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                         long ______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 /* workaround for GCC PR82365 if needed */
  90 #ifndef barrier_before_unreachable
  91 # define barrier_before_unreachable() do { } while (0)
  92 #endif
  93
  94 /* Unreachable code */
  95 #ifdef CONFIG_STACK_VALIDATION
  96 /*
  97  * These macros help objtool understand GCC code flow for unreachable code.
  98  * The __COUNTER__ based labels are a hack to make each instance of the macros
  99  * unique, to convince GCC not to merge duplicate inline asm statements.
 100  */
 101 #define annotate_reachable() ({                                         \
 102         asm volatile("%c0:\n\t"                                         \
 103                      ".pushsection .discard.reachable\n\t"              \
 104                      ".long %c0b - .\n\t"                               \
 105                      ".popsection\n\t" : : "i" (__COUNTER__));          \
 106 })
 107 #define annotate_unreachable() ({                                       \
 108         asm volatile("%c0:\n\t"                                         \
 109                      ".pushsection .discard.unreachable\n\t"            \
 110                      ".long %c0b - .\n\t"                               \
 111                      ".popsection\n\t" : : "i" (__COUNTER__));          \
 112 })
 113 #define ASM_UNREACHABLE                                                 \
 114         "999:\n\t"                                                      \
 115         ".pushsection .discard.unreachable\n\t"                         \
 116         ".long 999b - .\n\t"                                            \
 117         ".popsection\n\t"
 118 #else
 119 #define annotate_reachable()
 120 #define annotate_unreachable()
 121 #endif
 122
 123 #ifndef ASM_UNREACHABLE
 124 # define ASM_UNREACHABLE
 125 #endif
 126 #ifndef unreachable
 127 # define unreachable() do { annotate_reachable(); do { } while (1); } while (0)
 128 #endif
 129
 130 /*
 131  * KENTRY - kernel entry point
 132  * This can be used to annotate symbols (functions or data) that are used
 133  * without their linker symbol being referenced explicitly. For example,
 134  * interrupt vector handlers, or functions in the kernel image that are found
 135  * programatically.
 136  *
 137  * Not required for symbols exported with EXPORT_SYMBOL, or initcalls. Those
 138  * are handled in their own way (with KEEP() in linker scripts).
 139  *
 140  * KENTRY can be avoided if the symbols in question are marked as KEEP() in the
 141  * linker script. For example an architecture could KEEP() its entire
 142  * boot/exception vector code rather than annotate each function and data.
 143  */
 144 #ifndef KENTRY
 145 # define KENTRY(sym)                                            \
 146         extern typeof(sym) sym;                                 \
 147         static const unsigned long __kentry_##sym               \
 148         __used                                                  \
 149         __attribute__((section("___kentry" "+" #sym ), used))   \
 150         = (unsigned long)&sym;
 151 #endif
 152
 153 #ifndef RELOC_HIDE
 154 # define RELOC_HIDE(ptr, off)                                   \
 155   ({ unsigned long __ptr;                                       \
 156      __ptr = (unsigned long) (ptr);                             \
 157     (typeof(ptr)) (__ptr + (off)); })
 158 #endif
 159
 160 #ifndef OPTIMIZER_HIDE_VAR
 161 #define OPTIMIZER_HIDE_VAR(var) barrier()
 162 #endif
 163
 164 /* Not-quite-unique ID. */
 165 #ifndef __UNIQUE_ID
 166 # define __UNIQUE_ID(prefix) __PASTE(__PASTE(__UNIQUE_ID_, prefix), __LINE__)
 167 #endif
 168
 169 #include <uapi/linux/types.h>
 170
 171 #define __READ_ONCE_SIZE                                                \
 172 ({                                                                      \
 173         switch (size) {                                                 \
 174         case 1: *(__u8 *)res = *(volatile __u8 *)p; break;              \
 175         case 2: *(__u16 *)res = *(volatile __u16 *)p; break;            \
 176         case 4: *(__u32 *)res = *(volatile __u32 *)p; break;            \
 177         case 8: *(__u64 *)res = *(volatile __u64 *)p; break;            \
 178         default:                                                        \
 179                 barrier();                                              \
 180                 __builtin_memcpy((void *)res, (const void *)p, size);   \
 181                 barrier();                                              \
 182         }                                                               \
 183 })
 184
 185 static __always_inline
 186 void __read_once_size(const volatile void *p, void *res, int size)
 187 {
 188         __READ_ONCE_SIZE;
 189 }
 190
 191 #ifdef CONFIG_KASAN
 192 /*
 193  * We can't declare function 'inline' because __no_sanitize_address confilcts
 194  * with inlining. Attempt to inline it may cause a build failure.
