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

/* SPDX-License-Identifier: GPL-2.0 */
#ifndef __LINUX_COMPILER_TYPES_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 proved 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.
 * GCC does not warn about unused static inline functions for
 * -Wunused-function.  This turns out to avoid the need for complex #ifdef
 * directives.  Suppress the warning in clang as well by using "unused"
 * function attribute, which is redundant but not harmful for gcc.
 */
#if !defined(CONFIG_ARCH_SUPPORTS_OPTIMIZED_INLINING) ||		\
    !defined(CONFIG_OPTIMIZE_INLINING) || (__GNUC__ < 4)
#define inline inline		__attribute__((always_inline,unused)) notrace
#define __inline__ __inline__	__attribute__((always_inline,unused)) notrace
#define __inline __inline	__attribute__((always_inline,unused)) notrace
#else
/* A lot of inline functions can cause havoc with function tracing */
#define inline inline		__attribute__((unused)) notrace
#define __inline__ __inline__	__attribute__((unused)) notrace
#define __inline __inline	__attribute__((unused)) 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)))

#ifdef RETPOLINE
#define __noretpoline __attribute__((indirect_branch("keep")))
#endif

/*
 * 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 __aligned_largest	__attribute__((aligned))
#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))
#define __mode(x)               __attribute__((mode(x)))

/* 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))
#define __malloc		__attribute__((__malloc__))
#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
# 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 >= 40400
#define __optimize(level)	__attribute__((__optimize__(level)))
#define __nostackprotector	__optimize("no-stack-protector")
#endif /* GCC_VERSION >= 40400 */

#if GCC_VERSION >= 40500

#ifndef __CHECKER__
#ifdef LATENT_ENTROPY_PLUGIN
#define __latent_entropy __attribute__((latent_entropy))
#endif
#endif

/*
 * calling noreturn functions, __builtin_unreachable() and __builtin_trap()
 * confuse the stack allocation in gcc, leading to overly large stack
 * frames, see https://gcc.gnu.org/bugzilla/show_bug.cgi?id=82365
 *
 * Adding an empty inline assembly before it works around the problem
 */
#define barrier_before_unreachable() asm volatile("")

/*
 * 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() \
	do {					\
		annotate_unreachable();		\
		barrier_before_unreachable();	\
		__builtin_unreachable();	\
	} while (0)

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

#if defined(RANDSTRUCT_PLUGIN) && !defined(__CHECKER__)
#define __randomize_layout __attribute__((randomize_layout))
#define __no_randomize_layout __attribute__((no_randomize_layout))
/* This anon struct can add padding, so only enable it under randstruct. */
#define randomized_struct_fields_start	struct {
#define randomized_struct_fields_end	} __randomize_layout;
#endif

#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 /* GCC_VERSION >= 40600 */


#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)

/*
 * sparse (__CHECKER__) pretends to be gcc, but can't do constant
 * folding in __builtin_bswap*() (yet), so don't set these for it.
 */
#if defined(CONFIG_ARCH_USE_BUILTIN_BSWAP) && !defined(__CHECKER__)
#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 && !__CHECKER__ */

#if GCC_VERSION >= 70000
#define KASAN_ABI_VERSION 5
#elif 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

#if GCC_VERSION >= 50100
/*
 * Mark structures as requiring designated initializers.
 * https://gcc.gnu.org/onlinedocs/gcc/Designated-Inits.html
 */
#define __designated_init __attribute__((designated_init))
#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

#if GCC_VERSION >= 50100
#define COMPILER_HAS_GENERIC_BUILTIN_OVERFLOW 1
#endif

/*
 * Turn individual warnings and errors on and off locally, depending
 * on version.
 */
#define __diag_GCC(version, severity, s) \
	__diag_GCC_ ## version(__diag_GCC_ ## severity s)

/* Severity used in pragma directives */
#define __diag_GCC_ignore	ignored
#define __diag_GCC_warn		warning
#define __diag_GCC_error	error

/* Compilers before gcc-4.6 do not understand "#pragma GCC diagnostic push" */
#if GCC_VERSION >= 40600
#define __diag_str1(s)		#s
#define __diag_str(s)		__diag_str1(s)
#define __diag(s)		_Pragma(__diag_str(GCC diagnostic s))
#endif

