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1#ifndef _ASM_X86_ALTERNATIVE_ASM_H
2#define _ASM_X86_ALTERNATIVE_ASM_H
3
4#ifdef __ASSEMBLY__
5
6#include <asm/asm.h>
7
8#ifdef CONFIG_SMP
9 .macro LOCK_PREFIX
10672: lock
11 .pushsection .smp_locks,"a"
12 .balign 4
13 .long 672b - .
14 .popsection
15 .endm
16#else
17 .macro LOCK_PREFIX
18 .endm
19#endif
20
21/*
22 * Issue one struct alt_instr descriptor entry (need to put it into
23 * the section .altinstructions, see below). This entry contains
24 * enough information for the alternatives patching code to patch an
25 * instruction. See apply_alternatives().
26 */
27.macro altinstruction_entry orig alt feature orig_len alt_len pad_len
28 .long \orig - .
29 .long \alt - .
30 .word \feature
31 .byte \orig_len
32 .byte \alt_len
33 .byte \pad_len
34.endm
35
36/*
37 * Define an alternative between two instructions. If @feature is
38 * present, early code in apply_alternatives() replaces @oldinstr with
39 * @newinstr. ".skip" directive takes care of proper instruction padding
40 * in case @newinstr is longer than @oldinstr.
41 */
42.macro ALTERNATIVE oldinstr, newinstr, feature
43140:
44 \oldinstr
45141:
46 .skip -(((144f-143f)-(141b-140b)) > 0) * ((144f-143f)-(141b-140b)),0x90
47142:
48
49 .pushsection .altinstructions,"a"
50 altinstruction_entry 140b,143f,\feature,142b-140b,144f-143f,142b-141b
51 .popsection
52
53 .pushsection .altinstr_replacement,"ax"
54143:
55 \newinstr
56144:
57 .popsection
58.endm
59
60#define old_len 141b-140b
61#define new_len1 144f-143f
62#define new_len2 145f-144f
63
64/*
65 * max without conditionals. Idea adapted from:
66 * http://graphics.stanford.edu/~seander/bithacks.html#IntegerMinOrMax
67 */
68#define alt_max_short(a, b) ((a) ^ (((a) ^ (b)) & -(-((a) < (b)))))
69
70
71/*
72 * Same as ALTERNATIVE macro above but for two alternatives. If CPU
73 * has @feature1, it replaces @oldinstr with @newinstr1. If CPU has
74 * @feature2, it replaces @oldinstr with @feature2.
75 */
76.macro ALTERNATIVE_2 oldinstr, newinstr1, feature1, newinstr2, feature2
77140:
78 \oldinstr
79141:
80 .skip -((alt_max_short(new_len1, new_len2) - (old_len)) > 0) * \
81 (alt_max_short(new_len1, new_len2) - (old_len)),0x90
82142:
83
84 .pushsection .altinstructions,"a"
85 altinstruction_entry 140b,143f,\feature1,142b-140b,144f-143f,142b-141b
86 altinstruction_entry 140b,144f,\feature2,142b-140b,145f-144f,142b-141b
87 .popsection
88
89 .pushsection .altinstr_replacement,"ax"
90143:
91 \newinstr1
92144:
93 \newinstr2
94145:
95 .popsection
96.endm
97
98#endif /* __ASSEMBLY__ */
99
100#endif /* _ASM_X86_ALTERNATIVE_ASM_H */