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 #ifdef CONFIG_SPARSE_RCU_POINTER
  21 # define __rcu          __attribute__((noderef, address_space(4)))
  22 #else
  23 # define __rcu
  24 #endif
  25 extern void __chk_user_ptr(const volatile void __user *);
  26 extern void __chk_io_ptr(const volatile void __iomem *);
  27 #else
  28 # define __user
  29 # define __kernel
  30 # define __safe
  31 # define __force
  32 # define __nocast
  33 # define __iomem
  34 # define __chk_user_ptr(x) (void)0
  35 # define __chk_io_ptr(x) (void)0
  36 # define __builtin_warning(x, y...) (1)
  37 # define __must_hold(x)
  38 # define __acquires(x)
  39 # define __releases(x)
  40 # define __acquire(x) (void)0
  41 # define __release(x) (void)0
  42 # define __cond_lock(x,c) (c)
  43 # define __percpu
  44 # define __rcu
  45 #endif
  46
  47 /* Indirect macros required for expanded argument pasting, eg. __LINE__. */
  48 #define ___PASTE(a,b) a##b
  49 #define __PASTE(a,b) ___PASTE(a,b)
  50
  51 #ifdef __KERNEL__
  52
  53 #ifdef __GNUC__
  54 #include <linux/compiler-gcc.h>
  55 #endif
  56
  57 #define notrace __attribute__((no_instrument_function))
  58
  59 /* Intel compiler defines __GNUC__. So we will overwrite implementations
  60  * coming from above header files here
  61  */
  62 #ifdef __INTEL_COMPILER
  63 # include <linux/compiler-intel.h>
  64 #endif
  65
  66 /* Clang compiler defines __GNUC__. So we will overwrite implementations
  67  * coming from above header files here
  68  */
  69 #ifdef __clang__
  70 #include <linux/compiler-clang.h>
  71 #endif
  72
  73 /*
  74  * Generic compiler-dependent macros required for kernel
  75  * build go below this comment. Actual compiler/compiler version
  76  * specific implementations come from the above header files
  77  */
  78
  79 struct ftrace_branch_data {
  80         const char *func;
  81         const char *file;
  82         unsigned line;
  83         union {
  84                 struct {
  85                         unsigned long correct;
  86                         unsigned long incorrect;
  87                 };
  88                 struct {
  89                         unsigned long miss;
  90                         unsigned long hit;
  91                 };
  92                 unsigned long miss_hit[2];
  93         };
  94 };
  95
  96 /*
  97  * Note: DISABLE_BRANCH_PROFILING can be used by special lowlevel code
  98  * to disable branch tracing on a per file basis.
  99  */
 100 #if defined(CONFIG_TRACE_BRANCH_PROFILING) \
 101     && !defined(DISABLE_BRANCH_PROFILING) && !defined(__CHECKER__)
 102 void ftrace_likely_update(struct ftrace_branch_data *f, int val, int expect);
 103
 104 #define likely_notrace(x)       __builtin_expect(!!(x), 1)
 105 #define unlikely_notrace(x)     __builtin_expect(!!(x), 0)
 106
 107 #define __branch_check__(x, expect) ({                                  \
 108                         int ______r;                                    \
 109                         static struct ftrace_branch_data                \
 110                                 __attribute__((__aligned__(4)))         \
 111                                 __attribute__((section("_ftrace_annotated_branch"))) \
 112                                 ______f = {                             \
 113                                 .func = __func__,                       \
 114                                 .file = __FILE__,                       \
 115                                 .line = __LINE__,                       \
 116                         };                                              \
 117                         ______r = likely_notrace(x);                    \
 118                         ftrace_likely_update(&______f, ______r, expect); \
 119                         ______r;                                        \
 120                 })
 121
 122 /*
 123  * Using __builtin_constant_p(x) to ignore cases where the return
 124  * value is always the same.  This idea is taken from a similar patch
 125  * written by Daniel Walker.
