parted-1.8.7/libparted/fs/fat/bootsector.c - nest-learning-thermostat/5.1.6/parted - Git at Google

 /*
     libparted
     Copyright (C) 1998, 1999, 2000, 2002, 2004, 2007 Free Software Foundation, Inc.

     This program 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 2 of the License, or
     (at your option) any later version.

     This program 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 this program; if not, write to the Free Software
     Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301, USA
 */

 #include <config.h>
 #include "fat.h"

 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
 #include <sys/types.h>
 #include <sys/stat.h>
 #include <fcntl.h>
 #include <errno.h>

 /* Reads in the boot sector (superblock), and does a minimum of sanity
  * checking.  The goals are:
  *	- to detect fat file systems, even if they are damaged [i.e. not
  * return an error / throw an exception]
  *	- to fail detection if there's not enough information for
  * fat_boot_sector_probe_type() to work (or possibly crash on a divide-by-zero)
  */
 int
 fat_boot_sector_read (FatBootSector* bs, const PedGeometry *geom)
 {
 	PED_ASSERT (bs != NULL, return 0);
 	PED_ASSERT (geom != NULL, return 0);

 	if (!ped_geometry_read (geom, bs, 0, 1))
 		return 0;

 	if (PED_LE16_TO_CPU (bs->boot_sign) != 0xAA55) {
 		ped_exception_throw (PED_EXCEPTION_ERROR, PED_EXCEPTION_CANCEL,
 			_("File system has an invalid signature for a FAT "
 			  "file system."));
 		return 0;
 	}

 	if (!bs->system_id[0]) {
 		ped_exception_throw (PED_EXCEPTION_ERROR, PED_EXCEPTION_CANCEL,
 			_("File system has an invalid signature for a FAT "
 			  "file system."));
 		return 0;
 	}

 	if (!bs->sector_size
             || PED_LE16_TO_CPU (bs->sector_size) % PED_SECTOR_SIZE_DEFAULT) {
 		ped_exception_throw (PED_EXCEPTION_ERROR, PED_EXCEPTION_CANCEL,
 			_("File system has an invalid sector size for a FAT "
 			  "file system."));
 		return 0;
 	}

 	if (!bs->cluster_size) {
 		ped_exception_throw (PED_EXCEPTION_ERROR, PED_EXCEPTION_CANCEL,
 			_("File system has an invalid cluster size for a FAT "
 			  "file system."));
 		return 0;
 	}

 	if (!bs->reserved) {
 		ped_exception_throw (PED_EXCEPTION_ERROR, PED_EXCEPTION_CANCEL,
 			_("File system has an invalid number of reserved "
 			  "sectors for a FAT file system."));
 		return 0;
 	}

 	if (bs->fats < 1 || bs->fats > 4) {
 		ped_exception_throw (PED_EXCEPTION_ERROR, PED_EXCEPTION_CANCEL,
 			_("File system has an invalid number of FATs."));
 		return 0;
 	}

 	return 1;
 }

 /*
     Don't trust the FAT12, FAT16 or FAT32 label string.
  */
 FatType
 fat_boot_sector_probe_type (const FatBootSector* bs, const PedGeometry* geom)
 {
 	PedSector	logical_sector_size;
 	PedSector	first_cluster_sector;
 	FatCluster	cluster_count;

 	if (!PED_LE16_TO_CPU (bs->dir_entries))
 		return FAT_TYPE_FAT32;

 	logical_sector_size = PED_LE16_TO_CPU (bs->sector_size) / 512;

 	first_cluster_sector
 		= PED_LE16_TO_CPU (bs->reserved) * logical_sector_size
 		  + 2 * PED_LE16_TO_CPU (bs->fat_length) * logical_sector_size
 		  + PED_LE16_TO_CPU (bs->dir_entries)
 			/ (512 / sizeof (FatDirEntry));
 	cluster_count = (geom->length - first_cluster_sector)
 			/ bs->cluster_size / logical_sector_size;
 	if (cluster_count > MAX_FAT12_CLUSTERS)
 		return FAT_TYPE_FAT16;
 	else
 		return FAT_TYPE_FAT12;
 }

 /* Analyses the boot sector, and sticks appropriate numbers in
    fs->type_specific.

