arch/x86/include/asm/alternative.h - linux - Git at Google

 /* SPDX-License-Identifier: GPL-2.0 */
 #ifndef _ASM_X86_ALTERNATIVE_H
 #define _ASM_X86_ALTERNATIVE_H

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

 #define ALT_FLAGS_SHIFT		16

 #define ALT_FLAG_NOT		(1 << 0)
 #define ALT_NOT(feature)	((ALT_FLAG_NOT << ALT_FLAGS_SHIFT) | (feature))

 #ifndef __ASSEMBLY__

 #include <linux/stddef.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

 /*
  * objtool annotation to ignore the alternatives and only consider the original
  * instruction(s).
  */
 #define ANNOTATE_IGNORE_ALTERNATIVE				\
 	"999:\n\t"						\
 	".pushsection .discard.ignore_alts\n\t"			\
 	".long 999b - .\n\t"					\
 	".popsection\n\t"

 /*
  * The patching flags are part of the upper bits of the @ft_flags parameter when
  * specifying them. The split is currently like this:
  *
  * [31... flags ...16][15... CPUID feature bit ...0]
  *
  * but since this is all hidden in the macros argument being split, those fields can be
  * extended in the future to fit in a u64 or however the need arises.
  */
 struct alt_instr {
 	s32 instr_offset;	/* original instruction */
 	s32 repl_offset;	/* offset to replacement instruction */

 	union {
 		struct {
 			u32 cpuid: 16;	/* CPUID bit set for replacement */
 			u32 flags: 16;	/* patching control flags */
 		};
 		u32 ft_flags;
 	};

 	u8  instrlen;		/* length of original instruction */
 	u8  replacementlen;	/* length of new instruction */
 } __packed;

 /*
  * Debug flag that can be tested to see whether alternative
  * instructions were patched in already:
  */
 extern int alternatives_patched;

 extern void alternative_instructions(void);
 extern void apply_alternatives(struct alt_instr *start, struct alt_instr *end);
 extern void apply_retpolines(s32 *start, s32 *end);
 extern void apply_returns(s32 *start, s32 *end);
 extern void apply_ibt_endbr(s32 *start, s32 *end);
 extern void apply_fineibt(s32 *start_retpoline, s32 *end_retpoine,
 			  s32 *start_cfi, s32 *end_cfi);

 struct module;
 struct paravirt_patch_site;

 struct callthunk_sites {
 	s32				*call_start, *call_end;
 	struct paravirt_patch_site	*pv_start, *pv_end;
 };

 #ifdef CONFIG_CALL_THUNKS
 extern void callthunks_patch_builtin_calls(void);
 extern void callthunks_patch_module_calls(struct callthunk_sites *sites,
 					  struct module *mod);
 extern void *callthunks_translate_call_dest(void *dest);
 extern bool is_callthunk(void *addr);
 extern int x86_call_depth_emit_accounting(u8 **pprog, void *func);
 #else
 static __always_inline void callthunks_patch_builtin_calls(void) {}
 static __always_inline void
 callthunks_patch_module_calls(struct callthunk_sites *sites,
 			      struct module *mod) {}
 static __always_inline void *callthunks_translate_call_dest(void *dest)
 {
 	return dest;
 }
 static __always_inline bool is_callthunk(void *addr)
 {
 	return false;
 }
 static __always_inline int x86_call_depth_emit_accounting(u8 **pprog,
 							  void *func)
 {
 	return 0;
 }
 #endif

 #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_total_slen		alt_end_marker"b-661b"
 #define alt_rlen(num)		e_replacement(num)"f-"b_replacement(num)"f"

 #define OLDINSTR(oldinstr, num)						\
 	"# ALT: oldnstr\n"						\
 	"661:\n\t" oldinstr "\n662:\n"					\
 	"# ALT: padding\n"						\
 	".skip -(((" alt_rlen(num) ")-(" alt_slen ")) > 0) * "		\
 		"((" alt_rlen(num) ")-(" alt_slen ")),0x90\n"		\
 	alt_end_marker ":\n"

