aboutsummaryrefslogtreecommitdiffstats
path: root/include/asm-x86_64/alternative.h
diff options
context:
space:
mode:
Diffstat (limited to 'include/asm-x86_64/alternative.h')
-rw-r--r--include/asm-x86_64/alternative.h146
1 files changed, 146 insertions, 0 deletions
diff --git a/include/asm-x86_64/alternative.h b/include/asm-x86_64/alternative.h
new file mode 100644
index 000000000000..387c8f66af7d
--- /dev/null
+++ b/include/asm-x86_64/alternative.h
@@ -0,0 +1,146 @@
1#ifndef _X86_64_ALTERNATIVE_H
2#define _X86_64_ALTERNATIVE_H
3
4#ifdef __KERNEL__
5
6#include <linux/types.h>
7
8struct alt_instr {
9 u8 *instr; /* original instruction */
10 u8 *replacement;
11 u8 cpuid; /* cpuid bit set for replacement */
12 u8 instrlen; /* length of original instruction */
13 u8 replacementlen; /* length of new instruction, <= instrlen */
14 u8 pad[5];
15};
16
17extern void apply_alternatives(struct alt_instr *start, struct alt_instr *end);
18
19struct module;
20extern void alternatives_smp_module_add(struct module *mod, char *name,
21 void *locks, void *locks_end,
22 void *text, void *text_end);
23extern void alternatives_smp_module_del(struct module *mod);
24extern void alternatives_smp_switch(int smp);
25
26#endif
27
28/*
29 * Alternative instructions for different CPU types or capabilities.
30 *
31 * This allows to use optimized instructions even on generic binary
32 * kernels.
33 *
34 * length of oldinstr must be longer or equal the length of newinstr
35 * It can be padded with nops as needed.
36 *
37 * For non barrier like inlines please define new variants
38 * without volatile and memory clobber.
39 */
40#define alternative(oldinstr, newinstr, feature) \
41 asm volatile ("661:\n\t" oldinstr "\n662:\n" \
42 ".section .altinstructions,\"a\"\n" \
43 " .align 8\n" \
44 " .quad 661b\n" /* label */ \
45 " .quad 663f\n" /* new instruction */ \
46 " .byte %c0\n" /* feature bit */ \
47 " .byte 662b-661b\n" /* sourcelen */ \
48 " .byte 664f-663f\n" /* replacementlen */ \
49 ".previous\n" \
50 ".section .altinstr_replacement,\"ax\"\n" \
51 "663:\n\t" newinstr "\n664:\n" /* replacement */ \
52 ".previous" :: "i" (feature) : "memory")
53
54/*
55 * Alternative inline assembly with input.
56 *
57 * Pecularities:
58 * No memory clobber here.
59 * Argument numbers start with 1.
60 * Best is to use constraints that are fixed size (like (%1) ... "r")
61 * If you use variable sized constraints like "m" or "g" in the
62 * replacement make sure to pad to the worst case length.
63 */
64#define alternative_input(oldinstr, newinstr, feature, input...) \
65 asm volatile ("661:\n\t" oldinstr "\n662:\n" \
66 ".section .altinstructions,\"a\"\n" \
67 " .align 8\n" \
68 " .quad 661b\n" /* label */ \
69 " .quad 663f\n" /* new instruction */ \
70 " .byte %c0\n" /* feature bit */ \
71 " .byte 662b-661b\n" /* sourcelen */ \
72 " .byte 664f-663f\n" /* replacementlen */ \
73 ".previous\n" \
74 ".section .altinstr_replacement,\"ax\"\n" \
75 "663:\n\t" newinstr "\n664:\n" /* replacement */ \
76 ".previous" :: "i" (feature), ##input)
77
78/* Like alternative_input, but with a single output argument */
79#define alternative_io(oldinstr, newinstr, feature, output, input...) \
80 asm volatile ("661:\n\t" oldinstr "\n662:\n" \
81 ".section .altinstructions,\"a\"\n" \
82 " .align 8\n" \
83 " .quad 661b\n" /* label */ \
84 " .quad 663f\n" /* new instruction */ \
85 " .byte %c[feat]\n" /* feature bit */ \
86 " .byte 662b-661b\n" /* sourcelen */ \
87 " .byte 664f-663f\n" /* replacementlen */ \
88 ".previous\n" \
89 ".section .altinstr_replacement,\"ax\"\n" \
90 "663:\n\t" newinstr "\n664:\n" /* replacement */ \
91 ".previous" : output : [feat] "i" (feature), ##input)
92
93/*
94 * Alternative inline assembly for SMP.
95 *
96 * alternative_smp() takes two versions (SMP first, UP second) and is
97 * for more complex stuff such as spinlocks.
98 *
99 * The LOCK_PREFIX macro defined here replaces the LOCK and
100 * LOCK_PREFIX macros used everywhere in the source tree.
101 *
102 * SMP alternatives use the same data structures as the other
103 * alternatives and the X86_FEATURE_UP flag to indicate the case of a
104 * UP system running a SMP kernel. The existing apply_alternatives()
105 * works fine for patching a SMP kernel for UP.
106 *
107 * The SMP alternative tables can be kept after boot and contain both
108 * UP and SMP versions of the instructions to allow switching back to
109 * SMP at runtime, when hotplugging in a new CPU, which is especially
110 * useful in virtualized environments.
111 *
112 * The very common lock prefix is handled as special case in a
113 * separate table which is a pure address list without replacement ptr
114 * and size information. That keeps the table sizes small.
115 */
116
117#ifdef CONFIG_SMP
118#define alternative_smp(smpinstr, upinstr, args...) \
119 asm volatile ("661:\n\t" smpinstr "\n662:\n" \
120 ".section .smp_altinstructions,\"a\"\n" \
121 " .align 8\n" \
122 " .quad 661b\n" /* label */ \
123 " .quad 663f\n" /* new instruction */ \
124 " .byte 0x66\n" /* X86_FEATURE_UP */ \
125 " .byte 662b-661b\n" /* sourcelen */ \
126 " .byte 664f-663f\n" /* replacementlen */ \
127 ".previous\n" \
128 ".section .smp_altinstr_replacement,\"awx\"\n" \
129 "663:\n\t" upinstr "\n" /* replacement */ \
130 "664:\n\t.fill 662b-661b,1,0x42\n" /* space for original */ \
131 ".previous" : args)
132
133#define LOCK_PREFIX \
134 ".section .smp_locks,\"a\"\n" \
135 " .align 8\n" \
136 " .quad 661f\n" /* address */ \
137 ".previous\n" \
138 "661:\n\tlock; "
139
140#else /* ! CONFIG_SMP */
141#define alternative_smp(smpinstr, upinstr, args...) \
142 asm volatile (upinstr : args)
143#define LOCK_PREFIX ""
144#endif
145
146#endif /* _X86_64_ALTERNATIVE_H */
generated by cgit v1.2.2 (git 2.25.0) at 2024-11-26 16:53:12 -0500