    Note: you need to subtract (2 * cluster_sectors) off cluster offset,
    because the first cluster is number 2.  (0 and 1 are not real clusters,
    and referencing them is a bug)
  */
 int
 fat_boot_sector_analyse (FatBootSector* bs, PedFileSystem* fs)
 {
 	FatSpecific*		fs_info = FAT_SPECIFIC (fs);
 	int			fat_entry_size;

 	PED_ASSERT (bs != NULL, return 0);

 	if (PED_LE16_TO_CPU (bs->sector_size) != 512) {
 		if (ped_exception_throw (
 			PED_EXCEPTION_BUG,
 			PED_EXCEPTION_IGNORE_CANCEL,
 			_("This file system has a logical sector size of %d.  "
 			"GNU Parted is known not to work properly with sector "
 			"sizes other than 512 bytes."),
 			(int) PED_LE16_TO_CPU (bs->sector_size))
 				!= PED_EXCEPTION_IGNORE)
 			return 0;
 	}

 	fs_info->logical_sector_size = PED_LE16_TO_CPU (bs->sector_size) / 512;

 	fs_info->sectors_per_track = PED_LE16_TO_CPU (bs->secs_track);
 	fs_info->heads = PED_LE16_TO_CPU (bs->heads);
 	if (fs_info->sectors_per_track < 1 || fs_info->sectors_per_track > 63
 	    || fs_info->heads < 1 || fs_info->heads > 255) {
 		PedCHSGeometry* bios_geom = &fs->geom->dev->bios_geom;
 		int cyl_count = 0;

 		if (fs_info->heads > 0 && fs_info->sectors_per_track > 0)
 			cyl_count = fs->geom->dev->length / fs_info->heads
 					/ fs_info->sectors_per_track;

 		switch (ped_exception_throw (
 			PED_EXCEPTION_ERROR,
 			PED_EXCEPTION_FIX + PED_EXCEPTION_IGNORE
 			+ PED_EXCEPTION_CANCEL,
 			_("The file system's CHS geometry is (%d, %d, %d), "
 			  "which is invalid.  The partition table's CHS "
 			  "geometry is (%d, %d, %d).  If you select Ignore, "
 			  "the file system's CHS geometry will be left "
 			  "unchanged.  If you select Fix, the file system's "
 			  "CHS geometry will be set to match the partition "
 			  "table's CHS geometry."),
 			 cyl_count, fs_info->heads, fs_info->sectors_per_track,
 			 bios_geom->cylinders, bios_geom->heads,
 			 bios_geom->sectors)) {

 		case PED_EXCEPTION_FIX:
 			fs_info->sectors_per_track = bios_geom->sectors;
 			fs_info->heads = bios_geom->heads;
 			bs->secs_track
 				= PED_CPU_TO_LE16 (fs_info->sectors_per_track);
 			bs->heads = PED_CPU_TO_LE16 (fs_info->heads);
 			if (!fat_boot_sector_write (bs, fs))
 				return 0;
 			break;

 		case PED_EXCEPTION_CANCEL:
 			return 0;

 		case PED_EXCEPTION_IGNORE:
 			break;

                 default:
                         break;
 		}
 	}

 	if (bs->sectors)
 		fs_info->sector_count = PED_LE16_TO_CPU (bs->sectors)
 						* fs_info->logical_sector_size;
 	else
 		fs_info->sector_count = PED_LE32_TO_CPU (bs->sector_count)
 						* fs_info->logical_sector_size;

 	fs_info->fat_table_count = bs->fats;
 	fs_info->root_dir_entry_count = PED_LE16_TO_CPU (bs->dir_entries);
 	fs_info->fat_offset = PED_LE16_TO_CPU (bs->reserved)
 					* fs_info->logical_sector_size;
 	fs_info->cluster_sectors = bs->cluster_size
 				   * fs_info->logical_sector_size;
 	fs_info->cluster_size = fs_info->cluster_sectors * 512;

 	if (fs_info->logical_sector_size == 0) {
 		ped_exception_throw (PED_EXCEPTION_ERROR, PED_EXCEPTION_CANCEL,
 			_("FAT boot sector says logical sector size is 0.  "
 			  "This is weird. "));
 		return 0;
 	}
 	if (fs_info->fat_table_count == 0) {
 		ped_exception_throw (PED_EXCEPTION_ERROR, PED_EXCEPTION_CANCEL,
 			_("FAT boot sector says there are no FAT tables.  This "
 			  "is weird. "));
 		return 0;
 	}
 	if (fs_info->cluster_sectors == 0) {
 		ped_exception_throw (PED_EXCEPTION_ERROR, PED_EXCEPTION_CANCEL,
 			_("FAT boot sector says clusters are 0 sectors.  This "
 			  "is weird. "));
 		return 0;
 	}

