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);