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