#if GCC_VERSION >= 80000
#define __diag_GCC_8(s)		__diag(s)
#else
#define __diag_GCC_8(s)
#endif
Commit	Line	Data
b2441318	1	/* SPDX-License-Identifier: GPL-2.0 */
d1515582	2	#ifndef __LINUX_COMPILER_TYPES_H
94f582f8 RD	3	#error "Please don't include <linux/compiler-gcc.h> directly, include <linux/compiler.h> instead."
94f582f8 RD	4	#endif
1da177e4 LT	5
	6	/*
	7	* Common definitions for all gcc versions go here.
	8	*/
f6d133f8 JP	9	#define GCC_VERSION (__GNUC__ * 10000 \
	10	+ __GNUC_MINOR__ * 100 \
	11	+ __GNUC_PATCHLEVEL__)
1da177e4	12
1da177e4	13	/* Optimization barrier */
7829fb09	14
1da177e4 LT	15	/* The "volatile" is due to gcc bugs */
1da177e4 LT	16	#define barrier() __asm__ __volatile__("": : :"memory")
7829fb09 DB	17	/*
	18	* This version is i.e. to prevent dead stores elimination on @ptr
	19	* where gcc and llvm may behave differently when otherwise using
	20	* normal barrier(): while gcc behavior gets along with a normal
	21	* barrier(), llvm needs an explicit input variable to be assumed
	22	* clobbered. The issue is as follows: while the inline asm might
	23	* access any memory it wants, the compiler could have fit all of
	24	* @ptr into memory registers instead, and since @ptr never escaped
8e8780a5	25	* from that, it proved that the inline asm wasn't touching any of
7829fb09 DB	26	* it. This version works well with both compilers, i.e. we're telling
	27	* the compiler that the inline asm absolutely may see the contents
	28	* of @ptr. See also: https://llvm.org/bugs/show_bug.cgi?id=15495
	29	*/
	30	#define barrier_data(ptr) __asm__ __volatile__("": :"r"(ptr) :"memory")
1da177e4	31
c8d52465	32	/*
85c210ed AK	33	* This macro obfuscates arithmetic on a variable address so that gcc
	34	* shouldn't recognize the original var, and make assumptions about it.
	35	*
	36	* This is needed because the C standard makes it undefined to do
	37	* pointer arithmetic on "objects" outside their boundaries and the
	38	* gcc optimizers assume this is the case. In particular they
	39	* assume such arithmetic does not wrap.
	40	*
	41	* A miscompilation has been observed because of this on PPC.
	42	* To work around it we hide the relationship of the pointer and the object
	43	* using this macro.
	44	*
c8d52465 AB	45	* Versions of the ppc64 compiler before 4.1 had a bug where use of
	46	* RELOC_HIDE could trash r30. The bug can be worked around by changing
	47	* the inline assembly constraint from =g to =r, in this particular
	48	* case either is valid.
	49	*/
f6d133f8 JP	50	#define RELOC_HIDE(ptr, off) \
	51	({ \
	52	unsigned long __ptr; \
	53	__asm__ ("" : "=r"(__ptr) : "0"(ptr)); \
	54	(typeof(ptr)) (__ptr + (off)); \
	55	})
a1365647	56
fe8c8a12	57	/* Make the optimizer believe the variable can be manipulated arbitrarily. */
f6d133f8 JP	58	#define OPTIMIZER_HIDE_VAR(var) \
f6d133f8 JP	59	__asm__ ("" : "=r" (var) : "0" (var))
fe8c8a12	60
5bd7e6a3	61	#ifdef __CHECKER__
f6d133f8	62	#define __must_be_array(a) 0
5bd7e6a3	63	#else
c5e631cf	64	/* &a[0] degrades to a pointer: a different type from an array */
f6d133f8	65	#define __must_be_array(a) BUILD_BUG_ON_ZERO(__same_type((a), &(a)[0]))
5bd7e6a3	66	#endif
a1365647	67
60a3cdd0	68	/*
ae3a0064	69	* Force always-inline if the user requests it so via the .config,
9a04dbcf DR	70	* or if gcc is too old.
	71	* GCC does not warn about unused static inline functions for
	72	* -Wunused-function. This turns out to avoid the need for complex #ifdef
	73	* directives. Suppress the warning in clang as well by using "unused"
	74	* function attribute, which is redundant but not harmful for gcc.
60a3cdd0	75	*/
f6d133f8	76	#if !defined(CONFIG_ARCH_SUPPORTS_OPTIMIZED_INLINING) \|\| \
ae3a0064	77	!defined(CONFIG_OPTIMIZE_INLINING) \|\| (__GNUC__ < 4)
9a04dbcf DR	78	#define inline inline __attribute__((always_inline,unused)) notrace
