grub-savannah-mirror/grub-core/disk/memdisk.c

/* memdisk.c - Access embedded memory disk.  */
/*
 *  GRUB  --  GRand Unified Bootloader
 *  Copyright (C) 2007,2008  Free Software Foundation, Inc.
 *
 *  GRUB is free software: you can redistribute it and/or modify
 *  it under the terms of the GNU General Public License as published by
 *  the Free Software Foundation, either version 3 of the License, or
 *  (at your option) any later version.
 *
 *  GRUB is distributed in the hope that it will be useful,
 *  but WITHOUT ANY WARRANTY; without even the implied warranty of
 *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *  GNU General Public License for more details.
 *
 *  You should have received a copy of the GNU General Public License
 *  along with GRUB.  If not, see <http://www.gnu.org/licenses/>.
 */

#include <grub/disk.h>
#include <grub/dl.h>
#include <grub/kernel.h>
#include <grub/misc.h>
#include <grub/mm.h>
#include <grub/types.h>
#include <grub/safemath.h>

GRUB_MOD_LICENSE ("GPLv3+");

static char *memdisk_addr;
static grub_off_t memdisk_size = 0;

static int
grub_memdisk_iterate (grub_disk_dev_iterate_hook_t hook, void *hook_data,
		      grub_disk_pull_t pull)
{
  if (pull != GRUB_DISK_PULL_NONE)
    return 0;

  return hook ("memdisk", hook_data);
}

static grub_err_t
grub_memdisk_open (const char *name, grub_disk_t disk)
{
  if (grub_strcmp (name, "memdisk"))
      return grub_error (GRUB_ERR_UNKNOWN_DEVICE, "not a memdisk");

  disk->total_sectors = memdisk_size / GRUB_DISK_SECTOR_SIZE;
  disk->max_agglomerate = GRUB_DISK_MAX_MAX_AGGLOMERATE;
  disk->id = 0;

  return GRUB_ERR_NONE;
}

static void
grub_memdisk_close (grub_disk_t disk __attribute((unused)))
{
}

static grub_err_t
grub_memdisk_read (grub_disk_t disk __attribute((unused)), grub_disk_addr_t sector,
		    grub_size_t size, char *buf)
{
  grub_memcpy (buf, memdisk_addr + (sector << GRUB_DISK_SECTOR_BITS), size << GRUB_DISK_SECTOR_BITS);
  return 0;
}

static grub_err_t
grub_memdisk_write (grub_disk_t disk __attribute((unused)), grub_disk_addr_t sector,
		     grub_size_t size, const char *buf)
{
  grub_memcpy (memdisk_addr + (sector << GRUB_DISK_SECTOR_BITS), buf, size << GRUB_DISK_SECTOR_BITS);
  return 0;
}

static struct grub_disk_dev grub_memdisk_dev =
  {
    .name = "memdisk",
    .id = GRUB_DISK_DEVICE_MEMDISK_ID,
    .disk_iterate = grub_memdisk_iterate,
    .disk_open = grub_memdisk_open,
    .disk_close = grub_memdisk_close,
    .disk_read = grub_memdisk_read,
    .disk_write = grub_memdisk_write,
    .next = 0
  };

GRUB_MOD_INIT(memdisk)
{
  struct grub_module_header *header;
  FOR_MODULES (header)
    if (header->type == OBJ_TYPE_MEMDISK)
      {
	char *memdisk_orig_addr;
	memdisk_orig_addr = (char *) header + sizeof (struct grub_module_header);

	grub_dprintf ("memdisk", "Found memdisk image at %p\n", memdisk_orig_addr);

	if (grub_sub (header->size, sizeof (struct grub_module_header), &memdisk_size))
	  {
	    grub_error (GRUB_ERR_OUT_OF_RANGE, "underflow detected while obtaining memdisk size");
	    return;
	  }
	memdisk_addr = grub_malloc (memdisk_size);
	if (memdisk_addr == NULL)
	  return;

	grub_dprintf ("memdisk", "Copying memdisk image to dynamic memory\n");
	grub_memmove (memdisk_addr, memdisk_orig_addr, memdisk_size);

	grub_disk_dev_register (&grub_memdisk_dev);
	break;
      }
}

GRUB_MOD_FINI(memdisk)
{
  if (! memdisk_size)
    return;
  grub_free (memdisk_addr);
  grub_disk_dev_unregister (&grub_memdisk_dev);
}