 /*
  * gas compatible max based on the idea from:
  * http://graphics.stanford.edu/~seander/bithacks.html#IntegerMinOrMax
  *
  * The additional "-" is needed because gas uses a "true" value of -1.
  */
 #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) \
 	"# ALT: oldinstr2\n"									\
 	"661:\n\t" oldinstr "\n662:\n"								\
 	"# ALT: padding2\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 OLDINSTR_3(oldinsn, n1, n2, n3)								\
 	"# ALT: oldinstr3\n"									\
 	"661:\n\t" oldinsn "\n662:\n"								\
 	"# ALT: padding3\n"									\
 	".skip -((" alt_max_short(alt_max_short(alt_rlen(n1), alt_rlen(n2)), alt_rlen(n3))	\
 		" - (" alt_slen ")) > 0) * "							\
 		"(" alt_max_short(alt_max_short(alt_rlen(n1), alt_rlen(n2)), alt_rlen(n3))	\
 		" - (" alt_slen ")), 0x90\n"							\
 	alt_end_marker ":\n"

 #define ALTINSTR_ENTRY(ft_flags, num)					      \
 	" .long 661b - .\n"				/* label           */ \
 	" .long " b_replacement(num)"f - .\n"		/* new instruction */ \
 	" .4byte " __stringify(ft_flags) "\n"		/* feature + flags */ \
 	" .byte " alt_total_slen "\n"			/* source len      */ \
 	" .byte " alt_rlen(num) "\n"			/* replacement len */

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

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

 #define ALTERNATIVE_2(oldinstr, newinstr1, ft_flags1, newinstr2, ft_flags2) \
 	OLDINSTR_2(oldinstr, 1, 2)					\
 	".pushsection .altinstructions,\"a\"\n"				\
 	ALTINSTR_ENTRY(ft_flags1, 1)					\
 	ALTINSTR_ENTRY(ft_flags2, 2)					\
 	".popsection\n"							\
 	".pushsection .altinstr_replacement, \"ax\"\n"			\
 	ALTINSTR_REPLACEMENT(newinstr1, 1)				\
 	ALTINSTR_REPLACEMENT(newinstr2, 2)				\
 	".popsection\n"

 /* If @feature is set, patch in @newinstr_yes, otherwise @newinstr_no. */
 #define ALTERNATIVE_TERNARY(oldinstr, ft_flags, newinstr_yes, newinstr_no) \
 	ALTERNATIVE_2(oldinstr, newinstr_no, X86_FEATURE_ALWAYS,	\
 		      newinstr_yes, ft_flags)

 #define ALTERNATIVE_3(oldinsn, newinsn1, ft_flags1, newinsn2, ft_flags2, \
 			newinsn3, ft_flags3)				\
 	OLDINSTR_3(oldinsn, 1, 2, 3)					\
 	".pushsection .altinstructions,\"a\"\n"				\
 	ALTINSTR_ENTRY(ft_flags1, 1)					\
 	ALTINSTR_ENTRY(ft_flags2, 2)					\
 	ALTINSTR_ENTRY(ft_flags3, 3)					\
 	".popsection\n"							\
 	".pushsection .altinstr_replacement, \"ax\"\n"			\
 	ALTINSTR_REPLACEMENT(newinsn1, 1)				\
 	ALTINSTR_REPLACEMENT(newinsn2, 2)				\
 	ALTINSTR_REPLACEMENT(newinsn3, 3)				\
 	".popsection\n"

 /*
  * 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, ft_flags)			\
 	asm_inline volatile (ALTERNATIVE(oldinstr, newinstr, ft_flags) : : : "memory")

 #define alternative_2(oldinstr, newinstr1, ft_flags1, newinstr2, ft_flags2) \
 	asm_inline volatile(ALTERNATIVE_2(oldinstr, newinstr1, ft_flags1, newinstr2, ft_flags2) ::: "memory")