	79	#define __inline__ __inline__ __attribute__((always_inline,unused)) notrace
	80	#define __inline __inline __attribute__((always_inline,unused)) notrace
45959ee7 SR	81	#else
45959ee7 SR	82	/* A lot of inline functions can cause havoc with function tracing */
9a04dbcf DR	83	#define inline inline __attribute__((unused)) notrace
	84	#define __inline__ __inline__ __attribute__((unused)) notrace
	85	#define __inline __inline __attribute__((unused)) notrace
60a3cdd0 IM	86	#endif
60a3cdd0 IM	87
f6d133f8 JP	88	#define __always_inline inline __attribute__((always_inline))
	89	#define noinline __attribute__((noinline))
	90
	91	#define __deprecated __attribute__((deprecated))
	92	#define __packed __attribute__((packed))
	93	#define __weak __attribute__((weak))
	94	#define __alias(symbol) __attribute__((alias(#symbol)))
446c92b2	95
87358710 DW	96	#ifdef RETPOLINE
	97	#define __noretpoline __attribute__((indirect_branch("keep")))
	98	#endif
	99
446c92b2	100	/*
f6d133f8 JP	101	* it doesn't make sense on ARM (currently the only user of __naked)
	102	* to trace naked functions because then mcount is called without
	103	* stack and frame pointer being set up and there is no chance to
	104	* restore the lr register to the value before mcount was called.
	105	*
	106	* The asm() bodies of naked functions often depend on standard calling
	107	* conventions, therefore they must be noinline and noclone.
9c695203	108	*
f6d133f8 JP	109	* GCC 4.[56] currently fail to enforce this, so we must do so ourselves.
f6d133f8 JP	110	* See GCC PR44290.
446c92b2	111	*/
f6d133f8	112	#define __naked __attribute__((naked)) noinline __noclone notrace
446c92b2	113
f6d133f8	114	#define __noreturn __attribute__((noreturn))
e8c44319 RB	115
	116	/*
	117	* From the GCC manual:
	118	*
	119	* Many functions have no effects except the return value and their
	120	* return value depends only on the parameters and/or global
	121	* variables. Such a function can be subject to common subexpression
	122	* elimination and loop optimization just as an arithmetic operator
	123	* would be.
	124	* [...]
	125	*/
f6d133f8 JP	126	#define __pure __attribute__((pure))
f6d133f8 JP	127	#define __aligned(x) __attribute__((aligned(x)))
d8c34b94	128	#define __aligned_largest __attribute__((aligned))
f6d133f8 JP	129	#define __printf(a, b) __attribute__((format(printf, a, b)))
	130	#define __scanf(a, b) __attribute__((format(scanf, a, b)))
	131	#define __attribute_const__ __attribute__((__const__))
	132	#define __maybe_unused __attribute__((unused))
	133	#define __always_unused __attribute__((unused))
a3f0825e	134	#define __mode(x) __attribute__((mode(x)))
f153b821	135
cb984d10 JP	136	/* gcc version specific checks */
	137
	138	#if GCC_VERSION < 30200
	139	# error Sorry, your compiler is too old - please upgrade it.
	140	#endif
	141
	142	#if GCC_VERSION < 30300
	143	# define __used __attribute__((__unused__))
	144	#else
	145	# define __used __attribute__((__used__))
	146	#endif
	147
	148	#ifdef CONFIG_GCOV_KERNEL
	149	# if GCC_VERSION < 30400
	150	# error "GCOV profiling support for gcc versions below 3.4 not included"
	151	# endif /* __GNUC_MINOR__ */
	152	#endif /* CONFIG_GCOV_KERNEL */
	153
	154	#if GCC_VERSION >= 30400
	155	#define __must_check __attribute__((warn_unused_result))
d64e85d3	156	#define __malloc __attribute__((__malloc__))
cb984d10 JP	157	#endif
	158
	159	#if GCC_VERSION >= 40000
	160
	161	/* GCC 4.1.[01] miscompiles __weak */
	162	#ifdef __KERNEL__
	163	# if GCC_VERSION >= 40100 && GCC_VERSION <= 40101
	164	# error Your version of gcc miscompiles the __weak directive
	165	# endif
	166	#endif
	167
	168	#define __used __attribute__((__used__))
	169	#define __compiler_offsetof(a, b) \
	170	__builtin_offsetof(a, b)
	171
0d025d27	172	#if GCC_VERSION >= 40100
cb984d10 JP	173	# define __compiletime_object_size(obj) __builtin_object_size(obj, 0)
	174	#endif
	175
	176	#if GCC_VERSION >= 40300
