include/linux/compiler.h

   1 #ifndef __LINUX_COMPILER_H
   2 #define __LINUX_COMPILER_H
   3
   4 #ifndef __ASSEMBLY__
   5
   6 #ifdef __CHECKER__
   7 # define __user         __attribute__((noderef, address_space(1)))
   8 # define __kernel       __attribute__((address_space(0)))
   9 # define __safe         __attribute__((safe))
  10 # define __force        __attribute__((force))
  11 # define __nocast       __attribute__((nocast))
  12 # define __iomem        __attribute__((noderef, address_space(2)))
  13 # define __must_hold(x) __attribute__((context(x,1,1)))
  14 # define __acquires(x)  __attribute__((context(x,0,1)))
  15 # define __releases(x)  __attribute__((context(x,1,0)))
  16 # define __acquire(x)   __context__(x,1)
  17 # define __release(x)   __context__(x,-1)
  18 # define __cond_lock(x,c)       ((c) ? ({ __acquire(x); 1; }) : 0)
  19 # define __percpu       __attribute__((noderef, address_space(3)))
  20 # define __pmem         __attribute__((noderef, address_space(5)))
  21 #ifdef CONFIG_SPARSE_RCU_POINTER
  22 # define __rcu          __attribute__((noderef, address_space(4)))
  23 #else
  24 # define __rcu
  25 #endif
  26 extern void __chk_user_ptr(const volatile void __user *);
  27 extern void __chk_io_ptr(const volatile void __iomem *);
  28 #else
  29 # define __user
  30 # define __kernel
  31 # define __safe
  32 # define __force
  33 # define __nocast
  34 # define __iomem
  35 # define __chk_user_ptr(x) (void)0
  36 # define __chk_io_ptr(x) (void)0
  37 # define __builtin_warning(x, y...) (1)
  38 # define __must_hold(x)
  39 # define __acquires(x)
  40 # define __releases(x)
  41 # define __acquire(x) (void)0
  42 # define __release(x) (void)0
  43 # define __cond_lock(x,c) (c)
  44 # define __percpu
  45 # define __rcu
  46 # define __pmem
  47 #endif
  48
  49 /* Indirect macros required for expanded argument pasting, eg. __LINE__. */
  50 #define ___PASTE(a,b) a##b
  51 #define __PASTE(a,b) ___PASTE(a,b)
  52
  53 #ifdef __KERNEL__
  54
  55 #ifdef __GNUC__
  56 #include <linux/compiler-gcc.h>
  57 #endif
  58
  59 #ifdef CC_USING_HOTPATCH
  60 #define notrace __attribute__((hotpatch(0,0)))
  61 #else
  62 #define notrace __attribute__((no_instrument_function))
  63 #endif
  64
  65 /* Intel compiler defines __GNUC__. So we will overwrite implementations
  66  * coming from above header files here
  67  */
  68 #ifdef __INTEL_COMPILER
  69 # include <linux/compiler-intel.h>
  70 #endif
  71
  72 /* Clang compiler defines __GNUC__. So we will overwrite implementations
  73  * coming from above header files here
  74  */
  75 #ifdef __clang__
  76 #include <linux/compiler-clang.h>
  77 #endif
  78
  79 /*
  80  * Generic compiler-dependent macros required for kernel
  81  * build go below this comment. Actual compiler/compiler version
  82  * specific implementations come from the above header files
  83  */
  84
  85 struct ftrace_branch_data {
  86         const char *func;
  87         const char *file;
  88         unsigned line;
  89         union {
  90                 struct {
  91                         unsigned long correct;
  92                         unsigned long incorrect;
  93                 };
  94                 struct {
  95                         unsigned long miss;
  96                         unsigned long hit;
  97                 };
  98                 unsigned long miss_hit[2];
  99         };
 100 };
 101
 102 /*
 103  * Note: DISABLE_BRANCH_PROFILING can be used by special lowlevel code
 104  * to disable branch tracing on a per file basis.
