150 lines
3.8 KiB
C
150 lines
3.8 KiB
C
// SPDX-License-Identifier: GPL-2.0
|
|
|
|
#include <linux/buildid.h>
|
|
#include <linux/elf.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 inline int parse_build_id(void *page_addr,
|
|
unsigned char *build_id,
|
|
__u32 *size,
|
|
void *note_start,
|
|
Elf32_Word note_size)
|
|
{
|
|
Elf32_Word note_offs = 0, new_offs;
|
|
|
|
/* 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;
|
|
|
|
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") &&
|
|
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;
|
|
}
|
|
|
|
/* Parse build ID from 32-bit ELF */
|
|
static int get_build_id_32(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(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
|
|
*
|
|
* Returns 0 on success, otherwise error (< 0).
|
|
*/
|
|
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;
|
|
}
|