 #define alternative_ternary(oldinstr, ft_flags, newinstr_yes, newinstr_no) \
 	asm_inline volatile(ALTERNATIVE_TERNARY(oldinstr, ft_flags, newinstr_yes, newinstr_no) ::: "memory")

 /*
  * Alternative inline assembly with input.
  *
  * Peculiarities:
  * No memory clobber here.
  * Argument numbers start with 1.
  * Leaving an unused argument 0 to keep API compatibility.
  */
 #define alternative_input(oldinstr, newinstr, ft_flags, input...)	\
 	asm_inline volatile (ALTERNATIVE(oldinstr, newinstr, ft_flags)	\
 		: : "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, ft_flags1, newinstr2,	     \
 			   ft_flags2, input...)				     \
 	asm_inline volatile(ALTERNATIVE_2(oldinstr, newinstr1, ft_flags1,     \
 		newinstr2, ft_flags2)					     \
 		: : "i" (0), ## input)

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

 /* Like alternative_io, but for replacing a direct call with another one. */
 #define alternative_call(oldfunc, newfunc, ft_flags, output, input...)	\
 	asm_inline volatile (ALTERNATIVE("call %P[old]", "call %P[new]", ft_flags) \
 		: 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, ft_flags1, newfunc2, ft_flags2,   \
 			   output, input...)				      \
 	asm_inline volatile (ALTERNATIVE_2("call %P[old]", "call %P[new1]", ft_flags1,\
 		"call %P[new2]", ft_flags2)				      \
 		: output, ASM_CALL_CONSTRAINT				      \
 		: [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

 #else /* __ASSEMBLY__ */

 #ifdef CONFIG_SMP
 	.macro LOCK_PREFIX
 672:	lock
 	.pushsection .smp_locks,"a"
 	.balign 4
 	.long 672b - .
 	.popsection
 	.endm
 #else
 	.macro LOCK_PREFIX
 	.endm
 #endif

 /*
  * objtool annotation to ignore the alternatives and only consider the original
  * instruction(s).
  */
 .macro ANNOTATE_IGNORE_ALTERNATIVE
 	.Lannotate_\@:
 	.pushsection .discard.ignore_alts
 	.long .Lannotate_\@ - .
 	.popsection
 .endm

 /*
  * Issue one struct alt_instr descriptor entry (need to put it into
  * the section .altinstructions, see below). This entry contains
  * enough information for the alternatives patching code to patch an
  * instruction. See apply_alternatives().
  */
 .macro altinstr_entry orig alt ft_flags orig_len alt_len
 	.long \orig - .
 	.long \alt - .
 	.4byte \ft_flags
 	.byte \orig_len
 	.byte \alt_len
 .endm

 /*
  * Define an alternative between two instructions. If @feature is
  * present, early code in apply_alternatives() replaces @oldinstr with
  * @newinstr. ".skip" directive takes care of proper instruction padding
  * in case @newinstr is longer than @oldinstr.
  */
 .macro ALTERNATIVE oldinstr, newinstr, ft_flags
 140:
 	\oldinstr
 141:
 	.skip -(((144f-143f)-(141b-140b)) > 0) * ((144f-143f)-(141b-140b)),0x90
 142:

 	.pushsection .altinstructions,"a"
 	altinstr_entry 140b,143f,\ft_flags,142b-140b,144f-143f
 	.popsection

 	.pushsection .altinstr_replacement,"ax"
 143:
 	\newinstr
 144:
 	.popsection
 .endm

 #define old_len			141b-140b
 #define new_len1		144f-143f
 #define new_len2		145f-144f
 #define new_len3		146f-145f

 /*
  * gas compatible max based on the idea from:
  * http://graphics.stanford.edu/~seander/bithacks.html#IntegerMinOrMax
  *
  * The additional "-" is needed because gas uses a "true" value of -1.
  */
 #define alt_max_2(a, b)		((a) ^ (((a) ^ (b)) & -(-((a) < (b)))))
 #define alt_max_3(a, b, c)	(alt_max_2(alt_max_2(a, b), c))


