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_reachable(c) ({ \ 120 asm volatile(__stringify_label(c) ":\n\t" \ 121 ".pushsection .discard.reachable\n\t" \ 122 ".long " __stringify_label(c) "b - .\n\t" \ 123 ".popsection\n\t"); \ 124 }) 125 #define annotate_reachable() __annotate_reachable(__COUNTER__) 126 127 #define __annotate_unreachable(c) ({ \ 128 asm volatile(__stringify_label(c) ":\n\t" \ 129 ".pushsection .discard.unreachable\n\t" \ 130 ".long " __stringify_label(c) "b - .\n\t" \ 131 ".popsection\n\t" : : "i" (c)); \ 132 }) 133 #define annotate_unreachable() __annotate_unreachable(__COUNTER__) 134 135 /* Annotate a C jump table to allow objtool to follow the code flow */ 136 #define __annotate_jump_table __section(".rodata..c_jump_table") 137 138 #else /* !CONFIG_OBJTOOL */ 139 #define annotate_reachable() 140 #define annotate_unreachable() 141 #define __annotate_jump_table 142 #endif /* CONFIG_OBJTOOL */ 143 144 #ifndef unreachable 145 # define unreachable() do { \ 146 annotate_unreachable(); \ 147 __builtin_unreachable(); \ 148 } while (0) 149 #endif 150 151 /* 152 * KENTRY - kernel entry point 153 * This can be used to annotate symbols (functions or data) that are used 154 * without their linker symbol being referenced explicitly. For example, 155 * interrupt vector handlers, or functions in the kernel image that are found 156 * programatically. 157 * 158 * Not required for symbols exported with EXPORT_SYMBOL, or initcalls. Those 159 * are handled in their own way (with KEEP() in linker scripts). 160 * 161 * KENTRY can be avoided if the symbols in question are marked as KEEP() in the 162 * linker script. For example an architecture could KEEP() its entire 163 * boot/exception vector code rather than annotate each function and data. 164 */ 165 #ifndef KENTRY 166 # define KENTRY(sym) \ 167 extern typeof(sym) sym; \ 168 static const unsigned long __kentry_##sym \ 169 __used \ 170 __attribute__((__section__("___kentry+" #sym))) \ 171 = (unsigned long)&sym; 172 #endif 173 174 #ifndef RELOC_HIDE 175 # define RELOC_HIDE(ptr, off) \ 176 ({ unsigned long __ptr; \ 177 __ptr = (unsigned long) (ptr); \ 178 (typeof(ptr)) (__ptr + (off)); }) 179 #endif 180 181 #define absolute_pointer(val) RELOC_HIDE((void *)(val), 0) 182 183 #ifndef OPTIMIZER_HIDE_VAR 184 /* Make the optimizer believe the variable can be manipulated arbitrarily. */ 185 #define OPTIMIZER_HIDE_VAR(var) \ 186 __asm__ ("" : "=r" (var) : "0" (var)) 187 #endif 188 189 #define __UNIQUE_ID(prefix) __PASTE(__PASTE(__UNIQUE_ID_, prefix), __COUNTER__) 190 191 /** 192 * data_race - mark an expression as containing intentional data races 193 * 194 * This data_race() macro is useful for situations in which data races 195 * should be forgiven. One example is diagnostic code that accesses 196 * shared variables but is not a part of the core synchronization design. 197 * For example, if accesses to a given variable are protected by a lock, 198 * except for diagnostic code, then the accesses under the lock should 199 * be plain C-language accesses and those in the diagnostic code should 200 * use data_race(). This way, KCSAN will complain if buggy lockless 201 * accesses to that variable are introduced, even if the buggy accesses 202 * are protected by READ_ONCE() or WRITE_ONCE(). 203 * 204 * This macro *does not* affect normal code generation, but is a hint 205 * to tooling that data races here are to be ignored. If the access must 206 * be atomic *and* KCSAN should ignore the access, use both data_race() 207 * and READ_ONCE(), for example, data_race(READ_ONCE(x)). 208 */ 209 #define data_race(expr) \ 210 ({ \ 211 __kcsan_disable_current(); \ 212 __auto_type __v = (expr); \ 213 __kcsan_enable_current(); \ 214 __v; \ 215 }) 216 217 #endif /* __KERNEL__ */ 218 219 /* 220 * Force the compiler to emit 'sym' as a symbol, so that we can reference 221 * it from inline assembler. Necessary in case 'sym' could be inlined 222 * otherwise, or eliminated entirely due to lack of references that are 223 * visible to the compiler. 