150 строки
3.8 KiB
C
150 строки
3.8 KiB
C
// SPDX-License-Identifier: GPL-2.0
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#include <linux/buildid.h>
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#include <linux/elf.h>
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#include <linux/pagemap.h>
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#define BUILD_ID 3
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/*
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* Parse build id from the note segment. This logic can be shared between
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* 32-bit and 64-bit system, because Elf32_Nhdr and Elf64_Nhdr are
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* identical.
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*/
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static inline int parse_build_id(void *page_addr,
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unsigned char *build_id,
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__u32 *size,
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void *note_start,
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Elf32_Word note_size)
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{
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Elf32_Word note_offs = 0, new_offs;
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/* check for overflow */
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if (note_start < page_addr || note_start + note_size < note_start)
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return -EINVAL;
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/* only supports note that fits in the first page */
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if (note_start + note_size > page_addr + PAGE_SIZE)
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return -EINVAL;
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while (note_offs + sizeof(Elf32_Nhdr) < note_size) {
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Elf32_Nhdr *nhdr = (Elf32_Nhdr *)(note_start + note_offs);
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if (nhdr->n_type == BUILD_ID &&
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nhdr->n_namesz == sizeof("GNU") &&
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nhdr->n_descsz > 0 &&
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nhdr->n_descsz <= BUILD_ID_SIZE_MAX) {
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memcpy(build_id,
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note_start + note_offs +
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ALIGN(sizeof("GNU"), 4) + sizeof(Elf32_Nhdr),
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nhdr->n_descsz);
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memset(build_id + nhdr->n_descsz, 0,
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BUILD_ID_SIZE_MAX - nhdr->n_descsz);
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if (size)
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*size = nhdr->n_descsz;
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return 0;
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}
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new_offs = note_offs + sizeof(Elf32_Nhdr) +
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ALIGN(nhdr->n_namesz, 4) + ALIGN(nhdr->n_descsz, 4);
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if (new_offs <= note_offs) /* overflow */
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break;
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note_offs = new_offs;
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}
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return -EINVAL;
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}
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/* Parse build ID from 32-bit ELF */
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static int get_build_id_32(void *page_addr, unsigned char *build_id,
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__u32 *size)
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{
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Elf32_Ehdr *ehdr = (Elf32_Ehdr *)page_addr;
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Elf32_Phdr *phdr;
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int i;
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/* only supports phdr that fits in one page */
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if (ehdr->e_phnum >
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(PAGE_SIZE - sizeof(Elf32_Ehdr)) / sizeof(Elf32_Phdr))
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return -EINVAL;
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phdr = (Elf32_Phdr *)(page_addr + sizeof(Elf32_Ehdr));
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for (i = 0; i < ehdr->e_phnum; ++i) {
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if (phdr[i].p_type == PT_NOTE &&
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!parse_build_id(page_addr, build_id, size,
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page_addr + phdr[i].p_offset,
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phdr[i].p_filesz))
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return 0;
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}
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return -EINVAL;
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}
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/* Parse build ID from 64-bit ELF */
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static int get_build_id_64(void *page_addr, unsigned char *build_id,
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__u32 *size)
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{
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Elf64_Ehdr *ehdr = (Elf64_Ehdr *)page_addr;
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Elf64_Phdr *phdr;
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int i;
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/* only supports phdr that fits in one page */
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if (ehdr->e_phnum >
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(PAGE_SIZE - sizeof(Elf64_Ehdr)) / sizeof(Elf64_Phdr))
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return -EINVAL;
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phdr = (Elf64_Phdr *)(page_addr + sizeof(Elf64_Ehdr));
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for (i = 0; i < ehdr->e_phnum; ++i) {
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if (phdr[i].p_type == PT_NOTE &&
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!parse_build_id(page_addr, build_id, size,
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page_addr + phdr[i].p_offset,
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phdr[i].p_filesz))
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return 0;
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}
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return -EINVAL;
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}
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/*
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* Parse build ID of ELF file mapped to vma
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* @vma: vma object
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* @build_id: buffer to store build id, at least BUILD_ID_SIZE long
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* @size: returns actual build id size in case of success
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*
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* Returns 0 on success, otherwise error (< 0).
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*/
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int build_id_parse(struct vm_area_struct *vma, unsigned char *build_id,
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__u32 *size)
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{
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Elf32_Ehdr *ehdr;
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struct page *page;
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void *page_addr;
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int ret;
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/* only works for page backed storage */
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if (!vma->vm_file)
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return -EINVAL;
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page = find_get_page(vma->vm_file->f_mapping, 0);
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if (!page)
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return -EFAULT; /* page not mapped */
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ret = -EINVAL;
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page_addr = kmap_atomic(page);
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ehdr = (Elf32_Ehdr *)page_addr;
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/* compare magic x7f "ELF" */
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if (memcmp(ehdr->e_ident, ELFMAG, SELFMAG) != 0)
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goto out;
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/* only support executable file and shared object file */
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if (ehdr->e_type != ET_EXEC && ehdr->e_type != ET_DYN)
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goto out;
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if (ehdr->e_ident[EI_CLASS] == ELFCLASS32)
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ret = get_build_id_32(page_addr, build_id, size);
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else if (ehdr->e_ident[EI_CLASS] == ELFCLASS64)
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ret = get_build_id_64(page_addr, build_id, size);
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out:
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kunmap_atomic(page_addr);
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put_page(page);
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return ret;
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}
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