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("ANNOTATE_REACHABLE counter=%c0"                   \
 103                      : : "i" (__COUNTER__));                            \
 104 })
 105 #define annotate_unreachable() ({                                       \
 106         asm volatile("ANNOTATE_UNREACHABLE counter=%c0"                 \
 107                      : : "i" (__COUNTER__));                            \
 108 })
 109 #else
 110 #define annotate_reachable()
 111 #define annotate_unreachable()
 112 #endif
 113
 114 #ifndef ASM_UNREACHABLE
 115 # define ASM_UNREACHABLE
 116 #endif
 117 #ifndef unreachable
 118 # define unreachable() do {             \
 119         annotate_unreachable();         \
 120         __builtin_unreachable();        \
 121 } while (0)
 122 #endif
 123
 124 /*
 125  * KENTRY - kernel entry point
 126  * This can be used to annotate symbols (functions or data) that are used
 127  * without their linker symbol being referenced explicitly. For example,
 128  * interrupt vector handlers, or functions in the kernel image that are found
 129  * programatically.
 130  *
 131  * Not required for symbols exported with EXPORT_SYMBOL, or initcalls. Those
 132  * are handled in their own way (with KEEP() in linker scripts).
 133  *
 134  * KENTRY can be avoided if the symbols in question are marked as KEEP() in the
 135  * linker script. For example an architecture could KEEP() its entire
 136  * boot/exception vector code rather than annotate each function and data.
 137  */
 138 #ifndef KENTRY
 139 # define KENTRY(sym)                                            \
 140         extern typeof(sym) sym;                                 \
 141         static const unsigned long __kentry_##sym               \
 142         __used                                                  \
 143         __section("___kentry" "+" #sym )                        \
 144         = (unsigned long)&sym;
 145 #endif
 146
 147 #ifndef RELOC_HIDE
 148 # define RELOC_HIDE(ptr, off)                                   \
 149   ({ unsigned long __ptr;                                       \
 150      __ptr = (unsigned long) (ptr);                             \
 151     (typeof(ptr)) (__ptr + (off)); })
 152 #endif
 153
 154 #ifndef OPTIMIZER_HIDE_VAR
 155 #define OPTIMIZER_HIDE_VAR(var) barrier()
 156 #endif
 157
 158 /* Not-quite-unique ID. */
 159 #ifndef __UNIQUE_ID
 160 # define __UNIQUE_ID(prefix) __PASTE(__PASTE(__UNIQUE_ID_, prefix), __LINE__)
 161 #endif
 162
 163 #include <uapi/linux/types.h>
 164
 165 #define __READ_ONCE_SIZE                                                \
 166 ({                                                                      \
 167         switch (size) {                                                 \
 168         case 1: *(__u8 *)res = *(volatile __u8 *)p; break;              \
 169         case 2: *(__u16 *)res = *(volatile __u16 *)p; break;            \
 170         case 4: *(__u32 *)res = *(volatile __u32 *)p; break;            \
 171         case 8: *(__u64 *)res = *(volatile __u64 *)p; break;            \
 172         default:                                                        \
 173                 barrier();                                              \
 174                 __builtin_memcpy((void *)res, (const void *)p, size);   \
 175                 barrier();                                              \
 176         }                                                               \
 177 })
 178
 179 static __always_inline
 180 void __read_once_size(const volatile void *p, void *res, int size)
 181 {
 182         __READ_ONCE_SIZE;
 183 }
 184
 185 #ifdef CONFIG_KASAN
 186 /*
 187  * We can't declare function 'inline' because __no_sanitize_address confilcts
 188  * with inlining. Attempt to inline it may cause a build failure.
 189  *      https://gcc.gnu.org/bugzilla/show_bug.cgi?id=67368
 190  * '__maybe_unused' allows us to avoid defined-but-not-used warnings.