 126  */
 127 # ifndef likely
 128 #  define likely(x)     (__builtin_constant_p(x) ? !!(x) : __branch_check__(x, 1))
 129 # endif
 130 # ifndef unlikely
 131 #  define unlikely(x)   (__builtin_constant_p(x) ? !!(x) : __branch_check__(x, 0))
 132 # endif
 133
 134 #ifdef CONFIG_PROFILE_ALL_BRANCHES
 135 /*
 136  * "Define 'is'", Bill Clinton
 137  * "Define 'if'", Steven Rostedt
 138  */
 139 #define if(cond, ...) __trace_if( (cond , ## __VA_ARGS__) )
 140 #define __trace_if(cond) \
 141         if (__builtin_constant_p((cond)) ? !!(cond) :                   \
 142         ({                                                              \
 143                 int ______r;                                            \
 144                 static struct ftrace_branch_data                        \
 145                         __attribute__((__aligned__(4)))                 \
 146                         __attribute__((section("_ftrace_branch")))      \
 147                         ______f = {                                     \
 148                                 .func = __func__,                       \
 149                                 .file = __FILE__,                       \
 150                                 .line = __LINE__,                       \
 151                         };                                              \
 152                 ______r = !!(cond);                                     \
 153                 ______f.miss_hit[______r]++;                                    \
 154                 ______r;                                                \
 155         }))
 156 #endif /* CONFIG_PROFILE_ALL_BRANCHES */
 157
 158 #else
 159 # define likely(x)      __builtin_expect(!!(x), 1)
 160 # define unlikely(x)    __builtin_expect(!!(x), 0)
 161 #endif
 162
 163 /* Optimization barrier */
 164 #ifndef barrier
 165 # define barrier() __memory_barrier()
 166 #endif
 167
 168 /* Unreachable code */
 169 #ifndef unreachable
 170 # define unreachable() do { } while (1)
 171 #endif
 172
 173 #ifndef RELOC_HIDE
 174 # define RELOC_HIDE(ptr, off)                                   \
 175   ({ unsigned long __ptr;                                       \
 176      __ptr = (unsigned long) (ptr);                             \
 177     (typeof(ptr)) (__ptr + (off)); })
 178 #endif
 179
 180 #ifndef OPTIMIZER_HIDE_VAR
 181 #define OPTIMIZER_HIDE_VAR(var) barrier()
 182 #endif
 183
 184 /* Not-quite-unique ID. */
 185 #ifndef __UNIQUE_ID
 186 # define __UNIQUE_ID(prefix) __PASTE(__PASTE(__UNIQUE_ID_, prefix), __LINE__)
 187 #endif
 188
 189 #endif /* __KERNEL__ */
 190
 191 #endif /* __ASSEMBLY__ */
 192
 193 #ifdef __KERNEL__
 194 /*
 195  * Allow us to mark functions as 'deprecated' and have gcc emit a nice
 196  * warning for each use, in hopes of speeding the functions removal.
 197  * Usage is:
 198  *              int __deprecated foo(void)
 199  */
 200 #ifndef __deprecated
 201 # define __deprecated           /* unimplemented */
 202 #endif
 203
 204 #ifdef MODULE
 205 #define __deprecated_for_modules __deprecated
 206 #else
 207 #define __deprecated_for_modules
 208 #endif
 209
 210 #ifndef __must_check
 211 #define __must_check
 212 #endif
 213
 214 #ifndef CONFIG_ENABLE_MUST_CHECK
 215 #undef __must_check
 216 #define __must_check
 217 #endif
 218 #ifndef CONFIG_ENABLE_WARN_DEPRECATED
 219 #undef __deprecated
 220 #undef __deprecated_for_modules
 221 #define __deprecated
 222 #define __deprecated_for_modules
 223 #endif
 224
 225 /*
 226  * Allow us to avoid 'defined but not used' warnings on functions and data,
 227  * as well as force them to be emitted to the assembly file.
 228  *
 229  * As of gcc 3.4, static functions that are not marked with attribute((used))
 230  * may be elided from the assembly file.  As of gcc 3.4, static data not so
 231  * marked will not be elided, but this may change in a future gcc version.
 232  *
 233  * NOTE: Because distributions shipped with a backported unit-at-a-time
 234  * compiler in gcc 3.3, we must define __used to be __attribute__((used))
 235  * for gcc >=3.3 instead of 3.4.
 236  *
 237  * In prior versions of gcc, such functions and data would be emitted, but
 238  * would be warned about except with attribute((unused)).
 239  *
 240  * Mark functions that are referenced only in inline assembly as __used so
 241  * the code is emitted even though it appears to be unreferenced.
 242  */
 243 #ifndef __used
 244 # define __used                 /* unimplemented */
 245 #endif
 246
 247 #ifndef __maybe_unused
 248 # define __maybe_unused         /* unimplemented */
 249 #endif
 250
 251 #ifndef __always_unused
 252 # define __always_unused        /* unimplemented */
 253 #endif
 254
 255 #ifndef noinline
 256 #define noinline
 257 #endif
 258
 259 /*
 260  * Rather then using noinline to prevent stack consumption, use
 261  * noinline_for_stack instead.  For documentation reasons.
 262  */
 263 #define noinline_for_stack noinline
 264
 265 #ifndef __always_inline
 266 #define __always_inline inline
 267 #endif
 268
 269 #endif /* __KERNEL__ */
 270
 271 /*
 272  * From the GCC manual:
 273  *
 274  * Many functions do not examine any values except their arguments,
 275  * and have no effects except the return value.  Basically this is
 276  * just slightly more strict class than the `pure' attribute above,
 277  * since function is not allowed to read global memory.