 /*
  * Same as ALTERNATIVE macro above but for two alternatives. If CPU
  * has @feature1, it replaces @oldinstr with @newinstr1. If CPU has
  * @feature2, it replaces @oldinstr with @feature2.
  */
 .macro ALTERNATIVE_2 oldinstr, newinstr1, ft_flags1, newinstr2, ft_flags2
 140:
 	\oldinstr
 141:
 	.skip -((alt_max_2(new_len1, new_len2) - (old_len)) > 0) * \
 		(alt_max_2(new_len1, new_len2) - (old_len)),0x90
 142:

 	.pushsection .altinstructions,"a"
 	altinstr_entry 140b,143f,\ft_flags1,142b-140b,144f-143f
 	altinstr_entry 140b,144f,\ft_flags2,142b-140b,145f-144f
 	.popsection

 	.pushsection .altinstr_replacement,"ax"
 143:
 	\newinstr1
 144:
 	\newinstr2
 145:
 	.popsection
 .endm

 .macro ALTERNATIVE_3 oldinstr, newinstr1, ft_flags1, newinstr2, ft_flags2, newinstr3, ft_flags3
 140:
 	\oldinstr
 141:
 	.skip -((alt_max_3(new_len1, new_len2, new_len3) - (old_len)) > 0) * \
 		(alt_max_3(new_len1, new_len2, new_len3) - (old_len)),0x90
 142:

 	.pushsection .altinstructions,"a"
 	altinstr_entry 140b,143f,\ft_flags1,142b-140b,144f-143f
 	altinstr_entry 140b,144f,\ft_flags2,142b-140b,145f-144f
 	altinstr_entry 140b,145f,\ft_flags3,142b-140b,146f-145f
 	.popsection

 	.pushsection .altinstr_replacement,"ax"
 143:
 	\newinstr1
 144:
 	\newinstr2
 145:
 	\newinstr3
 146:
 	.popsection
 .endm

 /* If @feature is set, patch in @newinstr_yes, otherwise @newinstr_no. */
 #define ALTERNATIVE_TERNARY(oldinstr, ft_flags, newinstr_yes, newinstr_no) \
 	ALTERNATIVE_2 oldinstr, newinstr_no, X86_FEATURE_ALWAYS,	\
 	newinstr_yes, ft_flags

 #endif /* __ASSEMBLY__ */

 #endif /* _ASM_X86_ALTERNATIVE_H */
	/* SPDX-License-Identifier: GPL-2.0 */
	#ifndef _ASM_X86_ALTERNATIVE_H
	#define _ASM_X86_ALTERNATIVE_H

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

	#define ALT_FLAGS_SHIFT 16

	#define ALT_FLAG_NOT (1 << 0)
	#define ALT_NOT(feature) ((ALT_FLAG_NOT << ALT_FLAGS_SHIFT) \| (feature))

	#ifndef __ASSEMBLY__

	#include <linux/stddef.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

	/*
	* objtool annotation to ignore the alternatives and only consider the original
	* instruction(s).
	*/
	#define ANNOTATE_IGNORE_ALTERNATIVE \
	"999:\n\t" \
	".pushsection .discard.ignore_alts\n\t" \
	".long 999b - .\n\t" \
	".popsection\n\t"

	/*
	* The patching flags are part of the upper bits of the @ft_flags parameter when
	* specifying them. The split is currently like this:
	*
	* [31... flags ...16][15... CPUID feature bit ...0]
	*
	* but since this is all hidden in the macros argument being split, those fields can be
	* extended in the future to fit in a u64 or however the need arises.
	*/
	struct alt_instr {
	s32 instr_offset; /* original instruction */
	s32 repl_offset; /* offset to replacement instruction */

	union {
	struct {
	u32 cpuid: 16; /* CPUID bit set for replacement */
	u32 flags: 16; /* patching control flags */
	};
	u32 ft_flags;
	};

	u8 instrlen; /* length of original instruction */
	u8 replacementlen; /* length of new instruction */
	} __packed;