 191  */
 192 # define __no_kasan_or_inline __no_sanitize_address __maybe_unused
 193 #else
 194 # define __no_kasan_or_inline __always_inline
 195 #endif
 196
 197 static __no_kasan_or_inline
 198 void __read_once_size_nocheck(const volatile void *p, void *res, int size)
 199 {
 200         __READ_ONCE_SIZE;
 201 }
 202
 203 static __always_inline void __write_once_size(volatile void *p, void *res, int size)
 204 {
 205         switch (size) {
 206         case 1: *(volatile __u8 *)p = *(__u8 *)res; break;
 207         case 2: *(volatile __u16 *)p = *(__u16 *)res; break;
 208         case 4: *(volatile __u32 *)p = *(__u32 *)res; break;
 209         case 8: *(volatile __u64 *)p = *(__u64 *)res; break;
 210         default:
 211                 barrier();
 212                 __builtin_memcpy((void *)p, (const void *)res, size);
 213                 barrier();
 214         }
 215 }
 216
 217 /*
 218  * Prevent the compiler from merging or refetching reads or writes. The
 219  * compiler is also forbidden from reordering successive instances of
 220  * READ_ONCE and WRITE_ONCE, but only when the compiler is aware of some
 221  * particular ordering. One way to make the compiler aware of ordering is to
 222  * put the two invocations of READ_ONCE or WRITE_ONCE in different C
 223  * statements.
 224  *
 225  * These two macros will also work on aggregate data types like structs or
 226  * unions. If the size of the accessed data type exceeds the word size of
 227  * the machine (e.g., 32 bits or 64 bits) READ_ONCE() and WRITE_ONCE() will
 228  * fall back to memcpy(). There's at least two memcpy()s: one for the
 229  * __builtin_memcpy() and then one for the macro doing the copy of variable
 230  * - '__u' allocated on the stack.
 231  *
 232  * Their two major use cases are: (1) Mediating communication between
 233  * process-level code and irq/NMI handlers, all running on the same CPU,
 234  * and (2) Ensuring that the compiler does not fold, spindle, or otherwise
 235  * mutilate accesses that either do not require ordering or that interact
 236  * with an explicit memory barrier or atomic instruction that provides the
 237  * required ordering.
 238  */
 239 #include <asm/barrier.h>
 240 #include <linux/kasan-checks.h>
 241
 242 #define __READ_ONCE(x, check)                                           \
 243 ({                                                                      \
 244         union { typeof(x) __val; char __c[1]; } __u;                    \
 245         if (check)                                                      \
 246                 __read_once_size(&(x), __u.__c, sizeof(x));             \
 247         else                                                            \
 248                 __read_once_size_nocheck(&(x), __u.__c, sizeof(x));     \
 249         smp_read_barrier_depends(); /* Enforce dependency ordering from x */ \
 250         __u.__val;                                                      \
 251 })
 252 #define READ_ONCE(x) __READ_ONCE(x, 1)
 253
 254 /*
 255  * Use READ_ONCE_NOCHECK() instead of READ_ONCE() if you need
 256  * to hide memory access from KASAN.
 257  */
 258 #define READ_ONCE_NOCHECK(x) __READ_ONCE(x, 0)
 259
 260 static __no_kasan_or_inline
 261 unsigned long read_word_at_a_time(const void *addr)
 262 {
 263         kasan_check_read(addr, 1);
 264         return *(unsigned long *)addr;
 265 }
 266
 267 #define WRITE_ONCE(x, val) \
 268 ({                                                      \
 269         union { typeof(x) __val; char __c[1]; } __u =   \
 270                 { .__val = (__force typeof(x)) (val) }; \
 271         __write_once_size(&(x), __u.__c, sizeof(x));    \
 272         __u.__val;                                      \
 273 })
 274
 275 #endif /* __KERNEL__ */
 276
 277 /*
 278  * Force the compiler to emit 'sym' as a symbol, so that we can reference
 279  * it from inline assembler. Necessary in case 'sym' could be inlined
 280  * otherwise, or eliminated entirely due to lack of references that are
 281  * visible to the compiler.
