[mirror_ubuntu-bionic-kernel.git] / arch / x86 / include / asm / 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\n"

#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\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, 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 */
Commit	Line	Data
b2441318	1	/* SPDX-License-Identifier: GPL-2.0 */
1965aae3 PA	2	#ifndef _ASM_X86_ALTERNATIVE_H
1965aae3 PA	3	#define _ASM_X86_ALTERNATIVE_H
6b592570	4
f005f5d8 AL	5	#ifndef __ASSEMBLY__
f005f5d8 AL	6
6b592570 PA	7	#include <linux/types.h>
6b592570 PA	8	#include <linux/stddef.h>
edc953fa	9	#include <linux/stringify.h>
6b592570 PA	10	#include <asm/asm.h>
	11
	12	/*
	13	* Alternative inline assembly for SMP.
	14	*
	15	* The LOCK_PREFIX macro defined here replaces the LOCK and
	16	* LOCK_PREFIX macros used everywhere in the source tree.
	17	*
	18	* SMP alternatives use the same data structures as the other
	19	* alternatives and the X86_FEATURE_UP flag to indicate the case of a
	20	* UP system running a SMP kernel. The existing apply_alternatives()
	21	* works fine for patching a SMP kernel for UP.
	22	*
	23	* The SMP alternative tables can be kept after boot and contain both
	24	* UP and SMP versions of the instructions to allow switching back to
	25	* SMP at runtime, when hotplugging in a new CPU, which is especially
	26	* useful in virtualized environments.
	27	*
	28	* The very common lock prefix is handled as special case in a
	29	* separate table which is a pure address list without replacement ptr
	30	* and size information. That keeps the table sizes small.
	31	*/
	32
	33	#ifdef CONFIG_SMP
b3ac891b	34	#define LOCK_PREFIX_HERE \
9cebed42 PA	35	".pushsection .smp_locks,\"a\"\n" \
	36	".balign 4\n" \
	37	".long 671f - .\n" /* offset */ \
	38	".popsection\n" \
b3ac891b LB	39	"671:"
	40
	41	#define LOCK_PREFIX LOCK_PREFIX_HERE "\n\tlock; "
6b592570 PA	42
6b592570 PA	43	#else /* ! CONFIG_SMP */
b701a47b	44	#define LOCK_PREFIX_HERE ""
6b592570 PA	45	#define LOCK_PREFIX ""
	46	#endif
	47
6b592570	48	struct alt_instr {
59e97e4d AL	49	s32 instr_offset; /* original instruction */
59e97e4d AL	50	s32 repl_offset; /* offset to replacement instruction */
83a7a2ad	51	u16 cpuid; /* cpuid bit set for replacement */
6b592570	52	u8 instrlen; /* length of original instruction */
4332195c BP	53	u8 replacementlen; /* length of new instruction */
	54	u8 padlen; /* length of build-time padding */
	55	} __packed;
6b592570	56
5e907bb0 IM	57	/*
	58	* Debug flag that can be tested to see whether alternative
	59	* instructions were patched in already:
	60	*/
	61	extern int alternatives_patched;
	62
6b592570 PA	63	extern void alternative_instructions(void);
	64	extern void apply_alternatives(struct alt_instr start, struct alt_instr end);
	65
	66	struct module;
	67
	68	#ifdef CONFIG_SMP
	69	extern void alternatives_smp_module_add(struct module mod, char name,
	70	void locks, void locks_end,
	71	void text, void text_end);
	72	extern void alternatives_smp_module_del(struct module *mod);
816afe4f	73	extern void alternatives_enable_smp(void);
2cfa1978	74	extern int alternatives_text_reserved(void start, void end);
3fb82d56	75	extern bool skip_smp_alternatives;
6b592570 PA	76	#else
6b592570 PA	77	static inline void alternatives_smp_module_add(struct module mod, char name,
2ac1ea7c JP	78	void locks, void locks_end,
2ac1ea7c JP	79	void text, void text_end) {}
6b592570	80	static inline void alternatives_smp_module_del(struct module *mod) {}
816afe4f	81	static inline void alternatives_enable_smp(void) {}
2cfa1978 MH	82	static inline int alternatives_text_reserved(void start, void end)
	83	{
	84	return 0;
	85	}
6b592570 PA	86	#endif /* CONFIG_SMP */
6b592570 PA	87
4332195c BP	88	#define b_replacement(num) "664"#num
4332195c BP	89	#define e_replacement(num) "665"#num
954e482b	90
4332195c BP	91	#define alt_end_marker "663"
	92	#define alt_slen "662b-661b"
	93	#define alt_pad_len alt_end_marker"b-662b"
	94	#define alt_total_slen alt_end_marker"b-661b"
	95	#define alt_rlen(num) e_replacement(num)"f-"b_replacement(num)"f"
954e482b	96
4332195c BP	97	#define __OLDINSTR(oldinstr, num) \
	98	"661:\n\t" oldinstr "\n662:\n" \
	99	".skip -(((" alt_rlen(num) ")-(" alt_slen ")) > 0) * " \
	100	"((" alt_rlen(num) ")-(" alt_slen ")),0x90\n"
954e482b	101
4332195c BP	102	#define OLDINSTR(oldinstr, num) \
	103	__OLDINSTR(oldinstr, num) \
	104	alt_end_marker ":\n"
	105
dbe4058a	106	/*
6b32c126	107	* gas compatible max based on the idea from:
dbe4058a BP	108	* http://graphics.stanford.edu/~seander/bithacks.html#IntegerMinOrMax
dbe4058a BP	109	*
6b32c126	110	* The additional "-" is needed because gas uses a "true" value of -1.
