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 * Feature detection for gnu_inline (gnu89 extern inline semantics). Either
69 * __GNUC_STDC_INLINE__ is defined (not using gnu89 extern inline semantics,
70 * and we opt in to the gnu89 semantics), or __GNUC_STDC_INLINE__ is not
71 * defined so the gnu89 semantics are the default.
73 #ifdef __GNUC_STDC_INLINE__
74 # define __gnu_inline __attribute__((gnu_inline))
80 * Force always-inline if the user requests it so via the .config,
81 * or if gcc is too old.
82 * GCC does not warn about unused static inline functions for
83 * -Wunused-function. This turns out to avoid the need for complex #ifdef
84 * directives. Suppress the warning in clang as well by using "unused"
85 * function attribute, which is redundant but not harmful for gcc.
86 * Prefer gnu_inline, so that extern inline functions do not emit an
87 * externally visible function. This makes extern inline behave as per gnu89
88 * semantics rather than c99. This prevents multiple symbol definition errors
89 * of extern inline functions at link time.
90 * A lot of inline functions can cause havoc with function tracing.
92 #if !defined(CONFIG_ARCH_SUPPORTS_OPTIMIZED_INLINING) || \
93 !defined(CONFIG_OPTIMIZE_INLINING) || (__GNUC__ < 4)
95 inline __attribute__((always_inline, unused)) notrace __gnu_inline
97 #define inline inline __attribute__((unused)) notrace __gnu_inline
100 #define __inline__ inline
101 #define __inline inline
102 #define __always_inline inline __attribute__((always_inline))
103 #define noinline __attribute__((noinline))
105 #define __deprecated __attribute__((deprecated))
106 #define __packed __attribute__((packed))
107 #define __weak __attribute__((weak))
108 #define __alias(symbol) __attribute__((alias(#symbol)))
111 * it doesn't make sense on ARM (currently the only user of __naked)
112 * to trace naked functions because then mcount is called without
113 * stack and frame pointer being set up and there is no chance to
114 * restore the lr register to the value before mcount was called.
116 * The asm() bodies of naked functions often depend on standard calling
117 * conventions, therefore they must be noinline and noclone.
119 * GCC 4.[56] currently fail to enforce this, so we must do so ourselves.
122 #define __naked __attribute__((naked)) noinline __noclone notrace
124 #define __noreturn __attribute__((noreturn))
127 * From the GCC manual:
129 * Many functions have no effects except the return value and their
130 * return value depends only on the parameters and/or global
131 * variables. Such a function can be subject to common subexpression
132 * elimination and loop optimization just as an arithmetic operator
136 #define __pure __attribute__((pure))
137 #define __aligned(x) __attribute__((aligned(x)))
138 #define __printf(a, b) __attribute__((format(printf, a, b)))
139 #define __scanf(a, b) __attribute__((format(scanf, a, b)))
140 #define __attribute_const__ __attribute__((__const__))
141 #define __maybe_unused __attribute__((unused))
142 #define __always_unused __attribute__((unused))
144 /* gcc version specific checks */
146 #if GCC_VERSION < 30200
147 # error Sorry, your compiler is too old - please upgrade it.
148 #elif defined(CONFIG_ARM64) && GCC_VERSION < 50100 && !defined(__clang__)
150 * https://gcc.gnu.org/bugzilla/show_bug.cgi?id=63293
151 * https://lore.kernel.org/r/20210107111841.GN1551@shell.armlinux.org.uk
153 # error Sorry, your version of GCC is too old - please use 5.1 or newer.
156 #if GCC_VERSION < 30300
157 # define __used __attribute__((__unused__))
159 # define __used __attribute__((__used__))
162 #ifdef CONFIG_GCOV_KERNEL
163 # if GCC_VERSION < 30400
164 # error "GCOV profiling support for gcc versions below 3.4 not included"
165 # endif /* __GNUC_MINOR__ */
166 #endif /* CONFIG_GCOV_KERNEL */
168 #if GCC_VERSION >= 30400
169 #define __must_check __attribute__((warn_unused_result))
172 #if GCC_VERSION >= 40000
174 /* GCC 4.1.[01] miscompiles __weak */
176 # if GCC_VERSION >= 40100 && GCC_VERSION <= 40101
177 # error Your version of gcc miscompiles the __weak directive
181 #define __used __attribute__((__used__))
182 #define __compiler_offsetof(a, b) \
183 __builtin_offsetof(a, b)
185 #if GCC_VERSION >= 40100 && GCC_VERSION < 40600
186 # define __compiletime_object_size(obj) __builtin_object_size(obj, 0)
189 #if GCC_VERSION >= 40300
190 /* Mark functions as cold. gcc will assume any path leading to a call
191 * to them will be unlikely. This means a lot of manual unlikely()s
192 * are unnecessary now for any paths leading to the usual suspects
193 * like BUG(), printk(), panic() etc. [but let's keep them for now for
196 * Early snapshots of gcc 4.3 don't support this and we can't detect this
197 * in the preprocessor, but we can live with this because they're unreleased.
