LXR linux/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")))
 175