 105  */
 106 #if defined(CONFIG_TRACE_BRANCH_PROFILING) \
 107     && !defined(DISABLE_BRANCH_PROFILING) && !defined(__CHECKER__)
 108 void ftrace_likely_update(struct ftrace_branch_data *f, int val, int expect);
 109
 110 #define likely_notrace(x)       __builtin_expect(!!(x), 1)
 111 #define unlikely_notrace(x)     __builtin_expect(!!(x), 0)
 112
 113 #define __branch_check__(x, expect) ({                                  \
 114                         int ______r;                                    \
 115                         static struct ftrace_branch_data                \
 116                                 __attribute__((__aligned__(4)))         \
 117                                 __attribute__((section("_ftrace_annotated_branch"))) \
 118                                 ______f = {                             \
 119                                 .func = __func__,                       \
 120                                 .file = __FILE__,                       \
 121                                 .line = __LINE__,                       \
 122                         };                                              \
 123                         ______r = likely_notrace(x);                    \
 124                         ftrace_likely_update(&______f, ______r, expect); \
 125                         ______r;                                        \
 126                 })
 127
 128 /*
 129  * Using __builtin_constant_p(x) to ignore cases where the return
 130  * value is always the same.  This idea is taken from a similar patch
 131  * written by Daniel Walker.
 132  */
 133 # ifndef likely
 134 #  define likely(x)     (__builtin_constant_p(x) ? !!(x) : __branch_check__(x, 1))
 135 # endif
 136 # ifndef unlikely
 137 #  define unlikely(x)   (__builtin_constant_p(x) ? !!(x) : __branch_check__(x, 0))
 138 # endif
 139
 140 #ifdef CONFIG_PROFILE_ALL_BRANCHES
 141 /*
 142  * "Define 'is'", Bill Clinton
 143  * "Define 'if'", Steven Rostedt
 144  */
 145 #define if(cond, ...) __trace_if( (cond , ## __VA_ARGS__) )
 146 #define __trace_if(cond) \
 147         if (__builtin_constant_p((cond)) ? !!(cond) :                   \
 148         ({                                                              \
 149                 int ______r;                                            \
 150                 static struct ftrace_branch_data                        \
 151                         __attribute__((__aligned__(4)))                 \
 152                         __attribute__((section("_ftrace_branch")))      \
 153                         ______f = {                                     \
 154                                 .func = __func__,                       \
 155                                 .file = __FILE__,                       \
 156                                 .line = __LINE__,                       \
 157                         };                                              \
 158                 ______r = !!(cond);                                     \
 159                 ______f.miss_hit[______r]++;                                    \
 160                 ______r;                                                \
 161         }))
 162 #endif /* CONFIG_PROFILE_ALL_BRANCHES */
 163
 164 #else
 165 # define likely(x)      __builtin_expect(!!(x), 1)
 166 # define unlikely(x)    __builtin_expect(!!(x), 0)
 167 #endif
 168
 169 /* Optimization barrier */
 170 #ifndef barrier
 171 # define barrier() __memory_barrier()
 172 #endif
 173
 174 #ifndef barrier_data
 175 # define barrier_data(ptr) barrier()
 176 #endif
 177
 178 /* Unreachable code */
 179 #ifndef unreachable
 180 # define unreachable() do { } while (1)
 181 #endif
 182
 183 #ifndef RELOC_HIDE
 184 # define RELOC_HIDE(ptr, off)                                   \
 185   ({ unsigned long __ptr;                                       \
 186      __ptr = (unsigned long) (ptr);                             \
 187     (typeof(ptr)) (__ptr + (off)); })
 188 #endif
 189
 190 #ifndef OPTIMIZER_HIDE_VAR
 191 #define OPTIMIZER_HIDE_VAR(var) barrier()
 192 #endif
 193
 194 /* Not-quite-unique ID. */
 195 #ifndef __UNIQUE_ID
 196 # define __UNIQUE_ID(prefix) __PASTE(__PASTE(__UNIQUE_ID_, prefix), __LINE__)
 197 #endif
 198