 278  *
 279  * Note that a function that has pointer arguments and examines the
 280  * data pointed to must _not_ be declared `const'.  Likewise, a
 281  * function that calls a non-`const' function usually must not be
 282  * `const'.  It does not make sense for a `const' function to return
 283  * `void'.
 284  */
 285 #ifndef __attribute_const__
 286 # define __attribute_const__    /* unimplemented */
 287 #endif
 288
 289 /*
 290  * Tell gcc if a function is cold. The compiler will assume any path
 291  * directly leading to the call is unlikely.
 292  */
 293
 294 #ifndef __cold
 295 #define __cold
 296 #endif
 297
 298 /* Simple shorthand for a section definition */
 299 #ifndef __section
 300 # define __section(S) __attribute__ ((__section__(#S)))
 301 #endif
 302
 303 #ifndef __visible
 304 #define __visible
 305 #endif
 306
 307 /* Are two types/vars the same type (ignoring qualifiers)? */
 308 #ifndef __same_type
 309 # define __same_type(a, b) __builtin_types_compatible_p(typeof(a), typeof(b))
 310 #endif
 311
 312 /* Is this type a native word size -- useful for atomic operations */
 313 #ifndef __native_word
 314 # define __native_word(t) (sizeof(t) == sizeof(int) || sizeof(t) == sizeof(long))
 315 #endif
 316
 317 /* Compile time object size, -1 for unknown */
 318 #ifndef __compiletime_object_size
 319 # define __compiletime_object_size(obj) -1
 320 #endif
 321 #ifndef __compiletime_warning
 322 # define __compiletime_warning(message)
 323 #endif
 324 #ifndef __compiletime_error
 325 # define __compiletime_error(message)
 326 /*
 327  * Sparse complains of variable sized arrays due to the temporary variable in
 328  * __compiletime_assert. Unfortunately we can't just expand it out to make
 329  * sparse see a constant array size without breaking compiletime_assert on old
 330  * versions of GCC (e.g. 4.2.4), so hide the array from sparse altogether.
 331  */
 332 # ifndef __CHECKER__
 333 #  define __compiletime_error_fallback(condition) \
 334         do { ((void)sizeof(char[1 - 2 * condition])); } while (0)
 335 # endif
 336 #endif
 337 #ifndef __compiletime_error_fallback
 338 # define __compiletime_error_fallback(condition) do { } while (0)
 339 #endif
 340
 341 #define __compiletime_assert(condition, msg, prefix, suffix)            \
 342         do {                                                            \
 343                 bool __cond = !(condition);                             \
 344                 extern void prefix ## suffix(void) __compiletime_error(msg); \
 345                 if (__cond)                                             \
 346                         prefix ## suffix();                             \
 347                 __compiletime_error_fallback(__cond);                   \
 348         } while (0)
 349
 350 #define _compiletime_assert(condition, msg, prefix, suffix) \
 351         __compiletime_assert(condition, msg, prefix, suffix)
 352
 353 /**
 354  * compiletime_assert - break build and emit msg if condition is false
 355  * @condition: a compile-time constant condition to check
 356  * @msg:       a message to emit if condition is false
 357  *
 358  * In tradition of POSIX assert, this macro will break the build if the
 359  * supplied condition is *false*, emitting the supplied error message if the
 360  * compiler has support to do so.
 361  */
 362 #define compiletime_assert(condition, msg) \
 363         _compiletime_assert(condition, msg, __compiletime_assert_, __LINE__)
 364
 365 #define compiletime_assert_atomic_type(t)                               \
 366         compiletime_assert(__native_word(t),                            \
 367                 "Need native word sized stores/loads for atomicity.")
 368
 369 /*
 370  * Prevent the compiler from merging or refetching accesses.  The compiler
 371  * is also forbidden from reordering successive instances of ACCESS_ONCE(),
 372  * but only when the compiler is aware of some particular ordering.  One way
 373  * to make the compiler aware of ordering is to put the two invocations of
 374  * ACCESS_ONCE() in different C statements.
 375  *
 376  * This macro does absolutely -nothing- to prevent the CPU from reordering,
 377  * merging, or refetching absolutely anything at any time.  Its main intended
 378  * use is to mediate communication between process-level code and irq/NMI
 379  * handlers, all running on the same CPU.
 380  */
 381 #define ACCESS_ONCE(x) (*(volatile typeof(x) *)&(x))
 382
 383 /* Ignore/forbid kprobes attach on very low level functions marked by this attribute: */
 384 #ifdef CONFIG_KPROBES
 385 # define __kprobes      __attribute__((__section__(".kprobes.text")))
 386 # define nokprobe_inline        __always_inline
 387 #else
 388 # define __kprobes
 389 # define nokprobe_inline        inline
 390 #endif
 391 #endif /* __LINUX_COMPILER_H */