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Diffstat (limited to '')
| -rw-r--r-- | lib/buildid.c | 191 |
1 files changed, 191 insertions, 0 deletions
diff --git a/lib/buildid.c b/lib/buildid.c new file mode 100644 index 000000000..dfc62625c --- /dev/null +++ b/lib/buildid.c @@ -0,0 +1,191 @@ +// 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 |