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mkbugboot.c

/*
 * Makes a Motorola PPCBUG ROM bootable image which can be flashed
 * into one of the FLASH banks on a Motorola PowerPlus board.
 *
 * Author: Matt Porter <mporter@mvista.com>
 *
 * 2001 (c) MontaVista, Software, Inc.  This file is licensed under
 * the terms of the GNU General Public License version 2.  This program
 * is licensed "as is" without any warranty of any kind, whether express
 * or implied.
 */

#define ELF_HEADER_SIZE 65536

#include <unistd.h>
#include <sys/stat.h>
#include <string.h>
#include <stdio.h>
#include <stdlib.h>
#include <errno.h>
#include <fcntl.h>
#include <netinet/in.h>
#ifdef __sun__
#include <inttypes.h>
#else
#include <stdint.h>
#endif

/* size of read buffer */
#define SIZE 0x1000

/* PPCBUG ROM boot header */
typedef struct bug_boot_header {
  uint8_t   magic_word[4];          /* "BOOT" */
  uint32_t  entry_offset;           /* Offset from top of header to code */
  uint32_t  routine_length;         /* Length of code */
  uint8_t   routine_name[8];  /* Name of the boot code */
} bug_boot_header_t;

#define HEADER_SIZE     sizeof(bug_boot_header_t)

void update_checksum(void *buf, size_t size, uint16_t *sum)
{
      uint32_t csum = *sum;

      while (size) {
            csum += *(uint16_t *)buf;
            if (csum > 0xffff)
                  csum -= 0xffff;
            buf = (uint16_t *)buf + 1;
            size -= 2;
      }
      *sum = csum;
}

uint32_t copy_image(int in_fd, int out_fd, uint16_t *sum)
{
      uint8_t buf[SIZE];
      int offset = 0;
      int n;
      uint32_t image_size = 0;

      lseek(in_fd, ELF_HEADER_SIZE, SEEK_SET);

      /* Copy an image while recording its size */
      while ( (n = read(in_fd, buf + offset, SIZE - offset)) > 0 ) {
            n += offset;
            offset = n & 1;
            n -= offset;
            image_size = image_size + n;
            /* who's going to deal with short writes? */
            write(out_fd, buf, n);
            update_checksum(buf, n, sum);
            if (offset)
                  buf[0] = buf[n];
      }

      /* BUG romboot requires that our size is divisible by 2 */
      /* align image to 2 byte boundary */
      if (offset) {
            image_size += 2;
            buf[1] = '\0';
            write(out_fd, buf, 2);
            update_checksum(buf, 2, sum);
      }
      return image_size;
}

void write_bugboot_header(int out_fd, uint32_t boot_size, uint16_t *sum)
{
      static bug_boot_header_t bbh = {
            .magic_word = "BOOT",
            .routine_name = "LINUXROM"
      };

      /* Fill in the PPCBUG ROM boot header */
      bbh.entry_offset = htonl(HEADER_SIZE);    /* Entry address */
      bbh.routine_length= htonl(HEADER_SIZE+boot_size+2);   /* Routine length */

      /* Output the header and bootloader to the file */
      write(out_fd, &bbh, sizeof(bug_boot_header_t));
      update_checksum(&bbh, sizeof(bug_boot_header_t), sum);
}

int main(int argc, char *argv[])
{
      int image_fd, bugboot_fd;
      uint32_t kernel_size = 0;
      uint16_t checksum = 0;

      if (argc != 3) {
            fprintf(stderr, "usage: %s <kernel_image> <bugboot>\n",argv[0]);
            exit(-1);
      }

      /* Get file args */

      /* kernel image file */
      if ((image_fd = open(argv[1] , 0)) < 0)
            exit(-1);

      /* bugboot file */
      if (!strcmp(argv[2], "-"))
            bugboot_fd = 1;               /* stdout */
      else if ((bugboot_fd = creat(argv[2] , 0755)) < 0)
            exit(-1);

      /* Set file position after ROM header block where zImage will be written */
      lseek(bugboot_fd, HEADER_SIZE, SEEK_SET);

      /* Copy kernel image into bugboot image */
      kernel_size = copy_image(image_fd, bugboot_fd, &checksum);

      /* Set file position to beginning where header/romboot will be written */
      lseek(bugboot_fd, 0, SEEK_SET);

      /* Write out BUG header/romboot */
      write_bugboot_header(bugboot_fd, kernel_size, &checksum);

      /* Write out the calculated checksum */
      lseek(bugboot_fd, 0, SEEK_END);
      write(bugboot_fd, &checksum, 2);

      /* Close bugboot file */
      close(bugboot_fd);
      return 0;
}

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