Re: New command to check NT's hibernation state

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

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On 16.12.2011 10:30, Vladimir 'phcoder' Serbinenko wrote:
>> /* 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}
>> };
> Please remove this and use grub_command_t
I understand now.  What threw me off was seeing the 'hello' module use 
'extcmd.'
>> static grub_err_t
>> grub_cmd_nthibr (grub_extcmd_context_t ctxt __attribute__ ((unused)),
>>                   int argc, char **args)
>> {
>>    char *partition_name = 0, *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)
>>      return grub_error (GRUB_ERR_BAD_ARGUMENT, N_("too few arguments"));
>>    else if (argc>  1)
>>      return grub_error (GRUB_ERR_BAD_ARGUMENT, N_("too many 
>> arguments"));
>>
> Either ignore trailing argument or put both in one check != 1
>>    /* Make copy of partition specifier, so it can be modified (if 
>> needed) */
>>    name_length = grub_strlen (args[0]);
>>    partition_name = grub_zalloc (name_length + 3);
>>    if (!partition_name)
>>      goto exit;
>>    grub_strcpy (partition_name, args[0]);
>>
>>    /* Ensure partition specifier start with a '(' */
>>    if (partition_name[0] != '(')
>>      {
>>        grub_memmove (partition_name + 1, partition_name, name_length++);
>>        partition_name[0] = '(';
>>      }
>>
>>    /* Ensure partition specifier ends with a ')' */
>>    if (partition_name[name_length - 1] != ')')
>>      partition_name[(++name_length) - 1] = ')';
>>
>>    /* Check if partition actually exists */
>>    partition_name[name_length - 1] = '\0';
>>    partition = grub_disk_open (partition_name + 1);
>>    if (!partition)
>>      goto exit;
>>    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)
>>      goto exit;
>>    grub_strcpy (hibr_file_path, partition_name);
>>    grub_strcat (hibr_file_path, "/hiberfil.sys");
>>
> It would be more efficient if you just try to open file and see what 
> error you get. Actually you don't even need to distinguish between 
> error cases here since you return the error you encountered. This will 
> also save one useless alloc.
>>    /* Try to open 'hiberfil.sys' */
>>    hibr_file = grub_file_open (hibr_file_path);
>>    if (!hibr_file)
>>      {
>>        if (grub_errno == GRUB_ERR_FILE_NOT_FOUND)
>>          grub_error (GRUB_ERR_FILE_NOT_FOUND, N_("'hiberfil.sys' not 
>> found"));
> This overriding is unnecessary. FS code already provides this message
This was intentional:  the default message ('file not found') is not 
particularly helpful in this case since the
command's description nowhere mentions what file it's looking for (let 
alone that any file is needed for it to
function).  I've updated this section to pop the first error off the 
stack to eliminate the duplication (and added
a descriptive comment).
>>        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)
>>      {
>>        if (!grub_errno)
>>          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_error (GRUB_ERR_NONE, "true");
>>    else
>>      grub_error (GRUB_ERR_TEST_FAILURE, "false");
>>
>> exit:
>>    /* Ensure unmanaged resources are cleaned up */
>>    if (partition_name)
>>      grub_free (partition_name);
>>    if (hibr_file_path)
>>      grub_free (hibr_file_path);
> No need to check that argument to free is non-NULL.
>>    if (hibr_file)
>>      grub_file_close (hibr_file);
>>
>>    return grub_errno;
>> }
>>
>> 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);
>> }
>>
>
~Peter Lustig

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/* 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/file.h>
#include <grub/misc.h>
#include <grub/dl.h>
#include <grub/command.h>
#include <grub/err.h>
#include <grub/i18n.h>

GRUB_MOD_LICENSE("GPLv3+");

static grub_err_t 
grub_cmd_nthibr (grub_command_t cmd __attribute__ ((unused)),
                 int argc, char **args)
{
  char *partition_name = 0, *hibr_file_path = 0, hibr_file_magic[5];
  grub_size_t name_length;
  grub_ssize_t magic_size;
  grub_file_t hibr_file = 0;

  /* Check argument count */
  if (argc != 1)
    return grub_error (GRUB_ERR_BAD_ARGUMENT, N_("invalid argument count"));

  /* Make copy of partition specifier, so it can be modified (if needed) */
  name_length = grub_strlen (args[0]);
  partition_name = grub_zalloc (name_length + 3);
  if (!partition_name)
    goto exit;
  grub_strcpy (partition_name, args[0]);

  /* Ensure partition specifier start with a '(' */
  if (partition_name[0] != '(')
    {
      grub_memmove (partition_name + 1, partition_name, name_length++);
      partition_name[0] = '(';
    }

  /* Ensure partition specifier ends with a ')' */
  if (partition_name[name_length - 1] != ')')
    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)
    goto exit;
  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)
    {
      if (grub_errno == GRUB_ERR_FILE_NOT_FOUND)
        {
          /* make this message more descriptive */
          grub_error_pop ();
          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)
    {
      if (!grub_errno)
        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_error (GRUB_ERR_NONE, "true");
  else 
    grub_error (GRUB_ERR_TEST_FAILURE, "false");

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

  return grub_errno;
}
\f
static grub_command_t cmd;

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

GRUB_MOD_FINI (nthibr) 
{
  grub_unregister_command (cmd);
}