OpenWrt – Rev 4
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/*
* mkbrnimg.c - partially based on OpenWrt's wndr3700.c
*
* Copyright (C) 2011 Tobias Diedrich <ranma+openwrt@tdiedrich.de>
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License,
* version 2 as published by the Free Software Foundation.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to the Free Software
* Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
*/
#include <stdio.h>
#include <stdlib.h>
#include <stddef.h>
#include <unistd.h>
#include <errno.h>
#include <fcntl.h>
#include <sys/mman.h>
#include <string.h>
#include <netinet/in.h>
#include <inttypes.h>
#define BPB 8 /* bits/byte */
static uint32_t crc32[1<<BPB];
static char *output_file = "default-brnImage";
static uint32_t magic = 0x12345678;
static char *signature = "BRNDTW502";
static uint32_t crc32_poly = 0x2083b8ed;
static void init_crc32()
{
const uint32_t poly = ntohl(crc32_poly);
int n;
for (n = 0; n < 1<<BPB; n++) {
uint32_t crc = n;
int bit;
for (bit = 0; bit < BPB; bit++)
crc = (crc & 1) ? (poly ^ (crc >> 1)) : (crc >> 1);
crc32[n] = crc;
}
}
static uint32_t crc32buf(unsigned char *buf, size_t len)
{
uint32_t crc = 0xFFFFFFFF;
for (; len; len--, buf++)
crc = crc32[(uint8_t)crc ^ *buf] ^ (crc >> BPB);
return ~crc;
}
static void usage(const char *) __attribute__ (( __noreturn__ ));
static void usage(const char *mess)
{
fprintf(stderr, "Error: %s\n", mess);
fprintf(stderr, "Usage: mkbrnimg [-o output_file] [-m magic] [-s signature] [-p crc32 poly] kernel_file [additional files]\n");
fprintf(stderr, "\n");
exit(1);
}
static void parseopts(int *argc, char ***argv)
{
char *endptr;
int res;
while ((res = getopt(*argc, *argv, "o:m:s:p:")) != -1) {
switch (res) {
default:
usage("Unknown option");
break;
case 'o':
output_file = optarg;
break;
case 'm':
magic = strtoul(optarg, &endptr, 0);
if (endptr == optarg || *endptr != 0)
usage("magic must be a decimal or hexadecimal 32-bit value");
break;
case 's':
signature = optarg;
break;
case 'p':
crc32_poly = strtoul(optarg, &endptr, 0);
if (endptr == optarg || *endptr != 0)
usage("'crc32 poly' must be a decimal or hexadecimal 32-bit value");
break;
}
}
*argc -= optind;
*argv += optind;
}
static void appendfile(int outfd, char *path, int kernel) {
int fd;
size_t len, padded_len;
char *input_file;
uint32_t crc;
char padding[0x400];
char footer[12];
memset(padding, 0xff, sizeof(padding));
// mmap input_file
if ((fd = open(path, O_RDONLY)) < 0
|| (len = lseek(fd, 0, SEEK_END)) < 0
|| (input_file = mmap(0, len, PROT_READ, MAP_SHARED, fd, 0)) == (void *) (-1)
|| close(fd) < 0)
{
fprintf(stderr, "Error mapping file '%s': %s\n", path, strerror(errno));
exit(1);
}
// kernel should be lzma compressed image, not uImage
if (kernel &&
(input_file[0] != (char)0x5d ||
input_file[1] != (char)0x00 ||
input_file[2] != (char)0x00 ||
input_file[3] != (char)0x80)) {
fprintf(stderr, "lzma signature not found on kernel image.\n");
exit(1);
}
init_crc32();
crc = crc32buf(input_file, len);
fprintf(stderr, "crc32 for '%s' is %08x.\n", path, crc);
// write the file
write(outfd, input_file, len);
// write padding
padded_len = ((len + sizeof(footer) + sizeof(padding) - 1) & ~(sizeof(padding) - 1)) - sizeof(footer);
fprintf(stderr, "len=%08zx padded_len=%08zx\n", len, padded_len);
write(outfd, padding, padded_len - len);
// write footer
footer[0] = (len >> 0) & 0xff;
footer[1] = (len >> 8) & 0xff;
footer[2] = (len >> 16) & 0xff;
footer[3] = (len >> 24) & 0xff;
footer[4] = (magic >> 0) & 0xff;
footer[5] = (magic >> 8) & 0xff;
footer[6] = (magic >> 16) & 0xff;
footer[7] = (magic >> 24) & 0xff;
footer[8] = (crc >> 0) & 0xff;
footer[9] = (crc >> 8) & 0xff;
footer[10] = (crc >> 16) & 0xff;
footer[11] = (crc >> 24) & 0xff;
write(outfd, footer, sizeof(footer));
munmap(input_file, len);
}
int main(int argc, char **argv)
{
int outfd;
int i;
parseopts(&argc, &argv);
if (argc < 1)
usage("wrong number of arguments");
if ((outfd = open(output_file, O_WRONLY|O_CREAT|O_TRUNC, 0644)) == -1)
{
fprintf(stderr, "Error opening '%s' for writing: %s\n", output_file, strerror(errno));
exit(1);
}
for (i=0; i<argc; i++) {
appendfile(outfd, argv[i], i == 0);
}
write(outfd, signature, strlen(signature)+1);
close(outfd);
return 0;
}