pil-squasher.c

// SPDX-License-Identifier: BSD-3-Clause
/*
 * Copyright (c) 2019, Linaro Ltd. All rights reserved.
 */
#include <err.h>
#include <stdlib.h>
#include <string.h>
#include <stdio.h>
#include <stdbool.h>
#include <fcntl.h>
#include <unistd.h>
#include <elf.h>

static void usage(void)
{
	extern const char *__progname;

	fprintf(stderr, "%s: <mbn output> <mdt header>\n", __progname);
	exit(1);
}

int main(int argc, char **argv)
{
	unsigned char e_ident[EI_NIDENT];
	unsigned int phnum;
	size_t phoff;
	bool is_64bit;
	size_t offset;
	size_t hashoffset;
	void *segment;
	ssize_t n;
	char *ext;
	int mdt;
	int mbn;
	int bxx;
	int i;

	if (argc != 3)
		usage();

	ext = strstr(argv[2], ".mdt");
	if (!ext)
		errx(1, "%s is not a mdt file\n", argv[2]);

	mbn = open(argv[1], O_WRONLY | O_CREAT | O_TRUNC, 0644);
	if (mbn < 0)
		err(1, "failed to open %s", argv[1]);

	mdt = open(argv[2], O_RDONLY);
	if (mdt < 0)
		err(1, "failed to open %s", argv[2]);

	read(mdt, e_ident, sizeof(e_ident));
	if (memcmp(e_ident, ELFMAG, SELFMAG))
		errx(1, "not an ELF file %s", argv[2]);

	if (e_ident[EI_CLASS] == ELFCLASS32) {
		Elf32_Ehdr ehdr;
		Elf32_Phdr phdr;

		is_64bit = false;
		pread(mdt, &ehdr, sizeof(ehdr), 0);
		pwrite(mbn, &ehdr, sizeof(ehdr), 0);
		phoff = ehdr.e_phoff;
		phnum = ehdr.e_phnum;

		pread(mdt, &phdr, sizeof(phdr), phoff);
		hashoffset = phdr.p_filesz;
	} else if (e_ident[EI_CLASS] == ELFCLASS64) {
		Elf64_Ehdr ehdr;
		Elf64_Phdr phdr;

		is_64bit = true;
		pread(mdt, &ehdr, sizeof(ehdr), 0);
		pwrite(mbn, &ehdr, sizeof(ehdr), 0);
		phoff = ehdr.e_phoff;
		phnum = ehdr.e_phnum;

		pread(mdt, &phdr, sizeof(phdr), phoff);
		hashoffset = phdr.p_filesz;
	} else
		errx(1, "Unsupported ELF class %d\n", e_ident[EI_CLASS]);

	for (i = 0; i < phnum; i++) {
		size_t p_filesz, p_offset;
		unsigned long p_flags;

		if (is_64bit) {
			Elf64_Phdr phdr;

			offset = phoff + i * sizeof(phdr);

			pread(mdt, &phdr, sizeof(phdr), offset);
			pwrite(mbn, &phdr, sizeof(phdr), offset);
			p_offset = phdr.p_offset;
			p_filesz = phdr.p_filesz;
			p_flags = phdr.p_flags;
		} else {
			Elf32_Phdr phdr;
			size_t offset;

			offset = phoff + i * sizeof(phdr);

			pread(mdt, &phdr, sizeof(phdr), offset);
			pwrite(mbn, &phdr, sizeof(phdr), offset);
			p_offset = phdr.p_offset;
			p_filesz = phdr.p_filesz;
			p_flags = phdr.p_flags;
		}

		if (!p_filesz)
			continue;

		segment = malloc(p_filesz);

		/*
		 * Attempt to read the hash chunk (type 2) directly following
		 * the ELF header in the mdt, rather than the one stored in b%02d
		 */
		n = 0;
		if (((p_flags >> 24) & 7) == 2) {
			n = pread(mdt, segment, p_filesz, hashoffset);
			hashoffset += p_filesz;
			if (n && n != p_filesz)
				errx(1, "failed to load segment %d: %zd\n", i, n);
		}

		if (n == 0) {
			sprintf(ext, ".b%02d", i);

			bxx = open(argv[2], O_RDONLY);
			if (bxx < 0)
				warn("failed to open %s", argv[2]);

			read(bxx, segment, p_filesz);

			close(bxx);
		}
		pwrite(mbn, segment, p_filesz, p_offset);

		free(segment);
	}

	close(mdt);
	close(mbn);

	return 0;
}