grub/util/getroot.c

/* getroot.c - Get root device */
/*
 *  GRUB  --  GRand Unified Bootloader
 *  Copyright (C) 1999,2000,2001,2002,2003,2006,2007,2008  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 <sys/stat.h>
#include <unistd.h>
#include <string.h>
#include <dirent.h>

#ifdef __CYGWIN__
# include <sys/fcntl.h>
# include <sys/cygwin.h>
# include <limits.h>
# define DEV_CYGDRIVE_MAJOR 98
#endif

#include <grub/util/misc.h>
#include <grub/util/biosdisk.h>
#include <grub/util/getroot.h>

static void
strip_extra_slashes (char *dir)
{
  char *p = dir;

  while ((p = strchr (p, '/')) != 0)
    {
      if (p[1] == '/')
	{
	  memmove (p, p + 1, strlen (p));
	  continue;
	}
      else if (p[1] == '\0')
	{
	  if (p > dir)
	    p[0] = '\0';
	  break;
	}
      
      p++;
    }
}

static char *
xgetcwd (void)
{
  size_t size = 10;
  char *path;

  path = xmalloc (size);
  while (! getcwd (path, size))
    {
      size <<= 1;
      path = xrealloc (path, size);
    }

  return path;
}

#ifdef __CYGWIN__
/* Convert POSIX path to Win32 path,
   remove drive letter, replace backslashes.  */
static char *
get_win32_path (const char *path)
{
  char winpath[PATH_MAX];
  cygwin_conv_to_full_win32_path (path, winpath);

  int len = strlen (winpath);
  if (len > 2 && winpath[1] == ':')
    {
      len -= 2;
      memmove (winpath, winpath + 2, len + 1);
    }

  int i;
  for (i = 0; i < len; i++)
    if (winpath[i] == '\\')
      winpath[i] = '/';
  return xstrdup (winpath);
}
#endif

char *
grub_get_prefix (const char *dir)
{
  char *saved_cwd;
  char *abs_dir, *prev_dir;
  char *prefix;
  struct stat st, prev_st;
  
  /* Save the current directory.  */
  saved_cwd = xgetcwd ();

  if (chdir (dir) < 0)
    grub_util_error ("Cannot change directory to `%s'", dir);

  abs_dir = xgetcwd ();
  strip_extra_slashes (abs_dir);
  prev_dir = xstrdup (abs_dir);
  
  if (stat (".", &prev_st) < 0)
    grub_util_error ("Cannot stat `%s'", dir);

  if (! S_ISDIR (prev_st.st_mode))
    grub_util_error ("`%s' is not a directory", dir);

  while (1)
    {
      if (chdir ("..") < 0)
	grub_util_error ("Cannot change directory to the parent");

      if (stat (".", &st) < 0)
	grub_util_error ("Cannot stat current directory");

      if (! S_ISDIR (st.st_mode))
	grub_util_error ("Current directory is not a directory???");

      if (prev_st.st_dev != st.st_dev || prev_st.st_ino == st.st_ino)
	break;

      free (prev_dir);
      prev_dir = xgetcwd ();
      prev_st = st;
    }

  strip_extra_slashes (prev_dir);
  prefix = xmalloc (strlen (abs_dir) - strlen (prev_dir) + 2);
  prefix[0] = '/';
  strcpy (prefix + 1, abs_dir + strlen (prev_dir));
  strip_extra_slashes (prefix);

  if (chdir (saved_cwd) < 0)
    grub_util_error ("Cannot change directory to `%s'", dir);

#ifdef __CYGWIN__
  if (st.st_dev != (DEV_CYGDRIVE_MAJOR << 16))
    {
      /* Reached some mount point not below /cygdrive.
	 GRUB does not know Cygwin's emulated mounts,
	 convert to Win32 path.  */
      grub_util_info ("Cygwin prefix = %s", prefix);
      char * wprefix = get_win32_path (prefix);
      free (prefix);
      prefix = wprefix;
    }
#endif

  free (saved_cwd);
  free (abs_dir);
  free (prev_dir);

  grub_util_info ("prefix = %s", prefix);
  return prefix;
}

#ifndef __CYGWIN__

static char *
find_root_device (const char *dir, dev_t dev)
{
  DIR *dp;
  char *saved_cwd;
  struct dirent *ent;
  
  dp = opendir (dir);
  if (! dp)
    return 0;

  saved_cwd = xgetcwd ();

  grub_util_info ("changing current directory to %s", dir);
  if (chdir (dir) < 0)
    {
      free (saved_cwd);
      closedir (dp);
      return 0;
    }
  
  while ((ent = readdir (dp)) != 0)
    {
      struct stat st;
      