 	fs_info->fat_type = fat_boot_sector_probe_type (bs, fs->geom);
 	if (fs_info->fat_type == FAT_TYPE_FAT12) {
 		ped_exception_throw (
 			PED_EXCEPTION_NO_FEATURE,
 			PED_EXCEPTION_CANCEL,
 			_("File system is FAT12, which is unsupported."));
 		return 0;
 	}
 	if (fs_info->fat_type == FAT_TYPE_FAT16) {
 		fs_info->fat_sectors = PED_LE16_TO_CPU (bs->fat_length)
 				       * fs_info->logical_sector_size;
 		fs_info->serial_number
 			= PED_LE32_TO_CPU (bs->u.fat16.serial_number);
 		fs_info->root_cluster = 0;
 		fs_info->root_dir_offset
 			= fs_info->fat_offset
 			  + fs_info->fat_sectors * fs_info->fat_table_count;
 		fs_info->root_dir_sector_count
 			= fs_info->root_dir_entry_count * sizeof (FatDirEntry)
 			  / (512 * fs_info->logical_sector_size);
 		fs_info->cluster_offset
 			= fs_info->root_dir_offset
 			  + fs_info->root_dir_sector_count;
 	}
 	if (fs_info->fat_type == FAT_TYPE_FAT32) {
 		fs_info->fat_sectors = PED_LE32_TO_CPU (bs->u.fat32.fat_length)
 					* fs_info->logical_sector_size;
 		fs_info->serial_number
 			= PED_LE32_TO_CPU (bs->u.fat32.serial_number);
 		fs_info->info_sector_offset
 		    = PED_LE16_TO_CPU (fs_info->boot_sector.u.fat32.info_sector)
 			  * fs_info->logical_sector_size;
 		fs_info->boot_sector_backup_offset
 		  = PED_LE16_TO_CPU (fs_info->boot_sector.u.fat32.backup_sector)
 			  * fs_info->logical_sector_size;
 		fs_info->root_cluster
 			= PED_LE32_TO_CPU (bs->u.fat32.root_dir_cluster);
 		fs_info->root_dir_offset = 0;
 		fs_info->root_dir_sector_count = 0;
 		fs_info->cluster_offset
 			= fs_info->fat_offset
 			  + fs_info->fat_sectors * fs_info->fat_table_count;
 	}

 	fs_info->cluster_count
 		= (fs_info->sector_count - fs_info->cluster_offset)
 		  / fs_info->cluster_sectors;

 	fat_entry_size = fat_table_entry_size (fs_info->fat_type);
 	if (fs_info->cluster_count + 2
 			> fs_info->fat_sectors * 512 / fat_entry_size)
 		fs_info->cluster_count
 			= fs_info->fat_sectors * 512 / fat_entry_size - 2;

 	fs_info->dir_entries_per_cluster
 		= fs_info->cluster_size / sizeof (FatDirEntry);
 	return 1;
 }

 #ifndef DISCOVER_ONLY
 int
 fat_boot_sector_set_boot_code (FatBootSector* bs)
 {
 	PED_ASSERT (bs != NULL, return 0);

 	memset (bs, 0, 512);
 	memcpy (bs->boot_jump, FAT_BOOT_JUMP, 3);
 	memcpy (bs->u.fat32.boot_code, FAT_BOOT_CODE, FAT_BOOT_CODE_LENGTH);
 	return 1;
 }

 int
 fat_boot_sector_generate (FatBootSector* bs, const PedFileSystem* fs)
 {
 	FatSpecific*	fs_info = FAT_SPECIFIC (fs);

 	PED_ASSERT (bs != NULL, return 0);

 	memcpy (bs->system_id, "MSWIN4.1", 8);
 	bs->sector_size = PED_CPU_TO_LE16 (fs_info->logical_sector_size * 512);
 	bs->cluster_size = fs_info->cluster_sectors
 				/ fs_info->logical_sector_size;
 	bs->reserved = PED_CPU_TO_LE16 (fs_info->fat_offset
 					/ fs_info->logical_sector_size);
 	bs->fats = fs_info->fat_table_count;

 	bs->dir_entries = (fs_info->fat_type == FAT_TYPE_FAT16)
 			  ? PED_CPU_TO_LE16 (fs_info->root_dir_entry_count)
 			  : 0;

 	if (fs_info->sector_count / fs_info->logical_sector_size > 0xffff
 		|| fs_info->fat_type == FAT_TYPE_FAT32) {
 		bs->sectors = 0;
 		bs->sector_count = PED_CPU_TO_LE32 (fs_info->sector_count
 						/ fs_info->logical_sector_size);
 	} else {
 		bs->sectors = PED_CPU_TO_LE16 (fs_info->sector_count
 					       / fs_info->logical_sector_size);
 		bs->sector_count = 0;
 	}

 	bs->media = 0xf8;

 	bs->secs_track = PED_CPU_TO_LE16 (fs_info->sectors_per_track);
 	bs->heads = PED_CPU_TO_LE16 (fs_info->heads);
 	bs->hidden = PED_CPU_TO_LE32 (fs->geom->start);

