include/linux/compiler.h

   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 #if defined(CONFIG_TRACE_BRANCH_PROFILING) \
  16     && !defined(DISABLE_BRANCH_PROFILING) && !defined(__CHECKER__)
  17 void ftrace_likely_update(struct ftrace_likely_data *f, int val,
  18                           int expect, int is_constant);
  19
  20 #define likely_notrace(x)       __builtin_expect(!!(x), 1)
  21 #define unlikely_notrace(x)     __builtin_expect(!!(x), 0)
  22
  23 #define __branch_check__(x, expect, is_constant) ({                     \
  24                         int ______r;                                    \
  25                         static struct ftrace_likely_data                \
  26                                 __attribute__((__aligned__(4)))         \
  27                                 __attribute__((section("_ftrace_annotated_branch"))) \
  28                                 ______f = {                             \
  29                                 .data.func = __func__,                  \
  30                                 .data.file = __FILE__,                  \
  31                                 .data.line = __LINE__,                  \
  32                         };                                              \
  33                         ______r = __builtin_expect(!!(x), expect);      \
  34                         ftrace_likely_update(&______f, ______r,         \
  35                                              expect, is_constant);      \
  36                         ______r;                                        \
  37                 })
  38
  39 /*
  40  * Using __builtin_constant_p(x) to ignore cases where the return
  41  * value is always the same.  This idea is taken from a similar patch
  42  * written by Daniel Walker.
  43  */
  44 # ifndef likely
  45 #  define likely(x)     (__branch_check__(x, 1, __builtin_constant_p(x)))
  46 # endif
  47 # ifndef unlikely
  48 #  define unlikely(x)   (__branch_check__(x, 0, __builtin_constant_p(x)))
  49 # endif
  50
  51 #ifdef CONFIG_PROFILE_ALL_BRANCHES
  52 /*
  53  * "Define 'is'", Bill Clinton
  54  * "Define 'if'", Steven Rostedt
  55  */
  56 #define if(cond, ...) __trace_if( (cond , ## __VA_ARGS__) )
  57 #define __trace_if(cond) \
  58         if (__builtin_constant_p(!!(cond)) ? !!(cond) :                 \
  59         ({                                                              \
  60                 int ______r;                                            \
  61                 static struct ftrace_branch_data                        \
  62                         __attribute__((__aligned__(4)))                 \
  63                         __attribute__((section("_ftrace_branch")))      \
  64                         ______f = {                                     \
  65                                 .func = __func__,                       \
  66                                 .file = __FILE__,                       \
  67                                 .line = __LINE__,                       \
  68                         };                                              \
  69                 ______r = !!(cond);                                     \
  70                 ______f.miss_hit[______r]++;                                    \
  71                 ______r;                                                \
  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 #endif
  79
  80 /* Optimization barrier */
  81 #ifndef barrier
  82 # define barrier() __memory_barrier()
  83 #endif
  84
  85 #ifndef barrier_data
  86 # define barrier_data(ptr) barrier()
  87 #endif
  88
  89 /* Unreachable code */
  90 #ifdef CONFIG_STACK_VALIDATION
  91 /*
  92  * These macros help objtool understand GCC code flow for unreachable code.
  93  * The __COUNTER__ based labels are a hack to make each instance of the macros
  94  * unique, to convince GCC not to merge duplicate inline asm statements.
  95  */
  96 #define annotate_reachable() ({                                         \
  97         asm volatile("%c0:\n\t"                                         \
  98                      ".pushsection .discard.reachable\n\t"              \
  99                      ".long %c0b - .\n\t"                               \
 100                      ".popsection\n\t" : : "i" (__COUNTER__));          \
 101 })
 102 #define annotate_unreachable() ({                                       \
 103         asm volatile("%c0:\n\t"                                         \
 104                      ".pushsection .discard.unreachable\n\t"            \
 105                      ".long %c0b - .\n\t"                               \
 106                      ".popsection\n\t" : : "i" (__COUNTER__));          \
 107 })
 108 #define ASM_UNREACHABLE                                                 \
 109         "999:\n\t"                                                      \
 110         ".pushsection .discard.unreachable\n\t"                         \
 111         ".long 999b - .\n\t"                                            \
 112         ".popsection\n\t"
 113 #else
 114 #define annotate_reachable()
 115 #define annotate_unreachable()
 116 #endif
 117
 118 #ifndef ASM_UNREACHABLE
 119 # define ASM_UNREACHABLE
 120 #endif
 121 #ifndef unreachable
 122 # define unreachable() do { annotate_reachable(); do { } while (1); } while (0)
 123 #endif
 124
 125 /*
 126  * KENTRY - kernel entry point
 127  * This can be used to annotate symbols (functions or data) that are used
 128  * without their linker symbol being referenced explicitly. For example,
 129  * interrupt vector handlers, or functions in the kernel image that are found
 130  * programatically.
 131  *
 132  * Not required for symbols exported with EXPORT_SYMBOL, or initcalls. Those
 133  * are handled in their own way (with KEEP() in linker scripts).