dbe4058a	111	*/
6b32c126	112	#define alt_max_short(a, b) "((" a ") ^ (((" a ") ^ (" b ")) & -(-((" a ") < (" b ")))))"
dbe4058a	113
4332195c BP	114	/*
	115	* Pad the second replacement alternative with additional NOPs if it is
	116	* additionally longer than the first replacement alternative.
	117	*/
dbe4058a BP	118	#define OLDINSTR_2(oldinstr, num1, num2) \
	119	"661:\n\t" oldinstr "\n662:\n" \
	120	".skip -((" alt_max_short(alt_rlen(num1), alt_rlen(num2)) " - (" alt_slen ")) > 0) * " \
	121	"(" alt_max_short(alt_rlen(num1), alt_rlen(num2)) " - (" alt_slen ")), 0x90\n" \
4332195c BP	122	alt_end_marker ":\n"
	123
	124	#define ALTINSTR_ENTRY(feature, num) \
954e482b	125	" .long 661b - .\n" /* label */ \
4332195c	126	" .long " b_replacement(num)"f - .\n" /* new instruction */ \
954e482b	127	" .word " __stringify(feature) "\n" /* feature bit */ \
4332195c BP	128	" .byte " alt_total_slen "\n" /* source len */ \
	129	" .byte " alt_rlen(num) "\n" /* replacement len */ \
	130	" .byte " alt_pad_len "\n" /* pad len */
954e482b	131
4332195c BP	132	#define ALTINSTR_REPLACEMENT(newinstr, feature, num) /* replacement */ \
4332195c BP	133	b_replacement(num)":\n\t" newinstr "\n" e_replacement(num) ":\n\t"
954e482b	134
edc953fa MD	135	/* alternative assembly primitive: */
edc953fa MD	136	#define ALTERNATIVE(oldinstr, newinstr, feature) \
4332195c	137	OLDINSTR(oldinstr, 1) \
9cebed42	138	".pushsection .altinstructions,\"a\"\n" \
954e482b	139	ALTINSTR_ENTRY(feature, 1) \
9cebed42	140	".popsection\n" \
9cebed42	141	".pushsection .altinstr_replacement, \"ax\"\n" \
954e482b	142	ALTINSTR_REPLACEMENT(newinstr, feature, 1) \
b9e705ef	143	".popsection\n"
954e482b FY	144
954e482b FY	145	#define ALTERNATIVE_2(oldinstr, newinstr1, feature1, newinstr2, feature2)\
4332195c	146	OLDINSTR_2(oldinstr, 1, 2) \
9cebed42	147	".pushsection .altinstructions,\"a\"\n" \
954e482b FY	148	ALTINSTR_ENTRY(feature1, 1) \
954e482b FY	149	ALTINSTR_ENTRY(feature2, 2) \
9cebed42	150	".popsection\n" \
9cebed42	151	".pushsection .altinstr_replacement, \"ax\"\n" \
954e482b FY	152	ALTINSTR_REPLACEMENT(newinstr1, feature1, 1) \
954e482b FY	153	ALTINSTR_REPLACEMENT(newinstr2, feature2, 2) \
b9e705ef	154	".popsection\n"
edc953fa	155
6b592570 PA	156	/*
	157	* Alternative instructions for different CPU types or capabilities.
