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git.proxmox.com Git - mirror_ubuntu-jammy-kernel.git/blob - lib/buildid.c
1 // SPDX-License-Identifier: GPL-2.0
3 #include <linux/buildid.h>
4 #include <linux/cache.h>
6 #include <linux/kernel.h>
7 #include <linux/pagemap.h>
12 * Parse build id from the note segment. This logic can be shared between
13 * 32-bit and 64-bit system, because Elf32_Nhdr and Elf64_Nhdr are
16 static int parse_build_id_buf(unsigned char *build_id
,
18 const void *note_start
,
21 Elf32_Word note_offs
= 0, new_offs
;
23 while (note_offs
+ sizeof(Elf32_Nhdr
) < note_size
) {
24 Elf32_Nhdr
*nhdr
= (Elf32_Nhdr
*)(note_start
+ note_offs
);
26 if (nhdr
->n_type
== BUILD_ID
&&
27 nhdr
->n_namesz
== sizeof("GNU") &&
28 !strcmp((char *)(nhdr
+ 1), "GNU") &&
30 nhdr
->n_descsz
<= BUILD_ID_SIZE_MAX
) {
32 note_start
+ note_offs
+
33 ALIGN(sizeof("GNU"), 4) + sizeof(Elf32_Nhdr
),
35 memset(build_id
+ nhdr
->n_descsz
, 0,
36 BUILD_ID_SIZE_MAX
- nhdr
->n_descsz
);
38 *size
= nhdr
->n_descsz
;
41 new_offs
= note_offs
+ sizeof(Elf32_Nhdr
) +
42 ALIGN(nhdr
->n_namesz
, 4) + ALIGN(nhdr
->n_descsz
, 4);
43 if (new_offs
<= note_offs
) /* overflow */
51 static inline int parse_build_id(const void *page_addr
,
52 unsigned char *build_id
,
54 const void *note_start
,
57 /* check for overflow */
58 if (note_start
< page_addr
|| note_start
+ note_size
< note_start
)
61 /* only supports note that fits in the first page */
62 if (note_start
+ note_size
> page_addr
+ PAGE_SIZE
)
65 return parse_build_id_buf(build_id
, size
, note_start
, note_size
);
68 /* Parse build ID from 32-bit ELF */
69 static int get_build_id_32(const void *page_addr
, unsigned char *build_id
,
72 Elf32_Ehdr
*ehdr
= (Elf32_Ehdr
*)page_addr
;
76 /* only supports phdr that fits in one page */
78 (PAGE_SIZE
- sizeof(Elf32_Ehdr
)) / sizeof(Elf32_Phdr
))
81 phdr
= (Elf32_Phdr
*)(page_addr
+ sizeof(Elf32_Ehdr
));
83 for (i
= 0; i
< ehdr
->e_phnum
; ++i
) {
84 if (phdr
[i
].p_type
== PT_NOTE
&&
85 !parse_build_id(page_addr
, build_id
, size
,
86 page_addr
+ phdr
[i
].p_offset
,
93 /* Parse build ID from 64-bit ELF */
94 static int get_build_id_64(const void *page_addr
, unsigned char *build_id
,
97 Elf64_Ehdr
*ehdr
= (Elf64_Ehdr
*)page_addr
;
101 /* only supports phdr that fits in one page */
103 (PAGE_SIZE
- sizeof(Elf64_Ehdr
)) / sizeof(Elf64_Phdr
))
106 phdr
= (Elf64_Phdr
*)(page_addr
+ sizeof(Elf64_Ehdr
));
108 for (i
= 0; i
< ehdr
->e_phnum
; ++i
) {
109 if (phdr
[i
].p_type
== PT_NOTE
&&
110 !parse_build_id(page_addr
, build_id
, size
,
111 page_addr
+ phdr
[i
].p_offset
,
119 * Parse build ID of ELF file mapped to vma
121 * @build_id: buffer to store build id, at least BUILD_ID_SIZE long
122 * @size: returns actual build id size in case of success
124 * Return: 0 on success, -EINVAL otherwise
126 int build_id_parse(struct vm_area_struct
*vma
, unsigned char *build_id
,
134 /* only works for page backed storage */
138 page
= find_get_page(vma
->vm_file
->f_mapping
, 0);
140 return -EFAULT
; /* page not mapped */
143 page_addr
= kmap_atomic(page
);
144 ehdr
= (Elf32_Ehdr
*)page_addr
;
146 /* compare magic x7f "ELF" */
147 if (memcmp(ehdr
->e_ident
, ELFMAG
, SELFMAG
) != 0)
150 /* only support executable file and shared object file */
151 if (ehdr
->e_type
!= ET_EXEC
&& ehdr
->e_type
!= ET_DYN
)
154 if (ehdr
->e_ident
[EI_CLASS
] == ELFCLASS32
)
155 ret
= get_build_id_32(page_addr
, build_id
, size
);
156 else if (ehdr
->e_ident
[EI_CLASS
] == ELFCLASS64
)
157 ret
= get_build_id_64(page_addr
, build_id
, size
);
159 kunmap_atomic(page_addr
);
165 * build_id_parse_buf - Get build ID from a buffer
166 * @buf: Elf note section(s) to parse
167 * @buf_size: Size of @buf in bytes
168 * @build_id: Build ID parsed from @buf, at least BUILD_ID_SIZE_MAX long
170 * Return: 0 on success, -EINVAL otherwise
172 int build_id_parse_buf(const void *buf
, unsigned char *build_id
, u32 buf_size
)
174 return parse_build_id_buf(build_id
, NULL
, buf
, buf_size
);
177 #if IS_ENABLED(CONFIG_STACKTRACE_BUILD_ID) || IS_ENABLED(CONFIG_CRASH_CORE)
178 unsigned char vmlinux_build_id
[BUILD_ID_SIZE_MAX
] __ro_after_init
;
181 * init_vmlinux_build_id - Compute and stash the running kernel's build ID
183 void __init
init_vmlinux_build_id(void)
185 extern const void __start_notes __weak
;
186 extern const void __stop_notes __weak
;
187 unsigned int size
= &__stop_notes
- &__start_notes
;
189 build_id_parse_buf(&__start_notes
, vmlinux_build_id
, size
);