 	if (fs_info->fat_type == FAT_TYPE_FAT32) {
 		bs->fat_length = 0;
 		bs->u.fat32.fat_length = PED_CPU_TO_LE32 (fs_info->fat_sectors
 						/ fs_info->logical_sector_size);
 		bs->u.fat32.flags = 0;	/* FIXME: what the hell are these? */
 		bs->u.fat32.version = 0;  /* must be 0, for Win98 bootstrap */
 		bs->u.fat32.root_dir_cluster
 			= PED_CPU_TO_LE32 (fs_info->root_cluster);
 		bs->u.fat32.info_sector
 			= PED_CPU_TO_LE16 (fs_info->info_sector_offset
 					   / fs_info->logical_sector_size);
 		bs->u.fat32.backup_sector
 			= PED_CPU_TO_LE16 (fs_info->boot_sector_backup_offset
 					   / fs_info->logical_sector_size);

 		bs->u.fat32.drive_num = 0x80;	/* _ALWAYS_ 0x80.  silly DOS */

 		memset (bs->u.fat32.empty_1, 0, 12);

 		bs->u.fat32.ext_signature = 0x29;
 		bs->u.fat32.serial_number
 			= PED_CPU_TO_LE32 (fs_info->serial_number);
 		memcpy (bs->u.fat32.volume_name, "NO NAME    ", 11);
 		memcpy (bs->u.fat32.fat_name, "FAT32   ", 8);
 	} else {
 		bs->fat_length
 			= PED_CPU_TO_LE16 (fs_info->fat_sectors
 					   / fs_info->logical_sector_size);

 		bs->u.fat16.drive_num = 0x80;	/* _ALWAYS_ 0x80.  silly DOS */

 		bs->u.fat16.ext_signature = 0x29;
 		bs->u.fat16.serial_number
 			= PED_CPU_TO_LE32 (fs_info->serial_number);
 		memcpy (bs->u.fat16.volume_name, "NO NAME    ", 11);
 		memcpy (bs->u.fat16.fat_name, "FAT16   ", 8);
 	}

 	bs->boot_sign = PED_CPU_TO_LE16 (0xaa55);

 	return 1;
 }

 int
 fat_boot_sector_write (const FatBootSector* bs, PedFileSystem* fs)
 {
 	FatSpecific*	fs_info = FAT_SPECIFIC (fs);

 	PED_ASSERT (bs != NULL, return 0);

 	if (!ped_geometry_write (fs->geom, bs, 0, 1))
 		return 0;
 	if (fs_info->fat_type == FAT_TYPE_FAT32) {
 		if (!ped_geometry_write (fs->geom, bs,
 					 fs_info->boot_sector_backup_offset, 1))
 			return 0;
 	}
 	return ped_geometry_sync (fs->geom);
 }

 int
 fat_info_sector_read (FatInfoSector* is, const PedFileSystem* fs)
 {
 	FatSpecific*	fs_info = FAT_SPECIFIC (fs);
 	int		status;

 	PED_ASSERT (is != NULL, return 0);

 	if (!ped_geometry_read (fs->geom, is, fs_info->info_sector_offset, 1))
 		return 0;

 	if (PED_LE32_TO_CPU (is->signature_2) != FAT32_INFO_MAGIC2) {
 		status = ped_exception_throw (PED_EXCEPTION_WARNING,
 				PED_EXCEPTION_IGNORE_CANCEL,
 				_("The information sector has the wrong "
 				"signature (%x).  Select cancel for now, "
 				"and send in a bug report.  If you're "
 				"desperate, it's probably safe to ignore."),
 				PED_LE32_TO_CPU (is->signature_2));
 		if (status == PED_EXCEPTION_CANCEL) return 0;
 	}
 	return 1;
 }

 int
 fat_info_sector_generate (FatInfoSector* is, const PedFileSystem* fs)
 {
 	FatSpecific*	fs_info = FAT_SPECIFIC (fs);

 	PED_ASSERT (is != NULL, return 0);

 	fat_table_count_stats (fs_info->fat);

 	memset (is, 0, 512);

 	is->signature_1 = PED_CPU_TO_LE32 (FAT32_INFO_MAGIC1);
 	is->signature_2 = PED_CPU_TO_LE32 (FAT32_INFO_MAGIC2);
 	is->free_clusters = PED_CPU_TO_LE32 (fs_info->fat->free_cluster_count);
 	is->next_cluster = PED_CPU_TO_LE32 (fs_info->fat->last_alloc);
 	is->signature_3 = PED_CPU_TO_LE16 (FAT32_INFO_MAGIC3);

 	return 1;
 }

 int
 fat_info_sector_write (const FatInfoSector* is, PedFileSystem *fs)
 {
 	FatSpecific*	fs_info = FAT_SPECIFIC (fs);

 	PED_ASSERT (is != NULL, return 0);

 	if (!ped_geometry_write (fs->geom, is, fs_info->info_sector_offset, 1))
 		return 0;
 	return ped_geometry_sync (fs->geom);
 }
 #endif /* !DISCOVER_ONLY */
	/*
	libparted
	Copyright (C) 1998, 1999, 2000, 2002, 2004, 2007 Free Software Foundation, Inc.

