[linux-2.6-block.git] / include / linux / compiler-gcc.h

#ifndef __LINUX_COMPILER_H
#error "Please don't include <linux/compiler-gcc.h> directly, include <linux/compiler.h> instead."
#endif

/*
 * Common definitions for all gcc versions go here.
 */
#define GCC_VERSION (__GNUC__ * 10000		\
		     + __GNUC_MINOR__ * 100	\
		     + __GNUC_PATCHLEVEL__)

/* Optimization barrier */

/* The "volatile" is due to gcc bugs */
#define barrier() __asm__ __volatile__("": : :"memory")
/*
 * This version is i.e. to prevent dead stores elimination on @ptr
 * where gcc and llvm may behave differently when otherwise using
 * normal barrier(): while gcc behavior gets along with a normal
 * barrier(), llvm needs an explicit input variable to be assumed
 * clobbered. The issue is as follows: while the inline asm might
 * access any memory it wants, the compiler could have fit all of
 * @ptr into memory registers instead, and since @ptr never escaped
 * from that, it proofed that the inline asm wasn't touching any of
 * it. This version works well with both compilers, i.e. we're telling
 * the compiler that the inline asm absolutely may see the contents
 * of @ptr. See also: https://llvm.org/bugs/show_bug.cgi?id=15495
 */
#define barrier_data(ptr) __asm__ __volatile__("": :"r"(ptr) :"memory")

/*
 * This macro obfuscates arithmetic on a variable address so that gcc
 * shouldn't recognize the original var, and make assumptions about it.
 *
 * This is needed because the C standard makes it undefined to do
 * pointer arithmetic on "objects" outside their boundaries and the
 * gcc optimizers assume this is the case. In particular they
 * assume such arithmetic does not wrap.
 *
 * A miscompilation has been observed because of this on PPC.
 * To work around it we hide the relationship of the pointer and the object
 * using this macro.
 *
 * Versions of the ppc64 compiler before 4.1 had a bug where use of
 * RELOC_HIDE could trash r30. The bug can be worked around by changing
 * the inline assembly constraint from =g to =r, in this particular
 * case either is valid.
 */
#define RELOC_HIDE(ptr, off)						\
({									\
	unsigned long __ptr;						\
	__asm__ ("" : "=r"(__ptr) : "0"(ptr));				\
	(typeof(ptr)) (__ptr + (off));					\
})

/* Make the optimizer believe the variable can be manipulated arbitrarily. */
#define OPTIMIZER_HIDE_VAR(var)						\
	__asm__ ("" : "=r" (var) : "0" (var))

#ifdef __CHECKER__
#define __must_be_array(a)	0
#else
/* &a[0] degrades to a pointer: a different type from an array */
#define __must_be_array(a)	BUILD_BUG_ON_ZERO(__same_type((a), &(a)[0]))
#endif

/*
 * Force always-inline if the user requests it so via the .config,
 * or if gcc is too old:
 */
#if !defined(CONFIG_ARCH_SUPPORTS_OPTIMIZED_INLINING) ||		\
    !defined(CONFIG_OPTIMIZE_INLINING) || (__GNUC__ < 4)
#define inline		inline		__attribute__((always_inline)) notrace
#define __inline__	__inline__	__attribute__((always_inline)) notrace
#define __inline	__inline	__attribute__((always_inline)) notrace
#else
/* A lot of inline functions can cause havoc with function tracing */
#define inline		inline		notrace
#define __inline__	__inline__	notrace
#define __inline	__inline	notrace
#endif

#define __always_inline	inline __attribute__((always_inline))
#define  noinline	__attribute__((noinline))

#define __deprecated	__attribute__((deprecated))
#define __packed	__attribute__((packed))
#define __weak		__attribute__((weak))
#define __alias(symbol)	__attribute__((alias(#symbol)))

