Re: New command to check NT's hibernation state

[Peter Lustig <peter.lustig.7db@gmail.com>]

[-- Attachment #1: Type: text/plain, Size: 1798 bytes --]

On 02.12.2011 07:05, Vladimir Serbinenko wrote:

>> P.S.  Do you know if there are any plans in the future to implement
>> write operations for filesystems?  (I noticed raw disk writing is
>> currently supported.)  If not, is the reason due to the technical
>> challenges (e.g. NTFS only had read-only access in GNU/Linux for quite
>> a while) or just a general lack of interest?
> Neither. Reliability concerns. Writing to filesystem is potentially
> dangerous and needs to be throughly tested. Since writing is rare for
> bootloader we won't receive enough testing of these code pathes so every
> write will remain a risk. We can't have such risks
I see. Just curious.

>>> Thanks for this. However the coding style isn't according to our
>>> standards. Could you adjust to the standard? I recommend looking at
>>> other code and reading GNU Coding Standard. E.g. we don't use {0}
>>> initialiser, return value of commands, C++ comments or M$-$tyle
>>> variables.
>> Sorry about that.  I've reviewed the standard and perused the source
>> tree, as you suggested, to determine the best style.  Attached is my
>> updated file.
>>
> Much better. There are still few problems like the arbitrary limit (we
> avoid any arbitrary limits, you have one easy to avoid on filename
> length). Also we don't use such ABORT macros as they offer no
> readability advantage. Review in more details when time permits.
Argh. I remember reading about avoiding arbitrary limits too.

I would contend that in this case the macros do improve readability (each
reducing 4-5 lines of code down to 1-2 lines); yet, to be consistent with the
rest of the source base, I've removed them.

Here's the file again.  Maybe the third time's the charm?

Thanks for being a stickler for conformance ( I mean it :) ),
Peter Lustig


[-- Attachment #2: nthibr.c --]
[-- Type: text/plain, Size: 4609 bytes --]

/* nthibr.c - tests whether an MS Windows system partition is hibernated */
/*
 *  GRUB  --  GRand Unified Bootloader
 *  Copyright (C) 2007,2008,2009,2011  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/types.h>
#include <grub/mm.h>
#include <grub/disk.h>
#include <grub/file.h>
#include <grub/misc.h>
#include <grub/dl.h>
#include <grub/extcmd.h>
#include <grub/lib/arg.h>
#include <grub/err.h>
#include <grub/i18n.h>

GRUB_MOD_LICENSE("GPLv3+");

/* Define this 'empty' array to let the '-h' and '-u' switches be processed */
static const struct grub_arg_option options[] = {
  {0, 0, 0, 0, 0, 0}
};

static grub_err_t 
grub_cmd_nthibr (grub_extcmd_context_t ctxt __attribute__ ((unused)),
                 int argc, char **args)
{
  grub_err_t status = GRUB_ERR_NONE;
  char *partition_name, *hibr_file_path = 0, hibr_file_magic[5];
  grub_size_t name_length;
  grub_ssize_t magic_size;
  grub_disk_t partition;
  grub_file_t hibr_file = 0;

  /* Check argument count */
  if (!argc)
    {
      status = grub_error (GRUB_ERR_BAD_ARGUMENT, 
                           N_("too few arguments specified"));
      goto exit;
    }
  else if (argc > 1)
    {
      status = grub_error (GRUB_ERR_BAD_ARGUMENT, 
                           N_("too many arguments specified"));
      goto exit;
    }

  partition_name = args[0];
  name_length = grub_strlen (partition_name);

  /* Check if partition specifier 'looks right' */
  if (partition_name[0] != '(' || partition_name[name_length - 1] != ')')
    {
      status = grub_error (GRUB_ERR_BAD_FILENAME, 
                           N_("invalid partition specifier"));
      goto exit;
    }

  /* Check if partition actually exists */
  partition_name[name_length - 1] = '\0';
  partition = grub_disk_open (partition_name + 1);
  if (!partition)
    {
      status = grub_error (GRUB_ERR_UNKNOWN_DEVICE, 
                           N_("partition not found"));
      goto exit;
    }
  else 
    {
      grub_disk_close (partition);
      partition_name[name_length - 1] = ')';
    }

  /* Build path to 'hiberfil.sys' */
  hibr_file_path = grub_malloc (grub_strlen (partition_name) 
                                + grub_strlen ("/hiberfil.sys") + 1);
  if (!hibr_file_path)
    {
      status = grub_error (GRUB_ERR_OUT_OF_MEMORY,
                           N_("out of memory"));
      goto exit;
    }
  else
    {
      grub_strcpy (hibr_file_path, partition_name);
      grub_strcat (hibr_file_path, "/hiberfil.sys");
    }

  /* Try to open 'hiberfil.sys' */
  hibr_file = grub_file_open (hibr_file_path);
  if (!hibr_file)
    {
      status = grub_error (GRUB_ERR_FILE_NOT_FOUND, 
                           N_("'hiberfil.sys' not found"));
      goto exit;
    }

  /* Try to read magic number of 'hiberfil.sys' */
  magic_size = sizeof (hibr_file_magic) - 1;
  grub_memset (hibr_file_magic, 0, sizeof (hibr_file_magic));
  if (grub_file_read (hibr_file, hibr_file_magic, magic_size) < magic_size)
    {
      status = grub_error (GRUB_ERR_BAD_FILE_TYPE, 
                           N_("'hiberfil.sys' too small"));
      goto exit;
    }

  /* Return SUCCESS if magic indicates file is active; else return FAILURE */
  if (!grub_strncasecmp ("hibr", hibr_file_magic, magic_size))
    grub_puts (N_("The system is hibernated."));
  else 
    {
      grub_puts (N_("The system is NOT hibernated."));
      status = GRUB_ERR_TEST_FAILURE;
    }

exit: 
  /* Ensure unmanaged resources are cleaned up */
  if (hibr_file_path)
    grub_free (hibr_file_path);
  if (hibr_file)
    grub_file_close (hibr_file);

  return status;
}
\f
static grub_extcmd_t cmd;

GRUB_MOD_INIT (nthibr) 
{
  cmd = grub_register_extcmd ("nthibr", grub_cmd_nthibr, 0,
                              N_("DEVICE"),
                              N_("Test whether an NT system partition "
                                 "is hibernated."), 
                              options);
}

GRUB_MOD_FINI (nthibr) 
{
  grub_unregister_extcmd (cmd);
}