	This program 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 2 of the License, or
	(at your option) any later version.

	This program 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 this program; if not, write to the Free Software
	Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301, USA
	*/

	#include <config.h>
	#include "fat.h"

	#include <stdio.h>
	#include <stdlib.h>
	#include <string.h>
	#include <sys/types.h>
	#include <sys/stat.h>
	#include <fcntl.h>
	#include <errno.h>

	/* Reads in the boot sector (superblock), and does a minimum of sanity
	* checking. The goals are:
	* - to detect fat file systems, even if they are damaged [i.e. not
	* return an error / throw an exception]
	* - to fail detection if there's not enough information for
	* fat_boot_sector_probe_type() to work (or possibly crash on a divide-by-zero)
	*/
	int
	fat_boot_sector_read (FatBootSector* bs, const PedGeometry *geom)
	{
	PED_ASSERT (bs != NULL, return 0);
	PED_ASSERT (geom != NULL, return 0);

	if (!ped_geometry_read (geom, bs, 0, 1))
	return 0;

	if (PED_LE16_TO_CPU (bs->boot_sign) != 0xAA55) {
	ped_exception_throw (PED_EXCEPTION_ERROR, PED_EXCEPTION_CANCEL,
	_("File system has an invalid signature for a FAT "
	"file system."));
	return 0;
	}

	if (!bs->system_id[0]) {
	ped_exception_throw (PED_EXCEPTION_ERROR, PED_EXCEPTION_CANCEL,
	_("File system has an invalid signature for a FAT "
	"file system."));
	return 0;
	}

	if (!bs->sector_size
	\|\| PED_LE16_TO_CPU (bs->sector_size) % PED_SECTOR_SIZE_DEFAULT) {
	ped_exception_throw (PED_EXCEPTION_ERROR, PED_EXCEPTION_CANCEL,
	_("File system has an invalid sector size for a FAT "
	"file system."));
	return 0;
	}

	if (!bs->cluster_size) {
	ped_exception_throw (PED_EXCEPTION_ERROR, PED_EXCEPTION_CANCEL,
	_("File system has an invalid cluster size for a FAT "
	"file system."));
	return 0;
	}

	if (!bs->reserved) {
	ped_exception_throw (PED_EXCEPTION_ERROR, PED_EXCEPTION_CANCEL,
	_("File system has an invalid number of reserved "
	"sectors for a FAT file system."));
	return 0;
	}

	if (bs->fats < 1 \|\| bs->fats > 4) {
	ped_exception_throw (PED_EXCEPTION_ERROR, PED_EXCEPTION_CANCEL,
	_("File system has an invalid number of FATs."));
	return 0;
	}

	return 1;
	}

	/*
	Don't trust the FAT12, FAT16 or FAT32 label string.
	*/
	FatType
	fat_boot_sector_probe_type (const FatBootSector* bs, const PedGeometry* geom)
	{
	PedSector logical_sector_size;
	PedSector first_cluster_sector;
	FatCluster cluster_count;

	if (!PED_LE16_TO_CPU (bs->dir_entries))
	return FAT_TYPE_FAT32;

	logical_sector_size = PED_LE16_TO_CPU (bs->sector_size) / 512;

	first_cluster_sector
	= PED_LE16_TO_CPU (bs->reserved) * logical_sector_size
	+ 2 * PED_LE16_TO_CPU (bs->fat_length) * logical_sector_size
	+ PED_LE16_TO_CPU (bs->dir_entries)
	/ (512 / sizeof (FatDirEntry));
	cluster_count = (geom->length - first_cluster_sector)
	/ bs->cluster_size / logical_sector_size;
	if (cluster_count > MAX_FAT12_CLUSTERS)
	return FAT_TYPE_FAT16;
	else
	return FAT_TYPE_FAT12;
	}

	/* Analyses the boot sector, and sticks appropriate numbers in
	fs->type_specific.

