1/* SPDX-License-Identifier: GPL-2.0 */
2#ifndef _ASM_S390_ALTERNATIVE_H
3#define _ASM_S390_ALTERNATIVE_H
4
5#ifndef __ASSEMBLY__
6
7#include <linux/types.h>
8#include <linux/stddef.h>
9#include <linux/stringify.h>
10
11struct alt_instr {
12	s32 instr_offset;	/* original instruction */
13	s32 repl_offset;	/* offset to replacement instruction */
14	u16 facility;		/* facility bit set for replacement */
15	u8  instrlen;		/* length of original instruction */
16} __packed;
17
18void apply_alternative_instructions(void);
19void apply_alternatives(struct alt_instr *start, struct alt_instr *end);
20
21/*
22 * +---------------------------------+
23 * |661:			     |662:
24 * | oldinstr			     |
25 * +---------------------------------+
26 *
27 * .altinstr_replacement section
28 * +---------------------------------+
29 * |6641:			     |6651:
30 * | alternative instr 1	     |
31 * +---------------------------------+
32 * |6642:			     |6652:
33 * | alternative instr 2	     |
34 * +---------------------------------+
35 *
36 * .altinstructions section
37 * +---------------------------------+
38 * | alt_instr entries for each      |
39 * | alternative instr		     |
40 * +---------------------------------+
41 */
42
43#define b_altinstr(num)		"664"#num
44#define e_altinstr(num)		"665"#num
45#define oldinstr_len		"662b-661b"
46#define altinstr_len(num)	e_altinstr(num)"b-"b_altinstr(num)"b"
47
48#define OLDINSTR(oldinstr) \
49	"661:\n\t" oldinstr "\n662:\n"
50
51#define ALTINSTR_ENTRY(facility, num)					\
52	"\t.long 661b - .\n"			/* old instruction */	\
53	"\t.long " b_altinstr(num)"b - .\n"	/* alt instruction */	\
54	"\t.word " __stringify(facility) "\n"	/* facility bit    */	\
55	"\t.byte " oldinstr_len "\n"		/* instruction len */	\
56	"\t.org . - (" oldinstr_len ") + (" altinstr_len(num) ")\n"	\
57	"\t.org . - (" altinstr_len(num) ") + (" oldinstr_len ")\n"
58
59#define ALTINSTR_REPLACEMENT(altinstr, num)	/* replacement */	\
60	b_altinstr(num)":\n\t" altinstr "\n" e_altinstr(num) ":\n"
61
62/* alternative assembly primitive: */
63#define ALTERNATIVE(oldinstr, altinstr, facility) \
64	".pushsection .altinstr_replacement, \"ax\"\n"			\
65	ALTINSTR_REPLACEMENT(altinstr, 1)				\
66	".popsection\n"							\
67	OLDINSTR(oldinstr)						\
68	".pushsection .altinstructions,\"a\"\n"				\
69	ALTINSTR_ENTRY(facility, 1)					\
70	".popsection\n"
71
72#define ALTERNATIVE_2(oldinstr, altinstr1, facility1, altinstr2, facility2)\
73	".pushsection .altinstr_replacement, \"ax\"\n"			\
74	ALTINSTR_REPLACEMENT(altinstr1, 1)				\
75	ALTINSTR_REPLACEMENT(altinstr2, 2)				\
76	".popsection\n"							\
77	OLDINSTR(oldinstr)						\
78	".pushsection .altinstructions,\"a\"\n"				\
79	ALTINSTR_ENTRY(facility1, 1)					\
80	ALTINSTR_ENTRY(facility2, 2)					\
81	".popsection\n"
82
83/*
84 * Alternative instructions for different CPU types or capabilities.
85 *
86 * This allows to use optimized instructions even on generic binary
87 * kernels.
88 *
89 * oldinstr is padded with jump and nops at compile time if altinstr is
90 * longer. altinstr is padded with jump and nops at run-time during patching.
91 *
92 * For non barrier like inlines please define new variants
93 * without volatile and memory clobber.
94 */
95#define alternative(oldinstr, altinstr, facility)			\
96	asm_inline volatile(ALTERNATIVE(oldinstr, altinstr, facility) : : : "memory")
97
98#define alternative_2(oldinstr, altinstr1, facility1, altinstr2, facility2) \
99	asm_inline volatile(ALTERNATIVE_2(oldinstr, altinstr1, facility1,   \
100				   altinstr2, facility2) ::: "memory")
101
102/* Alternative inline assembly with input. */
103#define alternative_input(oldinstr, newinstr, feature, input...)	\
104	asm_inline volatile (ALTERNATIVE(oldinstr, newinstr, feature)	\
105		: : input)
106
107/* Like alternative_input, but with a single output argument */
108#define alternative_io(oldinstr, altinstr, facility, output, input...)	\
109	asm_inline volatile(ALTERNATIVE(oldinstr, altinstr, facility)	\
110		: output : input)
111
112/* Use this macro if more than one output parameter is needed. */
113#define ASM_OUTPUT2(a...) a
114
115/* Use this macro if clobbers are needed without inputs. */
116#define ASM_NO_INPUT_CLOBBER(clobber...) : clobber
117
118#endif /* __ASSEMBLY__ */
119
120#endif /* _ASM_S390_ALTERNATIVE_H */
121