[mirror_ubuntu-bionic-kernel.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

/*
 * Feature detection for gnu_inline (gnu89 extern inline semantics). Either
 * __GNUC_STDC_INLINE__ is defined (not using gnu89 extern inline semantics,
 * and we opt in to the gnu89 semantics), or __GNUC_STDC_INLINE__ is not
 * defined so the gnu89 semantics are the default.
 */
#ifdef __GNUC_STDC_INLINE__
# define __gnu_inline	__attribute__((gnu_inline))
#else
# define __gnu_inline
#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.
 * Prefer gnu_inline, so that extern inline functions do not emit an
 * externally visible function. This makes extern inline behave as per gnu89
 * semantics rather than c99. This prevents multiple symbol definition errors
 * of extern inline functions at link time.
 * A lot of inline functions can cause havoc with function tracing.
 */
#if !defined(CONFIG_ARCH_SUPPORTS_OPTIMIZED_INLINING) ||		\
    !defined(CONFIG_OPTIMIZE_INLINING) || (__GNUC__ < 4)
#define inline \
	inline __attribute__((always_inline, unused)) notrace __gnu_inline
#else
#define inline inline		__attribute__((unused)) notrace __gnu_inline
#endif

#define __inline__ inline
#define __inline inline
#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 CONFIG_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

#if GCC_VERSION >= 90100
#define __copy(symbol)                 __attribute__((__copy__(symbol)))
#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
Commit	Line	Data
	1	/* SPDX-License-Identifier: GPL-2.0 */
	2	#ifndef __LINUX_COMPILER_TYPES_H
	3	#error "Please don't include <linux/compiler-gcc.h> directly, include <linux/compiler.h> instead."
	4	#endif
	5
	6	/*
	7	* Common definitions for all gcc versions go here.
	8	*/
	9	#define GCC_VERSION (__GNUC__ * 10000 \
	10	+ __GNUC_MINOR__ * 100 \
	11	+ __GNUC_PATCHLEVEL__)
	12
	13	/* Optimization barrier */
	14
	15	/* The "volatile" is due to gcc bugs */
	16	#define barrier() __asm__ __volatile__("": : :"memory")
	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
	25	* from that, it proved that the inline asm wasn't touching any of
	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")
	31
	32	/*
	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	*
	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	*/
	50	#define RELOC_HIDE(ptr, off) \
	51	({ \
	52	unsigned long __ptr; \
	53	__asm__ ("" : "=r"(__ptr) : "0"(ptr)); \
	54	(typeof(ptr)) (__ptr + (off)); \
	55	})
	56
	57	/* Make the optimizer believe the variable can be manipulated arbitrarily. */
	58	#define OPTIMIZER_HIDE_VAR(var) \
	59	__asm__ ("" : "=r" (var) : "0" (var))
	60
	61	#ifdef __CHECKER__
	62	#define __must_be_array(a) 0
	63	#else
	64	/* &a[0] degrades to a pointer: a different type from an array */
	65	#define __must_be_array(a) BUILD_BUG_ON_ZERO(__same_type((a), &(a)[0]))
	66	#endif
	67
	68	/*
	69	* Feature detection for gnu_inline (gnu89 extern inline semantics). Either
	70	* __GNUC_STDC_INLINE__ is defined (not using gnu89 extern inline semantics,
	71	* and we opt in to the gnu89 semantics), or __GNUC_STDC_INLINE__ is not
	72	* defined so the gnu89 semantics are the default.
	73	*/
	74	#ifdef __GNUC_STDC_INLINE__
	75	# define __gnu_inline __attribute__((gnu_inline))
	76	#else
	77	# define __gnu_inline
	78	#endif
	79
	80	/*
	81	* Force always-inline if the user requests it so via the .config,
	82	* or if gcc is too old.
	83	* GCC does not warn about unused static inline functions for
	84	* -Wunused-function. This turns out to avoid the need for complex #ifdef
	85	* directives. Suppress the warning in clang as well by using "unused"
	86	* function attribute, which is redundant but not harmful for gcc.