	/*
	* Debug flag that can be tested to see whether alternative
	* instructions were patched in already:
	*/
	extern int alternatives_patched;

	extern void alternative_instructions(void);
	extern void apply_alternatives(struct alt_instr start, struct alt_instr end);
	extern void apply_retpolines(s32 start, s32 end);
	extern void apply_returns(s32 start, s32 end);
	extern void apply_ibt_endbr(s32 start, s32 end);
	extern void apply_fineibt(s32 start_retpoline, s32 end_retpoine,
	s32 start_cfi, s32 end_cfi);

	struct module;
	struct paravirt_patch_site;

	struct callthunk_sites {
	s32 call_start, call_end;
	struct paravirt_patch_site pv_start, pv_end;
	};

	#ifdef CONFIG_CALL_THUNKS
	extern void callthunks_patch_builtin_calls(void);
	extern void callthunks_patch_module_calls(struct callthunk_sites *sites,
	struct module *mod);
	extern void callthunks_translate_call_dest(void dest);
	extern bool is_callthunk(void *addr);
	extern int x86_call_depth_emit_accounting(u8 *pprog, void func);
	#else
	static __always_inline void callthunks_patch_builtin_calls(void) {}
	static __always_inline void
	callthunks_patch_module_calls(struct callthunk_sites *sites,
	struct module *mod) {}
	static __always_inline void callthunks_translate_call_dest(void dest)
	{
	return dest;
	}
	static __always_inline bool is_callthunk(void *addr)
	{
	return false;
	}
	static __always_inline int x86_call_depth_emit_accounting(u8 **pprog,
	void *func)
	{
	return 0;
	}
	#endif

	#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_total_slen alt_end_marker"b-661b"
	#define alt_rlen(num) e_replacement(num)"f-"b_replacement(num)"f"

	#define OLDINSTR(oldinstr, num) \
	"# ALT: oldnstr\n" \
	"661:\n\t" oldinstr "\n662:\n" \
	"# ALT: padding\n" \
	".skip -(((" alt_rlen(num) ")-(" alt_slen ")) > 0) * " \
	"((" alt_rlen(num) ")-(" alt_slen ")),0x90\n" \
	alt_end_marker ":\n"

	/*
	* gas compatible max based on the idea from:
	* http://graphics.stanford.edu/~seander/bithacks.html#IntegerMinOrMax
	*
	* The additional "-" is needed because gas uses a "true" value of -1.
	*/
	#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) \
	"# ALT: oldinstr2\n" \
	"661:\n\t" oldinstr "\n662:\n" \
	"# ALT: padding2\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 OLDINSTR_3(oldinsn, n1, n2, n3) \
	"# ALT: oldinstr3\n" \
	"661:\n\t" oldinsn "\n662:\n" \
	"# ALT: padding3\n" \
	".skip -((" alt_max_short(alt_max_short(alt_rlen(n1), alt_rlen(n2)), alt_rlen(n3)) \
	" - (" alt_slen ")) > 0) * " \
	"(" alt_max_short(alt_max_short(alt_rlen(n1), alt_rlen(n2)), alt_rlen(n3)) \
	" - (" alt_slen ")), 0x90\n" \
	alt_end_marker ":\n"

	#define ALTINSTR_ENTRY(ft_flags, num) \
	" .long 661b - .\n" /* label */ \
	" .long " b_replacement(num)"f - .\n" /* new instruction */ \
	" .4byte " __stringify(ft_flags) "\n" /* feature + flags */ \
	" .byte " alt_total_slen "\n" /* source len */ \
	" .byte " alt_rlen(num) "\n" /* replacement len */

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

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

	#define ALTERNATIVE_2(oldinstr, newinstr1, ft_flags1, newinstr2, ft_flags2) \
	OLDINSTR_2(oldinstr, 1, 2) \
	".pushsection .altinstructions,\"a\"\n" \
	ALTINSTR_ENTRY(ft_flags1, 1) \
	ALTINSTR_ENTRY(ft_flags2, 2) \
	".popsection\n" \
	".pushsection .altinstr_replacement, \"ax\"\n" \
	ALTINSTR_REPLACEMENT(newinstr1, 1) \
	ALTINSTR_REPLACEMENT(newinstr2, 2) \
	".popsection\n"

