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  1. #ifndef __LINUX_COMPILER_H
  2. #error "Please don't include <linux/compiler-gcc.h> directly, include <linux/compiler.h> instead."
  3. #endif
  4.  
  5. /*
  6.  * Common definitions for all gcc versions go here.
  7.  */
  8. #define GCC_VERSION (__GNUC__ * 10000           \
  9.                      + __GNUC_MINOR__ * 100     \
  10.                      + __GNUC_PATCHLEVEL__)
  11.  
  12. /* Optimization barrier */
  13.  
  14. /* The "volatile" is due to gcc bugs */
  15. #define barrier() __asm__ __volatile__("": : :"memory")
  16. /*
  17.  * This version is i.e. to prevent dead stores elimination on @ptr
  18.  * where gcc and llvm may behave differently when otherwise using
  19.  * normal barrier(): while gcc behavior gets along with a normal
  20.  * barrier(), llvm needs an explicit input variable to be assumed
  21.  * clobbered. The issue is as follows: while the inline asm might
  22.  * access any memory it wants, the compiler could have fit all of
  23.  * @ptr into memory registers instead, and since @ptr never escaped
  24.  * from that, it proofed that the inline asm wasn't touching any of
  25.  * it. This version works well with both compilers, i.e. we're telling
  26.  * the compiler that the inline asm absolutely may see the contents
  27.  * of @ptr. See also: https://llvm.org/bugs/show_bug.cgi?id=15495
  28.  */
  29. #define barrier_data(ptr) __asm__ __volatile__("": :"r"(ptr) :"memory")
  30.  
  31. /*
  32.  * This macro obfuscates arithmetic on a variable address so that gcc
  33.  * shouldn't recognize the original var, and make assumptions about it.
  34.  *
  35.  * This is needed because the C standard makes it undefined to do
  36.  * pointer arithmetic on "objects" outside their boundaries and the
  37.  * gcc optimizers assume this is the case. In particular they
  38.  * assume such arithmetic does not wrap.
  39.  *
  40.  * A miscompilation has been observed because of this on PPC.
  41.  * To work around it we hide the relationship of the pointer and the object
  42.  * using this macro.
  43.  *
  44.  * Versions of the ppc64 compiler before 4.1 had a bug where use of
  45.  * RELOC_HIDE could trash r30. The bug can be worked around by changing
  46.  * the inline assembly constraint from =g to =r, in this particular
  47.  * case either is valid.
  48.  */
  49. #define RELOC_HIDE(ptr, off)                                            \
  50. ({                                                                      \
  51.         unsigned long __ptr;                                            \
  52.         __asm__ ("" : "=r"(__ptr) : "0"(ptr));                          \
  53.         (typeof(ptr)) (__ptr + (off));                                  \
  54. })
  55.  
  56. /* Make the optimizer believe the variable can be manipulated arbitrarily. */
  57. #define OPTIMIZER_HIDE_VAR(var)                                         \
  58.         __asm__ ("" : "=r" (var) : "0" (var))
  59.  
  60. #ifdef __CHECKER__
  61. #define __must_be_array(a)      0
  62. #else
  63. /* &a[0] degrades to a pointer: a different type from an array */
  64. #define __must_be_array(a)      BUILD_BUG_ON_ZERO(__same_type((a), &(a)[0]))
  65. #endif
  66.  
  67. /*
  68.  * Force always-inline if the user requests it so via the .config,
  69.  * or if gcc is too old:
  70.  */
  71. #if !defined(CONFIG_ARCH_SUPPORTS_OPTIMIZED_INLINING) ||                \
  72.     !defined(CONFIG_OPTIMIZE_INLINING) || (__GNUC__ < 4)
  73. #define inline          inline          __attribute__((always_inline)) notrace
  74. #define __inline__      __inline__      __attribute__((always_inline)) notrace
  75. #define __inline        __inline        __attribute__((always_inline)) notrace
  76. #else
  77. /* A lot of inline functions can cause havoc with function tracing */
  78. #define inline          inline          notrace
  79. #define __inline__      __inline__      notrace
  80. #define __inline        __inline        notrace
  81. #endif
  82.  
  83. #define __always_inline inline __attribute__((always_inline))
  84. #define  noinline       __attribute__((noinline))
  85.  
  86. #define __deprecated    __attribute__((deprecated))
  87. #define __packed        __attribute__((packed))
  88. #define __weak          __attribute__((weak))
  89. #define __alias(symbol) __attribute__((alias(#symbol)))
  90.  
