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/* SPDX-License-Identifier: GPL-2.0-only */
/*
* MTD splitter for ELF loader firmware partitions
*
* Copyright (C) 2020 Sander Vanheule <sander@svanheule.net>
*
* This program is free software; you can redistribute it and/or modify it
* under the terms of the GNU General Public License as published by the Free
* Software Foundation; version 2.
*
* To parse the ELF kernel loader, a small ELF parser is used that can
* handle both ELF32 or ELF64 class loaders. The splitter assumes that the
* kernel is always located before the rootfs, whether it is embedded in the
* loader or not.
*
* The kernel image is preferably embedded inside the ELF loader, so the end
* of the loader equals the end of the kernel partition. This is due to the
* way mtd_find_rootfs_from searches for the the rootfs:
* - if the kernel image is embedded in the loader, the appended rootfs may
* follow the loader immediately, within the same erase block.
* - if the kernel image is not embedded in the loader, but placed at some
* offset behind the loader (OKLI-style loader), the rootfs must be
* aligned to an erase-block after the loader and kernel image.
*/
#include <linux/module.h>
#include <linux/init.h>
#include <linux/kernel.h>
#include <linux/slab.h>
#include <linux/mtd/mtd.h>
#include <linux/mtd/partitions.h>
#include <linux/of.h>
#include <linux/byteorder/generic.h>
#include "mtdsplit.h"
#define ELF_NR_PARTS 2
#define ELF_MAGIC 0x7f454c46 /* 0x7f E L F */
#define ELF_CLASS_32 1
#define ELF_CLASS_64 2
struct elf_header_ident {
uint32_t magic;
uint8_t class;
uint8_t data;
uint8_t version;
uint8_t osabi;
uint8_t abiversion;
uint8_t pad[7];
};
struct elf_header_32 {
uint16_t type;
uint16_t machine;
uint32_t version;
uint32_t entry;
uint32_t phoff;
uint32_t shoff;
uint32_t flags;
uint16_t ehsize;
uint16_t phentsize;
uint16_t phnum;
uint16_t shentsize;
uint16_t shnum;
uint16_t shstrndx;
};
struct elf_header_64 {
uint16_t type;
uint16_t machine;
uint32_t version;
uint64_t entry;
uint64_t phoff;
uint64_t shoff;
uint32_t flags;
uint16_t ehsize;
uint16_t phentsize;
uint16_t phnum;
uint16_t shentsize;
uint16_t shnum;
uint16_t shstrndx;
};
struct elf_header {
struct elf_header_ident ident;
union {
struct elf_header_32 elf32;
struct elf_header_64 elf64;
};
};
struct elf_program_header_32 {
uint32_t type;
uint32_t offset;
uint32_t vaddr;
uint32_t paddr;
uint32_t filesize;
uint32_t memsize;
uint32_t flags;
};
struct elf_program_header_64 {
uint32_t type;
uint32_t flags;
uint64_t offset;
uint64_t vaddr;
uint64_t paddr;
uint64_t filesize;
uint64_t memsize;
};
static int mtdsplit_elf_read_mtd(struct mtd_info *mtd, size_t offset,
uint8_t *dst, size_t len)
{
size_t retlen;
int ret;
ret = mtd_read(mtd, offset, len, &retlen, dst);
if (ret) {
pr_debug("read error in \"%s\"\n", mtd->name);
return ret;
}
if (retlen != len) {
pr_debug("short read in \"%s\"\n", mtd->name);
return -EIO;
}
return 0;
}
static int elf32_determine_size(struct mtd_info *mtd, struct elf_header *hdr,
size_t *size)
{
struct elf_header_32 *hdr32 = &(hdr->elf32);
int err;