/*
 * it doesn't make sense on ARM (currently the only user of __naked)
 * to trace naked functions because then mcount is called without
 * stack and frame pointer being set up and there is no chance to
 * restore the lr register to the value before mcount was called.
 *
 * The asm() bodies of naked functions often depend on standard calling
 * conventions, therefore they must be noinline and noclone.
 *
 * GCC 4.[56] currently fail to enforce this, so we must do so ourselves.
 * See GCC PR44290.
 */
#define __naked		__attribute__((naked)) noinline __noclone notrace

#define __noreturn	__attribute__((noreturn))

/*
 * From the GCC manual:
 *
 * Many functions have no effects except the return value and their
 * return value depends only on the parameters and/or global
 * variables.  Such a function can be subject to common subexpression
 * elimination and loop optimization just as an arithmetic operator
 * would be.
 * [...]
 */
#define __pure			__attribute__((pure))
#define __aligned(x)		__attribute__((aligned(x)))
#define __printf(a, b)		__attribute__((format(printf, a, b)))
#define __scanf(a, b)		__attribute__((format(scanf, a, b)))
#define __attribute_const__	__attribute__((__const__))
#define __maybe_unused		__attribute__((unused))
#define __always_unused		__attribute__((unused))

/* gcc version specific checks */

#if GCC_VERSION < 30200
# error Sorry, your compiler is too old - please upgrade it.
#endif

#if GCC_VERSION < 30300
# define __used			__attribute__((__unused__))
#else
# define __used			__attribute__((__used__))
#endif

#ifdef CONFIG_GCOV_KERNEL
# if GCC_VERSION < 30400
#   error "GCOV profiling support for gcc versions below 3.4 not included"
# endif /* __GNUC_MINOR__ */
#endif /* CONFIG_GCOV_KERNEL */

#if GCC_VERSION >= 30400
#define __must_check		__attribute__((warn_unused_result))
#endif

#if GCC_VERSION >= 40000

/* GCC 4.1.[01] miscompiles __weak */
#ifdef __KERNEL__
# if GCC_VERSION >= 40100 &&  GCC_VERSION <= 40101
#  error Your version of gcc miscompiles the __weak directive
# endif
#endif

#define __used			__attribute__((__used__))
#define __compiler_offsetof(a, b)					\
	__builtin_offsetof(a, b)

#if GCC_VERSION >= 40100 && GCC_VERSION < 40600
# define __compiletime_object_size(obj) __builtin_object_size(obj, 0)
#endif

#if GCC_VERSION >= 40300
/* Mark functions as cold. gcc will assume any path leading to a call
 * to them will be unlikely.  This means a lot of manual unlikely()s
 * are unnecessary now for any paths leading to the usual suspects
 * like BUG(), printk(), panic() etc. [but let's keep them for now for
 * older compilers]
 *
 * Early snapshots of gcc 4.3 don't support this and we can't detect this
 * in the preprocessor, but we can live with this because they're unreleased.
 * Maketime probing would be overkill here.
 *
 * gcc also has a __attribute__((__hot__)) to move hot functions into
 * a special section, but I don't see any sense in this right now in
 * the kernel context
 */
#define __cold			__attribute__((__cold__))

#define __UNIQUE_ID(prefix) __PASTE(__PASTE(__UNIQUE_ID_, prefix), __COUNTER__)

#ifndef __CHECKER__
# define __compiletime_warning(message) __attribute__((warning(message)))
# define __compiletime_error(message) __attribute__((error(message)))
#endif /* __CHECKER__ */
#endif /* GCC_VERSION >= 40300 */

#if GCC_VERSION >= 40500
/*
 * Mark a position in code as unreachable.  This can be used to
 * suppress control flow warnings after asm blocks that transfer
 * control elsewhere.
 *
 * Early snapshots of gcc 4.5 don't support this and we can't detect
 * this in the preprocessor, but we can live with this because they're
 * unreleased.  Really, we need to have autoconf for the kernel.
 */
#define unreachable() __builtin_unreachable()