 134  *
 135  * KENTRY can be avoided if the symbols in question are marked as KEEP() in the
 136  * linker script. For example an architecture could KEEP() its entire
 137  * boot/exception vector code rather than annotate each function and data.
 138  */
 139 #ifndef KENTRY
 140 # define KENTRY(sym)                                            \
 141         extern typeof(sym) sym;                                 \
 142         static const unsigned long __kentry_##sym               \
 143         __used                                                  \
 144         __attribute__((section("___kentry" "+" #sym ), used))   \
 145         = (unsigned long)&sym;
 146 #endif
 147
 148 #ifndef RELOC_HIDE
 149 # define RELOC_HIDE(ptr, off)                                   \
 150   ({ unsigned long __ptr;                                       \
 151      __ptr = (unsigned long) (ptr);                             \
 152     (typeof(ptr)) (__ptr + (off)); })
 153 #endif
 154
 155 #ifndef OPTIMIZER_HIDE_VAR
 156 #define OPTIMIZER_HIDE_VAR(var) barrier()
 157 #endif
 158
 159 /* Not-quite-unique ID. */
 160 #ifndef __UNIQUE_ID
 161 # define __UNIQUE_ID(prefix) __PASTE(__PASTE(__UNIQUE_ID_, prefix), __LINE__)
 162 #endif
 163
 164 #include <uapi/linux/types.h>
 165
 166 #define __READ_ONCE_SIZE                                                \
 167 ({                                                                      \
 168         switch (size) {                                                 \
 169         case 1: *(__u8 *)res = *(volatile __u8 *)p; break;              \
 170         case 2: *(__u16 *)res = *(volatile __u16 *)p; break;            \
 171         case 4: *(__u32 *)res = *(volatile __u32 *)p; break;            \
 172         case 8: *(__u64 *)res = *(volatile __u64 *)p; break;            \
 173         default:                                                        \
 174                 barrier();                                              \
 175                 __builtin_memcpy((void *)res, (const void *)p, size);   \
 176                 barrier();                                              \
 177         }                                                               \
 178 })
 179
 180 static __always_inline
 181 void __read_once_size(const volatile void *p, void *res, int size)
 182 {
 183         __READ_ONCE_SIZE;
 184 }
 185
 186 #ifdef CONFIG_KASAN
 187 /*
 188  * This function is not 'inline' because __no_sanitize_address confilcts
 189  * with inlining. Attempt to inline it may cause a build failure.
 190  *      https://gcc.gnu.org/bugzilla/show_bug.cgi?id=67368
 191  * '__maybe_unused' allows us to avoid defined-but-not-used warnings.
 192  */
 193 static __no_sanitize_address __maybe_unused
 194 void __read_once_size_nocheck(const volatile void *p, void *res, int size)
 195 {
 196         __READ_ONCE_SIZE;
 197 }
 198 #else
 199 static __always_inline
 200 void __read_once_size_nocheck(const volatile void *p, void *res, int size)
 201 {
 202         __READ_ONCE_SIZE;
 203 }
 204 #endif
 205
 206 static __always_inline void __write_once_size(volatile void *p, void *res, int size)
 207 {
 208         switch (size) {
 209         case 1: *(volatile __u8 *)p = *(__u8 *)res; break;
 210         case 2: *(volatile __u16 *)p = *(__u16 *)res; break;
 211         case 4: *(volatile __u32 *)p = *(__u32 *)res; break;
 212         case 8: *(volatile __u64 *)p = *(__u64 *)res; break;
 213         default:
 214                 barrier();
 215                 __builtin_memcpy((void *)p, (const void *)res, size);
 216                 barrier();
 217         }
 218 }
 219
 220 /*
 221  * Prevent the compiler from merging or refetching reads or writes. The
 222  * compiler is also forbidden from reordering successive instances of
 223  * READ_ONCE, WRITE_ONCE and ACCESS_ONCE (see below), but only when the
 224  * compiler is aware of some particular ordering.  One way to make the
 225  * compiler aware of ordering is to put the two invocations of READ_ONCE,
 226  * WRITE_ONCE or ACCESS_ONCE() in different C statements.
 227  *
 228  * In contrast to ACCESS_ONCE these two macros will also work on aggregate
 229  * data types like structs or unions. If the size of the accessed data
 230  * type exceeds the word size of the machine (e.g., 32 bits or 64 bits)
 231  * READ_ONCE() and WRITE_ONCE() will fall back to memcpy(). There's at
 232  * least two memcpy()s: one for the __builtin_memcpy() and then one for
 233  * the macro doing the copy of variable - '__u' allocated on the stack.
 234  *
 235  * Their two major use cases are: (1) Mediating communication between
 236  * process-level code and irq/NMI handlers, all running on the same CPU,
 237  * and (2) Ensuring that the compiler does not  fold, spindle, or otherwise
 238  * mutilate accesses that either do not require ordering or that interact
 239  * with an explicit memory barrier or atomic instruction that provides the
 240  * required ordering.