	Note: you need to subtract (2 * cluster_sectors) off cluster offset,
	because the first cluster is number 2. (0 and 1 are not real clusters,
	and referencing them is a bug)
	*/
	int
	fat_boot_sector_analyse (FatBootSector* bs, PedFileSystem* fs)
	{
	FatSpecific* fs_info = FAT_SPECIFIC (fs);
	int fat_entry_size;

	PED_ASSERT (bs != NULL, return 0);

	if (PED_LE16_TO_CPU (bs->sector_size) != 512) {
	if (ped_exception_throw (
	PED_EXCEPTION_BUG,
	PED_EXCEPTION_IGNORE_CANCEL,
	_("This file system has a logical sector size of %d. "
	"GNU Parted is known not to work properly with sector "
	"sizes other than 512 bytes."),
	(int) PED_LE16_TO_CPU (bs->sector_size))
	!= PED_EXCEPTION_IGNORE)
	return 0;
	}

	fs_info->logical_sector_size = PED_LE16_TO_CPU (bs->sector_size) / 512;

	fs_info->sectors_per_track = PED_LE16_TO_CPU (bs->secs_track);
	fs_info->heads = PED_LE16_TO_CPU (bs->heads);
	if (fs_info->sectors_per_track < 1 \|\| fs_info->sectors_per_track > 63
	\|\| fs_info->heads < 1 \|\| fs_info->heads > 255) {
	PedCHSGeometry* bios_geom = &fs->geom->dev->bios_geom;
	int cyl_count = 0;

	if (fs_info->heads > 0 && fs_info->sectors_per_track > 0)
	cyl_count = fs->geom->dev->length / fs_info->heads
	/ fs_info->sectors_per_track;

	switch (ped_exception_throw (
	PED_EXCEPTION_ERROR,
	PED_EXCEPTION_FIX + PED_EXCEPTION_IGNORE
	+ PED_EXCEPTION_CANCEL,
	_("The file system's CHS geometry is (%d, %d, %d), "
	"which is invalid. The partition table's CHS "
	"geometry is (%d, %d, %d). If you select Ignore, "
	"the file system's CHS geometry will be left "
	"unchanged. If you select Fix, the file system's "
	"CHS geometry will be set to match the partition "
	"table's CHS geometry."),
	cyl_count, fs_info->heads, fs_info->sectors_per_track,
	bios_geom->cylinders, bios_geom->heads,
	bios_geom->sectors)) {

	case PED_EXCEPTION_FIX:
	fs_info->sectors_per_track = bios_geom->sectors;
	fs_info->heads = bios_geom->heads;
	bs->secs_track
	= PED_CPU_TO_LE16 (fs_info->sectors_per_track);
	bs->heads = PED_CPU_TO_LE16 (fs_info->heads);
	if (!fat_boot_sector_write (bs, fs))
	return 0;
	break;

	case PED_EXCEPTION_CANCEL:
	return 0;

	case PED_EXCEPTION_IGNORE:
	break;

	default:
	break;
	}
	}

	if (bs->sectors)
	fs_info->sector_count = PED_LE16_TO_CPU (bs->sectors)
	* fs_info->logical_sector_size;
	else
	fs_info->sector_count = PED_LE32_TO_CPU (bs->sector_count)
	* fs_info->logical_sector_size;

	fs_info->fat_table_count = bs->fats;
	fs_info->root_dir_entry_count = PED_LE16_TO_CPU (bs->dir_entries);
	fs_info->fat_offset = PED_LE16_TO_CPU (bs->reserved)
	* fs_info->logical_sector_size;
	fs_info->cluster_sectors = bs->cluster_size
	* fs_info->logical_sector_size;
	fs_info->cluster_size = fs_info->cluster_sectors * 512;

	if (fs_info->logical_sector_size == 0) {
	ped_exception_throw (PED_EXCEPTION_ERROR, PED_EXCEPTION_CANCEL,
	_("FAT boot sector says logical sector size is 0. "
	"This is weird. "));
	return 0;
	}
	if (fs_info->fat_table_count == 0) {
	ped_exception_throw (PED_EXCEPTION_ERROR, PED_EXCEPTION_CANCEL,
	_("FAT boot sector says there are no FAT tables. This "
	"is weird. "));
	return 0;
	}
	if (fs_info->cluster_sectors == 0) {
	ped_exception_throw (PED_EXCEPTION_ERROR, PED_EXCEPTION_CANCEL,
	_("FAT boot sector says clusters are 0 sectors. This "
	"is weird. "));
	return 0;
	}