	87	* Prefer gnu_inline, so that extern inline functions do not emit an
	88	* externally visible function. This makes extern inline behave as per gnu89
	89	* semantics rather than c99. This prevents multiple symbol definition errors
	90	* of extern inline functions at link time.
	91	* A lot of inline functions can cause havoc with function tracing.
	92	*/
	93	#if !defined(CONFIG_ARCH_SUPPORTS_OPTIMIZED_INLINING) \|\| \
	94	!defined(CONFIG_OPTIMIZE_INLINING) \|\| (__GNUC__ < 4)
	95	#define inline \
	96	inline __attribute__((always_inline, unused)) notrace __gnu_inline
	97	#else
	98	#define inline inline __attribute__((unused)) notrace __gnu_inline
	99	#endif
	100
	101	#define __inline__ inline
	102	#define __inline inline
	103	#define __always_inline inline __attribute__((always_inline))
	104	#define noinline __attribute__((noinline))
	105
	106	#define __deprecated __attribute__((deprecated))
	107	#define __packed __attribute__((packed))
	108	#define __weak __attribute__((weak))
	109	#define __alias(symbol) __attribute__((alias(#symbol)))
	110
	111	#ifdef CONFIG_RETPOLINE
	112	#define __noretpoline __attribute__((indirect_branch("keep")))
	113	#endif
	114
	115	/*
	116	* it doesn't make sense on ARM (currently the only user of __naked)
	117	* to trace naked functions because then mcount is called without
	118	* stack and frame pointer being set up and there is no chance to
	119	* restore the lr register to the value before mcount was called.
	120	*
	121	* The asm() bodies of naked functions often depend on standard calling
	122	* conventions, therefore they must be noinline and noclone.
	123	*
	124	* GCC 4.[56] currently fail to enforce this, so we must do so ourselves.
	125	* See GCC PR44290.
	126	*/
	127	#define __naked __attribute__((naked)) noinline __noclone notrace
	128
	129	#define __noreturn __attribute__((noreturn))
	130
	131	/*
	132	* From the GCC manual:
	133	*
	134	* Many functions have no effects except the return value and their
	135	* return value depends only on the parameters and/or global
	136	* variables. Such a function can be subject to common subexpression
	137	* elimination and loop optimization just as an arithmetic operator
	138	* would be.
	139	* [...]
	140	*/
	141	#define __pure __attribute__((pure))
	142	#define __aligned(x) __attribute__((aligned(x)))
	143	#define __aligned_largest __attribute__((aligned))
	144	#define __printf(a, b) __attribute__((format(printf, a, b)))
	145	#define __scanf(a, b) __attribute__((format(scanf, a, b)))
	146	#define __attribute_const__ __attribute__((__const__))
	147	#define __maybe_unused __attribute__((unused))
	148	#define __always_unused __attribute__((unused))
	149	#define __mode(x) __attribute__((mode(x)))
	150
	151	/* gcc version specific checks */
	152
	153	#if GCC_VERSION < 30200
	154	# error Sorry, your compiler is too old - please upgrade it.
	155	#endif
	156
	157	#if GCC_VERSION < 30300
	158	# define __used __attribute__((__unused__))
	159	#else
	160	# define __used __attribute__((__used__))
	161	#endif
	162
	163	#ifdef CONFIG_GCOV_KERNEL
	164	# if GCC_VERSION < 30400
	165	# error "GCOV profiling support for gcc versions below 3.4 not included"
	166	# endif /* __GNUC_MINOR__ */
	167	#endif /* CONFIG_GCOV_KERNEL */
	168
	169	#if GCC_VERSION >= 30400
	170	#define __must_check __attribute__((warn_unused_result))
	171	#define __malloc __attribute__((__malloc__))
	172	#endif
	173
	174	#if GCC_VERSION >= 40000
	175
	176	/* GCC 4.1.[01] miscompiles __weak */
	177	#ifdef __KERNEL__
	178	# if GCC_VERSION >= 40100 && GCC_VERSION <= 40101
	179	# error Your version of gcc miscompiles the __weak directive
	180	# endif
	181	#endif
	182
	183	#define __used __attribute__((__used__))
	184	#define __compiler_offsetof(a, b) \
	185	__builtin_offsetof(a, b)
	186
	187	#if GCC_VERSION >= 40100
	188	# define __compiletime_object_size(obj) __builtin_object_size(obj, 0)
	189	#endif
	190
	191	#if GCC_VERSION >= 40300
	192	/* Mark functions as cold. gcc will assume any path leading to a call
	193	* to them will be unlikely. This means a lot of manual unlikely()s
	194	* are unnecessary now for any paths leading to the usual suspects
	195	* like BUG(), printk(), panic() etc. [but let's keep them for now for
	196	* older compilers]
	197	*
	198	* Early snapshots of gcc 4.3 don't support this and we can't detect this
	199	* in the preprocessor, but we can live with this because they're unreleased.
