1 files changed, 333 insertions, 0 deletions
diff --git a/util-linux/volume_id/fat.c b/util-linux/volume_id/fat.c
new file mode 100644
index 000000000..4c2a91749
--- /dev/null
+++ b/util-linux/volume_id/fat.c
@@ -0,0 +1,333 @@
+/*
+ * volume_id - reads filesystem label and uuid
+ *
+ * Copyright (C) 2004 Kay Sievers <kay.sievers@vrfy.org>
+ *
+ *	This library is free software; you can redistribute it and/or
+ *	modify it under the terms of the GNU Lesser General Public
+ *	License as published by the Free Software Foundation; either
+ *	version 2.1 of the License, or (at your option) any later version.
+ *
+ *	This library 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
+ *	Lesser General Public License for more details.
+ *
+ *	You should have received a copy of the GNU Lesser General Public
+ *	License along with this library; if not, write to the Free Software
+ *	Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
+ */
+
+#include "volume_id_internal.h"
+
+#define FAT12_MAX			0xff5
+#define FAT16_MAX			0xfff5
+#define FAT_ATTR_VOLUME_ID		0x08
+#define FAT_ATTR_DIR			0x10
+#define FAT_ATTR_LONG_NAME		0x0f
+#define FAT_ATTR_MASK			0x3f
+#define FAT_ENTRY_FREE			0xe5
+
+struct vfat_super_block {
+	uint8_t		boot_jump[3];
+	uint8_t		sysid[8];
+	uint16_t	sector_size;
+	uint8_t		sectors_per_cluster;
+	uint16_t	reserved;
+	uint8_t		fats;
+	uint16_t	dir_entries;
+	uint16_t	sectors;
+	uint8_t		media;
+	uint16_t	fat_length;
+	uint16_t	secs_track;
+	uint16_t	heads;
+	uint32_t	hidden;
+	uint32_t	total_sect;
+	union {
+		struct fat_super_block {
+			uint8_t		unknown[3];
+			uint8_t		serno[4];
+			uint8_t		label[11];
+			uint8_t		magic[8];
+			uint8_t		dummy2[192];
+			uint8_t		pmagic[2];
+		} __attribute__((__packed__)) fat;
+		struct fat32_super_block {
+			uint32_t	fat32_length;
+			uint16_t	flags;
+			uint8_t		version[2];
+			uint32_t	root_cluster;
+			uint16_t	insfo_sector;
+			uint16_t	backup_boot;
+			uint16_t	reserved2[6];
+			uint8_t		unknown[3];
+			uint8_t		serno[4];
+			uint8_t		label[11];
+			uint8_t		magic[8];
+			uint8_t		dummy2[164];
+			uint8_t		pmagic[2];
+		} __attribute__((__packed__)) fat32;
+	} __attribute__((__packed__)) type;
+} __attribute__((__packed__));
+
+struct vfat_dir_entry {
+	uint8_t		name[11];
+	uint8_t		attr;
+	uint16_t	time_creat;
+	uint16_t	date_creat;
+	uint16_t	time_acc;
+	uint16_t	date_acc;
+	uint16_t	cluster_high;
+	uint16_t	time_write;
+	uint16_t	date_write;
+	uint16_t	cluster_low;
+	uint32_t	size;
+} __attribute__((__packed__));
+
+static uint8_t *get_attr_volume_id(struct vfat_dir_entry *dir, unsigned count)
+{
+	unsigned i;
+
+	for (i = 0; i < count; i++) {
+		/* end marker */
+		if (dir[i].name[0] == 0x00) {
+			dbg("end of dir");
+			break;
+		}
+
+		/* empty entry */
+		if (dir[i].name[0] == FAT_ENTRY_FREE)
+			continue;
+
+		/* long name */
+		if ((dir[i].attr & FAT_ATTR_MASK) == FAT_ATTR_LONG_NAME)
+			continue;
+
+		if ((dir[i].attr & (FAT_ATTR_VOLUME_ID | FAT_ATTR_DIR)) == FAT_ATTR_VOLUME_ID) {
+			/* labels do not have file data */
