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	u8  replacementlen;	/* length of new instruction */
17} __packed;
18
19void apply_alternative_instructions(void);
20void apply_alternatives(struct alt_instr *start, struct alt_instr *end);
21
22/*
23 * |661:       |662:	  |6620      |663:
24 * +-----------+---------------------+
25 * | oldinstr  | oldinstr_padding    |
26 * |	       +----------+----------+
27 * |	       |	  |	     |
28 * |	       | >6 bytes |6/4/2 nops|
29 * |	       |6 bytes jg----------->
30 * +-----------+---------------------+
31 *		 ^^ static padding ^^
32 *
33 * .altinstr_replacement section
34 * +---------------------+-----------+
35 * |6641:			     |6651:
36 * | alternative instr 1	     |
37 * +-----------+---------+- - - - - -+
38 * |6642:		 |6652:      |
39 * | alternative instr 2 | padding
40 * +---------------------+- - - - - -+
41 *			  ^ runtime ^
42 *
43 * .altinstructions section
44 * +---------------------------------+
45 * | alt_instr entries for each      |
46 * | alternative instr		     |
47 * +---------------------------------+
48 */
49
50#define b_altinstr(num)	"664"#num
51#define e_altinstr(num)	"665"#num
52
53#define e_oldinstr_pad_end	"663"
54#define oldinstr_len		"662b-661b"
55#define oldinstr_total_len	e_oldinstr_pad_end"b-661b"
56#define altinstr_len(num)	e_altinstr(num)"b-"b_altinstr(num)"b"
57#define oldinstr_pad_len(num) \
58	"-(((" altinstr_len(num) ")-(" oldinstr_len ")) > 0) * " \
59	"((" altinstr_len(num) ")-(" oldinstr_len "))"
60
61#define INSTR_LEN_SANITY_CHECK(len)					\
62	".if " len " > 254\n"						\
63	"\t.error \"cpu alternatives does not support instructions "	\
64		"blocks > 254 bytes\"\n"				\
65	".endif\n"							\
66	".if (" len ") %% 2\n"						\
67	"\t.error \"cpu alternatives instructions length is odd\"\n"	\
68	".endif\n"
69
70#define OLDINSTR_PADDING(oldinstr, num)					\
71	".if " oldinstr_pad_len(num) " > 6\n"				\
72	"\tjg " e_oldinstr_pad_end "f\n"				\
73	"6620:\n"							\
74	"\t.fill (" oldinstr_pad_len(num) " - (6620b-662b)) / 2, 2, 0x0700\n" \
75	".else\n"							\
76	"\t.fill " oldinstr_pad_len(num) " / 6, 6, 0xc0040000\n"	\
77	"\t.fill " oldinstr_pad_len(num) " %% 6 / 4, 4, 0x47000000\n"	\
78	"\t.fill " oldinstr_pad_len(num) " %% 6 %% 4 / 2, 2, 0x0700\n"	\
79	".endif\n"
80
81#define OLDINSTR(oldinstr, num)						\
82	"661:\n\t" oldinstr "\n662:\n"					\
83	OLDINSTR_PADDING(oldinstr, num)					\
84	e_oldinstr_pad_end ":\n"					\
85	INSTR_LEN_SANITY_CHECK(oldinstr_len)
86
87#define OLDINSTR_2(oldinstr, num1, num2)				\
88	"661:\n\t" oldinstr "\n662:\n"					\
89	".if " altinstr_len(num1) " < " altinstr_len(num2) "\n"		\
90	OLDINSTR_PADDING(oldinstr, num2)				\
91	".else\n"							\
92	OLDINSTR_PADDING(oldinstr, num1)				\
93	".endif\n"							\
94	e_oldinstr_pad_end ":\n"					\
95	INSTR_LEN_SANITY_CHECK(oldinstr_len)
96
97#define ALTINSTR_ENTRY(facility, num)					\
98	"\t.long 661b - .\n"			/* old instruction */	\
99	"\t.long " b_altinstr(num)"b - .\n"	/* alt instruction */	\
100	"\t.word " __stringify(facility) "\n"	/* facility bit    */	\
101	"\t.byte " oldinstr_total_len "\n"	/* source len	   */	\
102	"\t.byte " altinstr_len(num) "\n"	/* alt instruction len */
103
104#define ALTINSTR_REPLACEMENT(altinstr, num)	/* replacement */	\
105	b_altinstr(num)":\n\t" altinstr "\n" e_altinstr(num) ":\n"	\
106	INSTR_LEN_SANITY_CHECK(altinstr_len(num))
107
108/* alternative assembly primitive: */
109#define ALTERNATIVE(oldinstr, altinstr, facility) \
110	".pushsection .altinstr_replacement, \"ax\"\n"			\
111	ALTINSTR_REPLACEMENT(altinstr, 1)				\
112	".popsection\n"							\
113	OLDINSTR(oldinstr, 1)						\
114	".pushsection .altinstructions,\"a\"\n"				\
115	ALTINSTR_ENTRY(facility, 1)					\
116	".popsection\n"
117
118#define ALTERNATIVE_2(oldinstr, altinstr1, facility1, altinstr2, facility2)\
119	".pushsection .altinstr_replacement, \"ax\"\n"			\
120	ALTINSTR_REPLACEMENT(altinstr1, 1)				\
121	ALTINSTR_REPLACEMENT(altinstr2, 2)				\
122	".popsection\n"							\
123	OLDINSTR_2(oldinstr, 1, 2)					\
124	".pushsection .altinstructions,\"a\"\n"				\
125	ALTINSTR_ENTRY(facility1, 1)					\
126	ALTINSTR_ENTRY(facility2, 2)					\
127	".popsection\n"
128
129/*
130 * Alternative instructions for different CPU types or capabilities.
131 *
132 * This allows to use optimized instructions even on generic binary
133 * kernels.
134 *
135 * oldinstr is padded with jump and nops at compile time if altinstr is
136 * longer. altinstr is padded with jump and nops at run-time during patching.
137 *
138 * For non barrier like inlines please define new variants
139 * without volatile and memory clobber.
140 */
141#define alternative(oldinstr, altinstr, facility)			\
142	asm_inline volatile(ALTERNATIVE(oldinstr, altinstr, facility) : : : "memory")
143
144#define alternative_2(oldinstr, altinstr1, facility1, altinstr2, facility2) \
145	asm_inline volatile(ALTERNATIVE_2(oldinstr, altinstr1, facility1,   \
146				   altinstr2, facility2) ::: "memory")
147
148#endif /* __ASSEMBLY__ */
149
150#endif /* _ASM_S390_ALTERNATIVE_H */
151