	fs_info->fat_type = fat_boot_sector_probe_type (bs, fs->geom);
	if (fs_info->fat_type == FAT_TYPE_FAT12) {
	ped_exception_throw (
	PED_EXCEPTION_NO_FEATURE,
	PED_EXCEPTION_CANCEL,
	_("File system is FAT12, which is unsupported."));
	return 0;
	}
	if (fs_info->fat_type == FAT_TYPE_FAT16) {
	fs_info->fat_sectors = PED_LE16_TO_CPU (bs->fat_length)
	* fs_info->logical_sector_size;
	fs_info->serial_number
	= PED_LE32_TO_CPU (bs->u.fat16.serial_number);
	fs_info->root_cluster = 0;
	fs_info->root_dir_offset
	= fs_info->fat_offset
	+ fs_info->fat_sectors * fs_info->fat_table_count;
	fs_info->root_dir_sector_count
	= fs_info->root_dir_entry_count * sizeof (FatDirEntry)
	/ (512 * fs_info->logical_sector_size);
	fs_info->cluster_offset
	= fs_info->root_dir_offset
	+ fs_info->root_dir_sector_count;
	}
	if (fs_info->fat_type == FAT_TYPE_FAT32) {
	fs_info->fat_sectors = PED_LE32_TO_CPU (bs->u.fat32.fat_length)
	* fs_info->logical_sector_size;
	fs_info->serial_number
	= PED_LE32_TO_CPU (bs->u.fat32.serial_number);
	fs_info->info_sector_offset
	= PED_LE16_TO_CPU (fs_info->boot_sector.u.fat32.info_sector)
	* fs_info->logical_sector_size;
	fs_info->boot_sector_backup_offset
	= PED_LE16_TO_CPU (fs_info->boot_sector.u.fat32.backup_sector)
	* fs_info->logical_sector_size;
	fs_info->root_cluster
	= PED_LE32_TO_CPU (bs->u.fat32.root_dir_cluster);
	fs_info->root_dir_offset = 0;
	fs_info->root_dir_sector_count = 0;
	fs_info->cluster_offset
	= fs_info->fat_offset
	+ fs_info->fat_sectors * fs_info->fat_table_count;
	}

	fs_info->cluster_count
	= (fs_info->sector_count - fs_info->cluster_offset)
	/ fs_info->cluster_sectors;

	fat_entry_size = fat_table_entry_size (fs_info->fat_type);
	if (fs_info->cluster_count + 2
	> fs_info->fat_sectors * 512 / fat_entry_size)
	fs_info->cluster_count
	= fs_info->fat_sectors * 512 / fat_entry_size - 2;

	fs_info->dir_entries_per_cluster
	= fs_info->cluster_size / sizeof (FatDirEntry);
	return 1;
	}

	#ifndef DISCOVER_ONLY
	int
	fat_boot_sector_set_boot_code (FatBootSector* bs)
	{
	PED_ASSERT (bs != NULL, return 0);

	memset (bs, 0, 512);
	memcpy (bs->boot_jump, FAT_BOOT_JUMP, 3);
	memcpy (bs->u.fat32.boot_code, FAT_BOOT_CODE, FAT_BOOT_CODE_LENGTH);
	return 1;
	}

	int
	fat_boot_sector_generate (FatBootSector* bs, const PedFileSystem* fs)
	{
	FatSpecific* fs_info = FAT_SPECIFIC (fs);

	PED_ASSERT (bs != NULL, return 0);

	memcpy (bs->system_id, "MSWIN4.1", 8);
	bs->sector_size = PED_CPU_TO_LE16 (fs_info->logical_sector_size * 512);
	bs->cluster_size = fs_info->cluster_sectors
	/ fs_info->logical_sector_size;
	bs->reserved = PED_CPU_TO_LE16 (fs_info->fat_offset
	/ fs_info->logical_sector_size);
	bs->fats = fs_info->fat_table_count;

	bs->dir_entries = (fs_info->fat_type == FAT_TYPE_FAT16)
	? PED_CPU_TO_LE16 (fs_info->root_dir_entry_count)
	: 0;

	if (fs_info->sector_count / fs_info->logical_sector_size > 0xffff
	\|\| fs_info->fat_type == FAT_TYPE_FAT32) {
	bs->sectors = 0;
	bs->sector_count = PED_CPU_TO_LE32 (fs_info->sector_count
	/ fs_info->logical_sector_size);
	} else {
	bs->sectors = PED_CPU_TO_LE16 (fs_info->sector_count
	/ fs_info->logical_sector_size);
	bs->sector_count = 0;
	}

	bs->media = 0xf8;

	bs->secs_track = PED_CPU_TO_LE16 (fs_info->sectors_per_track);
	bs->heads = PED_CPU_TO_LE16 (fs_info->heads);
	bs->hidden = PED_CPU_TO_LE32 (fs->geom->start);

