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(".data.rel.ro.c_jump_table") 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) ((typeof(ptr))((unsigned long)(ptr) + (off))) 153 #endif 154 155 #define absolute_pointer(val) RELOC_HIDE((void *)(val), 0) 156 157 #ifndef OPTIMIZER_HIDE_VAR 158 /* Make the optimizer believe the variable can be manipulated arbitrarily. */ 159 #define OPTIMIZER_HIDE_VAR(var) \ 160 __asm__ ("" : "=r" (var) : "0" (var)) 161 #endif 162 163 /* Format: __UNIQUE_ID_<name>_<__COUNTER__> */ 164 #define __UNIQUE_ID(name) \ 165 __PASTE(__UNIQUE_ID_, \ 166 __PASTE(name, \ 167 __PASTE(_, __COUNTER__))) 168 169 /** 170 * data_race - mark an expression as containing intentional data races 171 * 172 * This data_race() macro is useful for situations in which data races 173 * should be forgiven. One example is diagnostic code that accesses 174 * shared variables but is not a part of the core synchronization design. 175 * For example, if accesses to a given variable are protected by a lock, 176 * except for diagnostic code, then the accesses under the lock should 177 * be plain C-language accesses and those in the diagnostic code should 178 * use data_race(). This way, KCSAN will complain if buggy lockless 179 * accesses to that variable are introduced, even if the buggy accesses 180 * are protected by READ_ONCE() or WRITE_ONCE(). 181 * 182 * This macro *does not* affect normal code generation, but is a hint 183 * to tooling that data races here are to be ignored. If the access must 184 * be atomic *and* KCSAN should ignore the access, use both data_race() 185 * and READ_ONCE(), for example, data_race(READ_ONCE(x)). 186 */ 187 #define data_race(expr) \ 188 ({ \ 189 __kcsan_disable_current(); \ 190 disable_context_analysis(); \ 191 auto __v = (expr); \ 192 enable_context_analysis(); \ 193 __kcsan_enable_current(); \ 194 __v; \ 195 }) 196 197 #ifdef __CHECKER__ 198 #define __BUILD_BUG_ON_ZERO_MSG(e, msg, ...) (0) 199 #else /* __CHECKER__ */ 200 #define __BUILD_BUG_ON_ZERO_MSG(e, msg, ...) ((int)sizeof(struct {_Static_assert(!(e), msg);})) 201 #endif /* __CHECKER__ */ 202 203 /* &a[0] degrades to a pointer: a different type from an array */ 204 #define __is_array(a) (!__same_type((a), &(a)[0])) 205 #define __must_be_array(a) __BUILD_BUG_ON_ZERO_MSG(!__is_array(a), \ 206 "must be array") 207 208 #define __is_byte_array(a) (__is_array(a) && sizeof((a)[0]) == 1) 209 #define __must_be_byte_array(a) __BUILD_BUG_ON_ZERO_MSG(!__is_byte_array(a), \ 210 "must be byte array") 211 212 /* 213 * If the "nonstring" attribute isn't available, we have to return true 214 * so the __must_*() checks pass when "nonstring" isn't supported. 215 */ 216 #if __has_attribute(__nonstring__) && defined(__annotated) 217 #define __is_cstr(a) (!__annotated(a, nonstring)) 218 #define __is_noncstr(a) (__annotated(a, nonstring)) 219 #else 220 #define __is_cstr(a) (true) 221 #define __is_noncstr(a) (true) 222 #endif 223 224 /* Require C Strings (i.e. NUL-terminated) lack the "nonstring" attribute. */ 225 #define __must_be_cstr(p) \ 226 __BUILD_BUG_ON_ZERO_MSG(!__is_cstr(p), \ 227 "must be C-string (NUL-terminated)") 228 #define __must_be_noncstr(p) \ 229 __BUILD_BUG_ON_ZERO_MSG(!__is_noncstr(p), \ 230 "must be non-C-string (not NUL-terminated)") 231 232 /* 233 * Define TYPEOF_UNQUAL() to use __typeof_unqual__() as typeof 234 * operator when available, to return an unqualified type of the exp. 235 */ 236 #if defined(USE_TYPEOF_UNQUAL) 237 # define TYPEOF_UNQUAL(exp) __typeof_unqual__(exp) 238 #else 239 # define TYPEOF_UNQUAL(exp) __typeof__(exp) 240 #endif 241 242 #endif /* __KERNEL__ */ 243 244 #if defined(CONFIG_CFI) && !defined(__DISABLE_EXPORTS) && !defined(BUILD_VDSO) 245 /* 246 * Force a reference to the external symbol so the compiler generates 247 * __kcfi_typid. 248 */ 249 #define KCFI_REFERENCE(sym) __ADDRESSABLE(sym) 250 #else 251 #define KCFI_REFERENCE(sym) 252 #endif 253 254 /** 255 * offset_to_ptr - convert a relative memory offset to an absolute pointer 256 * @off: the address of the 32-bit offset value 257 */ 258 static inline void *offset_to_ptr(const int *off) 259 { 260 return (void *)((unsigned long)off + *off); 261 } 262 263 #endif /* __ASSEMBLY__ */ 264 265 /* 266 * Force the compiler to emit 'sym' as a symbol, so that we can reference 267 * it from inline assembler. Necessary in case 'sym' could be inlined 268 * otherwise, or eliminated entirely due to lack of references that are 269 * visible to the compiler. 