[mirror_ubuntu-zesty-kernel.git] / arch / x86 / include / asm / alternative.h

#ifndef _ASM_X86_ALTERNATIVE_H
#define _ASM_X86_ALTERNATIVE_H

#include <linux/types.h>
#include <linux/stddef.h>
#include <linux/stringify.h>
#include <asm/asm.h>
#include <asm/ptrace.h>

/*
 * Alternative inline assembly for SMP.
 *
 * The LOCK_PREFIX macro defined here replaces the LOCK and
 * LOCK_PREFIX macros used everywhere in the source tree.
 *
 * SMP alternatives use the same data structures as the other
 * alternatives and the X86_FEATURE_UP flag to indicate the case of a
 * UP system running a SMP kernel.  The existing apply_alternatives()
 * works fine for patching a SMP kernel for UP.
 *
 * The SMP alternative tables can be kept after boot and contain both
 * UP and SMP versions of the instructions to allow switching back to
 * SMP at runtime, when hotplugging in a new CPU, which is especially
 * useful in virtualized environments.
 *
 * The very common lock prefix is handled as special case in a
 * separate table which is a pure address list without replacement ptr
 * and size information.  That keeps the table sizes small.
 */

#ifdef CONFIG_SMP
#define LOCK_PREFIX_HERE \
		".pushsection .smp_locks,\"a\"\n"	\
		".balign 4\n"				\
		".long 671f - .\n" /* offset */		\
		".popsection\n"				\
		"671:"

#define LOCK_PREFIX LOCK_PREFIX_HERE "\n\tlock; "

#else /* ! CONFIG_SMP */
#define LOCK_PREFIX_HERE ""
#define LOCK_PREFIX ""
#endif

struct alt_instr {
	s32 instr_offset;	/* original instruction */
	s32 repl_offset;	/* offset to replacement instruction */
	u16 cpuid;		/* cpuid bit set for replacement */
	u8  instrlen;		/* length of original instruction */
	u8  replacementlen;	/* length of new instruction */
	u8  padlen;		/* length of build-time padding */
} __packed;

extern void alternative_instructions(void);
extern void apply_alternatives(struct alt_instr *start, struct alt_instr *end);

struct module;

#ifdef CONFIG_SMP
extern void alternatives_smp_module_add(struct module *mod, char *name,
					void *locks, void *locks_end,
					void *text, void *text_end);
extern void alternatives_smp_module_del(struct module *mod);
extern void alternatives_enable_smp(void);
extern int alternatives_text_reserved(void *start, void *end);
extern bool skip_smp_alternatives;
#else
static inline void alternatives_smp_module_add(struct module *mod, char *name,
					       void *locks, void *locks_end,
					       void *text, void *text_end) {}
static inline void alternatives_smp_module_del(struct module *mod) {}
static inline void alternatives_enable_smp(void) {}
static inline int alternatives_text_reserved(void *start, void *end)
{
	return 0;
}
#endif	/* CONFIG_SMP */

#define b_replacement(num)	"664"#num
#define e_replacement(num)	"665"#num

#define alt_end_marker		"663"
#define alt_slen		"662b-661b"
#define alt_pad_len		alt_end_marker"b-662b"
#define alt_total_slen		alt_end_marker"b-661b"
#define alt_rlen(num)		e_replacement(num)"f-"b_replacement(num)"f"

#define __OLDINSTR(oldinstr, num)					\
	"661:\n\t" oldinstr "\n662:\n"					\
	".skip -(((" alt_rlen(num) ")-(" alt_slen ")) > 0) * "		\
		"((" alt_rlen(num) ")-(" alt_slen ")),0x90\n"

#define OLDINSTR(oldinstr, num)						\
	__OLDINSTR(oldinstr, num)					\
	alt_end_marker ":\n"

/*
 * max without conditionals. Idea adapted from:
 * http://graphics.stanford.edu/~seander/bithacks.html#IntegerMinOrMax
 *
 * The additional "-" is needed because gas works with s32s.
 */
#define alt_max_short(a, b)	"((" a ") ^ (((" a ") ^ (" b ")) & -(-((" a ") - (" b ")))))"