198 * Maketime probing would be overkill here.
200 * gcc also has a __attribute__((__hot__)) to move hot functions into
201 * a special section, but I don't see any sense in this right now in
204 #define __cold __attribute__((__cold__))
206 #define __UNIQUE_ID(prefix) __PASTE(__PASTE(__UNIQUE_ID_, prefix), __COUNTER__)
209 # define __compiletime_warning(message) __attribute__((warning(message)))
210 # define __compiletime_error(message) __attribute__((error(message)))
211 #endif /* __CHECKER__ */
212 #endif /* GCC_VERSION >= 40300 */
214 #if GCC_VERSION >= 40500
216 * calling noreturn functions, __builtin_unreachable() and __builtin_trap()
217 * confuse the stack allocation in gcc, leading to overly large stack
218 * frames, see https://gcc.gnu.org/bugzilla/show_bug.cgi?id=82365
220 * Adding an empty inline assembly before it works around the problem
222 #define barrier_before_unreachable() asm volatile("")
225 * Mark a position in code as unreachable. This can be used to
226 * suppress control flow warnings after asm blocks that transfer
229 * Early snapshots of gcc 4.5 don't support this and we can't detect
230 * this in the preprocessor, but we can live with this because they're
231 * unreleased. Really, we need to have autoconf for the kernel.
233 #define unreachable() \
235 barrier_before_unreachable(); \
236 __builtin_unreachable(); \
239 /* Mark a function definition as prohibited from being cloned. */
240 #define __noclone __attribute__((__noclone__, __optimize__("no-tracer")))
242 #endif /* GCC_VERSION >= 40500 */
244 #if GCC_VERSION >= 40600
246 * When used with Link Time Optimization, gcc can optimize away C functions or
247 * variables which are referenced only from assembly code. __visible tells the
248 * optimizer that something else uses this function or variable, thus preventing
251 #define __visible __attribute__((externally_visible))
255 #if GCC_VERSION >= 40900 && !defined(__CHECKER__)
257 * __assume_aligned(n, k): Tell the optimizer that the returned
258 * pointer can be assumed to be k modulo n. The second argument is
259 * optional (default 0), so we use a variadic macro to make the
262 * Beware: Do not apply this to functions which may return
263 * ERR_PTRs. Also, it is probably unwise to apply it to functions
264 * returning extra information in the low bits (but in that case the
265 * compiler should see some alignment anyway, when the return value is
266 * massaged by 'flags = ptr & 3; ptr &= ~3;').
268 #define __assume_aligned(a, ...) __attribute__((__assume_aligned__(a, ## __VA_ARGS__)))
272 * GCC 'asm goto' miscompiles certain code sequences:
274 * http://gcc.gnu.org/bugzilla/show_bug.cgi?id=58670
276 * Work it around via a compiler barrier quirk suggested by Jakub Jelinek.
278 * (asm goto is automatically volatile - the naming reflects this.)
280 #define asm_volatile_goto(x...) do { asm goto(x); asm (""); } while (0)
282 #ifdef CONFIG_ARCH_USE_BUILTIN_BSWAP
283 #if GCC_VERSION >= 40400
284 #define __HAVE_BUILTIN_BSWAP32__
285 #define __HAVE_BUILTIN_BSWAP64__
287 #if GCC_VERSION >= 40800 || (defined(__powerpc__) && GCC_VERSION >= 40600)
288 #define __HAVE_BUILTIN_BSWAP16__
290 #endif /* CONFIG_ARCH_USE_BUILTIN_BSWAP */
292 #if GCC_VERSION >= 70000
293 #define KASAN_ABI_VERSION 5
294 #elif GCC_VERSION >= 50000
295 #define KASAN_ABI_VERSION 4
296 #elif GCC_VERSION >= 40902
297 #define KASAN_ABI_VERSION 3
300 #if GCC_VERSION >= 40902
302 * Tell the compiler that address safety instrumentation (KASAN)
303 * should not be applied to that function.
304 * Conflicts with inlining: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=67368
306 #define __no_sanitize_address __attribute__((no_sanitize_address))
309 #endif /* gcc version >= 40000 specific checks */
311 #if !defined(__noclone)
312 #define __noclone /* not needed */
315 #if !defined(__no_sanitize_address)
316 #define __no_sanitize_address
320 * A trick to suppress uninitialized variable warning without generating any
323 #define uninitialized_var(x) x = x
325 #if GCC_VERSION >= 50100
326 #define COMPILER_HAS_GENERIC_BUILTIN_OVERFLOW 1