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