/*
 * Pad the second replacement alternative with additional NOPs if it is
 * additionally longer than the first replacement alternative.
 */
#define OLDINSTR_2(oldinstr, num1, num2) \
	"661:\n\t" oldinstr "\n662:\n"								\
	".skip -((" alt_max_short(alt_rlen(num1), alt_rlen(num2)) " - (" alt_slen ")) > 0) * "	\
		"(" alt_max_short(alt_rlen(num1), alt_rlen(num2)) " - (" alt_slen ")), 0x90\n"	\
	alt_end_marker ":\n"

#define ALTINSTR_ENTRY(feature, num)					      \
	" .long 661b - .\n"				/* label           */ \
	" .long " b_replacement(num)"f - .\n"		/* new instruction */ \
	" .word " __stringify(feature) "\n"		/* feature bit     */ \
	" .byte " alt_total_slen "\n"			/* source len      */ \
	" .byte " alt_rlen(num) "\n"			/* replacement len */ \
	" .byte " alt_pad_len "\n"			/* pad len */

#define ALTINSTR_REPLACEMENT(newinstr, feature, num)	/* replacement */     \
	b_replacement(num)":\n\t" newinstr "\n" e_replacement(num) ":\n\t"

/* alternative assembly primitive: */
#define ALTERNATIVE(oldinstr, newinstr, feature)			\
	OLDINSTR(oldinstr, 1)						\
	".pushsection .altinstructions,\"a\"\n"				\
	ALTINSTR_ENTRY(feature, 1)					\
	".popsection\n"							\
	".pushsection .altinstr_replacement, \"ax\"\n"			\
	ALTINSTR_REPLACEMENT(newinstr, feature, 1)			\
	".popsection"

#define ALTERNATIVE_2(oldinstr, newinstr1, feature1, newinstr2, feature2)\
	OLDINSTR_2(oldinstr, 1, 2)					\
	".pushsection .altinstructions,\"a\"\n"				\
	ALTINSTR_ENTRY(feature1, 1)					\
	ALTINSTR_ENTRY(feature2, 2)					\
	".popsection\n"							\
	".pushsection .altinstr_replacement, \"ax\"\n"			\
	ALTINSTR_REPLACEMENT(newinstr1, feature1, 1)			\
	ALTINSTR_REPLACEMENT(newinstr2, feature2, 2)			\
	".popsection"

/*
 * This must be included *after* the definition of ALTERNATIVE due to
 * <asm/arch_hweight.h>
 */
#include <asm/cpufeature.h>

/*
 * Alternative instructions for different CPU types or capabilities.
 *
 * This allows to use optimized instructions even on generic binary
 * kernels.
 *
 * length of oldinstr must be longer or equal the length of newinstr
 * It can be padded with nops as needed.
 *
 * For non barrier like inlines please define new variants
 * without volatile and memory clobber.
 */
#define alternative(oldinstr, newinstr, feature)			\
	asm volatile (ALTERNATIVE(oldinstr, newinstr, feature) : : : "memory")

#define alternative_2(oldinstr, newinstr1, feature1, newinstr2, feature2) \
	asm volatile(ALTERNATIVE_2(oldinstr, newinstr1, feature1, newinstr2, feature2) ::: "memory")

/*
 * Alternative inline assembly with input.
 *
 * Pecularities:
 * No memory clobber here.
 * Argument numbers start with 1.
 * Best is to use constraints that are fixed size (like (%1) ... "r")
 * If you use variable sized constraints like "m" or "g" in the
 * replacement make sure to pad to the worst case length.
 * Leaving an unused argument 0 to keep API compatibility.
 */
#define alternative_input(oldinstr, newinstr, feature, input...)	\
	asm volatile (ALTERNATIVE(oldinstr, newinstr, feature)		\
		: : "i" (0), ## input)

/*
 * This is similar to alternative_input. But it has two features and
 * respective instructions.
 *
 * If CPU has feature2, newinstr2 is used.
 * Otherwise, if CPU has feature1, newinstr1 is used.
 * Otherwise, oldinstr is used.
 */
#define alternative_input_2(oldinstr, newinstr1, feature1, newinstr2,	     \
			   feature2, input...)				     \
	asm volatile(ALTERNATIVE_2(oldinstr, newinstr1, feature1,	     \
		newinstr2, feature2)					     \
		: : "i" (0), ## input)

