// 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