size_t section_end, ph_table_end, ph_entry;
struct elf_program_header_32 ph;
*size = 0;
if (hdr32->shoff > 0) {
*size = hdr32->shoff + hdr32->shentsize * hdr32->shnum;
return 0;
}
ph_entry = hdr32->phoff;
ph_table_end = hdr32->phoff + hdr32->phentsize * hdr32->phnum;
while (ph_entry < ph_table_end) {
err = mtdsplit_elf_read_mtd(mtd, ph_entry, (uint8_t *)(&ph),
sizeof(ph));
if (err)
return err;
section_end = ph.offset + ph.filesize;
if (section_end > *size)
*size = section_end;
ph_entry += hdr32->phentsize;
}
return 0;
}
static int elf64_determine_size(struct mtd_info *mtd, struct elf_header *hdr,
size_t *size)
{
struct elf_header_64 *hdr64 = &(hdr->elf64);
int err;
size_t section_end, ph_table_end, ph_entry;
struct elf_program_header_64 ph;
*size = 0;
if (hdr64->shoff > 0) {
*size = hdr64->shoff + hdr64->shentsize * hdr64->shnum;
return 0;
}
ph_entry = hdr64->phoff;
ph_table_end = hdr64->phoff + hdr64->phentsize * hdr64->phnum;
while (ph_entry < ph_table_end) {
err = mtdsplit_elf_read_mtd(mtd, ph_entry, (uint8_t *)(&ph),
sizeof(ph));
if (err)
return err;
section_end = ph.offset + ph.filesize;
if (section_end > *size)
*size = section_end;
ph_entry += hdr64->phentsize;
}
return 0;
}
static int mtdsplit_parse_elf(struct mtd_info *mtd,
const struct mtd_partition **pparts,
struct mtd_part_parser_data *data)
{
struct elf_header hdr;
size_t loader_size, rootfs_offset;
enum mtdsplit_part_type type;
struct mtd_partition *parts;
int err;
err = mtdsplit_elf_read_mtd(mtd, 0, (uint8_t *)&hdr, sizeof(hdr));
if (err)
return err;
if (be32_to_cpu(hdr.ident.magic) != ELF_MAGIC) {
pr_debug("invalid ELF magic %08x\n",
be32_to_cpu(hdr.ident.magic));
return -EINVAL;
}
switch (hdr.ident.class) {
case ELF_CLASS_32:
err = elf32_determine_size(mtd, &hdr, &loader_size);
break;
case ELF_CLASS_64:
err = elf64_determine_size(mtd, &hdr, &loader_size);
break;
default:
pr_debug("invalid ELF class %i\n", hdr.ident.class);
err = -EINVAL;
}
if (err)
return err;
err = mtd_find_rootfs_from(mtd, loader_size, mtd->size,
&rootfs_offset, &type);
if (err)
return err;
if (rootfs_offset == mtd->size) {
pr_debug("no rootfs found in \"%s\"\n", mtd->name);
return -ENODEV;
}
parts = kzalloc(ELF_NR_PARTS * sizeof(*parts), GFP_KERNEL);
if (!parts)
return -ENOMEM;
parts[0].name = KERNEL_PART_NAME;
parts[0].offset = 0;
parts[0].size = rootfs_offset;
if (type == MTDSPLIT_PART_TYPE_UBI)
parts[1].name = UBI_PART_NAME;
else
parts[1].name = ROOTFS_PART_NAME;
parts[1].offset = rootfs_offset;
parts[1].size = mtd->size - rootfs_offset;
*pparts = parts;
return ELF_NR_PARTS;
}
static const struct of_device_id mtdsplit_elf_of_match_table[] = {
{ .compatible = "openwrt,elf" },
{},
};
MODULE_DEVICE_TABLE(of, mtdsplit_elf_of_match_table);
static struct mtd_part_parser mtdsplit_elf_parser = {
.owner = THIS_MODULE,
.name = "elf-loader-fw",
.of_match_table = mtdsplit_elf_of_match_table,
.parse_fn = mtdsplit_parse_elf,
.type = MTD_PARSER_TYPE_FIRMWARE,
};
static int __init mtdsplit_elf_init(void)
{
register_mtd_parser(&mtdsplit_elf_parser);
return 0;
}
subsys_initcall(mtdsplit_elf_init);
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