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H. Peter Anvin1965aae2008-10-22 22:26:29 -07001#ifndef _ASM_X86_ALTERNATIVE_H
2#define _ASM_X86_ALTERNATIVE_H
H. Peter Anvin6b592572008-01-30 13:30:30 +01003
4#include <linux/types.h>
5#include <linux/stddef.h>
Mathieu Desnoyersedc953f2009-04-28 11:13:46 -04006#include <linux/stringify.h>
H. Peter Anvin6b592572008-01-30 13:30:30 +01007#include <asm/asm.h>
8
9/*
10 * Alternative inline assembly for SMP.
11 *
12 * The LOCK_PREFIX macro defined here replaces the LOCK and
13 * LOCK_PREFIX macros used everywhere in the source tree.
14 *
15 * SMP alternatives use the same data structures as the other
16 * alternatives and the X86_FEATURE_UP flag to indicate the case of a
17 * UP system running a SMP kernel. The existing apply_alternatives()
18 * works fine for patching a SMP kernel for UP.
19 *
20 * The SMP alternative tables can be kept after boot and contain both
21 * UP and SMP versions of the instructions to allow switching back to
22 * SMP at runtime, when hotplugging in a new CPU, which is especially
23 * useful in virtualized environments.
24 *
25 * The very common lock prefix is handled as special case in a
26 * separate table which is a pure address list without replacement ptr
27 * and size information. That keeps the table sizes small.
28 */
29
30#ifdef CONFIG_SMP
31#define LOCK_PREFIX \
32 ".section .smp_locks,\"a\"\n" \
33 _ASM_ALIGN "\n" \
34 _ASM_PTR "661f\n" /* address */ \
35 ".previous\n" \
36 "661:\n\tlock; "
37
38#else /* ! CONFIG_SMP */
39#define LOCK_PREFIX ""
Thomas Gleixner96a388d2007-10-11 11:20:03 +020040#endif
H. Peter Anvin6b592572008-01-30 13:30:30 +010041
42/* This must be included *after* the definition of LOCK_PREFIX */
43#include <asm/cpufeature.h>
44
45struct alt_instr {
46 u8 *instr; /* original instruction */
47 u8 *replacement;
48 u8 cpuid; /* cpuid bit set for replacement */
49 u8 instrlen; /* length of original instruction */
50 u8 replacementlen; /* length of new instruction, <= instrlen */
51 u8 pad1;
52#ifdef CONFIG_X86_64
53 u32 pad2;
54#endif
55};
56
57extern void alternative_instructions(void);
58extern void apply_alternatives(struct alt_instr *start, struct alt_instr *end);
59
60struct module;
61
62#ifdef CONFIG_SMP
63extern void alternatives_smp_module_add(struct module *mod, char *name,
64 void *locks, void *locks_end,
65 void *text, void *text_end);
66extern void alternatives_smp_module_del(struct module *mod);
67extern void alternatives_smp_switch(int smp);
Masami Hiramatsu2cfa1972010-02-02 16:49:11 -050068extern int alternatives_text_reserved(void *start, void *end);
H. Peter Anvin6b592572008-01-30 13:30:30 +010069#else
70static inline void alternatives_smp_module_add(struct module *mod, char *name,
Joe Perches2ac1ea72008-03-23 01:01:37 -070071 void *locks, void *locks_end,
72 void *text, void *text_end) {}
H. Peter Anvin6b592572008-01-30 13:30:30 +010073static inline void alternatives_smp_module_del(struct module *mod) {}
74static inline void alternatives_smp_switch(int smp) {}
Masami Hiramatsu2cfa1972010-02-02 16:49:11 -050075static inline int alternatives_text_reserved(void *start, void *end)
76{
77 return 0;
78}
H. Peter Anvin6b592572008-01-30 13:30:30 +010079#endif /* CONFIG_SMP */
80
Mathieu Desnoyersedc953f2009-04-28 11:13:46 -040081/* alternative assembly primitive: */
82#define ALTERNATIVE(oldinstr, newinstr, feature) \
83 \
84 "661:\n\t" oldinstr "\n662:\n" \
85 ".section .altinstructions,\"a\"\n" \
86 _ASM_ALIGN "\n" \
87 _ASM_PTR "661b\n" /* label */ \
88 _ASM_PTR "663f\n" /* new instruction */ \
89 " .byte " __stringify(feature) "\n" /* feature bit */ \
90 " .byte 662b-661b\n" /* sourcelen */ \
91 " .byte 664f-663f\n" /* replacementlen */ \
Jan Beulich01be50a2009-11-27 15:04:58 +000092 " .byte 0xff + (664f-663f) - (662b-661b)\n" /* rlen <= slen */ \
Mathieu Desnoyersedc953f2009-04-28 11:13:46 -040093 ".previous\n" \
94 ".section .altinstr_replacement, \"ax\"\n" \
95 "663:\n\t" newinstr "\n664:\n" /* replacement */ \
96 ".previous"
97
H. Peter Anvin6b592572008-01-30 13:30:30 +010098/*
99 * Alternative instructions for different CPU types or capabilities.