      /* Avoid:
	 - dotfiles (like "/dev/.tmp.md0") since they could be duplicates.
	 - dotdirs (like "/dev/.static") since they could contain duplicates.  */
      if (ent->d_name[0] == '.')
	continue;

      if (lstat (ent->d_name, &st) < 0)
	/* Ignore any error.  */
	continue;

      if (S_ISLNK (st.st_mode))
	/* Don't follow symbolic links.  */
	continue;
      
      if (S_ISDIR (st.st_mode))
	{
	  /* Find it recursively.  */
	  char *res;

	  res = find_root_device (ent->d_name, dev);

	  if (res)
	    {
	      if (chdir (saved_cwd) < 0)
		grub_util_error ("Cannot restore the original directory");
	      
	      free (saved_cwd);
	      closedir (dp);
	      return res;
	    }
	}

      if (S_ISBLK (st.st_mode) && st.st_rdev == dev)
	{
#ifdef __linux__
	  /* Skip device names like /dev/dm-0, which are short-hand aliases
	     to more descriptive device names, e.g. those under /dev/mapper */
	  if (ent->d_name[0] == 'd' &&
	      ent->d_name[1] == 'm' &&
	      ent->d_name[2] == '-' &&
	      ent->d_name[3] >= '0' &&
	      ent->d_name[3] <= '9')
	    continue;
#endif

	  /* Found!  */
	  char *res;
	  char *cwd;

	  cwd = xgetcwd ();
	  res = xmalloc (strlen (cwd) + strlen (ent->d_name) + 2);
	  sprintf (res, "%s/%s", cwd, ent->d_name);
	  strip_extra_slashes (res);
	  free (cwd);

	  /* /dev/root is not a real block device keep looking, takes care
	     of situation where root filesystem is on the same partition as
	     grub files */

	  if (strcmp(res, "/dev/root") == 0)
		continue;

	  if (chdir (saved_cwd) < 0)
	    grub_util_error ("Cannot restore the original directory");

	  free (saved_cwd);
	  closedir (dp);
	  return res;
	}
    }

  if (chdir (saved_cwd) < 0)
    grub_util_error ("Cannot restore the original directory");

  free (saved_cwd);
  closedir (dp);
  return 0;
}

#else /* __CYGWIN__ */

/* Read drive/partition serial number from mbr/boot sector,
   return 0 on read error, ~0 on unknown serial.  */
static unsigned
get_bootsec_serial (const char *os_dev, int mbr)
{
  /* Read boot sector.  */
  int fd = open (os_dev, O_RDONLY);
  if (fd < 0)
    return 0;
  unsigned char buf[0x200];
  int n = read (fd, buf, sizeof (buf));
  close (fd);
  if (n != sizeof(buf))
    return 0;

  /* Check signature.  */
  if (!(buf[0x1fe] == 0x55 && buf[0x1ff] == 0xaa))
    return ~0;

  /* Serial number offset depends on boot sector type.  */
  if (mbr)
    n = 0x1b8;
  else if (memcmp (buf + 0x03, "NTFS", 4) == 0)
    n = 0x048;
  else if (memcmp (buf + 0x52, "FAT32", 5) == 0)
    n = 0x043;
  else if (memcmp (buf + 0x36, "FAT", 3) == 0)
    n = 0x027;
  else
    return ~0;

  unsigned serial = *(unsigned *)(buf + n);
  if (serial == 0)
    return ~0;
  return serial;
}

static char *
find_cygwin_root_device (const char *path, dev_t dev)
{
  /* No root device for /cygdrive.  */
  if (dev == (DEV_CYGDRIVE_MAJOR << 16))
    return 0;

  /* Convert to full POSIX and Win32 path.  */
  char fullpath[PATH_MAX], winpath[PATH_MAX];
  cygwin_conv_to_full_posix_path (path, fullpath);
  cygwin_conv_to_full_win32_path (fullpath, winpath);

  /* If identical, this is no real filesystem path.  */
  if (strcmp (fullpath, winpath) == 0)
    return 0;

