: 264 * sizeof(*((int *)(...)) == sizeof(int) == 4 265 * - When one operand is a void pointer (i.e. when x is not an integer 266 * constant expression) and the other is an object pointer (i.e. our 267 * third operand), the conditional operator returns a "void *" type. 268 * Here, within the sizeof(), we would then get: 269 * sizeof(*((void *)(...)) == sizeof(void) == 1 270 * - The equality comparison to "sizeof(int)" therefore depends on (x): 271 * sizeof(int) == sizeof(int) (x) was a constant expression 272 * sizeof(int) != sizeof(void) (x) was not a constant expression 273 */ 274 #define __is_constexpr(x) \ 275 (sizeof(int) == sizeof(*(8 ? ((void *)((long)(x) * 0l)) : (int *)8))) 276 277 /* 278 * Whether 'type' is a signed type or an unsigned type. Supports scalar types, 279 * bool and also pointer types. 280 */ 281 #define is_signed_type(type) (((type)(-1)) < (__force type)1) 282 #define is_unsigned_type(type) (!is_signed_type(type)) 283 284 /* 285 * This is needed in functions which generate the stack canary, see 286 * arch/x86/kernel/smpboot.c::start_secondary() for an example. 287 */ 288 #define prevent_tail_call_optimization() mb() 289 290 #include <asm/rwonce.h> 291 292 #endif /* __LINUX_COMPILER_H */ 293