/* Mark a function definition as prohibited from being cloned. */
#define __noclone	__attribute__((__noclone__, __optimize__("no-tracer")))

#endif /* GCC_VERSION >= 40500 */

#if GCC_VERSION >= 40600
/*
 * When used with Link Time Optimization, gcc can optimize away C functions or
 * variables which are referenced only from assembly code.  __visible tells the
 * optimizer that something else uses this function or variable, thus preventing
 * this.
 */
#define __visible	__attribute__((externally_visible))
#endif


#if GCC_VERSION >= 40900 && !defined(__CHECKER__)
/*
 * __assume_aligned(n, k): Tell the optimizer that the returned
 * pointer can be assumed to be k modulo n. The second argument is
 * optional (default 0), so we use a variadic macro to make the
 * shorthand.
 *
 * Beware: Do not apply this to functions which may return
 * ERR_PTRs. Also, it is probably unwise to apply it to functions
 * returning extra information in the low bits (but in that case the
 * compiler should see some alignment anyway, when the return value is
 * massaged by 'flags = ptr & 3; ptr &= ~3;').
 */
#define __assume_aligned(a, ...) __attribute__((__assume_aligned__(a, ## __VA_ARGS__)))
#endif

/*
 * GCC 'asm goto' miscompiles certain code sequences:
 *
 *   http://gcc.gnu.org/bugzilla/show_bug.cgi?id=58670
 *
 * Work it around via a compiler barrier quirk suggested by Jakub Jelinek.
 *
 * (asm goto is automatically volatile - the naming reflects this.)
 */
#define asm_volatile_goto(x...)	do { asm goto(x); asm (""); } while (0)

#ifdef CONFIG_ARCH_USE_BUILTIN_BSWAP
#if GCC_VERSION >= 40400
#define __HAVE_BUILTIN_BSWAP32__
#define __HAVE_BUILTIN_BSWAP64__
#endif
#if GCC_VERSION >= 40800
#define __HAVE_BUILTIN_BSWAP16__
#endif
#endif /* CONFIG_ARCH_USE_BUILTIN_BSWAP */

#if GCC_VERSION >= 50000
#define KASAN_ABI_VERSION 4
#elif GCC_VERSION >= 40902
#define KASAN_ABI_VERSION 3
#endif

#if GCC_VERSION >= 40902
/*
 * Tell the compiler that address safety instrumentation (KASAN)
 * should not be applied to that function.
 * Conflicts with inlining: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=67368
 */
#define __no_sanitize_address __attribute__((no_sanitize_address))
#endif

