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 */ 15void 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 * 198 * This macro *does not* affect normal code generation, but is a hint 199 * to tooling that data races here are to be ignored. 200 */ 201#define data_race(expr) \ 202({ \ 203 __unqual_scalar_typeof(({ expr; })) __v = ({ \ 204 __kcsan_disable_current(); \ 205 expr; \ 206 }); \ 207 __kcsan_enable_current(); \ 208 __v; \ 209}) 210 211#endif /* __KERNEL__ */ 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#define __ADDRESSABLE(sym) \ 223 ___ADDRESSABLE(sym, __section(".discard.addressable")) 224 225/** 226 * offset_to_ptr - convert a relative memory offset to an absolute pointer 227 * @off: the address of the 32-bit offset value 228 */ 229static inline void *offset_to_ptr(const int *off) 230{ 231 return (void *)((unsigned long)off + *off); 232} 233 234#endif /* __ASSEMBLY__ */ 235 236/* &a[0] degrades to a pointer: a different type from an array */ 237#define __must_be_array(a) BUILD_BUG_ON_ZERO(__same_type((a), &(a)[0])) 238 239/* 240 * This returns a constant expression while determining if an argument is 241 * a constant expression, most importantly without evaluating the argument. 242 * Glory to Martin Uecker <Martin.Uecker@med.uni-goettingen.de> 243 * 244 * Details: 245 * - sizeof() return an integer constant expression, and does not evaluate 246 * the value of its operand; it only examines the type of its operand. 247 * - The results of comparing two integer constant expressions is also 248 * an integer constant expression. 249 * - The first literal "8" isn't important. It could be any literal value. 250 * - The second literal "8" is to avoid warnings about unaligned pointers; 251 * this could otherwise just be "1". 252 * - (long)(x) is used to avoid warnings about 64-bit types on 32-bit 253 * architectures. 254 * - The C Standard defines "null pointer constant", "(void *)0", as 255 * distinct from other void pointers. 256 * - If (x) is an integer constant expression, then the "* 0l" resolves 257 * it into an integer constant expression of value 0. Since it is cast to 258 * "void *", this makes the second operand a null pointer constant. 259 * - If (x) is not an integer constant expression, then the second operand 260 * resolves to a void pointer (but not a null pointer constant: the value 261 * is not an integer constant 0). 262 * - The conditional operator's third operand, "(int *)8", is an object 263 * pointer (to type "int"). 264 * - The behavior (including the return type) of the conditional operator 265 * ("operand1 ? operand2 : operand3") depends on the kind of expressions 266 * given for the second and third operands. This is the central mechanism 267 * of the macro: 268 * - When one operand is a null pointer constant (i.e. when x is an integer 269 * constant expression) and the other is an object pointer (i.e. our 270 * third operand), the conditional operator returns the type of the 271 * object pointer operand (i.e. "int *"). Here, within the sizeof(), we 272 * would then get: 273 * sizeof(*((int *)(...)) == sizeof(int) == 4 274 * - When one operand is a void pointer (i.e. when x is not an integer 275 * constant expression) and the other is an object pointer (i.e. our 276 * third operand), the conditional operator returns a "void *" type. 277 * Here, within the sizeof(), we would then get: 278 * sizeof(*((void *)(...)) == sizeof(void) == 1 279 * - The equality comparison to "sizeof(int)" therefore depends on (x): 280 * sizeof(int) == sizeof(int) (x) was a constant expression 281 * sizeof(int) != sizeof(void) (x) was not a constant expression 282 */ 283#define __is_constexpr(x) \ 284 (sizeof(int) == sizeof(*(8 ? ((void *)((long)(x) * 0l)) : (int *)8))) 285 286/* 287 * Whether 'type' is a signed type or an unsigned type. Supports scalar types, 288 * bool and also pointer types. 289 */ 290#define is_signed_type(type) (((type)(-1)) < (__force type)1) 291#define is_unsigned_type(type) (!is_signed_type(type)) 292 293/* 294 * This is needed in functions which generate the stack canary, see 295 * arch/x86/kernel/smpboot.c::start_secondary() for an example. 296 */ 297#define prevent_tail_call_optimization() mb() 298 299#include <asm/rwonce.h> 300 301#endif /* __LINUX_COMPILER_H */ 302