/* Like alternative_input, but with a single output argument */
#define alternative_io(oldinstr, newinstr, feature, output, input...)	\
	asm volatile (ALTERNATIVE(oldinstr, newinstr, feature)		\
		: output : "i" (0), ## input)

/* Like alternative_io, but for replacing a direct call with another one. */
#define alternative_call(oldfunc, newfunc, feature, output, input...)	\
	asm volatile (ALTERNATIVE("call %P[old]", "call %P[new]", feature) \
		: output : [old] "i" (oldfunc), [new] "i" (newfunc), ## input)

/*
 * Like alternative_call, but there are two features and respective functions.
 * If CPU has feature2, function2 is used.
 * Otherwise, if CPU has feature1, function1 is used.
 * Otherwise, old function is used.
 */
#define alternative_call_2(oldfunc, newfunc1, feature1, newfunc2, feature2,   \
			   output, input...)				      \
	asm volatile (ALTERNATIVE_2("call %P[old]", "call %P[new1]", feature1,\
		"call %P[new2]", feature2)				      \
		: output : [old] "i" (oldfunc), [new1] "i" (newfunc1),	      \
		[new2] "i" (newfunc2), ## input)

/*
 * use this macro(s) if you need more than one output parameter
 * in alternative_io
 */
#define ASM_OUTPUT2(a...) a

/*
 * use this macro if you need clobbers but no inputs in
 * alternative_{input,io,call}()
 */
#define ASM_NO_INPUT_CLOBBER(clbr...) "i" (0) : clbr

struct paravirt_patch_site;
#ifdef CONFIG_PARAVIRT
void apply_paravirt(struct paravirt_patch_site *start,
		    struct paravirt_patch_site *end);
#else
static inline void apply_paravirt(struct paravirt_patch_site *start,
				  struct paravirt_patch_site *end)
{}
#define __parainstructions	NULL
#define __parainstructions_end	NULL
#endif

extern void *text_poke_early(void *addr, const void *opcode, size_t len);

/*
 * Clear and restore the kernel write-protection flag on the local CPU.
 * Allows the kernel to edit read-only pages.
 * Side-effect: any interrupt handler running between save and restore will have
 * the ability to write to read-only pages.
 *
 * Warning:
 * Code patching in the UP case is safe if NMIs and MCE handlers are stopped and
 * no thread can be preempted in the instructions being modified (no iret to an
 * invalid instruction possible) or if the instructions are changed from a
 * consistent state to another consistent state atomically.
 * On the local CPU you need to be protected again NMI or MCE handlers seeing an
 * inconsistent instruction while you patch.
 */
extern void *text_poke(void *addr, const void *opcode, size_t len);
extern int poke_int3_handler(struct pt_regs *regs);
extern void *text_poke_bp(void *addr, const void *opcode, size_t len, void *handler);

