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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
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 bug_at(unsigned char *ip, int line)
28{
29 /*
30 * The location is not an op that we were expecting.
31 * Something went wrong. Crash the box, as something could be
32 * corrupting the kernel.
33 */
34 pr_crit("jump_label: Fatal kernel bug, unexpected op at %pS [%p] (%5ph) %d\n", ip, ip, ip, line);
35 BUG();
36}
37
38static void __jump_label_set_jump_code(struct jump_entry *entry,
39 enum jump_label_type type,
40 union jump_code_union *code,
41 int init)
42{
43 const unsigned char default_nop[] = { STATIC_KEY_INIT_NOP };
44 const unsigned char *ideal_nop = ideal_nops[NOP_ATOMIC5];
45 const void *expect;
46 int line;
47
48 code->jump = 0xe9;
49 code->offset = jump_entry_target(entry) -
50 (jump_entry_code(entry) + JUMP_LABEL_NOP_SIZE);
51
52 if (init) {
53 expect = default_nop; line = __LINE__;
54 } else if (type == JUMP_LABEL_JMP) {
55 expect = ideal_nop; line = __LINE__;
56 } else {
57 expect = code->code; line = __LINE__;
58 }
59
60 if (memcmp((void *)jump_entry_code(entry), expect, JUMP_LABEL_NOP_SIZE))
61 bug_at((void *)jump_entry_code(entry), line);
62
63 if (type == JUMP_LABEL_NOP)
64 memcpy(code, ideal_nop, JUMP_LABEL_NOP_SIZE);
65}
66
67static void __ref __jump_label_transform(struct jump_entry *entry,
68 enum jump_label_type type,
69 int init)
70{
71 union jump_code_union code;
72
73 __jump_label_set_jump_code(entry, type, &code, init);
74
75 /*
76 * As long as only a single processor is running and the code is still
77 * not marked as RO, text_poke_early() can be used; Checking that
78 * system_state is SYSTEM_BOOTING guarantees it. It will be set to
79 * SYSTEM_SCHEDULING before other cores are awaken and before the
80 * code is write-protected.
81 *
82 * At the time the change is being done, just ignore whether we
83 * are doing nop -> jump or jump -> nop transition, and assume
84 * always nop being the 'currently valid' instruction
85 */
86 if (init || system_state == SYSTEM_BOOTING) {
87 text_poke_early((void *)jump_entry_code(entry), &code,
88 JUMP_LABEL_NOP_SIZE);
89 return;
90 }
91
92 text_poke_bp((void *)jump_entry_code(entry), &code, JUMP_LABEL_NOP_SIZE,
93 (void *)jump_entry_code(entry) + JUMP_LABEL_NOP_SIZE);
94}
95
96void arch_jump_label_transform(struct jump_entry *entry,
97 enum jump_label_type type)
98{
99 mutex_lock(&text_mutex);
100 __jump_label_transform(entry, type, 0);
101 mutex_unlock(&text_mutex);
102}
103
104#define TP_VEC_MAX (PAGE_SIZE / sizeof(struct text_poke_loc))
105static struct text_poke_loc tp_vec[TP_VEC_MAX];
106static int tp_vec_nr;
107
108bool arch_jump_label_transform_queue(struct jump_entry *entry,
109 enum jump_label_type type)
110{
111 struct text_poke_loc *tp;
112 void *entry_code;
113
114 if (system_state == SYSTEM_BOOTING) {
115 /*
116 * Fallback to the non-batching mode.
117 */
118 arch_jump_label_transform(entry, type);
119 return true;
120 }
121
122 /*
123 * No more space in the vector, tell upper layer to apply
124 * the queue before continuing.
125 */
126 if (tp_vec_nr == TP_VEC_MAX)
127 return false;
128
129 tp = &tp_vec[tp_vec_nr];
130
131 entry_code = (void *)jump_entry_code(entry);
132
133 /*
134 * The INT3 handler will do a bsearch in the queue, so we need entries
135 * to be sorted. We can survive an unsorted list by rejecting the entry,
136 * forcing the generic jump_label code to apply the queue. Warning once,
137 * to raise the attention to the case of an unsorted entry that is
138 * better not happen, because, in the worst case we will perform in the
139 * same way as we do without batching - with some more overhead.
140 */
141 if (tp_vec_nr > 0) {
142 int prev = tp_vec_nr - 1;
143 struct text_poke_loc *prev_tp = &tp_vec[prev];
144
145 if (WARN_ON_ONCE(prev_tp->addr > entry_code))
146 return false;
147 }
148
149 __jump_label_set_jump_code(entry, type,
150 (union jump_code_union *) &tp->opcode, 0);
151
152 tp->addr = entry_code;
153 tp->detour = entry_code + JUMP_LABEL_NOP_SIZE;
154 tp->len = JUMP_LABEL_NOP_SIZE;
155
156 tp_vec_nr++;
157
158 return true;
159}
160
161void arch_jump_label_transform_apply(void)
162{
163 if (!tp_vec_nr)
164 return;
165
166 mutex_lock(&text_mutex);
167 text_poke_bp_batch(tp_vec, tp_vec_nr);
168 mutex_unlock(&text_mutex);
169
170 tp_vec_nr = 0;
171}
172
173static enum {
174 JL_STATE_START,
175 JL_STATE_NO_UPDATE,
176 JL_STATE_UPDATE,
177} jlstate __initdata_or_module = JL_STATE_START;
178
179__init_or_module void arch_jump_label_transform_static(struct jump_entry *entry,
180 enum jump_label_type type)
181{
182 /*
183 * This function is called at boot up and when modules are
184 * first loaded. Check if the default nop, the one that is
185 * inserted at compile time, is the ideal nop. If it is, then
186 * we do not need to update the nop, and we can leave it as is.
187 * If it is not, then we need to update the nop to the ideal nop.
188 */
189 if (jlstate == JL_STATE_START) {
190 const unsigned char default_nop[] = { STATIC_KEY_INIT_NOP };
191 const unsigned char *ideal_nop = ideal_nops[NOP_ATOMIC5];
192
193 if (memcmp(ideal_nop, default_nop, 5) != 0)
194 jlstate = JL_STATE_UPDATE;
195 else
196 jlstate = JL_STATE_NO_UPDATE;
197 }
198 if (jlstate == JL_STATE_UPDATE)
199 __jump_label_transform(entry, type, 1);
200}
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