1 #ifndef __LINUX_COMPILER_H
2 #error "Please don't include <linux/compiler-gcc.h> directly, include <linux/compiler.h> instead."
6 * Common definitions for all gcc versions go here.
8 #define GCC_VERSION (__GNUC__ * 10000 \
9 + __GNUC_MINOR__ * 100 \
10 + __GNUC_PATCHLEVEL__)
12 /* Optimization barrier */
14 /* The "volatile" is due to gcc bugs */
15 #define barrier() __asm__ __volatile__("": : :"memory")
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
29 #define barrier_data(ptr) __asm__ __volatile__("": :"r"(ptr) :"memory")
32 * This macro obfuscates arithmetic on a variable address so that gcc
33 * shouldn't recognize the original var, and make assumptions about it.
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.
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
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.
49 #define RELOC_HIDE(ptr, off) \
51 unsigned long __ptr; \
52 __asm__ ("" : "=r"(__ptr) : "0"(ptr)); \
53 (typeof(ptr)) (__ptr + (off)); \
56 /* Make the optimizer believe the variable can be manipulated arbitrarily. */
57 #define OPTIMIZER_HIDE_VAR(var) \
58 __asm__ ("" : "=r" (var) : "0" (var))
61 #define __must_be_array(a) 0
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]))
68 * Force always-inline if the user requests it so via the .config,
69 * or if gcc is too old:
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
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
83 #define __always_inline inline __attribute__((always_inline))
84 #define noinline __attribute__((noinline))
86 #define __deprecated __attribute__((deprecated))
87 #define __packed __attribute__((packed))
88 #define __weak __attribute__((weak))
89 #define __alias(symbol) __attribute__((alias(#symbol)))
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.
97 * The asm() bodies of naked functions often depend on standard calling
98 * conventions, therefore they must be noinline and noclone.
100 * GCC 4.[56] currently fail to enforce this, so we must do so ourselves.
103 #define __naked __attribute__((naked)) noinline __noclone notrace
105 #define __noreturn __attribute__((noreturn))
108 * From the GCC manual:
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
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))
125 /* gcc version specific checks */
127 #if GCC_VERSION < 30200
128 # error Sorry, your compiler is too old - please upgrade it.
131 #if GCC_VERSION < 30300
132 # define __used __attribute__((__unused__))
134 # define __used __attribute__((__used__))
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 */
143 #if GCC_VERSION >= 30400
144 #define __must_check __attribute__((warn_unused_result))
147 #if GCC_VERSION >= 40000
149 /* GCC 4.1.[01] miscompiles __weak */
151 # if GCC_VERSION >= 40100 && GCC_VERSION <= 40101
152 # error Your version of gcc miscompiles the __weak directive
156 #define __used __attribute__((__used__))
157 #define __compiler_offsetof(a, b) \
158 __builtin_offsetof(a, b)
160 #if GCC_VERSION >= 40100 && GCC_VERSION < 40600
161 # define __compiletime_object_size(obj) __builtin_object_size(obj, 0)
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
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.
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
179 #define __cold __attribute__((__cold__))
181 #define __UNIQUE_ID(prefix) __PASTE(__PASTE(__UNIQUE_ID_, prefix), __COUNTER__)
184 # define __compiletime_warning(message) __attribute__((warning(message)))
185 # define __compiletime_error(message) __attribute__((error(message)))
186 #endif /* __CHECKER__ */
187 #endif /* GCC_VERSION >= 40300 */
189 #if GCC_VERSION >= 40500
191 * Mark a position in code as unreachable. This can be used to
192 * suppress control flow warnings after asm blocks that transfer
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.
199 #define unreachable() __builtin_unreachable()
201 /* Mark a function definition as prohibited from being cloned. */
202 #define __noclone __attribute__((__noclone__))
204 #endif /* GCC_VERSION >= 40500 */
206 #if GCC_VERSION >= 40600
208 * Tell the optimizer that something else uses this function or variable.
210 #define __visible __attribute__((externally_visible))
214 * GCC 'asm goto' miscompiles certain code sequences:
216 * http://gcc.gnu.org/bugzilla/show_bug.cgi?id=58670
218 * Work it around via a compiler barrier quirk suggested by Jakub Jelinek.
220 * (asm goto is automatically volatile - the naming reflects this.)
222 #define asm_volatile_goto(x...) do { asm goto(x); asm (""); } while (0)
224 #ifdef CONFIG_ARCH_USE_BUILTIN_BSWAP
225 #if GCC_VERSION >= 40400
226 #define __HAVE_BUILTIN_BSWAP32__
227 #define __HAVE_BUILTIN_BSWAP64__
229 #if GCC_VERSION >= 40800 || (defined(__powerpc__) && GCC_VERSION >= 40600)
230 #define __HAVE_BUILTIN_BSWAP16__
232 #endif /* CONFIG_ARCH_USE_BUILTIN_BSWAP */
234 #if GCC_VERSION >= 50000
235 #define KASAN_ABI_VERSION 4
236 #elif GCC_VERSION >= 40902
237 #define KASAN_ABI_VERSION 3
240 #endif /* gcc version >= 40000 specific checks */
242 #if !defined(__noclone)
243 #define __noclone /* not needed */
247 * A trick to suppress uninitialized variable warning without generating any
250 #define uninitialized_var(x) x = x
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