#endif /* _ASM_X86_ALTERNATIVE_H */
Commit	Line	Data
1965aae3 PA	1	#ifndef _ASM_X86_ALTERNATIVE_H
1965aae3 PA	2	#define _ASM_X86_ALTERNATIVE_H
6b592570 PA	3
	4	#include <linux/types.h>
	5	#include <linux/stddef.h>
edc953fa	6	#include <linux/stringify.h>
6b592570	7	#include <asm/asm.h>
17f41571	8	#include <asm/ptrace.h>
6b592570 PA	9
	10	/*
	11	* Alternative inline assembly for SMP.
	12	*
	13	* The LOCK_PREFIX macro defined here replaces the LOCK and
	14	* LOCK_PREFIX macros used everywhere in the source tree.
	15	*
	16	* SMP alternatives use the same data structures as the other
	17	* alternatives and the X86_FEATURE_UP flag to indicate the case of a
	18	* UP system running a SMP kernel. The existing apply_alternatives()
	19	* works fine for patching a SMP kernel for UP.
	20	*
	21	* The SMP alternative tables can be kept after boot and contain both
	22	* UP and SMP versions of the instructions to allow switching back to
	23	* SMP at runtime, when hotplugging in a new CPU, which is especially
	24	* useful in virtualized environments.
	25	*
	26	* The very common lock prefix is handled as special case in a
	27	* separate table which is a pure address list without replacement ptr
	28	* and size information. That keeps the table sizes small.
	29	*/
	30
	31	#ifdef CONFIG_SMP
b3ac891b	32	#define LOCK_PREFIX_HERE \
9cebed42 PA	33	".pushsection .smp_locks,\"a\"\n" \
	34	".balign 4\n" \
	35	".long 671f - .\n" /* offset */ \
	36	".popsection\n" \
b3ac891b LB	37	"671:"
	38
	39	#define LOCK_PREFIX LOCK_PREFIX_HERE "\n\tlock; "
6b592570 PA	40
6b592570 PA	41	#else /* ! CONFIG_SMP */
b701a47b	42	#define LOCK_PREFIX_HERE ""
6b592570 PA	43	#define LOCK_PREFIX ""
	44	#endif
	45
6b592570	46	struct alt_instr {
59e97e4d AL	47	s32 instr_offset; /* original instruction */
59e97e4d AL	48	s32 repl_offset; /* offset to replacement instruction */
83a7a2ad	49	u16 cpuid; /* cpuid bit set for replacement */
6b592570	50	u8 instrlen; /* length of original instruction */
4332195c BP	51	u8 replacementlen; /* length of new instruction */
	52	u8 padlen; /* length of build-time padding */
	53	} __packed;
6b592570 PA	54
	55	extern void alternative_instructions(void);
	56	extern void apply_alternatives(struct alt_instr start, struct alt_instr end);
	57
	58	struct module;
	59
	60	#ifdef CONFIG_SMP
	61	extern void alternatives_smp_module_add(struct module mod, char name,
	62	void locks, void locks_end,
	63	void text, void text_end);
	64	extern void alternatives_smp_module_del(struct module *mod);
816afe4f	65	extern void alternatives_enable_smp(void);
2cfa1978	66	extern int alternatives_text_reserved(void start, void end);
3fb82d56	67	extern bool skip_smp_alternatives;
6b592570 PA	68	#else
6b592570 PA	69	static inline void alternatives_smp_module_add(struct module mod, char name,
2ac1ea7c JP	70	void locks, void locks_end,
2ac1ea7c JP	71	void text, void text_end) {}
6b592570	72	static inline void alternatives_smp_module_del(struct module *mod) {}
816afe4f	73	static inline void alternatives_enable_smp(void) {}
2cfa1978 MH	74	static inline int alternatives_text_reserved(void start, void end)
	75	{
	76	return 0;
	77	}
6b592570 PA	78	#endif /* CONFIG_SMP */
6b592570 PA	79
4332195c BP	80	#define b_replacement(num) "664"#num
4332195c BP	81	#define e_replacement(num) "665"#num
954e482b	82
4332195c BP	83	#define alt_end_marker "663"
	84	#define alt_slen "662b-661b"
	85	#define alt_pad_len alt_end_marker"b-662b"
	86	#define alt_total_slen alt_end_marker"b-661b"
	87	#define alt_rlen(num) e_replacement(num)"f-"b_replacement(num)"f"
954e482b	88
4332195c BP	89	#define __OLDINSTR(oldinstr, num) \
	90	"661:\n\t" oldinstr "\n662:\n" \
	91	".skip -(((" alt_rlen(num) ")-(" alt_slen ")) > 0) * " \
	92	"((" alt_rlen(num) ")-(" alt_slen ")),0x90\n"
954e482b	93
4332195c BP	94	#define OLDINSTR(oldinstr, num) \
	95	__OLDINSTR(oldinstr, num) \
	96	alt_end_marker ":\n"
