include/linux/compiler-gcc.h

   1 /* SPDX-License-Identifier: GPL-2.0 */
   2 #ifndef __LINUX_COMPILER_TYPES_H
   3 #error "Please don't include <linux/compiler-gcc.h> directly, include <linux/compiler.h> instead."
   4 #endif
   5
   6 /*
   7  * Common definitions for all gcc versions go here.
   8  */
   9 #define GCC_VERSION (__GNUC__ * 10000           \
  10                      + __GNUC_MINOR__ * 100     \
  11                      + __GNUC_PATCHLEVEL__)
  12
  13 #if GCC_VERSION < 40600
  14 # error Sorry, your compiler is too old - please upgrade it.
  15 #endif
  16
  17 /* Optimization barrier */
  18
  19 /* The "volatile" is due to gcc bugs */
  20 #define barrier() __asm__ __volatile__("": : :"memory")
  21 /*
  22  * This version is i.e. to prevent dead stores elimination on @ptr
  23  * where gcc and llvm may behave differently when otherwise using
  24  * normal barrier(): while gcc behavior gets along with a normal
  25  * barrier(), llvm needs an explicit input variable to be assumed
  26  * clobbered. The issue is as follows: while the inline asm might
  27  * access any memory it wants, the compiler could have fit all of
  28  * @ptr into memory registers instead, and since @ptr never escaped
  29  * from that, it proved that the inline asm wasn't touching any of
  30  * it. This version works well with both compilers, i.e. we're telling
  31  * the compiler that the inline asm absolutely may see the contents
  32  * of @ptr. See also: https://llvm.org/bugs/show_bug.cgi?id=15495
  33  */
  34 #define barrier_data(ptr) __asm__ __volatile__("": :"r"(ptr) :"memory")
  35
  36 /*
  37  * This macro obfuscates arithmetic on a variable address so that gcc
  38  * shouldn't recognize the original var, and make assumptions about it.
  39  *
  40  * This is needed because the C standard makes it undefined to do
  41  * pointer arithmetic on "objects" outside their boundaries and the
  42  * gcc optimizers assume this is the case. In particular they
  43  * assume such arithmetic does not wrap.
  44  *
  45  * A miscompilation has been observed because of this on PPC.
  46  * To work around it we hide the relationship of the pointer and the object
  47  * using this macro.
  48  *
  49  * Versions of the ppc64 compiler before 4.1 had a bug where use of
  50  * RELOC_HIDE could trash r30. The bug can be worked around by changing
  51  * the inline assembly constraint from =g to =r, in this particular
  52  * case either is valid.
  53  */
  54 #define RELOC_HIDE(ptr, off)                                            \
  55 ({                                                                      \
  56         unsigned long __ptr;                                            \
  57         __asm__ ("" : "=r"(__ptr) : "0"(ptr));                          \
  58         (typeof(ptr)) (__ptr + (off));                                  \
  59 })
  60
  61 /*
  62  * A trick to suppress uninitialized variable warning without generating any
  63  * code
  64  */
  65 #define uninitialized_var(x) x = x
  66
  67 #ifdef CONFIG_RETPOLINE
  68 #define __noretpoline __attribute__((__indirect_branch__("keep")))
  69 #endif
  70
  71 #define __UNIQUE_ID(prefix) __PASTE(__PASTE(__UNIQUE_ID_, prefix), __COUNTER__)
  72
  73 #define __compiletime_object_size(obj) __builtin_object_size(obj, 0)
  74
  75 #define __compiletime_warning(message) __attribute__((__warning__(message)))
  76 #define __compiletime_error(message) __attribute__((__error__(message)))
  77
  78 #if defined(LATENT_ENTROPY_PLUGIN) && !defined(__CHECKER__)
  79 #define __latent_entropy __attribute__((latent_entropy))
  80 #endif
  81
  82 /*
  83  * calling noreturn functions, __builtin_unreachable() and __builtin_trap()
  84  * confuse the stack allocation in gcc, leading to overly large stack
  85  * frames, see https://gcc.gnu.org/bugzilla/show_bug.cgi?id=82365
  86  *
  87  * Adding an empty inline assembly before it works around the problem
  88  */
  89 #define barrier_before_unreachable() asm volatile("")
  90
  91 /*
  92  * Mark a position in code as unreachable.  This can be used to
  93  * suppress control flow warnings after asm blocks that transfer
  94  * control elsewhere.