 199 #include <uapi/linux/types.h>
 200
 201 static __always_inline void __read_once_size(const volatile void *p, void *res, int size)
 202 {
 203         switch (size) {
 204         case 1: *(__u8 *)res = *(volatile __u8 *)p; break;
 205         case 2: *(__u16 *)res = *(volatile __u16 *)p; break;
 206         case 4: *(__u32 *)res = *(volatile __u32 *)p; break;
 207         case 8: *(__u64 *)res = *(volatile __u64 *)p; break;
 208         default:
 209                 barrier();
 210                 __builtin_memcpy((void *)res, (const void *)p, size);
 211                 barrier();
 212         }
 213 }
 214
 215 static __always_inline void __write_once_size(volatile void *p, void *res, int size)
 216 {
 217         switch (size) {
 218         case 1: *(volatile __u8 *)p = *(__u8 *)res; break;
 219         case 2: *(volatile __u16 *)p = *(__u16 *)res; break;
 220         case 4: *(volatile __u32 *)p = *(__u32 *)res; break;
 221         case 8: *(volatile __u64 *)p = *(__u64 *)res; break;
 222         default:
 223                 barrier();
 224                 __builtin_memcpy((void *)p, (const void *)res, size);
 225                 barrier();
 226         }
 227 }
 228
 229 /*
 230  * Prevent the compiler from merging or refetching reads or writes. The
 231  * compiler is also forbidden from reordering successive instances of
 232  * READ_ONCE, WRITE_ONCE and ACCESS_ONCE (see below), but only when the
 233  * compiler is aware of some particular ordering.  One way to make the
 234  * compiler aware of ordering is to put the two invocations of READ_ONCE,
 235  * WRITE_ONCE or ACCESS_ONCE() in different C statements.
 236  *
 237  * In contrast to ACCESS_ONCE these two macros will also work on aggregate
 238  * data types like structs or unions. If the size of the accessed data
 239  * type exceeds the word size of the machine (e.g., 32 bits or 64 bits)
 240  * READ_ONCE() and WRITE_ONCE()  will fall back to memcpy and print a
 241  * compile-time warning.
 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
 251 #define READ_ONCE(x) \
 252         ({ union { typeof(x) __val; char __c[1]; } __u; __read_once_size(&(x), __u.__c, sizeof(x)); __u.__val; })
 253
 254 #define WRITE_ONCE(x, val) \
 255 ({                                                      \
 256         union { typeof(x) __val; char __c[1]; } __u =   \
 257                 { .__val = (__force typeof(x)) (val) }; \
 258         __write_once_size(&(x), __u.__c, sizeof(x));    \
 259         __u.__val;                                      \
 260 })
 261
 262 /**
 263  * READ_ONCE_CTRL - Read a value heading a control dependency
 264  * @x: The value to be read, heading the control dependency
 265  *
 266  * Control dependencies are tricky.  See Documentation/memory-barriers.txt
 267  * for important information on how to use them.  Note that in many cases,
 268  * use of smp_load_acquire() will be much simpler.  Control dependencies
 269  * should be avoided except on the hottest of hotpaths.
 270  */
 271 #define READ_ONCE_CTRL(x) \
 272 ({ \
 273         typeof(x) __val = READ_ONCE(x); \
 274         smp_read_barrier_depends(); /* Enforce control dependency. */ \
 275         __val; \
 276 })
 277
 278 #endif /* __KERNEL__ */
 279
 280 #endif /* __ASSEMBLY__ */
 281
 282 #ifdef __KERNEL__
 283 /*
 284  * Allow us to mark functions as 'deprecated' and have gcc emit a nice
 285  * warning for each use, in hopes of speeding the functions removal.
 286  * Usage is:
 287  *              int __deprecated foo(void)
 288  */
 289 #ifndef __deprecated
 290 # define __deprecated           /* unimplemented */
 291 #endif
 292
 293 #ifdef MODULE
 294 #define __deprecated_for_modules __deprecated
 295 #else
 296 #define __deprecated_for_modules
 297 #endif
 298
 299 #ifndef __must_check
 300 #define __must_check
 301 #endif
 302
 303 #ifndef CONFIG_ENABLE_MUST_CHECK
 304 #undef __must_check
 305 #define __must_check
 306 #endif
 307 #ifndef CONFIG_ENABLE_WARN_DEPRECATED
 308 #undef __deprecated
 309 #undef __deprecated_for_modules
 310 #define __deprecated
 311 #define __deprecated_for_modules
 312 #endif
 313
 314 /*
 315  * Allow us to avoid 'defined but not used' warnings on functions and data,
 316  * as well as force them to be emitted to the assembly file.
