Linux kernel mirror (for testing)
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linux
1#ifndef __LINUX_COMPILER_H
2#error "Please don't include <linux/compiler-gcc.h> directly, include <linux/compiler.h> instead."
3#endif
4
5/*
6 * Common definitions for all gcc versions go here.
7 */
8#define GCC_VERSION (__GNUC__ * 10000 \
9 + __GNUC_MINOR__ * 100 \
10 + __GNUC_PATCHLEVEL__)
11
12/* Optimization barrier */
13
14/* The "volatile" is due to gcc bugs */
15#define barrier() __asm__ __volatile__("": : :"memory")
16/*
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 proved 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
28 */
29#define barrier_data(ptr) __asm__ __volatile__("": :"r"(ptr) :"memory")
30
31/*
32 * This macro obfuscates arithmetic on a variable address so that gcc
33 * shouldn't recognize the original var, and make assumptions about it.
34 *
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.
39 *
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
42 * using this macro.
43 *
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.
48 */
49#define RELOC_HIDE(ptr, off) \
50({ \
51 unsigned long __ptr; \
52 __asm__ ("" : "=r"(__ptr) : "0"(ptr)); \
53 (typeof(ptr)) (__ptr + (off)); \
54})
55
56/* Make the optimizer believe the variable can be manipulated arbitrarily. */
57#define OPTIMIZER_HIDE_VAR(var) \
58 __asm__ ("" : "=r" (var) : "0" (var))
59
60#ifdef __CHECKER__
61#define __must_be_array(a) 0
62#else
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]))
65#endif
66
67/*
68 * Force always-inline if the user requests it so via the .config,
69 * or if gcc is too old:
70 */
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
76#else
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
81#endif
82
83#define __always_inline inline __attribute__((always_inline))
84#define noinline __attribute__((noinline))
85
86#define __deprecated __attribute__((deprecated))
87#define __packed __attribute__((packed))
88#define __weak __attribute__((weak))
89#define __alias(symbol) __attribute__((alias(#symbol)))
90
91/*
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.
96 *
97 * The asm() bodies of naked functions often depend on standard calling
98 * conventions, therefore they must be noinline and noclone.
99 *
100 * GCC 4.[56] currently fail to enforce this, so we must do so ourselves.
101 * See GCC PR44290.
102 */
103#define __naked __attribute__((naked)) noinline __noclone notrace
104
105#define __noreturn __attribute__((noreturn))
106
107/*
108 * From the GCC manual:
109 *
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
114 * would be.
115 * [...]
116 */
117#define __pure __attribute__((pure))
118#define __aligned(x) __attribute__((aligned(x)))
119#define __aligned_largest __attribute__((aligned))
120#define __printf(a, b) __attribute__((format(printf, a, b)))
121#define __scanf(a, b) __attribute__((format(scanf, a, b)))
122#define __attribute_const__ __attribute__((__const__))
123#define __maybe_unused __attribute__((unused))
124#define __always_unused __attribute__((unused))
125#define __mode(x) __attribute__((mode(x)))
126
127/* gcc version specific checks */
128
129#if GCC_VERSION < 30200
130# error Sorry, your compiler is too old - please upgrade it.
131#endif
132
133#if GCC_VERSION < 30300
134# define __used __attribute__((__unused__))
135#else
136# define __used __attribute__((__used__))
137#endif
138
139#ifdef CONFIG_GCOV_KERNEL
140# if GCC_VERSION < 30400
141# error "GCOV profiling support for gcc versions below 3.4 not included"
142# endif /* __GNUC_MINOR__ */
143#endif /* CONFIG_GCOV_KERNEL */
144
145#if GCC_VERSION >= 30400
146#define __must_check __attribute__((warn_unused_result))
147#define __malloc __attribute__((__malloc__))
148#endif
149
150#if GCC_VERSION >= 40000
151
152/* GCC 4.1.[01] miscompiles __weak */
153#ifdef __KERNEL__
154# if GCC_VERSION >= 40100 && GCC_VERSION <= 40101
155# error Your version of gcc miscompiles the __weak directive
156# endif
157#endif
158
159#define __used __attribute__((__used__))
160#define __compiler_offsetof(a, b) \
161 __builtin_offsetof(a, b)
162
163#if GCC_VERSION >= 40100
164# define __compiletime_object_size(obj) __builtin_object_size(obj, 0)
165#endif
166
167#if GCC_VERSION >= 40300
168/* Mark functions as cold. gcc will assume any path leading to a call
169 * to them will be unlikely. This means a lot of manual unlikely()s
170 * are unnecessary now for any paths leading to the usual suspects
171 * like BUG(), printk(), panic() etc. [but let's keep them for now for
172 * older compilers]
173 *
174 * Early snapshots of gcc 4.3 don't support this and we can't detect this
175 * in the preprocessor, but we can live with this because they're unreleased.
176 * Maketime probing would be overkill here.