 282  */
 283 #define __ADDRESSABLE(sym) \
 284         static void * __section(".discard.addressable") __used \
 285                 __PASTE(__addressable_##sym, __LINE__) = (void *)&sym;
 286
 287 /**
 288  * offset_to_ptr - convert a relative memory offset to an absolute pointer
 289  * @off:        the address of the 32-bit offset value
 290  */
 291 static inline void *offset_to_ptr(const int *off)
 292 {
 293         return (void *)((unsigned long)off + *off);
 294 }
 295
 296 #else /* __ASSEMBLY__ */
 297
 298 #ifdef __KERNEL__
 299 #ifndef LINKER_SCRIPT
 300
 301 #ifdef CONFIG_STACK_VALIDATION
 302 .macro ANNOTATE_UNREACHABLE counter:req
 303 \counter:
 304         .pushsection .discard.unreachable
 305         .long \counter\()b -.
 306         .popsection
 307 .endm
 308
 309 .macro ANNOTATE_REACHABLE counter:req
 310 \counter:
 311         .pushsection .discard.reachable
 312         .long \counter\()b -.
 313         .popsection
 314 .endm
 315
 316 .macro ASM_UNREACHABLE
 317 999:
 318         .pushsection .discard.unreachable
 319         .long 999b - .
 320         .popsection
 321 .endm
 322 #else /* CONFIG_STACK_VALIDATION */
 323 .macro ANNOTATE_UNREACHABLE counter:req
 324 .endm
 325
 326 .macro ANNOTATE_REACHABLE counter:req
 327 .endm
 328
 329 .macro ASM_UNREACHABLE
 330 .endm
 331 #endif /* CONFIG_STACK_VALIDATION */
 332
 333 #endif /* LINKER_SCRIPT */
 334 #endif /* __KERNEL__ */
 335 #endif /* __ASSEMBLY__ */
 336
 337 /* Compile time object size, -1 for unknown */
 338 #ifndef __compiletime_object_size
 339 # define __compiletime_object_size(obj) -1
 340 #endif
 341 #ifndef __compiletime_warning
 342 # define __compiletime_warning(message)
 343 #endif
 344 #ifndef __compiletime_error
 345 # define __compiletime_error(message)
 346 #endif
 347
 348 #ifdef __OPTIMIZE__
 349 # define __compiletime_assert(condition, msg, prefix, suffix)           \
 350         do {                                                            \
 351                 extern void prefix ## suffix(void) __compiletime_error(msg); \
 352                 if (!(condition))                                       \
 353                         prefix ## suffix();                             \
 354         } while (0)
 355 #else
 356 # define __compiletime_assert(condition, msg, prefix, suffix) do { } while (0)
 357 #endif
 358
 359 #define _compiletime_assert(condition, msg, prefix, suffix) \
 360         __compiletime_assert(condition, msg, prefix, suffix)
 361
 362 /**
 363  * compiletime_assert - break build and emit msg if condition is false
 364  * @condition: a compile-time constant condition to check
 365  * @msg:       a message to emit if condition is false
 366  *
 367  * In tradition of POSIX assert, this macro will break the build if the
 368  * supplied condition is *false*, emitting the supplied error message if the
 369  * compiler has support to do so.
 370  */
 371 #define compiletime_assert(condition, msg) \
 372         _compiletime_assert(condition, msg, __compiletime_assert_, __LINE__)
 373
 374 #define compiletime_assert_atomic_type(t)                               \
 375         compiletime_assert(__native_word(t),                            \
 376                 "Need native word sized stores/loads for atomicity.")
 377
 378 /* &a[0] degrades to a pointer: a different type from an array */
 379 #define __must_be_array(a)      BUILD_BUG_ON_ZERO(__same_type((a), &(a)[0]))
 380
 381 #endif /* __LINUX_COMPILER_H */