  /* Check for floppy drive letter.  */
  if (winpath[0] && winpath[1] == ':' && strchr ("AaBb", winpath[0]))
    return xstrdup (strchr ("Aa", winpath[0]) ? "/dev/fd0" : "/dev/fd1");

  /* Cygwin returns the partition serial number in stat.st_dev.
     This is never identical to the device number of the emulated
     /dev/sdXN device, so above find_root_device () does not work.
     Search the partion with the same serial in boot sector instead.  */
  char devpath[sizeof ("/dev/sda15") + 13]; /* Size + Paranoia.  */
  int d;
  for (d = 'a'; d <= 'z'; d++)
    {
      sprintf (devpath, "/dev/sd%c", d);
      if (get_bootsec_serial (devpath, 1) == 0)
	continue;
      int p;
      for (p = 1; p <= 15; p++)
	{
	  sprintf (devpath, "/dev/sd%c%d", d, p);
	  unsigned ser = get_bootsec_serial (devpath, 0);
	  if (ser == 0)
	    break;
	  if (ser != (unsigned)~0 && dev == (dev_t)ser)
	    return xstrdup (devpath);
	}
    }
  return 0;
}

#endif /* __CYGWIN__ */

char *
grub_guess_root_device (const char *dir)
{
  struct stat st;
  char *os_dev;
  
  if (stat (dir, &st) < 0)
    grub_util_error ("Cannot stat `%s'", dir);

#ifdef __CYGWIN__
  /* Cygwin specific function.  */
  os_dev = find_cygwin_root_device (dir, st.st_dev);

#else

  /* This might be truly slow, but is there any better way?  */
  os_dev = find_root_device ("/dev", st.st_dev);
#endif

  return os_dev;
}

int
grub_util_get_dev_abstraction (const char *os_dev)
{
#ifdef __linux__
  /* Check for LVM.  */
  if (!strncmp (os_dev, "/dev/mapper/", 12))
    return GRUB_DEV_ABSTRACTION_LVM;

  /* Check for RAID.  */
  if (!strncmp (os_dev, "/dev/md", 7))
    return GRUB_DEV_ABSTRACTION_RAID;
#endif

  /* No abstraction found.  */
  return GRUB_DEV_ABSTRACTION_NONE;
}

char *
grub_util_get_grub_dev (const char *os_dev)
{
  char *grub_dev;

  switch (grub_util_get_dev_abstraction (os_dev))
    {
    case GRUB_DEV_ABSTRACTION_LVM:
      grub_dev = xmalloc (strlen (os_dev) - 12 + 1);

      strcpy (grub_dev, os_dev + 12);

      break;

    case GRUB_DEV_ABSTRACTION_RAID:
      grub_dev = xmalloc (20);

      if (os_dev[7] == '_' && os_dev[8] == 'd')
	{
	  const char *p;

	  /* This a partitionable RAID device of the form /dev/md_dNNpMM. */
	  int i;

	  grub_dev[0] = 'm';
	  grub_dev[1] = 'd';
	  i = 2;
	  
	  p = os_dev + 9;
	  while (*p >= '0' && *p <= '9')
	    {
	      grub_dev[i] = *p;
	      i++;
	      p++;
	    }

	  if (*p == '\0')
	    grub_dev[i] = '\0';
	  else if (*p == 'p')
	    {
	      p++;
	      grub_dev[i] = ',';
	      i++;

	      while (*p >= '0' && *p <= '9')
		{
		  grub_dev[i] = *p;
		  i++;
		  p++;
		}

	      grub_dev[i] = '\0';
	    }
	  else
	    grub_util_error ("Unknown kind of RAID device `%s'", os_dev);
	}
      else if (os_dev[7] >= '0' && os_dev[7] <= '9')
	{
	  memcpy (grub_dev, os_dev + 5, 7);
	  grub_dev[7] = '\0';
	}
      else
	grub_util_error ("Unknown kind of RAID device `%s'", os_dev);

      break;

    default:  /* GRUB_DEV_ABSTRACTION_NONE */
      grub_dev = grub_util_biosdisk_get_grub_dev (os_dev);
    }

  return grub_dev;
}

const char *
grub_util_check_block_device (const char *blk_dev)
{
  struct stat st;

  if (stat (blk_dev, &st) < 0)
    grub_util_error ("Cannot stat `%s'", blk_dev);

  if (S_ISBLK (st.st_mode))
    return (blk_dev);
  else
    return 0;
}