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1#ifndef _ASM_X86_ALTERNATIVE_H
2#define _ASM_X86_ALTERNATIVE_H
3
4#include <linux/types.h>
5#include <linux/stddef.h>
6#include <asm/asm.h>
7
8/*
9 * Alternative inline assembly for SMP.
10 *
11 * The LOCK_PREFIX macro defined here replaces the LOCK and
12 * LOCK_PREFIX macros used everywhere in the source tree.
13 *
14 * SMP alternatives use the same data structures as the other
15 * alternatives and the X86_FEATURE_UP flag to indicate the case of a
16 * UP system running a SMP kernel. The existing apply_alternatives()
17 * works fine for patching a SMP kernel for UP.
18 *
19 * The SMP alternative tables can be kept after boot and contain both
20 * UP and SMP versions of the instructions to allow switching back to
21 * SMP at runtime, when hotplugging in a new CPU, which is especially
22 * useful in virtualized environments.
23 *
24 * The very common lock prefix is handled as special case in a
25 * separate table which is a pure address list without replacement ptr
26 * and size information. That keeps the table sizes small.
27 */
28
29#ifdef CONFIG_SMP
30#define LOCK_PREFIX \
31 ".section .smp_locks,\"a\"\n" \
32 _ASM_ALIGN "\n" \
33 _ASM_PTR "661f\n" /* address */ \
34 ".previous\n" \
35 "661:\n\tlock; "
36
37#else /* ! CONFIG_SMP */
38#define LOCK_PREFIX ""
39#endif
40
41/* This must be included *after* the definition of LOCK_PREFIX */
42#include <asm/cpufeature.h>
43
44struct alt_instr {
45 u8 *instr; /* original instruction */
46 u8 *replacement;
47 u8 cpuid; /* cpuid bit set for replacement */
48 u8 instrlen; /* length of original instruction */
49 u8 replacementlen; /* length of new instruction, <= instrlen */
50 u8 pad1;
51#ifdef CONFIG_X86_64
52 u32 pad2;
53#endif
54};
55
56extern void alternative_instructions(void);
57extern void apply_alternatives(struct alt_instr *start, struct alt_instr *end);
58
59struct module;
60
61#ifdef CONFIG_SMP
62extern void alternatives_smp_module_add(struct module *mod, char *name,
63 void *locks, void *locks_end,
64 void *text, void *text_end);
65extern void alternatives_smp_module_del(struct module *mod);
66extern void alternatives_smp_switch(int smp);
67#else
68static inline void alternatives_smp_module_add(struct module *mod, char *name,
69 void *locks, void *locks_end,
70 void *text, void *text_end) {}
71static inline void alternatives_smp_module_del(struct module *mod) {}
72static inline void alternatives_smp_switch(int smp) {}
73#endif /* CONFIG_SMP */
74
75/*
76 * Alternative instructions for different CPU types or capabilities.
77 *
78 * This allows to use optimized instructions even on generic binary
79 * kernels.
80 *
81 * length of oldinstr must be longer or equal the length of newinstr
82 * It can be padded with nops as needed.
83 *
84 * For non barrier like inlines please define new variants
85 * without volatile and memory clobber.
86 */
87#define alternative(oldinstr, newinstr, feature) \
88 asm volatile ("661:\n\t" oldinstr "\n662:\n" \
89 ".section .altinstructions,\"a\"\n" \
90 _ASM_ALIGN "\n" \
91 _ASM_PTR "661b\n" /* label */ \
92 _ASM_PTR "663f\n" /* new instruction */ \
93 " .byte %c0\n" /* feature bit */ \
94 " .byte 662b-661b\n" /* sourcelen */ \
95 " .byte 664f-663f\n" /* replacementlen */ \
96 ".previous\n" \
97 ".section .altinstr_replacement,\"ax\"\n" \
98 "663:\n\t" newinstr "\n664:\n" /* replacement */ \
99 ".previous" :: "i" (feature) : "memory")
100
101/*
102 * Alternative inline assembly with input.
103 *
104 * Pecularities:
105 * No memory clobber here.
106 * Argument numbers start with 1.
107 * Best is to use constraints that are fixed size (like (%1) ... "r")
108 * If you use variable sized constraints like "m" or "g" in the
109 * replacement make sure to pad to the worst case length.
110 */
111#define alternative_input(oldinstr, newinstr, feature, input...) \
112 asm volatile ("661:\n\t" oldinstr "\n662:\n" \
113 ".section .altinstructions,\"a\"\n" \
114 _ASM_ALIGN "\n" \
115 _ASM_PTR "661b\n" /* label */ \
116 _ASM_PTR "663f\n" /* new instruction */ \
117 " .byte %c0\n" /* feature bit */ \
118 " .byte 662b-661b\n" /* sourcelen */ \
119 " .byte 664f-663f\n" /* replacementlen */ \
120 ".previous\n" \
121 ".section .altinstr_replacement,\"ax\"\n" \
122 "663:\n\t" newinstr "\n664:\n" /* replacement */ \
123 ".previous" :: "i" (feature), ##input)
124
125/* Like alternative_input, but with a single output argument */
126#define alternative_io(oldinstr, newinstr, feature, output, input...) \
127 asm volatile ("661:\n\t" oldinstr "\n662:\n" \
128 ".section .altinstructions,\"a\"\n" \
129 _ASM_ALIGN "\n" \
130 _ASM_PTR "661b\n" /* label */ \
131 _ASM_PTR "663f\n" /* new instruction */ \
132 " .byte %c[feat]\n" /* feature bit */ \
133 " .byte 662b-661b\n" /* sourcelen */ \
134 " .byte 664f-663f\n" /* replacementlen */ \
135 ".previous\n" \
136 ".section .altinstr_replacement,\"ax\"\n" \
137 "663:\n\t" newinstr "\n664:\n" /* replacement */ \
138 ".previous" : output : [feat] "i" (feature), ##input)
139
140/*
141 * use this macro(s) if you need more than one output parameter
142 * in alternative_io
143 */
144#define ASM_OUTPUT2(a, b) a, b
145
146struct paravirt_patch_site;
147#ifdef CONFIG_PARAVIRT
148void apply_paravirt(struct paravirt_patch_site *start,
149 struct paravirt_patch_site *end);
150#else
151static inline void apply_paravirt(struct paravirt_patch_site *start,
152 struct paravirt_patch_site *end)
153{}
154#define __parainstructions NULL
155#define __parainstructions_end NULL
156#endif
157
158extern void add_nops(void *insns, unsigned int len);
159
160/*
161 * Clear and restore the kernel write-protection flag on the local CPU.
162 * Allows the kernel to edit read-only pages.
163 * Side-effect: any interrupt handler running between save and restore will have
164 * the ability to write to read-only pages.
165 *
166 * Warning:
167 * Code patching in the UP case is safe if NMIs and MCE handlers are stopped and
168 * no thread can be preempted in the instructions being modified (no iret to an
169 * invalid instruction possible) or if the instructions are changed from a
170 * consistent state to another consistent state atomically.
171 * More care must be taken when modifying code in the SMP case because of
172 * Intel's errata.
173 * On the local CPU you need to be protected again NMI or MCE handlers seeing an
174 * inconsistent instruction while you patch.
175 * The _early version expects the memory to already be RW.
176 */
177
178extern void *text_poke(void *addr, const void *opcode, size_t len);
179extern void *text_poke_early(void *addr, const void *opcode, size_t len);
180
181#endif /* _ASM_X86_ALTERNATIVE_H */