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 /* Annotate a C jump table to allow objtool to follow the code flow */ 113 #define __annotate_jump_table __section(".rodata..c_jump_table,\"a\",@progbits #") 114 #else /* !CONFIG_OBJTOOL */ 115 #define __annotate_jump_table 116 #endif /* CONFIG_OBJTOOL */ 117 118 /* 119 * Mark a position in code as unreachable. This can be used to 120 * suppress control flow warnings after asm blocks that transfer 121 * control elsewhere. 122 */ 123 #define unreachable() do { \ 124 barrier_before_unreachable(); \ 125 __builtin_unreachable(); \ 126 } while (0) 127 128 /* 129 * KENTRY - kernel entry point 130 * This can be used to annotate symbols (functions or data) that are used 131 * without their linker symbol being referenced explicitly. For example, 132 * interrupt vector handlers, or functions in the kernel image that are found 133 * programatically. 134 * 135 * Not required for symbols exported with EXPORT_SYMBOL, or initcalls. Those 136 * are handled in their own way (with KEEP() in linker scripts). 137 * 138 * KENTRY can be avoided if the symbols in question are marked as KEEP() in the 139 * linker script. For example an architecture could KEEP() its entire 140 * boot/exception vector code rather than annotate each function and data. 141 */ 142 #ifndef KENTRY 143 # define KENTRY(sym) \ 144 extern typeof(sym) sym; \ 145 static const unsigned long __kentry_##sym \ 146 __used \ 147 __attribute__((__section__("___kentry+" #sym))) \ 148 = (unsigned long)&sym; 149 #endif 150 151 #ifndef RELOC_HIDE 152 # define RELOC_HIDE(ptr, off) \ 153 ({ unsigned long __ptr; \ 154 __ptr = (unsigned long) (ptr); \ 155 (typeof(ptr)) (__ptr + (off)); }) 156 #endif 157 158 #define absolute_pointer(val) RELOC_HIDE((void *)(val), 0) 159 160 #ifndef OPTIMIZER_HIDE_VAR 161 /* Make the optimizer believe the variable can be manipulated arbitrarily. */ 162 #define OPTIMIZER_HIDE_VAR(var) \ 163 __asm__ ("" : "=r" (var) : "0" (var)) 164 #endif 165 166 #define __UNIQUE_ID(prefix) __PASTE(__PASTE(__UNIQUE_ID_, prefix), __COUNTER__) 167 168 /** 169 * data_race - mark an expression as containing intentional data races 170 * 171 * This data_race() macro is useful for situations in which data races 172 * should be forgiven. One example is diagnostic code that accesses 173 * shared variables but is not a part of the core synchronization design. 174 * For example, if accesses to a given variable are protected by a lock, 175 * except for diagnostic code, then the accesses under the lock should 176 * be plain C-language accesses and those in the diagnostic code should 177 * use data_race(). This way, KCSAN will complain if buggy lockless 178 * accesses to that variable are introduced, even if the buggy accesses 179 * are protected by READ_ONCE() or WRITE_ONCE(). 180 * 181 * This macro *does not* affect normal code generation, but is a hint 182 * to tooling that data races here are to be ignored. If the access must 183 * be atomic *and* KCSAN should ignore the access, use both data_race() 184 * and READ_ONCE(), for example, data_race(READ_ONCE(x)). 185 */ 186 #define data_race(expr) \ 187 ({ \ 188 __kcsan_disable_current(); \ 189 __auto_type __v = (expr); \ 190 __kcsan_enable_current(); \ 191 __v; \ 192 }) 193 194 #endif /* __KERNEL__ */ 195 196 /** 197 * offset_to_ptr - convert a relative memory offset to an absolute pointer 198 * @off: the address of the 32-bit offset value 199 */ 200 static inline void *offset_to_ptr(const int *off) 201 { 202 return (void *)((unsigned long)off + *off); 203 } 204 205 #endif /* __ASSEMBLY__ */ 206 207 #ifdef CONFIG_64BIT 208 #define ARCH_SEL(a,b) a 209 #else 210 #define ARCH_SEL(a,b) b 211 #endif 212 213 /* 214 * Force the compiler to emit 'sym' as a symbol, so that we can reference 215 * it from inline assembler. Necessary in case 'sym' could be inlined 216 * otherwise, or eliminated entirely due to lack of references that are 217 * visible to the compiler. 218 */ 219 #define ___ADDRESSABLE(sym, __attrs) \ 220 static void * __used __attrs \ 221 __UNIQUE_ID(__PASTE(__addressable_,sym)) = (void *)(uintptr_t)&sym; 222 223 #define __ADDRESSABLE(sym) \ 224 ___ADDRESSABLE(sym, __section(".discard.addressable")) 225 226 #define __ADDRESSABLE_ASM(sym) \ 227 .pushsection .discard.addressable,"aw"; \ 228 .align ARCH_SEL(8,4); \ 229 ARCH_SEL(.quad, .long) __stringify(sym); \ 230 .popsection; 231 232 #define __ADDRESSABLE_ASM_STR(sym) __stringify(__ADDRESSABLE_ASM(sym)) 233 234 #ifdef __CHECKER__ 235 #define __BUILD_BUG_ON_ZERO_MSG(e, msg) (0) 236 #else /* __CHECKER__ */ 237 #define __BUILD_BUG_ON_ZERO_MSG(e, msg) ((int)sizeof(struct {_Static_assert(!