1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
|
// SPDX-License-Identifier: GPL-2.0-or-later
/*
* Copyright (C) 2015 Josh Poimboeuf <jpoimboe@redhat.com>
*/
/*
* This file reads all the special sections which have alternate instructions
* which can be patched in or redirected to at runtime.
*/
#include <stdlib.h>
#include <string.h>
#include <arch/special.h>
#include <objtool/builtin.h>
#include <objtool/special.h>
#include <objtool/warn.h>
#include <objtool/endianness.h>
struct special_entry {
const char *sec;
bool group, jump_or_nop;
unsigned char size, orig, new;
unsigned char orig_len, new_len; /* group only */
unsigned char feature; /* ALTERNATIVE macro CPU feature */
unsigned char key; /* jump_label key */
};
static const struct special_entry entries[] = {
{
.sec = ".altinstructions",
.group = true,
.size = ALT_ENTRY_SIZE,
.orig = ALT_ORIG_OFFSET,
.orig_len = ALT_ORIG_LEN_OFFSET,
.new = ALT_NEW_OFFSET,
.new_len = ALT_NEW_LEN_OFFSET,
.feature = ALT_FEATURE_OFFSET,
},
{
.sec = "__jump_table",
.jump_or_nop = true,
.size = JUMP_ENTRY_SIZE,
.orig = JUMP_ORIG_OFFSET,
.new = JUMP_NEW_OFFSET,
.key = JUMP_KEY_OFFSET,
},
{
.sec = "__ex_table",
.size = EX_ENTRY_SIZE,
.orig = EX_ORIG_OFFSET,
.new = EX_NEW_OFFSET,
},
{},
};
void __weak arch_handle_alternative(unsigned short feature, struct special_alt *alt)
{
}
static void reloc_to_sec_off(struct reloc *reloc, struct section **sec,
unsigned long *off)
{
*sec = reloc->sym->sec;
*off = reloc->sym->offset + reloc->addend;
}
static int get_alt_entry(struct elf *elf, const struct special_entry *entry,
struct section *sec, int idx,
struct special_alt *alt)
{
struct reloc *orig_reloc, *new_reloc;
unsigned long offset;
offset = idx * entry->size;
alt->group = entry->group;
alt->jump_or_nop = entry->jump_or_nop;
if (alt->group) {
alt->orig_len = *(unsigned char *)(sec->data->d_buf + offset +
entry->orig_len);
alt->new_len = *(unsigned char *)(sec->data->d_buf + offset +
entry->new_len);
}
if (entry->feature) {
unsigned short feature;
feature = bswap_if_needed(elf,
*(unsigned short *)(sec->data->d_buf +
offset +
entry->feature));
arch_handle_alternative(feature, alt);
}
orig_reloc = find_reloc_by_dest(elf, sec, offset + entry->orig);
if (!orig_reloc) {
WARN_FUNC("can't find orig reloc", sec, offset + entry->orig);
return -1;
}
reloc_to_sec_off(orig_reloc, &alt->orig_sec, &alt->orig_off);
if (!entry->group || alt->new_len) {
new_reloc = find_reloc_by_dest(elf, sec, offset + entry->new);
if (!new_reloc) {
WARN_FUNC("can't find new reloc",
sec, offset + entry->new);
return -1;
}
reloc_to_sec_off(new_reloc, &alt->new_sec, &alt->new_off);
/* _ASM_EXTABLE_EX hack */
if (alt->new_off >= 0x7ffffff0)
alt->new_off -= 0x7ffffff0;
}
if (entry->key) {
struct reloc *key_reloc;
key_reloc = find_reloc_by_dest(elf, sec, offset + entry->key);
if (!key_reloc) {
WARN_FUNC("can't find key reloc",
sec, offset + entry->key);
return -1;
}
alt->key_addend = key_reloc->addend;
}
return 0;
}
/*
* Read all the special sections and create a list of special_alt structs which
* describe all the alternate instructions which can be patched in or
* redirected to at runtime.
*/
int special_get_alts(struct elf *elf, struct list_head *alts)
{
const struct special_entry *entry;
struct section *sec;
unsigned int nr_entries;
struct special_alt *alt;
int idx, ret;
INIT_LIST_HEAD(alts);
for (entry = entries; entry->sec; entry++) {
sec = find_section_by_name(elf, entry->sec);
if (!sec)
continue;
if (sec->sh.sh_size % entry->size != 0) {
WARN("%s size not a multiple of %d",
sec->name, entry->size);
return -1;
}
nr_entries = sec->sh.sh_size / entry->size;
for (idx = 0; idx < nr_entries; idx++) {
alt = malloc(sizeof(*alt));
if (!alt) {
WARN("malloc failed");
return -1;
}
memset(alt, 0, sizeof(*alt));
ret = get_alt_entry(elf, entry, sec, idx, alt);
if (ret > 0)
continue;
if (ret < 0)
return ret;
list_add_tail(&alt->list, alts);
}
}
return 0;
}
|
