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Linux/include/linux/compiler-gcc.h

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  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 /* https://gcc.gnu.org/bugzilla/show_bug.cgi?id=58145 */
 14 #if GCC_VERSION < 40900
 15 # error Sorry, your compiler is too old - please upgrade it.
 16 #endif
 17 
 18 /* Optimization barrier */
 19 
 20 /* The "volatile" is due to gcc bugs */
 21 #define barrier() __asm__ __volatile__("": : :"memory")
 22 /*
 23  * This version is i.e. to prevent dead stores elimination on @ptr
 24  * where gcc and llvm may behave differently when otherwise using
 25  * normal barrier(): while gcc behavior gets along with a normal
 26  * barrier(), llvm needs an explicit input variable to be assumed
 27  * clobbered. The issue is as follows: while the inline asm might
 28  * access any memory it wants, the compiler could have fit all of
 29  * @ptr into memory registers instead, and since @ptr never escaped
 30  * from that, it proved that the inline asm wasn't touching any of
 31  * it. This version works well with both compilers, i.e. we're telling
 32  * the compiler that the inline asm absolutely may see the contents
 33  * of @ptr. See also: https://llvm.org/bugs/show_bug.cgi?id=15495
 34  */
 35 #define barrier_data(ptr) __asm__ __volatile__("": :"r"(ptr) :"memory")
 36 
 37 /*
 38  * This macro obfuscates arithmetic on a variable address so that gcc
 39  * shouldn't recognize the original var, and make assumptions about it.
 40  *
 41  * This is needed because the C standard makes it undefined to do
 42  * pointer arithmetic on "objects" outside their boundaries and the
 43  * gcc optimizers assume this is the case. In particular they
 44  * assume such arithmetic does not wrap.
 45  *
 46  * A miscompilation has been observed because of this on PPC.
 47  * To work around it we hide the relationship of the pointer and the object
 48  * using this macro.
 49  *
 50  * Versions of the ppc64 compiler before 4.1 had a bug where use of
 51  * RELOC_HIDE could trash r30. The bug can be worked around by changing
 52  * the inline assembly constraint from =g to =r, in this particular
 53  * case either is valid.
 54  */
 55 #define RELOC_HIDE(ptr, off)                                            \
 56 ({                                                                      \
 57         unsigned long __ptr;                                            \
 58         __asm__ ("" : "=r"(__ptr) : ""(ptr));                          \
 59         (typeof(ptr)) (__ptr + (off));                                  \
 60 })
 61 
 62 /*
 63  * A trick to suppress uninitialized variable warning without generating any
 64  * code
 65  */
 66 #define uninitialized_var(x) x = x
 67 
 68 #ifdef CONFIG_RETPOLINE
 69 #define __noretpoline __attribute__((__indirect_branch__("keep")))
 70 #endif
 71 
 72 #define __UNIQUE_ID(prefix) __PASTE(__PASTE(__UNIQUE_ID_, prefix), __COUNTER__)
 73 
 74 #define __compiletime_object_size(obj) __builtin_object_size(obj, 0)
 75 
 76 #define __compiletime_warning(message) __attribute__((__warning__(message)))
 77 #define __compiletime_error(message) __attribute__((__error__(message)))
 78 
 79 #if defined(LATENT_ENTROPY_PLUGIN) && !defined(__CHECKER__)
 80 #define __latent_entropy __attribute__((latent_entropy))
 81 #endif
 82 
 83 /*
 84  * calling noreturn functions, __builtin_unreachable() and __builtin_trap()
 85  * confuse the stack allocation in gcc, leading to overly large stack
 86  * frames, see https://gcc.gnu.org/bugzilla/show_bug.cgi?id=82365
 87  *
 88  * Adding an empty inline assembly before it works around the problem
 89  */
 90 #define barrier_before_unreachable() asm volatile("")
 91 
 92 /*
 93  * Mark a position in code as unreachable.  This can be used to
 94  * suppress control flow warnings after asm blocks that transfer
 95  * control elsewhere.
