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
183
184
185
186
187
188
189
190
191
|
// SPDX-License-Identifier: GPL-2.0
#include <linux/buildid.h>
#include <linux/cache.h>
#include <linux/elf.h>
#include <linux/kernel.h>
#include <linux/pagemap.h>
#define BUILD_ID 3
/*
* Parse build id from the note segment. This logic can be shared between
* 32-bit and 64-bit system, because Elf32_Nhdr and Elf64_Nhdr are
* identical.
*/
static int parse_build_id_buf(unsigned char *build_id,
__u32 *size,
const void *note_start,
Elf32_Word note_size)
{
Elf32_Word note_offs = 0, new_offs;
while (note_offs + sizeof(Elf32_Nhdr) < note_size) {
Elf32_Nhdr *nhdr = (Elf32_Nhdr *)(note_start + note_offs);
if (nhdr->n_type == BUILD_ID &&
nhdr->n_namesz == sizeof("GNU") &&
!strcmp((char *)(nhdr + 1), "GNU") &&
nhdr->n_descsz > 0 &&
nhdr->n_descsz <= BUILD_ID_SIZE_MAX) {
memcpy(build_id,
note_start + note_offs +
ALIGN(sizeof("GNU"), 4) + sizeof(Elf32_Nhdr),
nhdr->n_descsz);
memset(build_id + nhdr->n_descsz, 0,
BUILD_ID_SIZE_MAX - nhdr->n_descsz);
if (size)
*size = nhdr->n_descsz;
return 0;
}
new_offs = note_offs + sizeof(Elf32_Nhdr) +
ALIGN(nhdr->n_namesz, 4) + ALIGN(nhdr->n_descsz, 4);
if (new_offs <= note_offs) /* overflow */
break;
note_offs = new_offs;
}
return -EINVAL;
}
static inline int parse_build_id(const void *page_addr,
unsigned char *build_id,
__u32 *size,
const void *note_start,
Elf32_Word note_size)
{
/* check for overflow */
if (note_start < page_addr || note_start + note_size < note_start)
return -EINVAL;
/* only supports note that fits in the first page */
if (note_start + note_size > page_addr + PAGE_SIZE)
return -EINVAL;
return parse_build_id_buf(build_id, size, note_start, note_size);
}
/* Parse build ID from 32-bit ELF */
static int get_build_id_32(const void *page_addr, unsigned char *build_id,
__u32 *size)
{
Elf32_Ehdr *ehdr = (Elf32_Ehdr *)page_addr;
Elf32_Phdr *phdr;
int i;
/* only supports phdr that fits in one page */
if (ehdr->e_phnum >
(PAGE_SIZE - sizeof(Elf32_Ehdr)) / sizeof(Elf32_Phdr))
return -EINVAL;
phdr = (Elf32_Phdr *)(page_addr + sizeof(Elf32_Ehdr));
for (i = 0; i < ehdr->e_phnum; ++i) {
if (phdr[i].p_type == PT_NOTE &&
!parse_build_id(page_addr, build_id, size,
page_addr + phdr[i].p_offset,
phdr[i].p_filesz))
return 0;
}
return -EINVAL;
}
/* Parse build ID from 64-bit ELF */
static int get_build_id_64(const void *page_addr, unsigned char *build_id,
__u32 *size)
{
Elf64_Ehdr *ehdr = (Elf64_Ehdr *)page_addr;
Elf64_Phdr *phdr;
int i;
/* only supports phdr that fits in one page */
if (ehdr->e_phnum >
(PAGE_SIZE - sizeof(Elf64_Ehdr)) / sizeof(Elf64_Phdr))
return -EINVAL;
phdr = (Elf64_Phdr *)(page_addr + sizeof(Elf64_Ehdr));
for (i = 0; i < ehdr->e_phnum; ++i) {
if (phdr[i].p_type == PT_NOTE &&
!parse_build_id(page_addr, build_id, size,
page_addr + phdr[i].p_offset,
phdr[i].p_filesz))
return 0;
}
return -EINVAL;
}
/*
* Parse build ID of ELF file mapped to vma
* @vma: vma object
* @build_id: buffer to store build id, at least BUILD_ID_SIZE long
* @size: returns actual build id size in case of success
*
* Return: 0 on success, -EINVAL otherwise
*/
int build_id_parse(struct vm_area_struct *vma, unsigned char *build_id,
__u32 *size)
{
Elf32_Ehdr *ehdr;
struct page *page;
void *page_addr;
int ret;
/* only works for page backed storage */
if (!vma->vm_file)
return -EINVAL;
page = find_get_page(vma->vm_file->f_mapping, 0);
if (!page)
return -EFAULT; /* page not mapped */
ret = -EINVAL;
page_addr = kmap_atomic(page);
ehdr = (Elf32_Ehdr *)page_addr;
/* compare magic x7f "ELF" */
if (memcmp(ehdr->e_ident, ELFMAG, SELFMAG) != 0)
goto out;
/* only support executable file and shared object file */
if (ehdr->e_type != ET_EXEC && ehdr->e_type != ET_DYN)
goto out;
if (ehdr->e_ident[EI_CLASS] == ELFCLASS32)
ret = get_build_id_32(page_addr, build_id, size);
else if (ehdr->e_ident[EI_CLASS] == ELFCLASS64)
ret = get_build_id_64(page_addr, build_id, size);
out:
kunmap_atomic(page_addr);
put_page(page);
return ret;
}
/**
* build_id_parse_buf - Get build ID from a buffer
* @buf: Elf note section(s) to parse
* @buf_size: Size of @buf in bytes
* @build_id: Build ID parsed from @buf, at least BUILD_ID_SIZE_MAX long
*
* Return: 0 on success, -EINVAL otherwise
*/
int build_id_parse_buf(const void *buf, unsigned char *build_id, u32 buf_size)
{
return parse_build_id_buf(build_id, NULL, buf, buf_size);
}
#if IS_ENABLED(CONFIG_STACKTRACE_BUILD_ID) || IS_ENABLED(CONFIG_CRASH_CORE)
unsigned char vmlinux_build_id[BUILD_ID_SIZE_MAX] __ro_after_init;
/**
* init_vmlinux_build_id - Compute and stash the running kernel's build ID
*/
void __init init_vmlinux_build_id(void)
{
extern const void __start_notes __weak;
extern const void __stop_notes __weak;
unsigned int size = &__stop_notes - &__start_notes;
build_id_parse_buf(&__start_notes, vmlinux_build_id, size);
}
#endif
|