100 *
101 * This allows to use optimized instructions even on generic binary
102 * kernels.
103 *
104 * length of oldinstr must be longer or equal the length of newinstr
105 * It can be padded with nops as needed.
106 *
107 * For non barrier like inlines please define new variants
108 * without volatile and memory clobber.
109 */
110#define alternative(oldinstr, newinstr, feature) \
Mathieu Desnoyersedc953f2009-04-28 11:13:46 -0400111 asm volatile (ALTERNATIVE(oldinstr, newinstr, feature) : : : "memory")
H. Peter Anvin6b592572008-01-30 13:30:30 +0100112
113/*
114 * Alternative inline assembly with input.
115 *
116 * Pecularities:
117 * No memory clobber here.
118 * Argument numbers start with 1.
119 * Best is to use constraints that are fixed size (like (%1) ... "r")
120 * If you use variable sized constraints like "m" or "g" in the
121 * replacement make sure to pad to the worst case length.
Mathieu Desnoyersedc953f2009-04-28 11:13:46 -0400122 * Leaving an unused argument 0 to keep API compatibility.
H. Peter Anvin6b592572008-01-30 13:30:30 +0100123 */
124#define alternative_input(oldinstr, newinstr, feature, input...) \
Mathieu Desnoyersedc953f2009-04-28 11:13:46 -0400125 asm volatile (ALTERNATIVE(oldinstr, newinstr, feature) \
126 : : "i" (0), ## input)
H. Peter Anvin6b592572008-01-30 13:30:30 +0100127
128/* Like alternative_input, but with a single output argument */
129#define alternative_io(oldinstr, newinstr, feature, output, input...) \
Mathieu Desnoyersedc953f2009-04-28 11:13:46 -0400130 asm volatile (ALTERNATIVE(oldinstr, newinstr, feature) \
131 : output : "i" (0), ## input)
H. Peter Anvin6b592572008-01-30 13:30:30 +0100132
Jan Beulich1b1d9252009-12-18 16:12:56 +0000133/* Like alternative_io, but for replacing a direct call with another one. */
134#define alternative_call(oldfunc, newfunc, feature, output, input...) \
135 asm volatile (ALTERNATIVE("call %P[old]", "call %P[new]", feature) \
136 : output : [old] "i" (oldfunc), [new] "i" (newfunc), ## input)
137
H. Peter Anvin6b592572008-01-30 13:30:30 +0100138/*
139 * use this macro(s) if you need more than one output parameter
140 * in alternative_io
141 */
Jan Beulich1b1d9252009-12-18 16:12:56 +0000142#define ASM_OUTPUT2(a...) a
H. Peter Anvin6b592572008-01-30 13:30:30 +0100143
144struct paravirt_patch_site;
145#ifdef CONFIG_PARAVIRT
146void apply_paravirt(struct paravirt_patch_site *start,
147 struct paravirt_patch_site *end);
148#else
Joe Perches2ac1ea72008-03-23 01:01:37 -0700149static inline void apply_paravirt(struct paravirt_patch_site *start,
150 struct paravirt_patch_site *end)
H. Peter Anvin6b592572008-01-30 13:30:30 +0100151{}
152#define __parainstructions NULL
153#define __parainstructions_end NULL
154#endif
155
Mathieu Desnoyerse587cad2008-03-06 08:48:49 -0500156/*
157 * Clear and restore the kernel write-protection flag on the local CPU.
158 * Allows the kernel to edit read-only pages.
159 * Side-effect: any interrupt handler running between save and restore will have
160 * the ability to write to read-only pages.
161 *
162 * Warning:
163 * Code patching in the UP case is safe if NMIs and MCE handlers are stopped and
164 * no thread can be preempted in the instructions being modified (no iret to an
165 * invalid instruction possible) or if the instructions are changed from a
166 * consistent state to another consistent state atomically.
167 * More care must be taken when modifying code in the SMP case because of
Masami Hiramatsu3d55cc82010-02-25 08:34:38 -0500168 * Intel's errata. text_poke_smp() takes care that errata, but still
169 * doesn't support NMI/MCE handler code modifying.
Mathieu Desnoyerse587cad2008-03-06 08:48:49 -0500170 * On the local CPU you need to be protected again NMI or MCE handlers seeing an
171 * inconsistent instruction while you patch.
Mathieu Desnoyerse587cad2008-03-06 08:48:49 -0500172 */
Mathieu Desnoyerse587cad2008-03-06 08:48:49 -0500173extern void *text_poke(void *addr, const void *opcode, size_t len);
Masami Hiramatsu3d55cc82010-02-25 08:34:38 -0500174extern void *text_poke_smp(void *addr, const void *opcode, size_t len);
H. Peter Anvin6b592572008-01-30 13:30:30 +0100175
H. Peter Anvin1965aae2008-10-22 22:26:29 -0700176#endif /* _ASM_X86_ALTERNATIVE_H */