	158	*
	159	* This allows to use optimized instructions even on generic binary
	160	* kernels.
	161	*
	162	* length of oldinstr must be longer or equal the length of newinstr
	163	* It can be padded with nops as needed.
	164	*
	165	* For non barrier like inlines please define new variants
	166	* without volatile and memory clobber.
	167	*/
	168	#define alternative(oldinstr, newinstr, feature) \
edc953fa	169	asm volatile (ALTERNATIVE(oldinstr, newinstr, feature) : : : "memory")
6b592570	170
4332195c BP	171	#define alternative_2(oldinstr, newinstr1, feature1, newinstr2, feature2) \
	172	asm volatile(ALTERNATIVE_2(oldinstr, newinstr1, feature1, newinstr2, feature2) ::: "memory")
	173
6b592570 PA	174	/*
	175	* Alternative inline assembly with input.
	176	*
	177	* Pecularities:
	178	* No memory clobber here.
	179	* Argument numbers start with 1.
	180	* Best is to use constraints that are fixed size (like (%1) ... "r")
	181	* If you use variable sized constraints like "m" or "g" in the
	182	* replacement make sure to pad to the worst case length.
edc953fa	183	* Leaving an unused argument 0 to keep API compatibility.
6b592570 PA	184	*/
6b592570 PA	185	#define alternative_input(oldinstr, newinstr, feature, input...) \
edc953fa MD	186	asm volatile (ALTERNATIVE(oldinstr, newinstr, feature) \
edc953fa MD	187	: : "i" (0), ## input)
6b592570	188
5b3e83f4 FY	189	/*
	190	* This is similar to alternative_input. But it has two features and
	191	* respective instructions.
	192	*
	193	* If CPU has feature2, newinstr2 is used.
	194	* Otherwise, if CPU has feature1, newinstr1 is used.
	195	* Otherwise, oldinstr is used.
	196	*/
	197	#define alternative_input_2(oldinstr, newinstr1, feature1, newinstr2, \
	198	feature2, input...) \
	199	asm volatile(ALTERNATIVE_2(oldinstr, newinstr1, feature1, \
	200	newinstr2, feature2) \
	201	: : "i" (0), ## input)
	202
6b592570 PA	203	/* Like alternative_input, but with a single output argument */
6b592570 PA	204	#define alternative_io(oldinstr, newinstr, feature, output, input...) \
edc953fa MD	205	asm volatile (ALTERNATIVE(oldinstr, newinstr, feature) \
edc953fa MD	206	: output : "i" (0), ## input)
6b592570	207
1b1d9258 JB	208	/* Like alternative_io, but for replacing a direct call with another one. */
	209	#define alternative_call(oldfunc, newfunc, feature, output, input...) \
	210	asm volatile (ALTERNATIVE("call %P[old]", "call %P[new]", feature) \
	211	: output : [old] "i" (oldfunc), [new] "i" (newfunc), ## input)
	212
954e482b FY	213	/*
	214	* Like alternative_call, but there are two features and respective functions.
	215	* If CPU has feature2, function2 is used.
	216	* Otherwise, if CPU has feature1, function1 is used.
	217	* Otherwise, old function is used.
	218	*/
	219	#define alternative_call_2(oldfunc, newfunc1, feature1, newfunc2, feature2, \
	220	output, input...) \
	221	asm volatile (ALTERNATIVE_2("call %P[old]", "call %P[new1]", feature1,\
	222	"call %P[new2]", feature2) \
f5caf621	223	: output, ASM_CALL_CONSTRAINT \
317c2ce7	224	: [old] "i" (oldfunc), [new1] "i" (newfunc1), \
39e0211e	225	[new2] "i" (newfunc2), ## input)
954e482b	226
6b592570 PA	227	/*
	228	* use this macro(s) if you need more than one output parameter
	229	* in alternative_io
	230	*/
1b1d9258	231	#define ASM_OUTPUT2(a...) a
6b592570	232
819165fb JB	233	/*
	234	* use this macro if you need clobbers but no inputs in
	235	* alternative_{input,io,call}()
	236	*/
	237	#define ASM_NO_INPUT_CLOBBER(clbr...) "i" (0) : clbr
	238
f005f5d8 AL	239	#endif /* __ASSEMBLY__ */
f005f5d8 AL	240
1965aae3	241	#endif /* _ASM_X86_ALTERNATIVE_H */