/******************************************************************************/
/*                                                                            */
/*     This program merges an MFS root disk image into a kernel built with    */
/*     option MD_ROOT_SIZE.  It duplicates the functionality of the           */
/*     program of the same name that used to be part of FreeBSD 4.x.          */
/*                                                                            */
/******************************************************************************/

#include <errno.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>

#define KERNEL_FNAME		argv[1]
#define MFSROOT_FNAME		argv[2]
#define	MFSROOTSIGNATURE	"MFS Filesystem goes here"

int main(int argc, char *argv[])
{
  FILE *kernel, *mfsroot;
  int ksize, mfssize;
  unsigned char *kbuff;
  size_t len;
  unsigned char *mfsrootptr;

  fprintf(stderr, "\nFreeBSD MFS Root Image Merger\n\n");

/* Validate command line arguments */

  if (argc != 3)
  {
    fprintf(stderr, "Usage: write_mfs_in_kernel <kernel> <mfsroot>\n");
    exit(1);
  }

/* Open kernel image file */

  kernel = fopen(KERNEL_FNAME, "r+");
  if (kernel == NULL)
  {
    fprintf(stderr, "ERROR: Cannot open kernel image file %s, %s\n",
            KERNEL_FNAME, strerror(errno));
    exit(1);
  }

/* Figure out kernel image size */

  if (fseek(kernel, 0L, SEEK_END))
  {
    fprintf(stderr, "ERROR: fseek() failed, %s\n", strerror(errno));
    exit(1);
  }

  ksize = ftell(kernel);
  if (ksize < 0)
  {
    fprintf(stderr, "ERROR: ftell() failed, %s\n", strerror(errno));
    exit(1);
  }

  rewind(kernel);

  printf("Kernel image size:   %d bytes \n", ksize);

/* Open MFS root image file */

  mfsroot = fopen(MFSROOT_FNAME, "r");
  if (mfsroot == NULL)
  {
    fprintf(stderr, "ERROR: Cannot open MFS root image file %s, %s\n",
            MFSROOT_FNAME, strerror(errno));
    exit(1);
  }

/* Figure out MFS root image size */

  if (fseek(mfsroot, 0L, SEEK_END))
  {
    fprintf(stderr, "ERROR: fseek() failed, %s\n", strerror(errno));
    exit(1);
  }

  mfssize = ftell(mfsroot);
  if (mfssize < 0)
  {
    fprintf(stderr, "ERROR: ftell() failed, %s\n", strerror(errno));
    exit(1);
  }

  rewind(mfsroot);

  printf("MFS root image size: %d bytes\n", mfssize);

/* Allocate a big buffer for the kernel image */

  kbuff = malloc(ksize);
  if (kbuff == NULL)
  {
    fprintf(stderr, "ERROR: malloc() failed, %s\n", strerror(errno));
    exit(1);
  }

/* Read in kernel image */

  len = fread(kbuff, 1, ksize, kernel);
  if (len != ksize)
  {
    fprintf(stderr, "ERROR: fread() failed, %s\n", strerror(errno));
    exit(1);
  }

  mfsrootptr = memmem(kbuff, ksize, MFSROOTSIGNATURE, strlen(MFSROOTSIGNATURE));
  if (mfsrootptr == NULL)
  {
    fprintf(stderr, "ERROR: MFS root signature not found\n");
    exit(1);
  }

  len = fread(mfsrootptr, 1, ksize, mfsroot);

  rewind(kernel);

  len = fwrite(kbuff, 1, ksize, kernel);
  if (len != ksize)
  {
    fprintf(stderr, "ERROR: fwrite() failed, %s\n", strerror(errno));
    exit(1);
  }

  exit(0);
}