	if (fs_info->fat_type == FAT_TYPE_FAT32) {
	bs->fat_length = 0;
	bs->u.fat32.fat_length = PED_CPU_TO_LE32 (fs_info->fat_sectors
	/ fs_info->logical_sector_size);
	bs->u.fat32.flags = 0; /* FIXME: what the hell are these? */
	bs->u.fat32.version = 0; /* must be 0, for Win98 bootstrap */
	bs->u.fat32.root_dir_cluster
	= PED_CPU_TO_LE32 (fs_info->root_cluster);
	bs->u.fat32.info_sector
	= PED_CPU_TO_LE16 (fs_info->info_sector_offset
	/ fs_info->logical_sector_size);
	bs->u.fat32.backup_sector
	= PED_CPU_TO_LE16 (fs_info->boot_sector_backup_offset
	/ fs_info->logical_sector_size);

	bs->u.fat32.drive_num = 0x80; /* _ALWAYS_ 0x80. silly DOS */

	memset (bs->u.fat32.empty_1, 0, 12);

	bs->u.fat32.ext_signature = 0x29;
	bs->u.fat32.serial_number
	= PED_CPU_TO_LE32 (fs_info->serial_number);
	memcpy (bs->u.fat32.volume_name, "NO NAME ", 11);
	memcpy (bs->u.fat32.fat_name, "FAT32 ", 8);
	} else {
	bs->fat_length
	= PED_CPU_TO_LE16 (fs_info->fat_sectors
	/ fs_info->logical_sector_size);

	bs->u.fat16.drive_num = 0x80; /* _ALWAYS_ 0x80. silly DOS */

	bs->u.fat16.ext_signature = 0x29;
	bs->u.fat16.serial_number
	= PED_CPU_TO_LE32 (fs_info->serial_number);
	memcpy (bs->u.fat16.volume_name, "NO NAME ", 11);
	memcpy (bs->u.fat16.fat_name, "FAT16 ", 8);
	}

	bs->boot_sign = PED_CPU_TO_LE16 (0xaa55);

	return 1;
	}

	int
	fat_boot_sector_write (const FatBootSector* bs, PedFileSystem* fs)
	{
	FatSpecific* fs_info = FAT_SPECIFIC (fs);

	PED_ASSERT (bs != NULL, return 0);

	if (!ped_geometry_write (fs->geom, bs, 0, 1))
	return 0;
	if (fs_info->fat_type == FAT_TYPE_FAT32) {
	if (!ped_geometry_write (fs->geom, bs,
	fs_info->boot_sector_backup_offset, 1))
	return 0;
	}
	return ped_geometry_sync (fs->geom);
	}

	int
	fat_info_sector_read (FatInfoSector* is, const PedFileSystem* fs)
	{
	FatSpecific* fs_info = FAT_SPECIFIC (fs);
	int status;

	PED_ASSERT (is != NULL, return 0);

	if (!ped_geometry_read (fs->geom, is, fs_info->info_sector_offset, 1))
	return 0;

	if (PED_LE32_TO_CPU (is->signature_2) != FAT32_INFO_MAGIC2) {
	status = ped_exception_throw (PED_EXCEPTION_WARNING,
	PED_EXCEPTION_IGNORE_CANCEL,
	_("The information sector has the wrong "
	"signature (%x). Select cancel for now, "
	"and send in a bug report. If you're "
	"desperate, it's probably safe to ignore."),
	PED_LE32_TO_CPU (is->signature_2));
	if (status == PED_EXCEPTION_CANCEL) return 0;
	}
	return 1;
	}

	int
	fat_info_sector_generate (FatInfoSector* is, const PedFileSystem* fs)
	{
	FatSpecific* fs_info = FAT_SPECIFIC (fs);

	PED_ASSERT (is != NULL, return 0);

	fat_table_count_stats (fs_info->fat);

	memset (is, 0, 512);

	is->signature_1 = PED_CPU_TO_LE32 (FAT32_INFO_MAGIC1);
	is->signature_2 = PED_CPU_TO_LE32 (FAT32_INFO_MAGIC2);
	is->free_clusters = PED_CPU_TO_LE32 (fs_info->fat->free_cluster_count);
	is->next_cluster = PED_CPU_TO_LE32 (fs_info->fat->last_alloc);
	is->signature_3 = PED_CPU_TO_LE16 (FAT32_INFO_MAGIC3);

	return 1;
	}

	int
	fat_info_sector_write (const FatInfoSector* is, PedFileSystem *fs)
	{
	FatSpecific* fs_info = FAT_SPECIFIC (fs);

	PED_ASSERT (is != NULL, return 0);

	if (!ped_geometry_write (fs->geom, is, fs_info->info_sector_offset, 1))
	return 0;
	return ped_geometry_sync (fs->geom);
	}
	#endif /* !DISCOVER_ONLY */