#endif	/* gcc version >= 40000 specific checks */

#if !defined(__noclone)
#define __noclone	/* not needed */
#endif

#if !defined(__no_sanitize_address)
#define __no_sanitize_address
#endif

/*
 * A trick to suppress uninitialized variable warning without generating any
 * code
 */
#define uninitialized_var(x) x = x
Commit	Line	Data
94f582f8 RD	1	#ifndef __LINUX_COMPILER_H
	2	#error "Please don't include <linux/compiler-gcc.h> directly, include <linux/compiler.h> instead."
	3	#endif
1da177e4 LT	4
	5	/*
	6	* Common definitions for all gcc versions go here.
	7	*/
f6d133f8 JP	8	#define GCC_VERSION (__GNUC__ * 10000 \
	9	+ __GNUC_MINOR__ * 100 \
	10	+ __GNUC_PATCHLEVEL__)
1da177e4	11
1da177e4	12	/* Optimization barrier */
7829fb09	13
1da177e4 LT	14	/* The "volatile" is due to gcc bugs */
1da177e4 LT	15	#define barrier() __asm__ __volatile__("": : :"memory")
7829fb09 DB	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 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")
1da177e4	30
c8d52465	31	/*
85c210ed AK	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	*
c8d52465 AB	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	*/
f6d133f8 JP	49	#define RELOC_HIDE(ptr, off) \
	50	({ \
	51	unsigned long __ptr; \
	52	__asm__ ("" : "=r"(__ptr) : "0"(ptr)); \
	53	(typeof(ptr)) (__ptr + (off)); \
	54	})
a1365647	55
fe8c8a12	56	/* Make the optimizer believe the variable can be manipulated arbitrarily. */
f6d133f8 JP	57	#define OPTIMIZER_HIDE_VAR(var) \
f6d133f8 JP	58	__asm__ ("" : "=r" (var) : "0" (var))
fe8c8a12	59
5bd7e6a3	60	#ifdef __CHECKER__
f6d133f8	61	#define __must_be_array(a) 0
5bd7e6a3	62	#else
c5e631cf	63	/* &a[0] degrades to a pointer: a different type from an array */
f6d133f8	64	#define __must_be_array(a) BUILD_BUG_ON_ZERO(__same_type((a), &(a)[0]))
5bd7e6a3	65	#endif
a1365647	66
60a3cdd0	67	/*
ae3a0064 IM	68	* Force always-inline if the user requests it so via the .config,
ae3a0064 IM	69	* or if gcc is too old:
60a3cdd0	70	*/
f6d133f8	71	#if !defined(CONFIG_ARCH_SUPPORTS_OPTIMIZED_INLINING) \|\| \
ae3a0064	72	!defined(CONFIG_OPTIMIZE_INLINING) \|\| (__GNUC__ < 4)
f6d133f8 JP	73	#define inline inline __attribute__((always_inline)) notrace
	74	#define __inline__ __inline__ __attribute__((always_inline)) notrace
	75	#define __inline __inline __attribute__((always_inline)) notrace
45959ee7 SR	76	#else
45959ee7 SR	77	/* A lot of inline functions can cause havoc with function tracing */
f6d133f8 JP	78	#define inline inline notrace
	79	#define __inline__ __inline__ notrace
	80	#define __inline __inline notrace
60a3cdd0 IM	81	#endif
60a3cdd0 IM	82
f6d133f8 JP	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)))
446c92b2 UKK	90
446c92b2 UKK	91	/*
f6d133f8 JP	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.
9c695203	99	*
f6d133f8 JP	100	* GCC 4.[56] currently fail to enforce this, so we must do so ourselves.
f6d133f8 JP	101	* See GCC PR44290.
446c92b2	102	*/
f6d133f8	103	#define __naked __attribute__((naked)) noinline __noclone notrace
446c92b2	104
f6d133f8	105	#define __noreturn __attribute__((noreturn))
e8c44319 RB	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	*/
f6d133f8 JP	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))
f153b821	124
cb984d10 JP	125	/* 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. */
95272c29	202	#define __noclone __attribute__((__noclone__, __optimize__("no-tracer")))
cb984d10 JP	203
	204	#endif /* GCC_VERSION >= 40500 */
	205
	206	#if GCC_VERSION >= 40600
	207	/*
9add850c AM	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.
cb984d10 JP	212	*/
	213	#define __visible __attribute__((externally_visible))
	214	#endif
	215
a744fd17	216
8748dd5c	217	#if GCC_VERSION >= 40900 && !defined(__CHECKER__)
a744fd17 RV	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
cb984d10 JP	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
8634de6d	249	#if GCC_VERSION >= 40800
cb984d10 JP	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
d976441f AR	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
cb984d10	269	#endif /* gcc version >= 40000 specific checks */
9c695203 MP	270
	271	#if !defined(__noclone)
	272	#define __noclone /* not needed */
	273	#endif
c837fb37	274
d976441f AR	275	#if !defined(__no_sanitize_address)
	276	#define __no_sanitize_address
	277	#endif
	278
c837fb37 BP	279	/*
	280	* A trick to suppress uninitialized variable warning without generating any
	281	* code
	282	*/
	283	#define uninitialized_var(x) x = x