tools/firmware-utils/src/mkbrnimg.c

   1 // SPDX-License-Identifier: GPL-2.0-only
   2 /*
   3  * mkbrnimg.c - partially based on OpenWrt's wndr3700.c
   4  *
   5  * Copyright (C) 2011 Tobias Diedrich <ranma+openwrt@tdiedrich.de>
   6  */
   7
   8 #include <stdio.h>
   9 #include <stdlib.h>
  10 #include <stddef.h>
  11 #include <unistd.h>
  12 #include <errno.h>
  13 #include <fcntl.h>
  14 #include <sys/mman.h>
  15 #include <string.h>
  16 #include <netinet/in.h>
  17 #include <inttypes.h>
  18
  19 #define BPB 8 /* bits/byte */
  20
  21 static uint32_t crc32[1<<BPB];
  22
  23 static char *output_file = "default-brnImage";
  24 static uint32_t magic = 0x12345678;
  25 static char *signature = "BRNDTW502";
  26 static uint32_t crc32_poly = 0x2083b8ed;
  27
  28 static void init_crc32()
  29 {
  30         const uint32_t poly = ntohl(crc32_poly);
  31         int n;
  32
  33         for (n = 0; n < 1<<BPB; n++) {
  34                 uint32_t crc = n;
  35                 int bit;
  36
  37                 for (bit = 0; bit < BPB; bit++)
  38                         crc = (crc & 1) ? (poly ^ (crc >> 1)) : (crc >> 1);
  39                 crc32[n] = crc;
  40         }
  41 }
  42
  43 static uint32_t crc32buf(const void *buf, size_t len)
  44 {
  45         uint32_t crc = 0xFFFFFFFF;
  46         const uint8_t *in = buf;
  47
  48         for (; len; len--, in++)
  49                 crc = crc32[(uint8_t)crc ^ *in] ^ (crc >> BPB);
  50         return ~crc;
  51 }
  52
  53 static void usage(const char *) __attribute__ (( __noreturn__ ));
  54
  55 static void usage(const char *mess)
  56 {
  57         fprintf(stderr, "Error: %s\n", mess);
  58         fprintf(stderr, "Usage: mkbrnimg [-o output_file] [-m magic] [-s signature] [-p crc32 poly] kernel_file [additional files]\n");
  59         fprintf(stderr, "\n");
  60         exit(1);
  61 }
  62
  63 static void parseopts(int *argc, char ***argv)
  64 {
  65         char *endptr;
  66         int res;
  67
  68         while ((res = getopt(*argc, *argv, "o:m:s:p:")) != -1) {
  69                 switch (res) {
  70                 default:
  71                         usage("Unknown option");
  72                         break;
  73                 case 'o':
  74                         output_file = optarg;
  75                         break;
  76                 case 'm':
  77                         magic = strtoul(optarg, &endptr, 0);
  78                         if (endptr == optarg || *endptr != 0)
  79                                 usage("magic must be a decimal or hexadecimal 32-bit value");
  80                         break;
  81                 case 's':
  82                         signature = optarg;
  83                         break;
  84                 case 'p':
  85                         crc32_poly = strtoul(optarg, &endptr, 0);
  86                         if (endptr == optarg || *endptr != 0)
  87                                 usage("'crc32 poly' must be a decimal or hexadecimal 32-bit value");
  88                         break;
  89                 }
  90         }
  91         *argc -= optind;
  92         *argv += optind;
  93 }
  94
  95 static void appendfile(int outfd, char *path, int kernel) {
  96         int fd;
  97         size_t len, padded_len;
  98         char *input_file;
  99         uint32_t crc;
 100         char padding[0x400];
 101         char footer[12];
 102
 103         memset(padding, 0xff, sizeof(padding));
 104
 105         // mmap input_file
 106         if ((fd = open(path, O_RDONLY))  < 0
 107         || (len = lseek(fd, 0, SEEK_END)) < 0
 108         || (input_file = mmap(0, len, PROT_READ, MAP_SHARED, fd, 0)) == (void *) (-1)
 109         || close(fd) < 0)
 110         {
 111                 fprintf(stderr, "Error mapping file '%s': %s\n", path, strerror(errno));
 112                 exit(1);
 113         }
 114
 115         // kernel should be lzma compressed image, not uImage
 116         if (kernel &&
 117             (input_file[0] != (char)0x5d ||
 118              input_file[1] != (char)0x00 ||
 119              input_file[2] != (char)0x00 ||
 120              input_file[3] != (char)0x80)) {
 121                 fprintf(stderr, "lzma signature not found on kernel image.\n");
 122                 exit(1);
 123         }
 124
 125         init_crc32();
 126         crc = crc32buf(input_file, len);
 127         fprintf(stderr, "crc32 for '%s' is %08x.\n", path, crc);
 128
 129         // write the file
 130         write(outfd, input_file, len);
 131
 132         // write padding
 133         padded_len = ((len + sizeof(footer) + sizeof(padding) - 1) & ~(sizeof(padding) - 1)) - sizeof(footer);
 134         fprintf(stderr, "len=%08zx padded_len=%08zx\n", len, padded_len);
 135         write(outfd, padding, padded_len - len);
 136
 137         // write footer
 138         footer[0]  = (len   >>  0) & 0xff;
 139         footer[1]  = (len   >>  8) & 0xff;
 140         footer[2]  = (len   >> 16) & 0xff;
 141         footer[3]  = (len   >> 24) & 0xff;
 142         footer[4]  = (magic >>  0) & 0xff;
 143         footer[5]  = (magic >>  8) & 0xff;
 144         footer[6]  = (magic >> 16) & 0xff;
 145         footer[7]  = (magic >> 24) & 0xff;
 146         footer[8]  = (crc   >>  0) & 0xff;
 147         footer[9]  = (crc   >>  8) & 0xff;
 148         footer[10] = (crc   >> 16) & 0xff;
 149         footer[11] = (crc   >> 24) & 0xff;
 150         write(outfd, footer, sizeof(footer));
 151
 152         munmap(input_file, len);
 153 }
 154
 155 int main(int argc, char **argv)
 156 {
 157         int outfd;
 158         int i;
 159
 160         parseopts(&argc, &argv);
 161
 162         if (argc < 1)
 163                 usage("wrong number of arguments");
 164
 165         if ((outfd = open(output_file, O_WRONLY|O_CREAT|O_TRUNC, 0644)) == -1)
 166         {
 167                 fprintf(stderr, "Error opening '%s' for writing: %s\n", output_file, strerror(errno));
 168                 exit(1);
 169         }
 170
 171         for (i=0; i<argc; i++) {
 172                 appendfile(outfd, argv[i], i == 0);
 173         }
 174         write(outfd, signature, strlen(signature)+1);
 175         close(outfd);
 176
 177         return 0;
 178 }