  91. /*
  92.  * it doesn't make sense on ARM (currently the only user of __naked)
  93.  * to trace naked functions because then mcount is called without
  94.  * stack and frame pointer being set up and there is no chance to
  95.  * restore the lr register to the value before mcount was called.
  96.  *
  97.  * The asm() bodies of naked functions often depend on standard calling
  98.  * conventions, therefore they must be noinline and noclone.
  99.  *
  100.  * GCC 4.[56] currently fail to enforce this, so we must do so ourselves.
  101.  * See GCC PR44290.
  102.  */
  103. #define __naked         __attribute__((naked)) noinline __noclone notrace
  104.  
  105. #define __noreturn      __attribute__((noreturn))
  106.  
  107. /*
  108.  * From the GCC manual:
  109.  *
  110.  * Many functions have no effects except the return value and their
  111.  * return value depends only on the parameters and/or global
  112.  * variables.  Such a function can be subject to common subexpression
  113.  * elimination and loop optimization just as an arithmetic operator
  114.  * would be.
  115.  * [...]
  116.  */
  117. #define __pure                  __attribute__((pure))
  118. #define __aligned(x)            __attribute__((aligned(x)))
  119. #define __printf(a, b)          __attribute__((format(printf, a, b)))
  120. #define __scanf(a, b)           __attribute__((format(scanf, a, b)))
  121. #define __attribute_const__     __attribute__((__const__))
  122. #define __maybe_unused          __attribute__((unused))
  123. #define __always_unused         __attribute__((unused))
  124.  
  125. /* gcc version specific checks */
  126.  
  127. #if GCC_VERSION < 30200
  128. # error Sorry, your compiler is too old - please upgrade it.
  129. #endif
  130.  
  131. #if GCC_VERSION < 30300
  132. # define __used                 __attribute__((__unused__))
  133. #else
  134. # define __used                 __attribute__((__used__))
  135. #endif
  136.  
  137. #ifdef CONFIG_GCOV_KERNEL
  138. # if GCC_VERSION < 30400
  139. #   error "GCOV profiling support for gcc versions below 3.4 not included"
  140. # endif /* __GNUC_MINOR__ */
  141. #endif /* CONFIG_GCOV_KERNEL */
  142.  
  143. #if GCC_VERSION >= 30400
  144. #define __must_check            __attribute__((warn_unused_result))
  145. #endif
  146.  
  147. #if GCC_VERSION >= 40000
  148.  
  149. /* GCC 4.1.[01] miscompiles __weak */
  150. #ifdef __KERNEL__
  151. # if GCC_VERSION >= 40100 &&  GCC_VERSION <= 40101
  152. #  error Your version of gcc miscompiles the __weak directive
  153. # endif
  154. #endif
  155.  
  156. #define __used                  __attribute__((__used__))
  157. #define __compiler_offsetof(a, b)                                       \
  158.         __builtin_offsetof(a, b)
  159.  
  160. #if GCC_VERSION >= 40100 && GCC_VERSION < 40600
  161. # define __compiletime_object_size(obj) __builtin_object_size(obj, 0)
  162. #endif
  163.  
  164. #if GCC_VERSION >= 40300
  165. /* Mark functions as cold. gcc will assume any path leading to a call
  166.  * to them will be unlikely.  This means a lot of manual unlikely()s
  167.  * are unnecessary now for any paths leading to the usual suspects
  168.  * like BUG(), printk(), panic() etc. [but let's keep them for now for
  169.  * older compilers]
  170.  *
  171.  * Early snapshots of gcc 4.3 don't support this and we can't detect this
  172.  * in the preprocessor, but we can live with this because they're unreleased.
  173.  * Maketime probing would be overkill here.
  174.  *
  175.  * gcc also has a __attribute__((__hot__)) to move hot functions into
  176.  * a special section, but I don't see any sense in this right now in
  177.  * the kernel context
  178.  */
  179. #define __cold                  __attribute__((__cold__))
  180.  
  181. #define __UNIQUE_ID(prefix) __PASTE(__PASTE(__UNIQUE_ID_, prefix), __COUNTER__)
  182.  
  183. #ifndef __CHECKER__
  184. # define __compiletime_warning(message) __attribute__((warning(message)))
  185. # define __compiletime_error(message) __attribute__((error(message)))
  186. #endif /* __CHECKER__ */
  187. #endif /* GCC_VERSION >= 40300 */
  188.  