(e), msg);})) 238 #endif /* __CHECKER__ */ 239 240 /* &a[0] degrades to a pointer: a different type from an array */ 241 #define __must_be_array(a) __BUILD_BUG_ON_ZERO_MSG(__same_type((a), &(a)[0]), "must be array") 242 243 /* Require C Strings (i.e. NUL-terminated) lack the "nonstring" attribute. */ 244 #define __must_be_cstr(p) \ 245 __BUILD_BUG_ON_ZERO_MSG(__annotated(p, nonstring), "must be cstr (NUL-terminated)") 246 247 /* 248 * This returns a constant expression while determining if an argument is 249 * a constant expression, most importantly without evaluating the argument. 250 * Glory to Martin Uecker <Martin.Uecker@med.uni-goettingen.de> 251 * 252 * Details: 253 * - sizeof() return an integer constant expression, and does not evaluate 254 * the value of its operand; it only examines the type of its operand. 255 * - The results of comparing two integer constant expressions is also 256 * an integer constant expression. 257 * - The first literal "8" isn't important. It could be any literal value. 258 * - The second literal "8" is to avoid warnings about unaligned pointers; 259 * this could otherwise just be "1". 260 * - (long)(x) is used to avoid warnings about 64-bit types on 32-bit 261 * architectures. 262 * - The C Standard defines "null pointer constant", "(void *)0", as 263 * distinct from other void pointers. 264 * - If (x) is an integer constant expression, then the "* 0l" resolves 265 * it into an integer constant expression of value 0. Since it is cast to 266 * "void *", this makes the second operand a null pointer constant. 267 * - If (x) is not an integer constant expression, then the second operand 268 * resolves to a void pointer (but not a null pointer constant: the value 269 * is not an integer constant 0). 270 * - The conditional operator's third operand, "(int *)8", is an object 271 * pointer (to type "int"). 272 * - The behavior (including the return type) of the conditional operator 273 * ("operand1 ? operand2 : operand3") depends on the kind of expressions 274 * given for the second and third operands. This is the central mechanism 275 * of the macro: 276 * - When one operand is a null pointer constant (i.e. when x is an integer 277 * constant expression) and the other is an object pointer (i.e. our 278 * third operand), the conditional operator returns the type of the 279 * object pointer operand (i.e. "int *"). Here, within the sizeof(), we 280 * would then get: 281 * sizeof(*((int *)(...)) == sizeof(int) == 4 282 * - When one operand is a void pointer (i.e. when x is not an integer 283 * constant expression) and the other is an object pointer (i.e. our 284 * third operand), the conditional operator returns a "void *" type. 285 * Here, within the sizeof(), we would then get: 286 * sizeof(*((void *)(...)) == sizeof(void) == 1 287 * - The equality comparison to "sizeof(int)" therefore depends on (x): 288 * sizeof(int) == sizeof(int) (x) was a constant expression 289 * sizeof(int) != sizeof(void) (x) was not a constant expression 290 */ 291 #define __is_constexpr(x) \ 292 (sizeof(int) == sizeof(*(8 ? ((void *)((long)(x) * 0l)) : (int *)8))) 293 294 /* 295 * Whether 'type' is a signed type or an unsigned type. Supports scalar types, 296 * bool and also pointer types. 297 */ 298 #define is_signed_type(type) (((type)(-1)) < (__force type)1) 299 #define is_unsigned_type(type) (!is_signed_type(type)) 300 301 /* 302 * Useful shorthand for "is this condition known at compile-time?" 303 * 304 * Note that the condition may involve non-constant values, 305 * but the compiler may know enough about the details of the 306 * values to determine that the condition is statically true. 307 */ 308 #define statically_true(x) (__builtin_constant_p(x) && (x)) 309 310 /* 311 * This is needed in functions which generate the stack canary, see 312 * arch/x86/kernel/smpboot.c::start_secondary() for an example. 313 */ 314 #define prevent_tail_call_optimization() mb() 315 316 #include <asm/rwonce.h> 317 318 #endif /* __LINUX_COMPILER_H */ 319