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1/*
2 * jump label x86 support
3 *
4 * Copyright (C) 2009 Jason Baron <jbaron@redhat.com>
5 *
6 */
7#include <linux/jump_label.h>
8#include <linux/memory.h>
9#include <linux/uaccess.h>
10#include <linux/module.h>
11#include <linux/list.h>
12#include <linux/jhash.h>
13#include <linux/cpu.h>
14#include <asm/kprobes.h>
15#include <asm/alternative.h>
16
17#ifdef HAVE_JUMP_LABEL
18
19union jump_code_union {
20 char code[JUMP_LABEL_NOP_SIZE];
21 struct {
22 char jump;
23 int offset;
24 } __attribute__((packed));
25};
26
27static void __jump_label_transform(struct jump_entry *entry,
28 enum jump_label_type type,
29 void *(*poker)(void *, const void *, size_t))
30{
31 union jump_code_union code;
32
33 if (type == JUMP_LABEL_ENABLE) {
34 code.jump = 0xe9;
35 code.offset = entry->target -
36 (entry->code + JUMP_LABEL_NOP_SIZE);
37 } else
38 memcpy(&code, ideal_nops[NOP_ATOMIC5], JUMP_LABEL_NOP_SIZE);
39
40 (*poker)((void *)entry->code, &code, JUMP_LABEL_NOP_SIZE);
41}
42
43void arch_jump_label_transform(struct jump_entry *entry,
44 enum jump_label_type type)
45{
46 get_online_cpus();
47 mutex_lock(&text_mutex);
48 __jump_label_transform(entry, type, text_poke_smp);
49 mutex_unlock(&text_mutex);
50 put_online_cpus();
51}
52
53__init_or_module void arch_jump_label_transform_static(struct jump_entry *entry,
54 enum jump_label_type type)
55{
56 __jump_label_transform(entry, type, text_poke_early);
57}
58
59#endif
1/*
2 * jump label x86 support
3 *
4 * Copyright (C) 2009 Jason Baron <jbaron@redhat.com>
5 *
6 */
7#include <linux/jump_label.h>
8#include <linux/memory.h>
9#include <linux/uaccess.h>
10#include <linux/module.h>
11#include <linux/list.h>
12#include <linux/jhash.h>
13#include <linux/cpu.h>
14#include <asm/kprobes.h>
15#include <asm/alternative.h>
16#include <asm/text-patching.h>
17
18#ifdef HAVE_JUMP_LABEL
19
20union jump_code_union {
21 char code[JUMP_LABEL_NOP_SIZE];
22 struct {
23 char jump;
24 int offset;
25 } __attribute__((packed));
26};
27
28static void bug_at(unsigned char *ip, int line)
29{
30 /*
31 * The location is not an op that we were expecting.
32 * Something went wrong. Crash the box, as something could be
33 * corrupting the kernel.
34 */
35 pr_warning("Unexpected op at %pS [%p] (%02x %02x %02x %02x %02x) %s:%d\n",
36 ip, ip, ip[0], ip[1], ip[2], ip[3], ip[4], __FILE__, line);
37 BUG();
38}
39
40static void __jump_label_transform(struct jump_entry *entry,
41 enum jump_label_type type,
42 void *(*poker)(void *, const void *, size_t),
43 int init)
44{
45 union jump_code_union code;
46 const unsigned char default_nop[] = { STATIC_KEY_INIT_NOP };
47 const unsigned char *ideal_nop = ideal_nops[NOP_ATOMIC5];
48
49 if (type == JUMP_LABEL_JMP) {
50 if (init) {
51 /*
52 * Jump label is enabled for the first time.
53 * So we expect a default_nop...
54 */
55 if (unlikely(memcmp((void *)entry->code, default_nop, 5)
56 != 0))
57 bug_at((void *)entry->code, __LINE__);
58 } else {
59 /*
60 * ...otherwise expect an ideal_nop. Otherwise
61 * something went horribly wrong.
62 */
63 if (unlikely(memcmp((void *)entry->code, ideal_nop, 5)
64 != 0))
65 bug_at((void *)entry->code, __LINE__);
66 }
67
68 code.jump = 0xe9;
69 code.offset = entry->target -
70 (entry->code + JUMP_LABEL_NOP_SIZE);
71 } else {
72 /*
73 * We are disabling this jump label. If it is not what
74 * we think it is, then something must have gone wrong.
75 * If this is the first initialization call, then we
76 * are converting the default nop to the ideal nop.
77 */
78 if (init) {
79 if (unlikely(memcmp((void *)entry->code, default_nop, 5) != 0))
80 bug_at((void *)entry->code, __LINE__);
81 } else {
82 code.jump = 0xe9;
83 code.offset = entry->target -
84 (entry->code + JUMP_LABEL_NOP_SIZE);
85 if (unlikely(memcmp((void *)entry->code, &code, 5) != 0))
86 bug_at((void *)entry->code, __LINE__);
87 }
88 memcpy(&code, ideal_nops[NOP_ATOMIC5], JUMP_LABEL_NOP_SIZE);
89 }
90
91 /*
92 * Make text_poke_bp() a default fallback poker.
93 *
94 * At the time the change is being done, just ignore whether we
95 * are doing nop -> jump or jump -> nop transition, and assume
96 * always nop being the 'currently valid' instruction
97 *
98 */
99 if (poker)
100 (*poker)((void *)entry->code, &code, JUMP_LABEL_NOP_SIZE);
101 else
102 text_poke_bp((void *)entry->code, &code, JUMP_LABEL_NOP_SIZE,
103 (void *)entry->code + JUMP_LABEL_NOP_SIZE);
104}
105
106void arch_jump_label_transform(struct jump_entry *entry,
107 enum jump_label_type type)
108{
109 get_online_cpus();
110 mutex_lock(&text_mutex);
111 __jump_label_transform(entry, type, NULL, 0);
112 mutex_unlock(&text_mutex);
113 put_online_cpus();
114}
115
116static enum {
117 JL_STATE_START,
118 JL_STATE_NO_UPDATE,
119 JL_STATE_UPDATE,
120} jlstate __initdata_or_module = JL_STATE_START;
121
122__init_or_module void arch_jump_label_transform_static(struct jump_entry *entry,
123 enum jump_label_type type)
124{
125 /*
126 * This function is called at boot up and when modules are
127 * first loaded. Check if the default nop, the one that is
128 * inserted at compile time, is the ideal nop. If it is, then
129 * we do not need to update the nop, and we can leave it as is.
130 * If it is not, then we need to update the nop to the ideal nop.
131 */
132 if (jlstate == JL_STATE_START) {
133 const unsigned char default_nop[] = { STATIC_KEY_INIT_NOP };
134 const unsigned char *ideal_nop = ideal_nops[NOP_ATOMIC5];
135
136 if (memcmp(ideal_nop, default_nop, 5) != 0)
137 jlstate = JL_STATE_UPDATE;
138 else
139 jlstate = JL_STATE_NO_UPDATE;
140 }
141 if (jlstate == JL_STATE_UPDATE)
142 __jump_label_transform(entry, type, text_poke_early, 1);
143}
144
145#endif