	177	/* Mark functions as cold. gcc will assume any path leading to a call
	178	* to them will be unlikely. This means a lot of manual unlikely()s
	179	* are unnecessary now for any paths leading to the usual suspects
	180	* like BUG(), printk(), panic() etc. [but let's keep them for now for
	181	* older compilers]
	182	*
	183	* Early snapshots of gcc 4.3 don't support this and we can't detect this
	184	* in the preprocessor, but we can live with this because they're unreleased.
	185	* Maketime probing would be overkill here.
	186	*
	187	* gcc also has a __attribute__((__hot__)) to move hot functions into
	188	* a special section, but I don't see any sense in this right now in
	189	* the kernel context
	190	*/
	191	#define __cold __attribute__((__cold__))
	192
	193	#define __UNIQUE_ID(prefix) __PASTE(__PASTE(__UNIQUE_ID_, prefix), __COUNTER__)
	194
	195	#ifndef __CHECKER__
	196	# define __compiletime_warning(message) __attribute__((warning(message)))
	197	# define __compiletime_error(message) __attribute__((error(message)))
	198	#endif /* __CHECKER__ */
	199	#endif /* GCC_VERSION >= 40300 */
	200
df5d45aa GU	201	#if GCC_VERSION >= 40400
df5d45aa GU	202	#define __optimize(level) __attribute__((__optimize__(level)))
d9afaaa4	203	#define __nostackprotector __optimize("no-stack-protector")
df5d45aa GU	204	#endif /* GCC_VERSION >= 40400 */
df5d45aa GU	205
cb984d10	206	#if GCC_VERSION >= 40500
0766f788 ER	207
	208	#ifndef __CHECKER__
	209	#ifdef LATENT_ENTROPY_PLUGIN
	210	#define __latent_entropy __attribute__((latent_entropy))
	211	#endif
	212	#endif
	213
173a3efd AB	214	/*
	215	* calling noreturn functions, __builtin_unreachable() and __builtin_trap()
	216	* confuse the stack allocation in gcc, leading to overly large stack
	217	* frames, see https://gcc.gnu.org/bugzilla/show_bug.cgi?id=82365
	218	*
	219	* Adding an empty inline assembly before it works around the problem
	220	*/
	221	#define barrier_before_unreachable() asm volatile("")
	222
cb984d10 JP	223	/*
	224	* Mark a position in code as unreachable. This can be used to
	225	* suppress control flow warnings after asm blocks that transfer
	226	* control elsewhere.
	227	*
	228	* Early snapshots of gcc 4.5 don't support this and we can't detect
	229	* this in the preprocessor, but we can live with this because they're
	230	* unreleased. Really, we need to have autoconf for the kernel.
	231	*/
4e4636cf	232	#define unreachable() \
173a3efd AB	233	do { \
	234	annotate_unreachable(); \
	235	barrier_before_unreachable(); \
	236	__builtin_unreachable(); \
	237	} while (0)
cb984d10 JP	238
cb984d10 JP	239	/* Mark a function definition as prohibited from being cloned. */
95272c29	240	#define __noclone __attribute__((__noclone__, __optimize__("no-tracer")))
cb984d10	241
a3d6c976	242	#if defined(RANDSTRUCT_PLUGIN) && !defined(__CHECKER__)
313dd1b6 KC	243	#define __randomize_layout __attribute__((randomize_layout))
313dd1b6 KC	244	#define __no_randomize_layout __attribute__((no_randomize_layout))
2cfe0d30 KC	245	/* This anon struct can add padding, so only enable it under randstruct. */
	246	#define randomized_struct_fields_start struct {
	247	#define randomized_struct_fields_end } __randomize_layout;
313dd1b6 KC	248	#endif
313dd1b6 KC	249
cb984d10 JP	250	#endif /* GCC_VERSION >= 40500 */
	251
	252	#if GCC_VERSION >= 40600
29e48ce8	253
cb984d10	254	/*
9add850c AM	255	* When used with Link Time Optimization, gcc can optimize away C functions or
	256	* variables which are referenced only from assembly code. __visible tells the
	257	* optimizer that something else uses this function or variable, thus preventing
	258	* this.
cb984d10 JP	259	*/
cb984d10 JP	260	#define __visible __attribute__((externally_visible))
29e48ce8	261
29e48ce8	262	#endif /* GCC_VERSION >= 40600 */
cb984d10	263
a744fd17	264
8748dd5c	265	#if GCC_VERSION >= 40900 && !defined(__CHECKER__)
