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1// SPDX-License-Identifier: GPL-2.0
2/*
3 * jump label x86 support
4 *
5 * Copyright (C) 2009 Jason Baron <jbaron@redhat.com>
6 *
7 */
8#include <linux/jump_label.h>
9#include <linux/memory.h>
10#include <linux/uaccess.h>
11#include <linux/module.h>
12#include <linux/list.h>
13#include <linux/jhash.h>
14#include <linux/cpu.h>
15#include <asm/kprobes.h>
16#include <asm/alternative.h>
17#include <asm/text-patching.h>
18
19#ifdef HAVE_JUMP_LABEL
20
21union jump_code_union {
22 char code[JUMP_LABEL_NOP_SIZE];
23 struct {
24 char jump;
25 int offset;
26 } __attribute__((packed));
27};
28
29static void bug_at(unsigned char *ip, int line)
30{
31 /*
32 * The location is not an op that we were expecting.
33 * Something went wrong. Crash the box, as something could be
34 * corrupting the kernel.
35 */
36 pr_crit("jump_label: Fatal kernel bug, unexpected op at %pS [%p] (%5ph) %d\n", ip, ip, ip, 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 mutex_lock(&text_mutex);
110 __jump_label_transform(entry, type, NULL, 0);
111 mutex_unlock(&text_mutex);
112}
113
114static enum {
115 JL_STATE_START,
116 JL_STATE_NO_UPDATE,
117 JL_STATE_UPDATE,
118} jlstate __initdata_or_module = JL_STATE_START;
119
120__init_or_module void arch_jump_label_transform_static(struct jump_entry *entry,
121 enum jump_label_type type)
122{
123 /*
124 * This function is called at boot up and when modules are
125 * first loaded. Check if the default nop, the one that is
126 * inserted at compile time, is the ideal nop. If it is, then
127 * we do not need to update the nop, and we can leave it as is.
128 * If it is not, then we need to update the nop to the ideal nop.
129 */
130 if (jlstate == JL_STATE_START) {
131 const unsigned char default_nop[] = { STATIC_KEY_INIT_NOP };
132 const unsigned char *ideal_nop = ideal_nops[NOP_ATOMIC5];
133
134 if (memcmp(ideal_nop, default_nop, 5) != 0)
135 jlstate = JL_STATE_UPDATE;
136 else
137 jlstate = JL_STATE_NO_UPDATE;
138 }
139 if (jlstate == JL_STATE_UPDATE)
140 __jump_label_transform(entry, type, text_poke_early, 1);
141}
142
143#endif
1// SPDX-License-Identifier: GPL-2.0
2/*
3 * jump label x86 support
4 *
5 * Copyright (C) 2009 Jason Baron <jbaron@redhat.com>
6 *
7 */
8#include <linux/jump_label.h>
9#include <linux/memory.h>
10#include <linux/uaccess.h>
11#include <linux/module.h>
12#include <linux/list.h>
13#include <linux/jhash.h>
14#include <linux/cpu.h>
15#include <asm/kprobes.h>
16#include <asm/alternative.h>
17#include <asm/text-patching.h>
18#include <asm/insn.h>
19
20int arch_jump_entry_size(struct jump_entry *entry)
21{
22 struct insn insn = {};
23
24 insn_decode_kernel(&insn, (void *)jump_entry_code(entry));
25 BUG_ON(insn.length != 2 && insn.length != 5);
26
27 return insn.length;
28}
29
30struct jump_label_patch {
31 const void *code;
32 int size;
33};
34
35static struct jump_label_patch
36__jump_label_patch(struct jump_entry *entry, enum jump_label_type type)
37{
38 const void *expect, *code, *nop;
39 const void *addr, *dest;
40 int size;
41
42 addr = (void *)jump_entry_code(entry);
43 dest = (void *)jump_entry_target(entry);
44
45 size = arch_jump_entry_size(entry);
46 switch (size) {
47 case JMP8_INSN_SIZE:
48 code = text_gen_insn(JMP8_INSN_OPCODE, addr, dest);
49 nop = x86_nops[size];
50 break;
51
52 case JMP32_INSN_SIZE:
53 code = text_gen_insn(JMP32_INSN_OPCODE, addr, dest);
54 nop = x86_nops[size];
55 break;
56
57 default: BUG();
58 }
59
60 if (type == JUMP_LABEL_JMP)
61 expect = nop;
62 else
63 expect = code;
64
65 if (memcmp(addr, expect, size)) {
66 /*
67 * The location is not an op that we were expecting.
68 * Something went wrong. Crash the box, as something could be
69 * corrupting the kernel.
70 */
71 pr_crit("jump_label: Fatal kernel bug, unexpected op at %pS [%p] (%5ph != %5ph)) size:%d type:%d\n",
72 addr, addr, addr, expect, size, type);
73 BUG();
74 }
75
76 if (type == JUMP_LABEL_NOP)
77 code = nop;
78
79 return (struct jump_label_patch){.code = code, .size = size};
80}
81
82static __always_inline void
83__jump_label_transform(struct jump_entry *entry,
84 enum jump_label_type type,
85 int init)
86{
87 const struct jump_label_patch jlp = __jump_label_patch(entry, type);
88
89 /*
90 * As long as only a single processor is running and the code is still
91 * not marked as RO, text_poke_early() can be used; Checking that
92 * system_state is SYSTEM_BOOTING guarantees it. It will be set to
93 * SYSTEM_SCHEDULING before other cores are awaken and before the
94 * code is write-protected.
95 *
96 * At the time the change is being done, just ignore whether we
97 * are doing nop -> jump or jump -> nop transition, and assume
98 * always nop being the 'currently valid' instruction
99 */
100 if (init || system_state == SYSTEM_BOOTING) {
101 text_poke_early((void *)jump_entry_code(entry), jlp.code, jlp.size);
102 return;
103 }
104
105 text_poke_bp((void *)jump_entry_code(entry), jlp.code, jlp.size, NULL);
106}
107
108static void __ref jump_label_transform(struct jump_entry *entry,
109 enum jump_label_type type,
110 int init)
111{
112 mutex_lock(&text_mutex);
113 __jump_label_transform(entry, type, init);
114 mutex_unlock(&text_mutex);
115}
116
117void arch_jump_label_transform(struct jump_entry *entry,
118 enum jump_label_type type)
119{
120 jump_label_transform(entry, type, 0);
121}
122
123bool arch_jump_label_transform_queue(struct jump_entry *entry,
124 enum jump_label_type type)
125{
126 struct jump_label_patch jlp;
127
128 if (system_state == SYSTEM_BOOTING) {
129 /*
130 * Fallback to the non-batching mode.
131 */
132 arch_jump_label_transform(entry, type);
133 return true;
134 }
135
136 mutex_lock(&text_mutex);
137 jlp = __jump_label_patch(entry, type);
138 text_poke_queue((void *)jump_entry_code(entry), jlp.code, jlp.size, NULL);
139 mutex_unlock(&text_mutex);
140 return true;
141}
142
143void arch_jump_label_transform_apply(void)
144{
145 mutex_lock(&text_mutex);
146 text_poke_finish();
147 mutex_unlock(&text_mutex);
148}
149
150static enum {
151 JL_STATE_START,
152 JL_STATE_NO_UPDATE,
153 JL_STATE_UPDATE,
154} jlstate __initdata_or_module = JL_STATE_START;
155
156__init_or_module void arch_jump_label_transform_static(struct jump_entry *entry,
157 enum jump_label_type type)
158{
159 if (jlstate == JL_STATE_UPDATE)
160 jump_label_transform(entry, type, 1);
161}