	/* If @feature is set, patch in @newinstr_yes, otherwise @newinstr_no. */
	#define ALTERNATIVE_TERNARY(oldinstr, ft_flags, newinstr_yes, newinstr_no) \
	ALTERNATIVE_2(oldinstr, newinstr_no, X86_FEATURE_ALWAYS, \
	newinstr_yes, ft_flags)

	#define ALTERNATIVE_3(oldinsn, newinsn1, ft_flags1, newinsn2, ft_flags2, \
	newinsn3, ft_flags3) \
	OLDINSTR_3(oldinsn, 1, 2, 3) \
	".pushsection .altinstructions,\"a\"\n" \
	ALTINSTR_ENTRY(ft_flags1, 1) \
	ALTINSTR_ENTRY(ft_flags2, 2) \
	ALTINSTR_ENTRY(ft_flags3, 3) \
	".popsection\n" \
	".pushsection .altinstr_replacement, \"ax\"\n" \
	ALTINSTR_REPLACEMENT(newinsn1, 1) \
	ALTINSTR_REPLACEMENT(newinsn2, 2) \
	ALTINSTR_REPLACEMENT(newinsn3, 3) \
	".popsection\n"

	/*
	* 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, ft_flags) \
	asm_inline volatile (ALTERNATIVE(oldinstr, newinstr, ft_flags) : : : "memory")

	#define alternative_2(oldinstr, newinstr1, ft_flags1, newinstr2, ft_flags2) \
	asm_inline volatile(ALTERNATIVE_2(oldinstr, newinstr1, ft_flags1, newinstr2, ft_flags2) ::: "memory")

	#define alternative_ternary(oldinstr, ft_flags, newinstr_yes, newinstr_no) \
	asm_inline volatile(ALTERNATIVE_TERNARY(oldinstr, ft_flags, newinstr_yes, newinstr_no) ::: "memory")

	/*
	* Alternative inline assembly with input.
	*
	* Peculiarities:
	* No memory clobber here.
	* Argument numbers start with 1.
	* Leaving an unused argument 0 to keep API compatibility.
	*/
	#define alternative_input(oldinstr, newinstr, ft_flags, input...) \
	asm_inline volatile (ALTERNATIVE(oldinstr, newinstr, ft_flags) \
	: : "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, ft_flags1, newinstr2, \
	ft_flags2, input...) \
	asm_inline volatile(ALTERNATIVE_2(oldinstr, newinstr1, ft_flags1, \
	newinstr2, ft_flags2) \
	: : "i" (0), ## input)

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

	/* Like alternative_io, but for replacing a direct call with another one. */
	#define alternative_call(oldfunc, newfunc, ft_flags, output, input...) \
	asm_inline volatile (ALTERNATIVE("call %P[old]", "call %P[new]", ft_flags) \
	: 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, ft_flags1, newfunc2, ft_flags2, \
	output, input...) \
	asm_inline volatile (ALTERNATIVE_2("call %P[old]", "call %P[new1]", ft_flags1,\
	"call %P[new2]", ft_flags2) \
	: output, ASM_CALL_CONSTRAINT \
	: [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

	#else /* __ASSEMBLY__ */

	#ifdef CONFIG_SMP
	.macro LOCK_PREFIX
	672: lock
	.pushsection .smp_locks,"a"
	.balign 4
	.long 672b - .
	.popsection
	.endm
	#else
	.macro LOCK_PREFIX
	.endm
	#endif

	/*
	* objtool annotation to ignore the alternatives and only consider the original
	* instruction(s).
	*/
	.macro ANNOTATE_IGNORE_ALTERNATIVE
	.Lannotate_\@:
	.pushsection .discard.ignore_alts
	.long .Lannotate_\@ - .
	.popsection
	.endm

