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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 * objtool annotation to ignore the alternatives and only consider the original
24 * instruction(s).
25 */
26.macro ANNOTATE_IGNORE_ALTERNATIVE
27 .Lannotate_\@:
28 .pushsection .discard.ignore_alts
29 .long .Lannotate_\@ - .
30 .popsection
31.endm
32
33/*
34 * Issue one struct alt_instr descriptor entry (need to put it into
35 * the section .altinstructions, see below). This entry contains
36 * enough information for the alternatives patching code to patch an
37 * instruction. See apply_alternatives().
38 */
39.macro altinstruction_entry orig alt feature orig_len alt_len pad_len
40 .long \orig - .
41 .long \alt - .
42 .word \feature
43 .byte \orig_len
44 .byte \alt_len
45 .byte \pad_len
46.endm
47
48/*
49 * Define an alternative between two instructions. If @feature is
50 * present, early code in apply_alternatives() replaces @oldinstr with
51 * @newinstr. ".skip" directive takes care of proper instruction padding
52 * in case @newinstr is longer than @oldinstr.
53 */
54.macro ALTERNATIVE oldinstr, newinstr, feature
55140:
56 \oldinstr
57141:
58 .skip -(((144f-143f)-(141b-140b)) > 0) * ((144f-143f)-(141b-140b)),0x90
59142:
60
61 .pushsection .altinstructions,"a"
62 altinstruction_entry 140b,143f,\feature,142b-140b,144f-143f,142b-141b
63 .popsection
64
65 .pushsection .altinstr_replacement,"ax"
66143:
67 \newinstr
68144:
69 .popsection
70.endm
71
72#define old_len 141b-140b
73#define new_len1 144f-143f
74#define new_len2 145f-144f
75
76/*
77 * gas compatible max based on the idea from:
78 * http://graphics.stanford.edu/~seander/bithacks.html#IntegerMinOrMax
79 *
80 * The additional "-" is needed because gas uses a "true" value of -1.
81 */
82#define alt_max_short(a, b) ((a) ^ (((a) ^ (b)) & -(-((a) < (b)))))
83
84
85/*
86 * Same as ALTERNATIVE macro above but for two alternatives. If CPU
87 * has @feature1, it replaces @oldinstr with @newinstr1. If CPU has
88 * @feature2, it replaces @oldinstr with @feature2.
89 */
90.macro ALTERNATIVE_2 oldinstr, newinstr1, feature1, newinstr2, feature2
91140:
92 \oldinstr
93141:
94 .skip -((alt_max_short(new_len1, new_len2) - (old_len)) > 0) * \
95 (alt_max_short(new_len1, new_len2) - (old_len)),0x90
96142:
97
98 .pushsection .altinstructions,"a"
99 altinstruction_entry 140b,143f,\feature1,142b-140b,144f-143f,142b-141b
100 altinstruction_entry 140b,144f,\feature2,142b-140b,145f-144f,142b-141b
101 .popsection
102
103 .pushsection .altinstr_replacement,"ax"
104143:
105 \newinstr1
106144:
107 \newinstr2
108145:
109 .popsection
110.endm
111
112#endif /* __ASSEMBLY__ */
113
114#endif /* _ASM_X86_ALTERNATIVE_ASM_H */