	97
dbe4058a BP	98	/*
	99	* max without conditionals. Idea adapted from:
	100	* http://graphics.stanford.edu/~seander/bithacks.html#IntegerMinOrMax
	101	*
	102	* The additional "-" is needed because gas works with s32s.
	103	*/
	104	#define alt_max_short(a, b) "((" a ") ^ (((" a ") ^ (" b ")) & -(-((" a ") - (" b ")))))"
	105
4332195c BP	106	/*
	107	* Pad the second replacement alternative with additional NOPs if it is
	108	* additionally longer than the first replacement alternative.
	109	*/
dbe4058a BP	110	#define OLDINSTR_2(oldinstr, num1, num2) \
	111	"661:\n\t" oldinstr "\n662:\n" \
	112	".skip -((" alt_max_short(alt_rlen(num1), alt_rlen(num2)) " - (" alt_slen ")) > 0) * " \
	113	"(" alt_max_short(alt_rlen(num1), alt_rlen(num2)) " - (" alt_slen ")), 0x90\n" \
4332195c BP	114	alt_end_marker ":\n"
	115
	116	#define ALTINSTR_ENTRY(feature, num) \
954e482b	117	" .long 661b - .\n" /* label */ \
4332195c	118	" .long " b_replacement(num)"f - .\n" /* new instruction */ \
954e482b	119	" .word " __stringify(feature) "\n" /* feature bit */ \
4332195c BP	120	" .byte " alt_total_slen "\n" /* source len */ \
	121	" .byte " alt_rlen(num) "\n" /* replacement len */ \
	122	" .byte " alt_pad_len "\n" /* pad len */
954e482b	123
4332195c BP	124	#define ALTINSTR_REPLACEMENT(newinstr, feature, num) /* replacement */ \
4332195c BP	125	b_replacement(num)":\n\t" newinstr "\n" e_replacement(num) ":\n\t"
954e482b	126
edc953fa MD	127	/* alternative assembly primitive: */
edc953fa MD	128	#define ALTERNATIVE(oldinstr, newinstr, feature) \
4332195c	129	OLDINSTR(oldinstr, 1) \
9cebed42	130	".pushsection .altinstructions,\"a\"\n" \
954e482b	131	ALTINSTR_ENTRY(feature, 1) \
9cebed42	132	".popsection\n" \
9cebed42	133	".pushsection .altinstr_replacement, \"ax\"\n" \
954e482b	134	ALTINSTR_REPLACEMENT(newinstr, feature, 1) \
9cebed42	135	".popsection"
954e482b FY	136
954e482b FY	137	#define ALTERNATIVE_2(oldinstr, newinstr1, feature1, newinstr2, feature2)\
4332195c	138	OLDINSTR_2(oldinstr, 1, 2) \
9cebed42	139	".pushsection .altinstructions,\"a\"\n" \
954e482b FY	140	ALTINSTR_ENTRY(feature1, 1) \
954e482b FY	141	ALTINSTR_ENTRY(feature2, 2) \
9cebed42	142	".popsection\n" \
9cebed42	143	".pushsection .altinstr_replacement, \"ax\"\n" \
954e482b FY	144	ALTINSTR_REPLACEMENT(newinstr1, feature1, 1) \
954e482b FY	145	ALTINSTR_REPLACEMENT(newinstr2, feature2, 2) \
9cebed42	146	".popsection"
edc953fa	147
d61931d8 BP	148	/*
	149	* This must be included after the definition of ALTERNATIVE due to
	150	* <asm/arch_hweight.h>
	151	*/
	152	#include <asm/cpufeature.h>
	153
6b592570 PA	154	/*
	155	* Alternative instructions for different CPU types or capabilities.
	156	*
	157	* This allows to use optimized instructions even on generic binary
	158	* kernels.
	159	*
	160	* length of oldinstr must be longer or equal the length of newinstr
	161	* It can be padded with nops as needed.
	162	*
	163	* For non barrier like inlines please define new variants
	164	* without volatile and memory clobber.
	165	*/
	166	#define alternative(oldinstr, newinstr, feature) \
edc953fa	167	asm volatile (ALTERNATIVE(oldinstr, newinstr, feature) : : : "memory")
6b592570	168
4332195c BP	169	#define alternative_2(oldinstr, newinstr1, feature1, newinstr2, feature2) \
	170	asm volatile(ALTERNATIVE_2(oldinstr, newinstr1, feature1, newinstr2, feature2) ::: "memory")
	171
6b592570 PA	172	/*
	173	* Alternative inline assembly with input.
	174	*
	175	* Pecularities:
	176	* No memory clobber here.
	177	* Argument numbers start with 1.
	178	* Best is to use constraints that are fixed size (like (%1) ... "r")
	179	* If you use variable sized constraints like "m" or "g" in the
	180	* replacement make sure to pad to the worst case length.
edc953fa	181	* Leaving an unused argument 0 to keep API compatibility.
6b592570 PA	182	*/
6b592570 PA	183	#define alternative_input(oldinstr, newinstr, feature, input...) \
