blob: 22ab246feed34c104038d3f94e1401ea9a587f8f [file] [log] [blame]
Graeme Russ95ffaba2010-04-24 00:05:49 +10001#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 */
Tom Rini9b2c2822016-02-29 11:34:15 -05008#define GCC_VERSION (__GNUC__ * 10000 \
9 + __GNUC_MINOR__ * 100 \
10 + __GNUC_PATCHLEVEL__)
Graeme Russ95ffaba2010-04-24 00:05:49 +100011
12/* Optimization barrier */
Tom Rini9b2c2822016-02-29 11:34:15 -050013
Graeme Russ95ffaba2010-04-24 00:05:49 +100014/* The "volatile" is due to gcc bugs */
15#define barrier() __asm__ __volatile__("": : :"memory")
Tom Rini9b2c2822016-02-29 11:34:15 -050016/*
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
28 */
29#define barrier_data(ptr) __asm__ __volatile__("": :"r"(ptr) :"memory")
Graeme Russ95ffaba2010-04-24 00:05:49 +100030
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 */
Tom Rini9b2c2822016-02-29 11:34:15 -050049#define RELOC_HIDE(ptr, off) \
50({ \
51 unsigned long __ptr; \
52 __asm__ ("" : "=r"(__ptr) : "0"(ptr)); \
53 (typeof(ptr)) (__ptr + (off)); \
54})
Graeme Russ95ffaba2010-04-24 00:05:49 +100055
Masahiro Yamadafb8ffd72014-09-04 02:40:58 +090056/* Make the optimizer believe the variable can be manipulated arbitrarily. */
Tom Rini9b2c2822016-02-29 11:34:15 -050057#define OPTIMIZER_HIDE_VAR(var) \
58 __asm__ ("" : "=r" (var) : "0" (var))
Masahiro Yamadafb8ffd72014-09-04 02:40:58 +090059
60#ifdef __CHECKER__
Tom Rini9b2c2822016-02-29 11:34:15 -050061#define __must_be_array(a) 0
Masahiro Yamadafb8ffd72014-09-04 02:40:58 +090062#else
Graeme Russ95ffaba2010-04-24 00:05:49 +100063/* &a[0] degrades to a pointer: a different type from an array */
Tom Rini9b2c2822016-02-29 11:34:15 -050064#define __must_be_array(a) BUILD_BUG_ON_ZERO(__same_type((a), &(a)[0]))
Masahiro Yamadafb8ffd72014-09-04 02:40:58 +090065#endif
Graeme Russ95ffaba2010-04-24 00:05:49 +100066
67/*
68 * Force always-inline if the user requests it so via the .config,
69 * or if gcc is too old:
70 */
Tom Rini9b2c2822016-02-29 11:34:15 -050071#if !defined(CONFIG_ARCH_SUPPORTS_OPTIMIZED_INLINING) || \
Graeme Russ95ffaba2010-04-24 00:05:49 +100072 !defined(CONFIG_OPTIMIZE_INLINING) || (__GNUC__ < 4)
Tom Rini9b2c2822016-02-29 11:34:15 -050073#define inline inline __attribute__((always_inline)) notrace
74#define __inline__ __inline__ __attribute__((always_inline)) notrace
75#define __inline __inline __attribute__((always_inline)) notrace
Masahiro Yamadafb8ffd72014-09-04 02:40:58 +090076#else
77/* A lot of inline functions can cause havoc with function tracing */
Tom Rini9b2c2822016-02-29 11:34:15 -050078#define inline inline notrace
79#define __inline__ __inline__ notrace
80#define __inline __inline notrace
Graeme Russ95ffaba2010-04-24 00:05:49 +100081#endif
82
Tom Rini9b2c2822016-02-29 11:34:15 -050083#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)))
Graeme Russ95ffaba2010-04-24 00:05:49 +100090
91/*
Tom Rini9b2c2822016-02-29 11:34:15 -050092 * 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.
Masahiro Yamadafb8ffd72014-09-04 02:40:58 +090096 *
Tom Rini9b2c2822016-02-29 11:34:15 -050097 * 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.
Graeme Russ95ffaba2010-04-24 00:05:49 +1000102 */
Tom Rini9b2c2822016-02-29 11:34:15 -0500103#define __naked __attribute__((naked)) noinline __noclone notrace
Graeme Russ95ffaba2010-04-24 00:05:49 +1000104
Tom Rini9b2c2822016-02-29 11:34:15 -0500105#define __noreturn __attribute__((noreturn))
Graeme Russ95ffaba2010-04-24 00:05:49 +1000106
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 */
Tom Rini9b2c2822016-02-29 11:34:15 -0500117#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))
Graeme Russ95ffaba2010-04-24 00:05:49 +1000124
Tom Rini9b2c2822016-02-29 11:34:15 -0500125/* gcc version specific checks */
126
127#if GCC_VERSION < 30200
128# error Sorry, your compiler is too old - please upgrade it.