  95  */
  96 #define unreachable() \
  97         do {                                    \
  98                 annotate_unreachable();         \
  99                 barrier_before_unreachable();   \
 100                 __builtin_unreachable();        \
 101         } while (0)
 102
 103 #if defined(RANDSTRUCT_PLUGIN) && !defined(__CHECKER__)
 104 #define __randomize_layout __attribute__((randomize_layout))
 105 #define __no_randomize_layout __attribute__((no_randomize_layout))
 106 /* This anon struct can add padding, so only enable it under randstruct. */
 107 #define randomized_struct_fields_start  struct {
 108 #define randomized_struct_fields_end    } __randomize_layout;
 109 #endif
 110
 111 /*
 112  * GCC 'asm goto' miscompiles certain code sequences:
 113  *
 114  *   http://gcc.gnu.org/bugzilla/show_bug.cgi?id=58670
 115  *
 116  * Work it around via a compiler barrier quirk suggested by Jakub Jelinek.
 117  *
 118  * (asm goto is automatically volatile - the naming reflects this.)
 119  */
 120 #define asm_volatile_goto(x...) do { asm goto(x); asm (""); } while (0)
 121
 122 /*
 123  * sparse (__CHECKER__) pretends to be gcc, but can't do constant
 124  * folding in __builtin_bswap*() (yet), so don't set these for it.
 125  */
 126 #if defined(CONFIG_ARCH_USE_BUILTIN_BSWAP) && !defined(__CHECKER__)
 127 #define __HAVE_BUILTIN_BSWAP32__
 128 #define __HAVE_BUILTIN_BSWAP64__
 129 #if GCC_VERSION >= 40800
 130 #define __HAVE_BUILTIN_BSWAP16__
 131 #endif
 132 #endif /* CONFIG_ARCH_USE_BUILTIN_BSWAP && !__CHECKER__ */
 133
 134 #if GCC_VERSION >= 70000
 135 #define KASAN_ABI_VERSION 5
 136 #elif GCC_VERSION >= 50000
 137 #define KASAN_ABI_VERSION 4
 138 #elif GCC_VERSION >= 40902
 139 #define KASAN_ABI_VERSION 3
 140 #endif
 141
 142 #if __has_attribute(__no_sanitize_address__)
 143 #define __no_sanitize_address __attribute__((no_sanitize_address))
 144 #else
 145 #define __no_sanitize_address
 146 #endif
 147
 148 #if GCC_VERSION >= 50100
 149 #define COMPILER_HAS_GENERIC_BUILTIN_OVERFLOW 1
 150 #endif
 151
 152 /*
 153  * Turn individual warnings and errors on and off locally, depending
 154  * on version.
 155  */
 156 #define __diag_GCC(version, severity, s) \
 157         __diag_GCC_ ## version(__diag_GCC_ ## severity s)
 158
 159 /* Severity used in pragma directives */
 160 #define __diag_GCC_ignore       ignored
 161 #define __diag_GCC_warn         warning
 162 #define __diag_GCC_error        error
 163
 164 #define __diag_str1(s)          #s
 165 #define __diag_str(s)           __diag_str1(s)
 166 #define __diag(s)               _Pragma(__diag_str(GCC diagnostic s))
 167
 168 #if GCC_VERSION >= 80000
 169 #define __diag_GCC_8(s)         __diag(s)
 170 #else
 171 #define __diag_GCC_8(s)
 172 #endif
 173
 174 #define __no_fgcse __attribute__((optimize("-fno-gcse")))