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// SPDX-License-Identifier: GPL-2.0-only
/*
* add_header.c - partially based on OpenWrt's motorola-bin.c
*
* Copyright (C) 2008 Imre Kaloz <kaloz@openwrt.org>
* Gabor Juhos <juhosg@openwrt.org>
*/
/*
* The add_header utility used by various vendors preprends the buf
* image with a header containing a CRC32 value which is generated for the
* model id + reserved space for CRC32 + buf, then replaces the reserved
* area with the actual CRC32. This replacement tool mimics this behavior.
*/
#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 void init_crc32()
{
const uint32_t poly = ntohl(0x2083b8ed);
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;
}
struct header {
char model[16];
uint32_t crc;
};
static void usage(const char *) __attribute__ (( __noreturn__ ));
static void usage(const char *mess)
{
fprintf(stderr, "Error: %s\n", mess);
fprintf(stderr, "Usage: add_header model_id input_file output_file\n");
fprintf(stderr, "\n");
exit(1);
}
int main(int argc, char **argv)
{
off_t len; // of original buf
off_t buflen; // of the output file
int fd;
void *input_file; // pointer to the input file (mmmapped)
struct header header;
unsigned char *buf; // pointer to prefix + copy of original buf
// verify parameters
if (argc != 4)
usage("wrong number of arguments");
// mmap input_file
if ((fd = open(argv[2], 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 loading file %s: %s\n", argv[2], strerror(errno));
exit(1);
}
buflen = len + sizeof(header);
init_crc32();
// copy model name into header
strncpy(header.model, argv[1], sizeof(header.model));
header.crc = 0;
// create a firmware image in memory and copy the input_file to it
buf = malloc(buflen);
memcpy(buf, &header, sizeof(header));
memcpy(&buf[sizeof(header)], input_file, len);
// CRC of temporary header + buf
header.crc = htonl(crc32buf(buf, buflen));
memcpy(buf, &header, sizeof(header));
// write the buf
if ((fd = open(argv[3], O_CREAT|O_WRONLY|O_TRUNC,0644)) < 0
|| write(fd, buf, buflen) != buflen
|| close(fd) < 0)
{
fprintf(stderr, "Error storing file %s: %s\n", argv[3], strerror(errno));
exit(2);
}
free(buf);
munmap(input_file,len);
return 0;
}
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