edc953fa MD	184	asm volatile (ALTERNATIVE(oldinstr, newinstr, feature) \
edc953fa MD	185	: : "i" (0), ## input)
6b592570	186
5b3e83f4 FY	187	/*
	188	* This is similar to alternative_input. But it has two features and
	189	* respective instructions.
	190	*
	191	* If CPU has feature2, newinstr2 is used.
	192	* Otherwise, if CPU has feature1, newinstr1 is used.
	193	* Otherwise, oldinstr is used.
	194	*/
	195	#define alternative_input_2(oldinstr, newinstr1, feature1, newinstr2, \
	196	feature2, input...) \
	197	asm volatile(ALTERNATIVE_2(oldinstr, newinstr1, feature1, \
	198	newinstr2, feature2) \
	199	: : "i" (0), ## input)
	200
6b592570 PA	201	/* Like alternative_input, but with a single output argument */
6b592570 PA	202	#define alternative_io(oldinstr, newinstr, feature, output, input...) \
edc953fa MD	203	asm volatile (ALTERNATIVE(oldinstr, newinstr, feature) \
edc953fa MD	204	: output : "i" (0), ## input)
6b592570	205
1b1d9258 JB	206	/* Like alternative_io, but for replacing a direct call with another one. */
	207	#define alternative_call(oldfunc, newfunc, feature, output, input...) \
	208	asm volatile (ALTERNATIVE("call %P[old]", "call %P[new]", feature) \
	209	: output : [old] "i" (oldfunc), [new] "i" (newfunc), ## input)
	210
954e482b FY	211	/*
	212	* Like alternative_call, but there are two features and respective functions.
	213	* If CPU has feature2, function2 is used.
	214	* Otherwise, if CPU has feature1, function1 is used.
	215	* Otherwise, old function is used.
	216	*/
	217	#define alternative_call_2(oldfunc, newfunc1, feature1, newfunc2, feature2, \
	218	output, input...) \
	219	asm volatile (ALTERNATIVE_2("call %P[old]", "call %P[new1]", feature1,\
	220	"call %P[new2]", feature2) \
	221	: output : [old] "i" (oldfunc), [new1] "i" (newfunc1), \
	222	[new2] "i" (newfunc2), ## input)
	223
6b592570 PA	224	/*
	225	* use this macro(s) if you need more than one output parameter
	226	* in alternative_io
	227	*/
1b1d9258	228	#define ASM_OUTPUT2(a...) a
6b592570	229
819165fb JB	230	/*
	231	* use this macro if you need clobbers but no inputs in
	232	* alternative_{input,io,call}()
	233	*/
	234	#define ASM_NO_INPUT_CLOBBER(clbr...) "i" (0) : clbr
	235
6b592570 PA	236	struct paravirt_patch_site;
	237	#ifdef CONFIG_PARAVIRT
	238	void apply_paravirt(struct paravirt_patch_site *start,
	239	struct paravirt_patch_site *end);
96a388de	240	#else
2ac1ea7c JP	241	static inline void apply_paravirt(struct paravirt_patch_site *start,
2ac1ea7c JP	242	struct paravirt_patch_site *end)
6b592570 PA	243	{}
	244	#define __parainstructions NULL
	245	#define __parainstructions_end NULL
96a388de	246	#endif
6b592570	247
fa6f2cc7 JB	248	extern void text_poke_early(void addr, const void *opcode, size_t len);
fa6f2cc7 JB	249
e587cadd MD	250	/*
	251	* Clear and restore the kernel write-protection flag on the local CPU.
	252	* Allows the kernel to edit read-only pages.
	253	* Side-effect: any interrupt handler running between save and restore will have
	254	* the ability to write to read-only pages.
	255	*
	256	* Warning:
	257	* Code patching in the UP case is safe if NMIs and MCE handlers are stopped and
	258	* no thread can be preempted in the instructions being modified (no iret to an
	259	* invalid instruction possible) or if the instructions are changed from a
	260	* consistent state to another consistent state atomically.
e587cadd MD	261	* On the local CPU you need to be protected again NMI or MCE handlers seeing an
e587cadd MD	262	* inconsistent instruction while you patch.
e587cadd	263	*/
e587cadd	264	extern void text_poke(void addr, const void *opcode, size_t len);
17f41571	265	extern int poke_int3_handler(struct pt_regs *regs);
fd4363ff	266	extern void text_poke_bp(void addr, const void opcode, size_t len, void handler);
6b592570	267
1965aae3	268	#endif /* _ASM_X86_ALTERNATIVE_H */