177 *
178 * gcc also has a __attribute__((__hot__)) to move hot functions into
179 * a special section, but I don't see any sense in this right now in
180 * the kernel context
181 */
182#define __cold __attribute__((__cold__))
183
184#define __UNIQUE_ID(prefix) __PASTE(__PASTE(__UNIQUE_ID_, prefix), __COUNTER__)
185
186#ifndef __CHECKER__
187# define __compiletime_warning(message) __attribute__((warning(message)))
188# define __compiletime_error(message) __attribute__((error(message)))
189#endif /* __CHECKER__ */
190#endif /* GCC_VERSION >= 40300 */
191
192#if GCC_VERSION >= 40500
193
194#ifndef __CHECKER__
195#ifdef LATENT_ENTROPY_PLUGIN
196#define __latent_entropy __attribute__((latent_entropy))
197#endif
198#endif
199
200#ifdef CONFIG_STACK_VALIDATION
201#define annotate_unreachable() ({ \
202 asm("%c0:\t\n" \
203 ".pushsection .discard.unreachable\t\n" \
204 ".long %c0b - .\t\n" \
205 ".popsection\t\n" : : "i" (__LINE__)); \
206})
207#else
208#define annotate_unreachable()
209#endif
210
211/*
212 * Mark a position in code as unreachable. This can be used to
213 * suppress control flow warnings after asm blocks that transfer
214 * control elsewhere.
215 *
216 * Early snapshots of gcc 4.5 don't support this and we can't detect
217 * this in the preprocessor, but we can live with this because they're
218 * unreleased. Really, we need to have autoconf for the kernel.
219 */
220#define unreachable() \
221 do { annotate_unreachable(); __builtin_unreachable(); } while (0)
222
223/* Mark a function definition as prohibited from being cloned. */
224#define __noclone __attribute__((__noclone__, __optimize__("no-tracer")))
225
226#endif /* GCC_VERSION >= 40500 */
227
228#if GCC_VERSION >= 40600
229/*
230 * When used with Link Time Optimization, gcc can optimize away C functions or
231 * variables which are referenced only from assembly code. __visible tells the
232 * optimizer that something else uses this function or variable, thus preventing
233 * this.
234 */
235#define __visible __attribute__((externally_visible))
236#endif
237
238
239#if GCC_VERSION >= 40900 && !defined(__CHECKER__)
240/*
241 * __assume_aligned(n, k): Tell the optimizer that the returned
242 * pointer can be assumed to be k modulo n. The second argument is
243 * optional (default 0), so we use a variadic macro to make the
244 * shorthand.
245 *
246 * Beware: Do not apply this to functions which may return
247 * ERR_PTRs. Also, it is probably unwise to apply it to functions
248 * returning extra information in the low bits (but in that case the
249 * compiler should see some alignment anyway, when the return value is
250 * massaged by 'flags = ptr & 3; ptr &= ~3;').
251 */
252#define __assume_aligned(a, ...) __attribute__((__assume_aligned__(a, ## __VA_ARGS__)))
253#endif
254
255/*
256 * GCC 'asm goto' miscompiles certain code sequences:
257 *
258 * http://gcc.gnu.org/bugzilla/show_bug.cgi?id=58670
259 *
260 * Work it around via a compiler barrier quirk suggested by Jakub Jelinek.
261 *
262 * (asm goto is automatically volatile - the naming reflects this.)
263 */
264#define asm_volatile_goto(x...) do { asm goto(x); asm (""); } while (0)
265
266/*
267 * sparse (__CHECKER__) pretends to be gcc, but can't do constant
268 * folding in __builtin_bswap*() (yet), so don't set these for it.
269 */
270#if defined(CONFIG_ARCH_USE_BUILTIN_BSWAP) && !defined(__CHECKER__)
271#if GCC_VERSION >= 40400
272#define __HAVE_BUILTIN_BSWAP32__
273#define __HAVE_BUILTIN_BSWAP64__
274#endif
275#if GCC_VERSION >= 40800
276#define __HAVE_BUILTIN_BSWAP16__
277#endif
278#endif /* CONFIG_ARCH_USE_BUILTIN_BSWAP && !__CHECKER__ */
279
280#if GCC_VERSION >= 70000
281#define KASAN_ABI_VERSION 5
282#elif GCC_VERSION >= 50000
283#define KASAN_ABI_VERSION 4
284#elif GCC_VERSION >= 40902
285#define KASAN_ABI_VERSION 3
286#endif
287
288#if GCC_VERSION >= 40902
289/*
290 * Tell the compiler that address safety instrumentation (KASAN)
291 * should not be applied to that function.
292 * Conflicts with inlining: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=67368
293 */
294#define __no_sanitize_address __attribute__((no_sanitize_address))
295#endif
296
297#endif /* gcc version >= 40000 specific checks */
298
299#if !defined(__noclone)
300#define __noclone /* not needed */
301#endif
302
303#if !defined(__no_sanitize_address)
304#define __no_sanitize_address
305#endif
306
307/*
308 * A trick to suppress uninitialized variable warning without generating any
309 * code
310 */
311#define uninitialized_var(x) x = x