129#endif
130
131#if GCC_VERSION < 30300
132# define __used __attribute__((__unused__))
133#else
134# define __used __attribute__((__used__))
135#endif
136
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 */
142
143#if GCC_VERSION >= 30400
144#define __must_check __attribute__((warn_unused_result))
145#endif
146
147#if GCC_VERSION >= 40000
148
149/* GCC 4.1.[01] miscompiles __weak */
150#ifdef __KERNEL__
151# if GCC_VERSION >= 40100 && GCC_VERSION <= 40101
152# error Your version of gcc miscompiles the __weak directive
153# endif
154#endif
155
156#define __used __attribute__((__used__))
157#define __compiler_offsetof(a, b) \
158 __builtin_offsetof(a, b)
159
160#if GCC_VERSION >= 40100 && GCC_VERSION < 40600
161# define __compiletime_object_size(obj) __builtin_object_size(obj, 0)
162#endif
163
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
169 * older compilers]
170 *
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.
174 *
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
177 * the kernel context
178 */
179#define __cold __attribute__((__cold__))
180
181#define __UNIQUE_ID(prefix) __PASTE(__PASTE(__UNIQUE_ID_, prefix), __COUNTER__)
182
183#ifndef __CHECKER__
184# define __compiletime_warning(message) __attribute__((warning(message)))
185# define __compiletime_error(message) __attribute__((error(message)))
186#endif /* __CHECKER__ */
187#endif /* GCC_VERSION >= 40300 */
188
189#if GCC_VERSION >= 40500
190/*
191 * Mark a position in code as unreachable. This can be used to
192 * suppress control flow warnings after asm blocks that transfer
193 * control elsewhere.
194 *
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.
198 */
199#define unreachable() __builtin_unreachable()
200
201/* Mark a function definition as prohibited from being cloned. */
202#define __noclone __attribute__((__noclone__))
203
204#endif /* GCC_VERSION >= 40500 */
205
206#if GCC_VERSION >= 40600
207/*
208 * When used with Link Time Optimization, gcc can optimize away C functions or
209 * variables which are referenced only from assembly code. __visible tells the
210 * optimizer that something else uses this function or variable, thus preventing
211 * this.
212 */
213#define __visible __attribute__((externally_visible))
214#endif
215
216
217#if GCC_VERSION >= 40900 && !defined(__CHECKER__)
218/*
219 * __assume_aligned(n, k): Tell the optimizer that the returned
220 * pointer can be assumed to be k modulo n. The second argument is
221 * optional (default 0), so we use a variadic macro to make the
222 * shorthand.
223 *
224 * Beware: Do not apply this to functions which may return
225 * ERR_PTRs. Also, it is probably unwise to apply it to functions
226 * returning extra information in the low bits (but in that case the
227 * compiler should see some alignment anyway, when the return value is
228 * massaged by 'flags = ptr & 3; ptr &= ~3;').
229 */
230#define __assume_aligned(a, ...) __attribute__((__assume_aligned__(a, ## __VA_ARGS__)))
231#endif
232
233/*
234 * GCC 'asm goto' miscompiles certain code sequences:
235 *
236 * http://gcc.gnu.org/bugzilla/show_bug.cgi?id=58670
237 *
238 * Work it around via a compiler barrier quirk suggested by Jakub Jelinek.
239 *
240 * (asm goto is automatically volatile - the naming reflects this.)
241 */
242#define asm_volatile_goto(x...) do { asm goto(x); asm (""); } while (0)
243
244#ifdef CONFIG_ARCH_USE_BUILTIN_BSWAP
245#if GCC_VERSION >= 40400
246#define __HAVE_BUILTIN_BSWAP32__
247#define __HAVE_BUILTIN_BSWAP64__
248#endif
249#if GCC_VERSION >= 40800 || (defined(__powerpc__) && GCC_VERSION >= 40600)
250#define __HAVE_BUILTIN_BSWAP16__
251#endif
252#endif /* CONFIG_ARCH_USE_BUILTIN_BSWAP */
253
254#if GCC_VERSION >= 50000
255#define KASAN_ABI_VERSION 4
256#elif GCC_VERSION >= 40902
257#define KASAN_ABI_VERSION 3
258#endif
259
260#if GCC_VERSION >= 40902
261/*
262 * Tell the compiler that address safety instrumentation (KASAN)
263 * should not be applied to that function.
264 * Conflicts with inlining: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=67368
265 */
266#define __no_sanitize_address __attribute__((no_sanitize_address))
267#endif
268
269#endif /* gcc version >= 40000 specific checks */
Masahiro Yamadafb8ffd72014-09-04 02:40:58 +0900270
271#if !defined(__noclone)
272#define __noclone /* not needed */
273#endif
274
Tom Rini9b2c2822016-02-29 11:34:15 -0500275#if !defined(__no_sanitize_address)
276#define __no_sanitize_address
277#endif
278
Masahiro Yamadafb8ffd72014-09-04 02:40:58 +0900279/*
280 * A trick to suppress uninitialized variable warning without generating any
281 * code
282 */
283#define uninitialized_var(x) x = x