a744fd17 RV	266	/*
	267	* __assume_aligned(n, k): Tell the optimizer that the returned
	268	* pointer can be assumed to be k modulo n. The second argument is
	269	* optional (default 0), so we use a variadic macro to make the
	270	* shorthand.
	271	*
	272	* Beware: Do not apply this to functions which may return
	273	* ERR_PTRs. Also, it is probably unwise to apply it to functions
	274	* returning extra information in the low bits (but in that case the
	275	* compiler should see some alignment anyway, when the return value is
	276	* massaged by 'flags = ptr & 3; ptr &= ~3;').
	277	*/
	278	#define __assume_aligned(a, ...) __attribute__((__assume_aligned__(a, ## __VA_ARGS__)))
	279	#endif
	280
cb984d10 JP	281	/*
	282	* GCC 'asm goto' miscompiles certain code sequences:
	283	*
	284	* http://gcc.gnu.org/bugzilla/show_bug.cgi?id=58670
	285	*
	286	* Work it around via a compiler barrier quirk suggested by Jakub Jelinek.
	287	*
	288	* (asm goto is automatically volatile - the naming reflects this.)
	289	*/
	290	#define asm_volatile_goto(x...) do { asm goto(x); asm (""); } while (0)
	291
101b29a2 JB	292	/*
	293	* sparse (__CHECKER__) pretends to be gcc, but can't do constant
	294	* folding in __builtin_bswap*() (yet), so don't set these for it.
	295	*/
	296	#if defined(CONFIG_ARCH_USE_BUILTIN_BSWAP) && !defined(__CHECKER__)
cb984d10 JP	297	#if GCC_VERSION >= 40400
	298	#define __HAVE_BUILTIN_BSWAP32__
	299	#define __HAVE_BUILTIN_BSWAP64__
	300	#endif
8634de6d	301	#if GCC_VERSION >= 40800
cb984d10 JP	302	#define __HAVE_BUILTIN_BSWAP16__
cb984d10 JP	303	#endif
101b29a2	304	#endif /* CONFIG_ARCH_USE_BUILTIN_BSWAP && !__CHECKER__ */
cb984d10	305
045d599a DV	306	#if GCC_VERSION >= 70000
	307	#define KASAN_ABI_VERSION 5
	308	#elif GCC_VERSION >= 50000
cb984d10 JP	309	#define KASAN_ABI_VERSION 4
	310	#elif GCC_VERSION >= 40902
	311	#define KASAN_ABI_VERSION 3
	312	#endif
	313
d976441f AR	314	#if GCC_VERSION >= 40902
	315	/*
	316	* Tell the compiler that address safety instrumentation (KASAN)
	317	* should not be applied to that function.
	318	* Conflicts with inlining: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=67368
	319	*/
	320	#define __no_sanitize_address __attribute__((no_sanitize_address))
	321	#endif
	322
0aa5e49c KC	323	#if GCC_VERSION >= 50100
	324	/*
	325	* Mark structures as requiring designated initializers.
	326	* https://gcc.gnu.org/onlinedocs/gcc/Designated-Inits.html
	327	*/
	328	#define __designated_init __attribute__((designated_init))
	329	#endif
	330
cb984d10	331	#endif /* gcc version >= 40000 specific checks */
9c695203 MP	332
	333	#if !defined(__noclone)
	334	#define __noclone /* not needed */
	335	#endif
c837fb37	336
d976441f AR	337	#if !defined(__no_sanitize_address)
	338	#define __no_sanitize_address
	339	#endif
	340
c837fb37 BP	341	/*
	342	* A trick to suppress uninitialized variable warning without generating any
	343	* code
	344	*/
	345	#define uninitialized_var(x) x = x
f0907827 RV	346
	347	#if GCC_VERSION >= 50100
	348	#define COMPILER_HAS_GENERIC_BUILTIN_OVERFLOW 1
	349	#endif
8793bb7f AB	350
	351	/*
	352	* Turn individual warnings and errors on and off locally, depending
	353	* on version.
	354	*/
	355	#define __diag_GCC(version, severity, s) \
	356	__diag_GCC_ ## version(__diag_GCC_ ## severity s)
	357
	358	/* Severity used in pragma directives */
	359	#define __diag_GCC_ignore ignored
	360	#define __diag_GCC_warn warning
	361	#define __diag_GCC_error error
	362
	363	/* Compilers before gcc-4.6 do not understand "#pragma GCC diagnostic push" */
	364	#if GCC_VERSION >= 40600
	365	#define __diag_str1(s) #s
	366	#define __diag_str(s) __diag_str1(s)
	367	#define __diag(s) _Pragma(__diag_str(GCC diagnostic s))
	368	#endif
	369
	370	#if GCC_VERSION >= 80000
	371	#define __diag_GCC_8(s) __diag(s)
	372	#else
	373	#define __diag_GCC_8(s)
	374	#endif