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

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

 #ifndef __ASSEMBLY__

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

 /*
  * 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);

 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"

 /*
  * 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) \
 	"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"

 /*
  * 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, 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

 #endif /* __ASSEMBLY__ */

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

	#ifndef __ASSEMBLY__

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

	/*
	* 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);

	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"

	/*
	* 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) \
	"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"

	/*
	* 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, 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

	#endif /* __ASSEMBLY__ */

	#endif /* _ASM_X86_ALTERNATIVE_H */