src/bcm4908kernel.c

   1 // SPDX-License-Identifier: GPL-2.0-or-later
   2 /*
   3  * Copyright (C) 2021 Rafał Miłecki <rafal@milecki.pl>
   4  */
   5
   6 #include <byteswap.h>
   7 #include <endian.h>
   8 #include <errno.h>
   9 #include <stdint.h>
  10 #include <stdio.h>
  11 #include <stdlib.h>
  12 #include <string.h>
  13 #include <unistd.h>
  14
  15 #if !defined(__BYTE_ORDER)
  16 #error "Unknown byte order"
  17 #endif
  18
  19 #if __BYTE_ORDER == __BIG_ENDIAN
  20 #define cpu_to_le32(x)  bswap_32(x)
  21 #define le32_to_cpu(x)  bswap_32(x)
  22 #elif __BYTE_ORDER == __LITTLE_ENDIAN
  23 #define cpu_to_le32(x)  (x)
  24 #define le32_to_cpu(x)  (x)
  25 #else
  26 #error "Unsupported endianness"
  27 #endif
  28
  29 struct bcm4908kernel_header {
  30         uint32_t boot_load_addr;        /* AKA la_address */
  31         uint32_t boot_addr;             /* AKA la_entrypt */
  32         uint32_t data_len;
  33         uint8_t magic[4];
  34         uint32_t uncomplen;             /* Empty for LZMA, used for LZ4 */
  35 };
  36
  37 static void usage() {
  38         printf("Usage:\n");
  39         printf("\n");
  40         printf("\t-i pathname\t\t\tinput kernel filepath\n");
  41         printf("\t-o pathname\t\t\toutput kernel filepath\n");
  42 }
  43
  44 int main(int argc, char **argv) {
  45         struct bcm4908kernel_header header;
  46         uint8_t buf[1024];
  47         FILE *out = NULL;
  48         FILE *in = NULL;
  49         size_t length;
  50         size_t bytes;
  51         int err = 0;
  52         char c;
  53
  54         if (argc >= 2 && !strcmp(argv[1], "-h")) {
  55                 usage();
  56                 return 0;
  57         }
  58
  59         while ((c = getopt(argc, argv, "i:o:")) != -1) {
  60                 switch (c) {
  61                 case 'i':
  62                         in = fopen(optarg, "r");
  63                         break;
  64                 case 'o':
  65                         out = fopen(optarg, "w+");
  66                         break;
  67                 }
  68         }
  69
  70         if (!in || !out) {
  71                 fprintf(stderr, "Failed to open input and/or output file\n");
  72                 usage();
  73                 return -EINVAL;
  74         }
  75
  76         if (fread(&header, 1, sizeof(header), in) != sizeof(header)) {
  77                 fprintf(stderr, "Failed to read %zu bytes from input file\n", sizeof(header));
  78                 err = -EIO;
  79                 goto err_close;
  80         }
  81
  82         if (!memcmp(header.magic, "BRCM", 4)) {
  83                 fprintf(stderr, "Input file already contains BCM4908 kernel header\n");
  84                 err = -EIO;
  85                 goto err_close;
  86         }
  87
  88         err = fseek(out, sizeof(header), SEEK_SET);
  89         if (err) {
  90                 err = -errno;
  91                 fprintf(stderr, "Failed to fseek(): %d\n", err);
  92                 goto err_close;
  93         }
  94
  95         length = 0;
  96         rewind(in);
  97         while ((bytes = fread(buf, 1, sizeof(buf), in)) > 0) {
  98                 if (fwrite(buf, 1, bytes, out) != bytes) {
  99                         fprintf(stderr, "Failed to write %zu B to the output file\n", bytes);
 100                         err = -EIO;
 101                         goto err_close;
 102                 }
 103                 length += bytes;
 104         }
 105
 106         header.boot_load_addr = cpu_to_le32(0x00080000);
 107         header.boot_addr = cpu_to_le32(0x00080000);
 108         header.data_len = cpu_to_le32(length);
 109         header.magic[0] = 'B';
 110         header.magic[1] = 'R';
 111         header.magic[2] = 'C';
 112         header.magic[3] = 'M';
 113         header.uncomplen = 0;
 114
 115         fseek(out, 0, SEEK_SET);
 116
 117         if (fwrite(&header, 1, sizeof(header), out) != sizeof(header)) {
 118                 fprintf(stderr, "Failed to write header to the output file\n");
 119                 err = -EIO;
 120                 goto err_close;
 121         }
 122
 123 err_close:
 124         fclose(out);
 125         fclose(in);
 126         return err;
 127 }