 96  */
 97 #define unreachable() \
 98         do {                                    \
 99                 annotate_unreachable();         \
100                 barrier_before_unreachable();   \
101                 __builtin_unreachable();        \
102         } while (0)
103 
104 #if defined(RANDSTRUCT_PLUGIN) && !defined(__CHECKER__)
105 #define __randomize_layout __attribute__((randomize_layout))
106 #define __no_randomize_layout __attribute__((no_randomize_layout))
107 /* This anon struct can add padding, so only enable it under randstruct. */
108 #define randomized_struct_fields_start  struct {
109 #define randomized_struct_fields_end    } __randomize_layout;
110 #endif
111 
112 /*
113  * GCC 'asm goto' miscompiles certain code sequences:
114  *
115  *   http://gcc.gnu.org/bugzilla/show_bug.cgi?id=58670
116  *
117  * Work it around via a compiler barrier quirk suggested by Jakub Jelinek.
118  *
119  * (asm goto is automatically volatile - the naming reflects this.)
120  */
121 #define asm_volatile_goto(x...) do { asm goto(x); asm (""); } while (0)
122 
123 /*
124  * sparse (__CHECKER__) pretends to be gcc, but can't do constant
125  * folding in __builtin_bswap*() (yet), so don't set these for it.
126  */
127 #if defined(CONFIG_ARCH_USE_BUILTIN_BSWAP) && !defined(__CHECKER__)
128 #define __HAVE_BUILTIN_BSWAP32__
129 #define __HAVE_BUILTIN_BSWAP64__
130 #define __HAVE_BUILTIN_BSWAP16__
131 #endif /* CONFIG_ARCH_USE_BUILTIN_BSWAP && !__CHECKER__ */
132 
133 #if GCC_VERSION >= 70000
134 #define KASAN_ABI_VERSION 5
135 #elif GCC_VERSION >= 50000
136 #define KASAN_ABI_VERSION 4
137 #elif GCC_VERSION >= 40902
138 #define KASAN_ABI_VERSION 3
139 #endif
140 
141 #if __has_attribute(__no_sanitize_address__)
142 #define __no_sanitize_address __attribute__((no_sanitize_address))
143 #else
144 #define __no_sanitize_address
145 #endif
146 
147 #if defined(__SANITIZE_THREAD__) && __has_attribute(__no_sanitize_thread__)
148 #define __no_sanitize_thread __attribute__((no_sanitize_thread))
149 #else
150 #define __no_sanitize_thread
151 #endif
152 
153 #if __has_attribute(__no_sanitize_undefined__)
154 #define __no_sanitize_undefined __attribute__((no_sanitize_undefined))
155 #else
156 #define __no_sanitize_undefined
157 #endif
158 
159 #if GCC_VERSION >= 50100
160 #define COMPILER_HAS_GENERIC_BUILTIN_OVERFLOW 1
161 #endif
162 
163 /*
164  * Turn individual warnings and errors on and off locally, depending
165  * on version.
166  */
167 #define __diag_GCC(version, severity, s) \
168         __diag_GCC_ ## version(__diag_GCC_ ## severity s)
169 
170 /* Severity used in pragma directives */
171 #define __diag_GCC_ignore       ignored
172 #define __diag_GCC_warn         warning
173 #define __diag_GCC_error        error
174 
175 #define __diag_str1(s)          #s
176 #define __diag_str(s)           __diag_str1(s)
177 #define __diag(s)               _Pragma(__diag_str(GCC diagnostic s))
178 
179 #if GCC_VERSION >= 80000
180 #define __diag_GCC_8(s)         __diag(s)
181 #else
182 #define __diag_GCC_8(s)
183 #endif
184 
185 #define __no_fgcse __attribute__((optimize("-fno-gcse")))
186 

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