1/*
2 * add_header.c - partially based on OpenWrt's motorola-bin.c
3 *
4 * Copyright (C) 2008 Imre Kaloz  <kaloz@openwrt.org>
5 *                    Gabor Juhos <juhosg@openwrt.org>
6 *
7 * This program is free software; you can redistribute it and/or
8 * modify it under the terms of the GNU General Public License,
9 * version 2 as published by the Free Software Foundation.
10 *
11 * This program is distributed in the hope that it will be useful,
12 * but WITHOUT ANY WARRANTY; without even the implied warranty of
13 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
14 * GNU General Public License for more details.
15 *
16 * You should have received a copy of the GNU General Public License
17 * along with this program; if not, write to the Free Software
18 * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.
19 */
20
21/*
22 * The add_header utility used by various vendors preprends the buf
23 * image with a header containing a CRC32 value which is generated for the
24 * model id + reserved space for CRC32 + buf, then replaces the reserved
25 * area with the actual CRC32. This replacement tool mimics this behavior.
26 */
27
28#include <stdio.h>
29#include <stdlib.h>
30#include <stddef.h>
31#include <unistd.h>
32#include <errno.h>
33#include <fcntl.h>
34#include <sys/mman.h>
35#include <string.h>
36#include <netinet/in.h>
37#include <inttypes.h>
38
39#define BPB 8 /* bits/byte */
40
41static uint32_t crc32[1<<BPB];
42
43static void init_crc32()
44{
45	const uint32_t poly = ntohl(0x2083b8ed);
46	int n;
47
48	for (n = 0; n < 1<<BPB; n++) {
49		uint32_t crc = n;
50		int bit;
51
52		for (bit = 0; bit < BPB; bit++)
53			crc = (crc & 1) ? (poly ^ (crc >> 1)) : (crc >> 1);
54		crc32[n] = crc;
55	}
56}
57
58static uint32_t crc32buf(unsigned char *buf, size_t len)
59{
60	uint32_t crc = 0xFFFFFFFF;
61
62	for (; len; len--, buf++)
63		crc = crc32[(uint8_t)crc ^ *buf] ^ (crc >> BPB);
64	return ~crc;
65}
66
67struct header {
68	unsigned char model[16];
69	uint32_t crc;
70};
71
72static void usage(const char *) __attribute__ (( __noreturn__ ));
73
74static void usage(const char *mess)
75{
76	fprintf(stderr, "Error: %s\n", mess);
77	fprintf(stderr, "Usage: add_header model_id input_file output_file\n");
78	fprintf(stderr, "\n");
79	exit(1);
80}
81
82int main(int argc, char **argv)
83{
84	off_t len;			// of original buf
85	off_t buflen;			// of the output file
86	int fd;
87	void *input_file;		// pointer to the input file (mmmapped)
88	struct header header;
89	unsigned char *buf;	// pointer to prefix + copy of original buf
90
91	// verify parameters
92
93	if (argc != 4)
94		usage("wrong number of arguments");
95
96	// mmap input_file
97	if ((fd = open(argv[2], O_RDONLY))  < 0
98	|| (len = lseek(fd, 0, SEEK_END)) < 0
99	|| (input_file = mmap(0, len, PROT_READ, MAP_SHARED, fd, 0)) == (void *) (-1)
100	|| close(fd) < 0)
101	{
102		fprintf(stderr, "Error loading file %s: %s\n", argv[2], strerror(errno));
103		exit(1);
104	}
105
106	buflen = len + sizeof(header);
107
108	init_crc32();
109
110	// copy model name into header
111	strncpy(header.model, argv[1], sizeof(header.model));
112	header.crc = 0;
113
114	// create a firmware image in memory and copy the input_file to it
115	buf = malloc(buflen);
116	memcpy(buf, &header, sizeof(header));
117	memcpy(&buf[sizeof(header)], input_file, len);
118
119	// CRC of temporary header + buf
120	header.crc = htonl(crc32buf(buf, buflen));
121
122	memcpy(buf, &header, sizeof(header));
123
124	// write the buf
125	if ((fd = open(argv[3], O_CREAT|O_WRONLY|O_TRUNC,0644)) < 0
126	|| write(fd, buf, buflen) != buflen
127	|| close(fd) < 0)
128	{
129		fprintf(stderr, "Error storing file %s: %s\n", argv[3], strerror(errno));
130		exit(2);
131 	}
132
133	free(buf);
134
135	munmap(input_file,len);
136
137	return 0;
138}
139