 195  *      https://gcc.gnu.org/bugzilla/show_bug.cgi?id=67368
 196  * '__maybe_unused' allows us to avoid defined-but-not-used warnings.
 197  */
 198 # define __no_kasan_or_inline __no_sanitize_address __maybe_unused
 199 #else
 200 # define __no_kasan_or_inline __always_inline
 201 #endif
 202
 203 static __no_kasan_or_inline
 204 void __read_once_size_nocheck(const volatile void *p, void *res, int size)
 205 {
 206         __READ_ONCE_SIZE;
 207 }
 208
 209 static __always_inline void __write_once_size(volatile void *p, void *res, int size)
 210 {
 211         switch (size) {
 212         case 1: *(volatile __u8 *)p = *(__u8 *)res; break;
 213         case 2: *(volatile __u16 *)p = *(__u16 *)res; break;
 214         case 4: *(volatile __u32 *)p = *(__u32 *)res; break;
 215         case 8: *(volatile __u64 *)p = *(__u64 *)res; break;
 216         default:
 217                 barrier();
 218                 __builtin_memcpy((void *)p, (const void *)res, size);
 219                 barrier();
 220         }
 221 }
 222
 223 /*
 224  * Prevent the compiler from merging or refetching reads or writes. The
 225  * compiler is also forbidden from reordering successive instances of
 226  * READ_ONCE and WRITE_ONCE, but only when the compiler is aware of some
 227  * particular ordering. One way to make the compiler aware of ordering is to
 228  * put the two invocations of READ_ONCE or WRITE_ONCE in different C
 229  * statements.
 230  *
 231  * These two macros will also work on aggregate data types like structs or
 232  * unions. If the size of the accessed data type exceeds the word size of
 233  * the machine (e.g., 32 bits or 64 bits) READ_ONCE() and WRITE_ONCE() will
 234  * fall back to memcpy(). There's at least two memcpy()s: one for the
 235  * __builtin_memcpy() and then one for the macro doing the copy of variable
 236  * - '__u' allocated on the stack.
 237  *
 238  * Their two major use cases are: (1) Mediating communication between
 239  * process-level code and irq/NMI handlers, all running on the same CPU,
 240  * and (2) Ensuring that the compiler does not fold, spindle, or otherwise
 241  * mutilate accesses that either do not require ordering or that interact
 242  * with an explicit memory barrier or atomic instruction that provides the
 243  * required ordering.
 244  */
 245 #include <asm/barrier.h>
 246 #include <linux/kasan-checks.h>
 247
 248 #define __READ_ONCE(x, check)                                           \
 249 ({                                                                      \
 250         union { typeof(x) __val; char __c[1]; } __u;                    \
 251         if (check)                                                      \
 252                 __read_once_size(&(x), __u.__c, sizeof(x));             \
 253         else                                                            \
 254                 __read_once_size_nocheck(&(x), __u.__c, sizeof(x));     \
 255         smp_read_barrier_depends(); /* Enforce dependency ordering from x */ \
 256         __u.__val;                                                      \
 257 })
 258 #define READ_ONCE(x) __READ_ONCE(x, 1)
 259
 260 /*
 261  * Use READ_ONCE_NOCHECK() instead of READ_ONCE() if you need
 262  * to hide memory access from KASAN.