	200	* Maketime probing would be overkill here.
	201	*
	202	* gcc also has a __attribute__((__hot__)) to move hot functions into
	203	* a special section, but I don't see any sense in this right now in
	204	* the kernel context
	205	*/
	206	#define __cold __attribute__((__cold__))
	207
	208	#define __UNIQUE_ID(prefix) __PASTE(__PASTE(__UNIQUE_ID_, prefix), __COUNTER__)
	209
	210	#ifndef __CHECKER__
	211	# define __compiletime_warning(message) __attribute__((warning(message)))
	212	# define __compiletime_error(message) __attribute__((error(message)))
	213	#endif /* __CHECKER__ */
	214	#endif /* GCC_VERSION >= 40300 */
	215
	216	#if GCC_VERSION >= 40400
	217	#define __optimize(level) __attribute__((__optimize__(level)))
	218	#define __nostackprotector __optimize("no-stack-protector")
	219	#endif /* GCC_VERSION >= 40400 */
	220
	221	#if GCC_VERSION >= 40500
	222
	223	#ifndef __CHECKER__
	224	#ifdef LATENT_ENTROPY_PLUGIN
	225	#define __latent_entropy __attribute__((latent_entropy))
	226	#endif
	227	#endif
	228
	229	/*
	230	* calling noreturn functions, __builtin_unreachable() and __builtin_trap()
	231	* confuse the stack allocation in gcc, leading to overly large stack
	232	* frames, see https://gcc.gnu.org/bugzilla/show_bug.cgi?id=82365
	233	*
	234	* Adding an empty inline assembly before it works around the problem
	235	*/
	236	#define barrier_before_unreachable() asm volatile("")
	237
	238	/*
	239	* Mark a position in code as unreachable. This can be used to
	240	* suppress control flow warnings after asm blocks that transfer
	241	* control elsewhere.
	242	*
	243	* Early snapshots of gcc 4.5 don't support this and we can't detect
	244	* this in the preprocessor, but we can live with this because they're
	245	* unreleased. Really, we need to have autoconf for the kernel.
	246	*/
	247	#define unreachable() \
	248	do { \
	249	annotate_unreachable(); \
	250	barrier_before_unreachable(); \
	251	__builtin_unreachable(); \
	252	} while (0)
	253
	254	/* Mark a function definition as prohibited from being cloned. */
	255	#define __noclone __attribute__((__noclone__, __optimize__("no-tracer")))
	256
	257	#if defined(RANDSTRUCT_PLUGIN) && !defined(__CHECKER__)
	258	#define __randomize_layout __attribute__((randomize_layout))
	259	#define __no_randomize_layout __attribute__((no_randomize_layout))
	260	/* This anon struct can add padding, so only enable it under randstruct. */
	261	#define randomized_struct_fields_start struct {
	262	#define randomized_struct_fields_end } __randomize_layout;
	263	#endif
	264
	265	#endif /* GCC_VERSION >= 40500 */
	266
	267	#if GCC_VERSION >= 40600
	268
	269	/*
	270	* When used with Link Time Optimization, gcc can optimize away C functions or
	271	* variables which are referenced only from assembly code. __visible tells the
	272	* optimizer that something else uses this function or variable, thus preventing
	273	* this.