 241  */
 242 #include <asm/barrier.h>
 243
 244 #define __READ_ONCE(x, check)                                           \
 245 ({                                                                      \
 246         union { typeof(x) __val; char __c[1]; } __u;                    \
 247         if (check)                                                      \
 248                 __read_once_size(&(x), __u.__c, sizeof(x));             \
 249         else                                                            \
 250                 __read_once_size_nocheck(&(x), __u.__c, sizeof(x));     \
 251         smp_read_barrier_depends(); /* Enforce dependency ordering from x */ \
 252         __u.__val;                                                      \
 253 })
 254 #define READ_ONCE(x) __READ_ONCE(x, 1)
 255
 256 /*
 257  * Use READ_ONCE_NOCHECK() instead of READ_ONCE() if you need
 258  * to hide memory access from KASAN.
 259  */
 260 #define READ_ONCE_NOCHECK(x) __READ_ONCE(x, 0)
 261
 262 #define WRITE_ONCE(x, val) \
 263 ({                                                      \
 264         union { typeof(x) __val; char __c[1]; } __u =   \
 265                 { .__val = (__force typeof(x)) (val) }; \
 266         __write_once_size(&(x), __u.__c, sizeof(x));    \
 267         __u.__val;                                      \
 268 })
 269
 270 #endif /* __KERNEL__ */
 271
 272 #endif /* __ASSEMBLY__ */
 273
 274 /* Compile time object size, -1 for unknown */
 275 #ifndef __compiletime_object_size
 276 # define __compiletime_object_size(obj) -1
 277 #endif
 278 #ifndef __compiletime_warning
 279 # define __compiletime_warning(message)
 280 #endif
 281 #ifndef __compiletime_error
 282 # define __compiletime_error(message)
 283 /*
 284  * Sparse complains of variable sized arrays due to the temporary variable in
 285  * __compiletime_assert. Unfortunately we can't just expand it out to make
 286  * sparse see a constant array size without breaking compiletime_assert on old
 287  * versions of GCC (e.g. 4.2.4), so hide the array from sparse altogether.
 288  */
 289 # ifndef __CHECKER__
 290 #  define __compiletime_error_fallback(condition) \
 291         do { ((void)sizeof(char[1 - 2 * condition])); } while (0)
 292 # endif
 293 #endif
 294 #ifndef __compiletime_error_fallback
 295 # define __compiletime_error_fallback(condition) do { } while (0)
 296 #endif
 297
 298 #ifdef __OPTIMIZE__
 299 # define __compiletime_assert(condition, msg, prefix, suffix)           \
 300         do {                                                            \
 301                 bool __cond = !(condition);                             \
 302                 extern void prefix ## suffix(void) __compiletime_error(msg); \
 303                 if (__cond)                                             \
 304                         prefix ## suffix();                             \
 305                 __compiletime_error_fallback(__cond);                   \
 306         } while (0)
 307 #else
 308 # define __compiletime_assert(condition, msg, prefix, suffix) do { } while (0)
 309 #endif
 310
 311 #define _compiletime_assert(condition, msg, prefix, suffix) \
 312         __compiletime_assert(condition, msg, prefix, suffix)
 313
 314 /**
 315  * compiletime_assert - break build and emit msg if condition is false
 316  * @condition: a compile-time constant condition to check
 317  * @msg:       a message to emit if condition is false
 318  *
 319  * In tradition of POSIX assert, this macro will break the build if the
 320  * supplied condition is *false*, emitting the supplied error message if the
 321  * compiler has support to do so.
 322  */
 323 #define compiletime_assert(condition, msg) \
 324         _compiletime_assert(condition, msg, __compiletime_assert_, __LINE__)
 325
 326 #define compiletime_assert_atomic_type(t)                               \
 327         compiletime_assert(__native_word(t),                            \
 328                 "Need native word sized stores/loads for atomicity.")
 329
 330 /*
 331  * Prevent the compiler from merging or refetching accesses.  The compiler
 332  * is also forbidden from reordering successive instances of ACCESS_ONCE(),
 333  * but only when the compiler is aware of some particular ordering.  One way
 334  * to make the compiler aware of ordering is to put the two invocations of
 335  * ACCESS_ONCE() in different C statements.
 336  *
 337  * ACCESS_ONCE will only work on scalar types. For union types, ACCESS_ONCE
 338  * on a union member will work as long as the size of the member matches the
 339  * size of the union and the size is smaller than word size.
 340  *
 341  * The major use cases of ACCESS_ONCE used to be (1) Mediating communication
 342  * between process-level code and irq/NMI handlers, all running on the same CPU,
 343  * and (2) Ensuring that the compiler does not  fold, spindle, or otherwise
 344  * mutilate accesses that either do not require ordering or that interact
 345  * with an explicit memory barrier or atomic instruction that provides the
 346  * required ordering.
 347  *
 348  * If possible use READ_ONCE()/WRITE_ONCE() instead.
 349  */
 350 #define __ACCESS_ONCE(x) ({ \
 351          __maybe_unused typeof(x) __var = (__force typeof(x)) 0; \
 352         (volatile typeof(x) *)&(x); })
 353 #define ACCESS_ONCE(x) (*__ACCESS_ONCE(x))
 354
 355 #endif /* __LINUX_COMPILER_H */