	/*
	* Issue one struct alt_instr descriptor entry (need to put it into
	* the section .altinstructions, see below). This entry contains
	* enough information for the alternatives patching code to patch an
	* instruction. See apply_alternatives().
	*/
	.macro altinstr_entry orig alt ft_flags orig_len alt_len
	.long \orig - .
	.long \alt - .
	.4byte \ft_flags
	.byte \orig_len
	.byte \alt_len
	.endm

	/*
	* Define an alternative between two instructions. If @feature is
	* present, early code in apply_alternatives() replaces @oldinstr with
	* @newinstr. ".skip" directive takes care of proper instruction padding
	* in case @newinstr is longer than @oldinstr.
	*/
	.macro ALTERNATIVE oldinstr, newinstr, ft_flags
	140:
	\oldinstr
	141:
	.skip -(((144f-143f)-(141b-140b)) > 0) * ((144f-143f)-(141b-140b)),0x90
	142:

	.pushsection .altinstructions,"a"
	altinstr_entry 140b,143f,\ft_flags,142b-140b,144f-143f
	.popsection

	.pushsection .altinstr_replacement,"ax"
	143:
	\newinstr
	144:
	.popsection
	.endm

	#define old_len 141b-140b
	#define new_len1 144f-143f
	#define new_len2 145f-144f
	#define new_len3 146f-145f

	/*
	* gas compatible max based on the idea from:
	* http://graphics.stanford.edu/~seander/bithacks.html#IntegerMinOrMax
	*
	* The additional "-" is needed because gas uses a "true" value of -1.
	*/
	#define alt_max_2(a, b) ((a) ^ (((a) ^ (b)) & -(-((a) < (b)))))
	#define alt_max_3(a, b, c) (alt_max_2(alt_max_2(a, b), c))


	/*
	* Same as ALTERNATIVE macro above but for two alternatives. If CPU
	* has @feature1, it replaces @oldinstr with @newinstr1. If CPU has
	* @feature2, it replaces @oldinstr with @feature2.
	*/
	.macro ALTERNATIVE_2 oldinstr, newinstr1, ft_flags1, newinstr2, ft_flags2
	140:
	\oldinstr
	141:
	.skip -((alt_max_2(new_len1, new_len2) - (old_len)) > 0) * \
	(alt_max_2(new_len1, new_len2) - (old_len)),0x90
	142:

	.pushsection .altinstructions,"a"
	altinstr_entry 140b,143f,\ft_flags1,142b-140b,144f-143f
	altinstr_entry 140b,144f,\ft_flags2,142b-140b,145f-144f
	.popsection

	.pushsection .altinstr_replacement,"ax"
	143:
	\newinstr1
	144:
	\newinstr2
	145:
	.popsection
	.endm

	.macro ALTERNATIVE_3 oldinstr, newinstr1, ft_flags1, newinstr2, ft_flags2, newinstr3, ft_flags3
	140:
	\oldinstr
	141:
	.skip -((alt_max_3(new_len1, new_len2, new_len3) - (old_len)) > 0) * \
	(alt_max_3(new_len1, new_len2, new_len3) - (old_len)),0x90
	142:

	.pushsection .altinstructions,"a"
	altinstr_entry 140b,143f,\ft_flags1,142b-140b,144f-143f
	altinstr_entry 140b,144f,\ft_flags2,142b-140b,145f-144f
	altinstr_entry 140b,145f,\ft_flags3,142b-140b,146f-145f
	.popsection

	.pushsection .altinstr_replacement,"ax"
	143:
	\newinstr1
	144:
	\newinstr2
	145:
	\newinstr3
	146:
	.popsection
	.endm

	/* If @feature is set, patch in @newinstr_yes, otherwise @newinstr_no. */
	#define ALTERNATIVE_TERNARY(oldinstr, ft_flags, newinstr_yes, newinstr_no) \
	ALTERNATIVE_2 oldinstr, newinstr_no, X86_FEATURE_ALWAYS, \
	newinstr_yes, ft_flags

	#endif /* __ASSEMBLY__ */

	#endif /* _ASM_X86_ALTERNATIVE_H */