	274	*/
	275	#define __visible __attribute__((externally_visible))
	276
	277	#endif /* GCC_VERSION >= 40600 */
	278
	279
	280	#if GCC_VERSION >= 40900 && !defined(__CHECKER__)
	281	/*
	282	* __assume_aligned(n, k): Tell the optimizer that the returned
	283	* pointer can be assumed to be k modulo n. The second argument is
	284	* optional (default 0), so we use a variadic macro to make the
	285	* shorthand.
	286	*
	287	* Beware: Do not apply this to functions which may return
	288	* ERR_PTRs. Also, it is probably unwise to apply it to functions
	289	* returning extra information in the low bits (but in that case the
	290	* compiler should see some alignment anyway, when the return value is
	291	* massaged by 'flags = ptr & 3; ptr &= ~3;').
	292	*/
	293	#define __assume_aligned(a, ...) __attribute__((__assume_aligned__(a, ## __VA_ARGS__)))
	294	#endif
	295
	296	/*
	297	* GCC 'asm goto' miscompiles certain code sequences:
	298	*
	299	* http://gcc.gnu.org/bugzilla/show_bug.cgi?id=58670
	300	*
	301	* Work it around via a compiler barrier quirk suggested by Jakub Jelinek.
	302	*
	303	* (asm goto is automatically volatile - the naming reflects this.)
	304	*/
	305	#define asm_volatile_goto(x...) do { asm goto(x); asm (""); } while (0)
	306
	307	/*
	308	* sparse (__CHECKER__) pretends to be gcc, but can't do constant
	309	* folding in __builtin_bswap*() (yet), so don't set these for it.
	310	*/
	311	#if defined(CONFIG_ARCH_USE_BUILTIN_BSWAP) && !defined(__CHECKER__)
	312	#if GCC_VERSION >= 40400
	313	#define __HAVE_BUILTIN_BSWAP32__
	314	#define __HAVE_BUILTIN_BSWAP64__
	315	#endif
	316	#if GCC_VERSION >= 40800
	317	#define __HAVE_BUILTIN_BSWAP16__
	318	#endif
	319	#endif /* CONFIG_ARCH_USE_BUILTIN_BSWAP && !__CHECKER__ */
	320
	321	#if GCC_VERSION >= 70000
	322	#define KASAN_ABI_VERSION 5
	323	#elif GCC_VERSION >= 50000
	324	#define KASAN_ABI_VERSION 4
	325	#elif GCC_VERSION >= 40902
	326	#define KASAN_ABI_VERSION 3
	327	#endif
	328
	329	#if GCC_VERSION >= 40902
	330	/*
	331	* Tell the compiler that address safety instrumentation (KASAN)
	332	* should not be applied to that function.
	333	* Conflicts with inlining: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=67368
	334	*/
	335	#define __no_sanitize_address __attribute__((no_sanitize_address))
	336	#endif
	337
	338	#if GCC_VERSION >= 50100
	339	/*
	340	* Mark structures as requiring designated initializers.
	341	* https://gcc.gnu.org/onlinedocs/gcc/Designated-Inits.html
	342	*/
	343	#define __designated_init __attribute__((designated_init))
	344	#endif
	345
	346	#if GCC_VERSION >= 90100
	347	#define __copy(symbol) __attribute__((__copy__(symbol)))
	348	#endif
	349
	350	#endif /* gcc version >= 40000 specific checks */
	351
	352	#if !defined(__noclone)
	353	#define __noclone /* not needed */
	354	#endif
	355
	356	#if !defined(__no_sanitize_address)
	357	#define __no_sanitize_address
	358	#endif
	359
	360	/*
	361	* A trick to suppress uninitialized variable warning without generating any
	362	* code
	363	*/
	364	#define uninitialized_var(x) x = x
	365
	366	#if GCC_VERSION >= 50100
	367	#define COMPILER_HAS_GENERIC_BUILTIN_OVERFLOW 1
	368	#endif