270 */ 271 #define ___ADDRESSABLE(sym, __attrs) \ 272 static void * __used __attrs \ 273 __UNIQUE_ID(__PASTE(addressable_, sym)) = (void *)(uintptr_t)&sym; 274 275 #define __ADDRESSABLE(sym) \ 276 ___ADDRESSABLE(sym, __section(".discard.addressable")) 277 278 /* 279 * This returns a constant expression while determining if an argument is 280 * a constant expression, most importantly without evaluating the argument. 281 * Glory to Martin Uecker <Martin.Uecker@med.uni-goettingen.de> 282 * 283 * Details: 284 * - sizeof() return an integer constant expression, and does not evaluate 285 * the value of its operand; it only examines the type of its operand. 286 * - The results of comparing two integer constant expressions is also 287 * an integer constant expression. 288 * - The first literal "8" isn't important. It could be any literal value. 289 * - The second literal "8" is to avoid warnings about unaligned pointers; 290 * this could otherwise just be "1". 291 * - (long)(x) is used to avoid warnings about 64-bit types on 32-bit 292 * architectures. 293 * - The C Standard defines "null pointer constant", "(void *)0", as 294 * distinct from other void pointers. 295 * - If (x) is an integer constant expression, then the "* 0l" resolves 296 * it into an integer constant expression of value 0. Since it is cast to 297 * "void *", this makes the second operand a null pointer constant. 298 * - If (x) is not an integer constant expression, then the second operand 299 * resolves to a void pointer (but not a null pointer constant: the value 300 * is not an integer constant 0). 301 * - The conditional operator's third operand, "(int *)8", is an object 302 * pointer (to type "int"). 303 * - The behavior (including the return type) of the conditional operator 304 * ("operand1 ? operand2 : operand3") depends on the kind of expressions 305 * given for the second and third operands. This is the central mechanism 306 * of the macro: 307 * - When one operand is a null pointer constant (i.e. when x is an integer 308 * constant expression) and the other is an object pointer (i.e. our 309 * third operand), the conditional operator returns the type of the 310 * object pointer operand (i.e. "int *"). Here, within the sizeof(), we 311 * would then get: 312 * sizeof(*((int *)(...)) == sizeof(int) == 4 313 * - When one operand is a void pointer (i.e. when x is not an integer 314 * constant expression) and the other is an object pointer (i.e. our 315 * third operand), the conditional operator returns a "void *" type. 316 * Here, within the sizeof(), we would then get: 317 * sizeof(*((void *)(...)) == sizeof(void) == 1 318 * - The equality comparison to "sizeof(int)" therefore depends on (x): 319 * sizeof(int) == sizeof(int) (x) was a constant expression 320 * sizeof(int) != sizeof(void) (x) was not a constant expression 321 */ 322 #define __is_constexpr(x) \ 323 (sizeof(int) == sizeof(*(8 ? ((void *)((long)(x) * 0l)) : (int *)8))) 324 325 /* 326 * Whether 'type' is a signed type or an unsigned type. Supports scalar types, 327 * bool and also pointer types. 328 */ 329 #define is_signed_type(type) (((type)(-1)) < (__force type)1) 330 #define is_unsigned_type(type) (!is_signed_type(type)) 331 332 /* 333 * Useful shorthand for "is this condition known at compile-time?" 334 * 335 * Note that the condition may involve non-constant values, 336 * but the compiler may know enough about the details of the 337 * values to determine that the condition is statically true. 338 */ 339 #define statically_true(x) (__builtin_constant_p(x) && (x)) 340 341 /* 342 * Similar to statically_true() but produces a constant expression 343 * 344 * To be used in conjunction with macros, such as BUILD_BUG_ON_ZERO(), 345 * which require their input to be a constant expression and for which 346 * statically_true() would otherwise fail. 347 * 348 * This is a trade-off: const_true() requires all its operands to be 349 * compile time constants. Else, it would always returns false even on 350 * the most trivial cases like: 351 * 352 * true || non_const_var 353 * 354 * On the opposite, statically_true() is able to fold more complex 355 * tautologies and will return true on expressions such as: 356 * 357 * !(non_const_var * 8 % 4) 358 * 359 * For the general case, statically_true() is better. 360 */ 361 #define const_true(x) __builtin_choose_expr(__is_constexpr(x), x, false) 362 363 /* 364 * This is needed in functions which generate the stack canary, see 365 * arch/x86/kernel/smpboot.c::start_secondary() for an example. 366 */ 367 #define prevent_tail_call_optimization() mb() 368 369 #include <asm/rwonce.h> 370 371 #endif /* __LINUX_COMPILER_H */ 372