  189. #if GCC_VERSION >= 40500
  190. /*
  191.  * Mark a position in code as unreachable.  This can be used to
  192.  * suppress control flow warnings after asm blocks that transfer
  193.  * control elsewhere.
  194.  *
  195.  * Early snapshots of gcc 4.5 don't support this and we can't detect
  196.  * this in the preprocessor, but we can live with this because they're
  197.  * unreleased.  Really, we need to have autoconf for the kernel.
  198.  */
  199. #define unreachable() __builtin_unreachable()
  200.  
  201. /* Mark a function definition as prohibited from being cloned. */
  202. #define __noclone       __attribute__((__noclone__, __optimize__("no-tracer")))
  203.  
  204. #endif /* GCC_VERSION >= 40500 */
  205.  
  206. #if GCC_VERSION >= 40600
  207. /*
  208.  * When used with Link Time Optimization, gcc can optimize away C functions or
  209.  * variables which are referenced only from assembly code.  __visible tells the
  210.  * optimizer that something else uses this function or variable, thus preventing
  211.  * this.
  212.  */
  213. #define __visible       __attribute__((externally_visible))
  214. #endif
  215.  
  216.  
  217. #if GCC_VERSION >= 40900 && !defined(__CHECKER__)
  218. /*
  219.  * __assume_aligned(n, k): Tell the optimizer that the returned
  220.  * pointer can be assumed to be k modulo n. The second argument is
  221.  * optional (default 0), so we use a variadic macro to make the
  222.  * shorthand.
  223.  *
  224.  * Beware: Do not apply this to functions which may return
  225.  * ERR_PTRs. Also, it is probably unwise to apply it to functions
  226.  * returning extra information in the low bits (but in that case the
  227.  * compiler should see some alignment anyway, when the return value is
  228.  * massaged by 'flags = ptr & 3; ptr &= ~3;').
  229.  */
  230. #define __assume_aligned(a, ...) __attribute__((__assume_aligned__(a, ## __VA_ARGS__)))
  231. #endif
  232.  
  233. /*
  234.  * GCC 'asm goto' miscompiles certain code sequences:
  235.  *
  236.  *   http://gcc.gnu.org/bugzilla/show_bug.cgi?id=58670
  237.  *
  238.  * Work it around via a compiler barrier quirk suggested by Jakub Jelinek.
  239.  *
  240.  * (asm goto is automatically volatile - the naming reflects this.)
  241.  */
  242. #define asm_volatile_goto(x...) do { asm goto(x); asm (""); } while (0)
  243.  
  244. #ifdef CONFIG_ARCH_USE_BUILTIN_BSWAP
  245. #if GCC_VERSION >= 40400
  246. #define __HAVE_BUILTIN_BSWAP32__
  247. #define __HAVE_BUILTIN_BSWAP64__
  248. #endif
  249. #if GCC_VERSION >= 40800 || (defined(__powerpc__) && GCC_VERSION >= 40600)
  250. #define __HAVE_BUILTIN_BSWAP16__
  251. #endif
  252. #endif /* CONFIG_ARCH_USE_BUILTIN_BSWAP */
  253.  
  254. #if GCC_VERSION >= 70000
  255. #define KASAN_ABI_VERSION 5
  256. #elif GCC_VERSION >= 50000
  257. #define KASAN_ABI_VERSION 4
  258. #elif GCC_VERSION >= 40902
  259. #define KASAN_ABI_VERSION 3
  260. #endif
  261.  
  262. #if GCC_VERSION >= 40902
  263. /*
  264.  * Tell the compiler that address safety instrumentation (KASAN)
  265.  * should not be applied to that function.
  266.  * Conflicts with inlining: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=67368
  267.  */
  268. #define __no_sanitize_address __attribute__((no_sanitize_address))
  269. #endif
  270.  
  271. #endif  /* gcc version >= 40000 specific checks */
  272.  
  273. #if !defined(__noclone)
  274. #define __noclone       /* not needed */
  275. #endif
  276.  
  277. #if !defined(__no_sanitize_address)
  278. #define __no_sanitize_address
  279. #endif
  280.  
  281. /*
  282.  * A trick to suppress uninitialized variable warning without generating any
  283.  * code
  284.  */
  285. #define uninitialized_var(x) x = x
  286.