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