1/* 2 * mkbrnimg.c - partially based on OpenWrt's wndr3700.c 3 * 4 * Copyright (C) 2011 Tobias Diedrich <ranma+openwrt@tdiedrich.de> 5 * 6 * This program is free software; you can redistribute it and/or 7 * modify it under the terms of the GNU General Public License, 8 * version 2 as published by the Free Software Foundation. 9 * 10 * This program is distributed in the hope that it will be useful, 11 * but WITHOUT ANY WARRANTY; without even the implied warranty of 12 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 13 * GNU General Public License for more details. 14 * 15 * You should have received a copy of the GNU General Public License 16 * along with this program; if not, write to the Free Software 17 * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA. 18 */ 19 20#include <stdio.h> 21#include <stdlib.h> 22#include <stddef.h> 23#include <unistd.h> 24#include <errno.h> 25#include <fcntl.h> 26#include <sys/mman.h> 27#include <string.h> 28#include <netinet/in.h> 29#include <inttypes.h> 30 31#define BPB 8 /* bits/byte */ 32 33static uint32_t crc32[1<<BPB]; 34 35static void init_crc32() 36{ 37 const uint32_t poly = ntohl(0x2083b8ed); 38 int n; 39 40 for (n = 0; n < 1<<BPB; n++) { 41 uint32_t crc = n; 42 int bit; 43 44 for (bit = 0; bit < BPB; bit++) 45 crc = (crc & 1) ? (poly ^ (crc >> 1)) : (crc >> 1); 46 crc32[n] = crc; 47 } 48} 49 50static uint32_t crc32buf(unsigned char *buf, size_t len) 51{ 52 uint32_t crc = 0xFFFFFFFF; 53 54 for (; len; len--, buf++) 55 crc = crc32[(uint8_t)crc ^ *buf] ^ (crc >> BPB); 56 return ~crc; 57} 58 59static void usage(const char *) __attribute__ (( __noreturn__ )); 60 61static void usage(const char *mess) 62{ 63 fprintf(stderr, "Error: %s\n", mess); 64 fprintf(stderr, "Usage: mkbrnimg [-o output_file] [-m magic] [-s signature] kernel_file [additional files]\n"); 65 fprintf(stderr, "\n"); 66 exit(1); 67} 68 69static char *output_file = "default-brnImage"; 70static uint32_t magic = 0x12345678; 71static char *signature = "BRNDTW502"; 72 73static void parseopts(int *argc, char ***argv) 74{ 75 char *endptr; 76 int res; 77 78 while ((res = getopt(*argc, *argv, "o:m:s:")) != -1) { 79 switch (res) { 80 default: 81 usage("Unknown option"); 82 break; 83 case 'o': 84 output_file = optarg; 85 break; 86 case 'm': 87 magic = strtoul(optarg, &endptr, 0); 88 if (endptr == optarg || *endptr != 0) 89 usage("magic must be a decimal or hexadecimal 32-bit value"); 90 break; 91 case 's': 92 signature = optarg; 93 break; 94 } 95 } 96 *argc -= optind; 97 *argv += optind; 98} 99 100static void appendfile(int outfd, char *path, int kernel) { 101 int fd; 102 size_t len, padded_len; 103 char *input_file; 104 uint32_t crc; 105 char padding[0x400]; 106 char footer[12]; 107 108 memset(padding, 0xff, sizeof(padding)); 109 110 // mmap input_file 111 if ((fd = open(path, O_RDONLY)) < 0 112 || (len = lseek(fd, 0, SEEK_END)) < 0 113 || (input_file = mmap(0, len, PROT_READ, MAP_SHARED, fd, 0)) == (void *) (-1) 114 || close(fd) < 0) 115 { 116 fprintf(stderr, "Error mapping file '%s': %s\n", path, strerror(errno)); 117 exit(1); 118 } 119 120 // kernel should be lzma compressed image, not uImage 121 if (kernel && 122 (input_file[0] != (char)0x5d || 123 input_file[1] != (char)0x00 || 124 input_file[2] != (char)0x00 || 125 input_file[3] != (char)0x80)) { 126 fprintf(stderr, "lzma signature not found on kernel image.\n"); 127 exit(1); 128 } 129 130 init_crc32(); 131 crc = crc32buf(input_file, len); 132 fprintf(stderr, "crc32 for '%s' is %08x.\n", path, crc); 133 134 // write the file 135 write(outfd, input_file, len); 136 137 // write padding 138 padded_len = ((len + sizeof(footer) + sizeof(padding) - 1) & ~(sizeof(padding) - 1)) - sizeof(footer); 139 fprintf(stderr, "len=%08x padded_len=%08x\n", len, padded_len); 140 write(outfd, padding, padded_len - len); 141 142 // write footer 143 footer[0] = (len >> 0) & 0xff; 144 footer[1] = (len >> 8) & 0xff; 145 footer[2] = (len >> 16) & 0xff; 146 footer[3] = (len >> 24) & 0xff; 147 footer[4] = (magic >> 0) & 0xff; 148 footer[5] = (magic >> 8) & 0xff; 149 footer[6] = (magic >> 16) & 0xff; 150 footer[7] = (magic >> 24) & 0xff; 151 footer[8] = (crc >> 0) & 0xff; 152 footer[9] = (crc >> 8) & 0xff; 153 footer[10] = (crc >> 16) & 0xff; 154 footer[11] = (crc >> 24) & 0xff; 155 write(outfd, footer, sizeof(footer)); 156 157 munmap(input_file, len); 158} 159 160int main(int argc, char **argv) 161{ 162 int outfd; 163 int i; 164 165 parseopts(&argc, &argv); 166 167 if (argc < 1) 168 usage("wrong number of arguments"); 169 170 if ((outfd = open(output_file, O_WRONLY|O_CREAT|O_TRUNC, 0644)) == -1) 171 { 172 fprintf(stderr, "Error opening '%s' for writing: %s\n", output_file, strerror(errno)); 173 exit(1); 174 } 175 176 for (i=0; i<argc; i++) { 177 appendfile(outfd, argv[i], i == 0); 178 } 179 write(outfd, signature, strlen(signature)+1); 180 close(outfd); 181 182 return 0; 183} 184