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1/* SPDX-License-Identifier: GPL-2.0 */
2#ifndef _ASM_X86_ALTERNATIVE_ASM_H
3#define _ASM_X86_ALTERNATIVE_ASM_H
4
5#ifdef __ASSEMBLY__
6
7#include <asm/asm.h>
8
9#ifdef CONFIG_SMP
10 .macro LOCK_PREFIX
11672: lock
12 .pushsection .smp_locks,"a"
13 .balign 4
14 .long 672b - .
15 .popsection
16 .endm
17#else
18 .macro LOCK_PREFIX
19 .endm
20#endif
21
22/*
23 * Issue one struct alt_instr descriptor entry (need to put it into
24 * the section .altinstructions, see below). This entry contains
25 * enough information for the alternatives patching code to patch an
26 * instruction. See apply_alternatives().
27 */
28.macro altinstruction_entry orig alt feature orig_len alt_len pad_len
29 .long \orig - .
30 .long \alt - .
31 .word \feature
32 .byte \orig_len
33 .byte \alt_len
34 .byte \pad_len
35.endm
36
37/*
38 * Define an alternative between two instructions. If @feature is
39 * present, early code in apply_alternatives() replaces @oldinstr with
40 * @newinstr. ".skip" directive takes care of proper instruction padding
41 * in case @newinstr is longer than @oldinstr.
42 */
43.macro ALTERNATIVE oldinstr, newinstr, feature
44140:
45 \oldinstr
46141:
47 .skip -(((144f-143f)-(141b-140b)) > 0) * ((144f-143f)-(141b-140b)),0x90
48142:
49
50 .pushsection .altinstructions,"a"
51 altinstruction_entry 140b,143f,\feature,142b-140b,144f-143f,142b-141b
52 .popsection
53
54 .pushsection .altinstr_replacement,"ax"
55143:
56 \newinstr
57144:
58 .popsection
59.endm
60
61#define old_len 141b-140b
62#define new_len1 144f-143f
63#define new_len2 145f-144f
64
65/*
66 * gas compatible max based on the idea from:
67 * http://graphics.stanford.edu/~seander/bithacks.html#IntegerMinOrMax
68 *
69 * The additional "-" is needed because gas uses a "true" value of -1.
70 */
71#define alt_max_short(a, b) ((a) ^ (((a) ^ (b)) & -(-((a) < (b)))))
72
73
74/*
75 * Same as ALTERNATIVE macro above but for two alternatives. If CPU
76 * has @feature1, it replaces @oldinstr with @newinstr1. If CPU has
77 * @feature2, it replaces @oldinstr with @feature2.
78 */
79.macro ALTERNATIVE_2 oldinstr, newinstr1, feature1, newinstr2, feature2
80140:
81 \oldinstr
82141:
83 .skip -((alt_max_short(new_len1, new_len2) - (old_len)) > 0) * \
84 (alt_max_short(new_len1, new_len2) - (old_len)),0x90
85142:
86
87 .pushsection .altinstructions,"a"
88 altinstruction_entry 140b,143f,\feature1,142b-140b,144f-143f,142b-141b
89 altinstruction_entry 140b,144f,\feature2,142b-140b,145f-144f,142b-141b
90 .popsection
91
92 .pushsection .altinstr_replacement,"ax"
93143:
94 \newinstr1
95144:
96 \newinstr2
97145:
98 .popsection
99.endm
100
101#endif /* __ASSEMBLY__ */
102
103#endif /* _ASM_X86_ALTERNATIVE_ASM_H */