224 */ 225 #define ___ADDRESSABLE(sym, __attrs) \ 226 static void * __used __attrs \ 227 __UNIQUE_ID(__PASTE(__addressable_,sym)) = (void *)(uintptr_t)&sym; 228 #define __ADDRESSABLE(sym) \ 229 ___ADDRESSABLE(sym, __section(".discard.addressable")) 230 231 /** 232 * offset_to_ptr - convert a relative memory offset to an absolute pointer 233 * @off: the address of the 32-bit offset value 234 */ 235 static inline void *offset_to_ptr(const int *off) 236 { 237 return (void *)((unsigned long)off + *off); 238 } 239 240 #endif /* __ASSEMBLY__ */ 241 242 /* &a[0] degrades to a pointer: a different type from an array */ 243 #define __must_be_array(a) BUILD_BUG_ON_ZERO(__same_type((a), &(a)[0])) 244 245 /* 246 * This returns a constant expression while determining if an argument is 247 * a constant expression, most importantly without evaluating the argument. 248 * Glory to Martin Uecker <Martin.Uecker@med.uni-goettingen.de> 249 * 250 * Details: 251 * - sizeof() return an integer constant expression, and does not evaluate 252 * the value of its operand; it only examines the type of its operand. 253 * - The results of comparing two integer constant expressions is also 254 * an integer constant expression. 255 * - The first literal "8" isn't important. It could be any literal value. 256 * - The second literal "8" is to avoid warnings about unaligned pointers; 257 * this could otherwise just be "1". 258 * - (long)(x) is used to avoid warnings about 64-bit types on 32-bit 259 * architectures. 260 * - The C Standard defines "null pointer constant", "(void *)0", as 261 * distinct from other void pointers. 262 * - If (x) is an integer constant expression, then the "* 0l" resolves 263 * it into an integer constant expression of value 0. Since it is cast to 264 * "void *", this makes the second operand a null pointer constant. 265 * - If (x) is not an integer constant expression, then the second operand 266 * resolves to a void pointer (but not a null pointer constant: the value 267 * is not an integer constant 0). 268 * - The conditional operator's third operand, "(int *)8", is an object 269 * pointer (to type "int"). 270 * - The behavior (including the return type) of the conditional operator 271 * ("operand1 ? operand2 : operand3") depends on the kind of expressions 272 * given for the second and third operands. This is the central mechanism 273 * of the macro: 274 * - When one operand is a null pointer constant (i.e. when x is an integer 275 * constant expression) and the other is an object pointer (i.e. our 276 * third operand), the conditional operator returns the type of the 277 * object pointer operand (i.e. "int *"). Here, within the sizeof(), we 278 * would then get: 279 * sizeof(*((int *)(...)) == sizeof(int) == 4 280 * - When one operand is a void pointer (i.e. when x is not an integer 281 * constant expression) and the other is an object pointer (i.e. our 282 * third operand), the conditional operator returns a "void *" type. 283 * Here, within the sizeof(), we would then get: 284 * sizeof(*((void *)(...)) == sizeof(void) == 1 285 * - The equality comparison to "sizeof(int)" therefore depends on (x): 286 * sizeof(int) == sizeof(int) (x) was a constant expression 287 * sizeof(int) != sizeof(void) (x) was not a constant expression 288 */ 289 #define __is_constexpr(x) \ 290 (sizeof(int) == sizeof(*(8 ? ((void *)((long)(x) * 0l)) : (int *)8))) 291 292 /* 293 * Whether 'type' is a signed type or an unsigned type. Supports scalar types, 294 * bool and also pointer types. 295 */ 296 #define is_signed_type(type) (((type)(-1)) < (__force type)1) 297 #define is_unsigned_type(type) (!is_signed_type(type)) 298 299 /* 300 * Useful shorthand for "is this condition known at compile-time?" 301 * 302 * Note that the condition may involve non-constant values, 303 * but the compiler may know enough about the details of the 304 * values to determine that the condition is statically true. 305 */ 306 #define statically_true(x) (__builtin_constant_p(x) && (x)) 307 308 /* 309 * This is needed in functions which generate the stack canary, see 310 * arch/x86/kernel/smpboot.c::start_secondary() for an example. 311 */ 312 #define prevent_tail_call_optimization() mb() 313 314 #include <asm/rwonce.h> 315 316 #endif /* __LINUX_COMPILER_H */ 317