 317  *
 318  * As of gcc 3.4, static functions that are not marked with attribute((used))
 319  * may be elided from the assembly file.  As of gcc 3.4, static data not so
 320  * marked will not be elided, but this may change in a future gcc version.
 321  *
 322  * NOTE: Because distributions shipped with a backported unit-at-a-time
 323  * compiler in gcc 3.3, we must define __used to be __attribute__((used))
 324  * for gcc >=3.3 instead of 3.4.
 325  *
 326  * In prior versions of gcc, such functions and data would be emitted, but
 327  * would be warned about except with attribute((unused)).
 328  *
 329  * Mark functions that are referenced only in inline assembly as __used so
 330  * the code is emitted even though it appears to be unreferenced.
 331  */
 332 #ifndef __used
 333 # define __used                 /* unimplemented */
 334 #endif
 335
 336 #ifndef __maybe_unused
 337 # define __maybe_unused         /* unimplemented */
 338 #endif
 339
 340 #ifndef __always_unused
 341 # define __always_unused        /* unimplemented */
 342 #endif
 343
 344 #ifndef noinline
 345 #define noinline
 346 #endif
 347
 348 /*
 349  * Rather then using noinline to prevent stack consumption, use
 350  * noinline_for_stack instead.  For documentation reasons.
 351  */
 352 #define noinline_for_stack noinline
 353
 354 #ifndef __always_inline
 355 #define __always_inline inline
 356 #endif
 357
 358 #endif /* __KERNEL__ */
 359
 360 /*
 361  * From the GCC manual:
 362  *
 363  * Many functions do not examine any values except their arguments,
 364  * and have no effects except the return value.  Basically this is
 365  * just slightly more strict class than the `pure' attribute above,
 366  * since function is not allowed to read global memory.
 367  *
 368  * Note that a function that has pointer arguments and examines the
 369  * data pointed to must _not_ be declared `const'.  Likewise, a
 370  * function that calls a non-`const' function usually must not be
 371  * `const'.  It does not make sense for a `const' function to return
 372  * `void'.
 373  */
 374 #ifndef __attribute_const__
 375 # define __attribute_const__    /* unimplemented */
 376 #endif
 377
 378 /*
 379  * Tell gcc if a function is cold. The compiler will assume any path
 380  * directly leading to the call is unlikely.
 381  */
 382
 383 #ifndef __cold
 384 #define __cold
 385 #endif
 386
 387 /* Simple shorthand for a section definition */
 388 #ifndef __section
 389 # define __section(S) __attribute__ ((__section__(#S)))
 390 #endif
 391
 392 #ifndef __visible
 393 #define __visible
 394 #endif
 395
 396 /* Are two types/vars the same type (ignoring qualifiers)? */
 397 #ifndef __same_type
 398 # define __same_type(a, b) __builtin_types_compatible_p(typeof(a), typeof(b))
 399 #endif
 400
 401 /* Is this type a native word size -- useful for atomic operations */
 402 #ifndef __native_word
 403 # define __native_word(t) (sizeof(t) == sizeof(char) || sizeof(t) == sizeof(short) || sizeof(t) == sizeof(int) || sizeof(t) == sizeof(long))
 404 #endif
 405
 406 /* Compile time object size, -1 for unknown */
 407 #ifndef __compiletime_object_size
 408 # define __compiletime_object_size(obj) -1
 409 #endif
 410 #ifndef __compiletime_warning
 411 # define __compiletime_warning(message)
 412 #endif
 413 #ifndef __compiletime_error
 414 # define __compiletime_error(message)
 415 /*
 416  * Sparse complains of variable sized arrays due to the temporary variable in
 417  * __compiletime_assert. Unfortunately we can't just expand it out to make
 418  * sparse see a constant array size without breaking compiletime_assert on old
 419  * versions of GCC (e.g. 4.2.4), so hide the array from sparse altogether.