 263  */
 264 #define READ_ONCE_NOCHECK(x) __READ_ONCE(x, 0)
 265
 266 static __no_kasan_or_inline
 267 unsigned long read_word_at_a_time(const void *addr)
 268 {
 269         kasan_check_read(addr, 1);
 270         return *(unsigned long *)addr;
 271 }
 272
 273 #define WRITE_ONCE(x, val) \
 274 ({                                                      \
 275         union { typeof(x) __val; char __c[1]; } __u =   \
 276                 { .__val = (__force typeof(x)) (val) }; \
 277         __write_once_size(&(x), __u.__c, sizeof(x));    \
 278         __u.__val;                                      \
 279 })
 280
 281 #endif /* __KERNEL__ */
 282
 283 /*
 284  * Force the compiler to emit 'sym' as a symbol, so that we can reference
 285  * it from inline assembler. Necessary in case 'sym' could be inlined
 286  * otherwise, or eliminated entirely due to lack of references that are
 287  * visible to the compiler.
 288  */
 289 #define __ADDRESSABLE(sym) \
 290         static void * __attribute__((section(".discard.addressable"), used)) \
 291                 __PASTE(__addressable_##sym, __LINE__) = (void *)&sym;
 292
 293 /**
 294  * offset_to_ptr - convert a relative memory offset to an absolute pointer
 295  * @off:        the address of the 32-bit offset value
 296  */
 297 static inline void *offset_to_ptr(const int *off)
 298 {
 299         return (void *)((unsigned long)off + *off);
 300 }
 301
 302 #endif /* __ASSEMBLY__ */
 303
 304 #ifndef __optimize
 305 # define __optimize(level)
 306 #endif
 307
 308 /* Compile time object size, -1 for unknown */
 309 #ifndef __compiletime_object_size
 310 # define __compiletime_object_size(obj) -1
 311 #endif
 312 #ifndef __compiletime_warning
 313 # define __compiletime_warning(message)
 314 #endif
 315 #ifndef __compiletime_error
 316 # define __compiletime_error(message)
 317 /*
 318  * Sparse complains of variable sized arrays due to the temporary variable in
 319  * __compiletime_assert. Unfortunately we can't just expand it out to make
 320  * sparse see a constant array size without breaking compiletime_assert on old
 321  * versions of GCC (e.g. 4.2.4), so hide the array from sparse altogether.
 322  */
 323 # ifndef __CHECKER__
 324 #  define __compiletime_error_fallback(condition) \
 325         do { ((void)sizeof(char[1 - 2 * condition])); } while (0)
 326 # endif
 327 #endif
 328 #ifndef __compiletime_error_fallback
 329 # define __compiletime_error_fallback(condition) do { } while (0)
 330 #endif
 331
 332 #ifdef __OPTIMIZE__
 333 # define __compiletime_assert(condition, msg, prefix, suffix)           \
 334         do {                                                            \
 335                 int __cond = !(condition);                              \
 336                 extern void prefix ## suffix(void) __compiletime_error(msg); \
 337                 if (__cond)                                             \
 338                         prefix ## suffix();                             \
 339                 __compiletime_error_fallback(__cond);                   \
 340         } while (0)
 341 #else
 342 # define __compiletime_assert(condition, msg, prefix, suffix) do { } while (0)
 343 #endif
 344
 345 #define _compiletime_assert(condition, msg, prefix, suffix) \
 346         __compiletime_assert(condition, msg, prefix, suffix)
 347
 348 /**
 349  * compiletime_assert - break build and emit msg if condition is false
 350  * @condition: a compile-time constant condition to check
 351  * @msg:       a message to emit if condition is false
 352  *
 353  * In tradition of POSIX assert, this macro will break the build if the
 354  * supplied condition is *false*, emitting the supplied error message if the
 355  * compiler has support to do so.
 356  */
 357 #define compiletime_assert(condition, msg) \
 358         _compiletime_assert(condition, msg, __compiletime_assert_, __LINE__)
 359
 360 #define compiletime_assert_atomic_type(t)                               \
 361         compiletime_assert(__native_word(t),                            \
 362                 "Need native word sized stores/loads for atomicity.")
 363
 364 #endif /* __LINUX_COMPILER_H */