 420  */
 421 # ifndef __CHECKER__
 422 #  define __compiletime_error_fallback(condition) \
 423         do { ((void)sizeof(char[1 - 2 * condition])); } while (0)
 424 # endif
 425 #endif
 426 #ifndef __compiletime_error_fallback
 427 # define __compiletime_error_fallback(condition) do { } while (0)
 428 #endif
 429
 430 #define __compiletime_assert(condition, msg, prefix, suffix)            \
 431         do {                                                            \
 432                 bool __cond = !(condition);                             \
 433                 extern void prefix ## suffix(void) __compiletime_error(msg); \
 434                 if (__cond)                                             \
 435                         prefix ## suffix();                             \
 436                 __compiletime_error_fallback(__cond);                   \
 437         } while (0)
 438
 439 #define _compiletime_assert(condition, msg, prefix, suffix) \
 440         __compiletime_assert(condition, msg, prefix, suffix)
 441
 442 /**
 443  * compiletime_assert - break build and emit msg if condition is false
 444  * @condition: a compile-time constant condition to check
 445  * @msg:       a message to emit if condition is false
 446  *
 447  * In tradition of POSIX assert, this macro will break the build if the
 448  * supplied condition is *false*, emitting the supplied error message if the
 449  * compiler has support to do so.
 450  */
 451 #define compiletime_assert(condition, msg) \
 452         _compiletime_assert(condition, msg, __compiletime_assert_, __LINE__)
 453
 454 #define compiletime_assert_atomic_type(t)                               \
 455         compiletime_assert(__native_word(t),                            \
 456                 "Need native word sized stores/loads for atomicity.")
 457
 458 /*
 459  * Prevent the compiler from merging or refetching accesses.  The compiler
 460  * is also forbidden from reordering successive instances of ACCESS_ONCE(),
 461  * but only when the compiler is aware of some particular ordering.  One way
 462  * to make the compiler aware of ordering is to put the two invocations of
 463  * ACCESS_ONCE() in different C statements.
 464  *
 465  * ACCESS_ONCE will only work on scalar types. For union types, ACCESS_ONCE
 466  * on a union member will work as long as the size of the member matches the
 467  * size of the union and the size is smaller than word size.
 468  *
 469  * The major use cases of ACCESS_ONCE used to be (1) Mediating communication
 470  * between process-level code and irq/NMI handlers, all running on the same CPU,
 471  * and (2) Ensuring that the compiler does not  fold, spindle, or otherwise
 472  * mutilate accesses that either do not require ordering or that interact
 473  * with an explicit memory barrier or atomic instruction that provides the
 474  * required ordering.
 475  *
 476  * If possible use READ_ONCE()/WRITE_ONCE() instead.
 477  */
 478 #define __ACCESS_ONCE(x) ({ \
 479          __maybe_unused typeof(x) __var = (__force typeof(x)) 0; \
 480         (volatile typeof(x) *)&(x); })
 481 #define ACCESS_ONCE(x) (*__ACCESS_ONCE(x))
 482
 483 /**
 484  * lockless_dereference() - safely load a pointer for later dereference
 485  * @p: The pointer to load
 486  *
 487  * Similar to rcu_dereference(), but for situations where the pointed-to
 488  * object's lifetime is managed by something other than RCU.  That
 489  * "something other" might be reference counting or simple immortality.
 490  */
 491 #define lockless_dereference(p) \
 492 ({ \
 493         typeof(p) _________p1 = READ_ONCE(p); \
 494         smp_read_barrier_depends(); /* Dependency order vs. p above. */ \
 495         (_________p1); \
 496 })
 497
 498 /* Ignore/forbid kprobes attach on very low level functions marked by this attribute: */
 499 #ifdef CONFIG_KPROBES
 500 # define __kprobes      __attribute__((__section__(".kprobes.text")))
 501 # define nokprobe_inline        __always_inline
 502 #else
 503 # define __kprobes
 504 # define nokprobe_inline        inline
 505 #endif
 506 #endif /* __LINUX_COMPILER_H */