+			if (dir[i].cluster_high != 0 || dir[i].cluster_low != 0)
+				continue;
+
+			dbg("found ATTR_VOLUME_ID id in root dir");
+			return dir[i].name;
+		}
+
+		dbg("skip dir entry");
+	}
+
+	return NULL;
+}
+
+int volume_id_probe_vfat(struct volume_id *id, uint64_t off)
+{
+	struct vfat_super_block *vs;
+	struct vfat_dir_entry *dir;
+	uint16_t sector_size;
+	uint16_t dir_entries;
+	uint32_t sect_count;
+	uint16_t reserved;
+	uint32_t fat_size;
+	uint32_t root_cluster;
+	uint32_t dir_size;
+	uint32_t cluster_count;
+	uint32_t fat_length;
+	uint64_t root_start;
+	uint32_t start_data_sect;
+	uint16_t root_dir_entries;
+	uint8_t *buf;
+	uint32_t buf_size;
+	uint8_t *label = NULL;
+	uint32_t next;
+	int maxloop;
+
+	dbg("probing at offset 0x%llx", (unsigned long long) off);
+
+	vs = volume_id_get_buffer(id, off, 0x200);
+	if (vs == NULL)
+		return -1;
+
+	/* believe only that's fat, don't trust the version
+	 * the cluster_count will tell us
+	 */
+	if (memcmp(vs->sysid, "NTFS", 4) == 0)
+		return -1;
+
+	if (memcmp(vs->type.fat32.magic, "MSWIN", 5) == 0)
+		goto valid;
+
+	if (memcmp(vs->type.fat32.magic, "FAT32   ", 8) == 0)
+		goto valid;
+
+	if (memcmp(vs->type.fat.magic, "FAT16   ", 8) == 0)
+		goto valid;
+
+	if (memcmp(vs->type.fat.magic, "MSDOS", 5) == 0)
+		goto valid;
+
+	if (memcmp(vs->type.fat.magic, "FAT12   ", 8) == 0)
+		goto valid;
+
+	/*
+	 * There are old floppies out there without a magic, so we check
+	 * for well known values and guess if it's a fat volume
+	 */
+
+	/* boot jump address check */
+	if ((vs->boot_jump[0] != 0xeb || vs->boot_jump[2] != 0x90) &&
+	     vs->boot_jump[0] != 0xe9)
+		return -1;
+
+	/* heads check */
+	if (vs->heads == 0)
+		return -1;
+
+	/* cluster size check*/	
+	if (vs->sectors_per_cluster == 0 ||
+	    (vs->sectors_per_cluster & (vs->sectors_per_cluster-1)))
+		return -1;
+
+	/* media check */
+	if (vs->media < 0xf8 && vs->media != 0xf0)
+		return -1;
+
+	/* fat count*/
+	if (vs->fats != 2)
+		return -1;
+
+ valid:
+	/* sector size check */
+	sector_size = le16_to_cpu(vs->sector_size);
+	if (sector_size != 0x200 && sector_size != 0x400 &&
+	    sector_size != 0x800 && sector_size != 0x1000)
+		return -1;
+
+	dbg("sector_size 0x%x", sector_size);
+	dbg("sectors_per_cluster 0x%x", vs->sectors_per_cluster);
+
+	dir_entries = le16_to_cpu(vs->dir_entries);
+	reserved = le16_to_cpu(vs->reserved);
+	dbg("reserved 0x%x", reserved);
+
+	sect_count = le16_to_cpu(vs->sectors);
+	if (sect_count == 0)
+		sect_count = le32_to_cpu(vs->total_sect);
+	dbg("sect_count 0x%x", sect_count);
+
+	fat_length = le16_to_cpu(vs->fat_length);
+	if (fat_length == 0)
+		fat_length = le32_to_cpu(vs->type.fat32.fat32_length);
+	dbg("fat_length 0x%x", fat_length);
+
+	fat_size = fat_length * vs->fats;
+	dir_size = ((dir_entries * sizeof(struct vfat_dir_entry)) +
+			(sector_size-1)) / sector_size;
+	dbg("dir_size 0x%x", dir_size);
+
+	cluster_count = sect_count - (reserved + fat_size + dir_size);
+	cluster_count /= vs->sectors_per_cluster;
+	dbg("cluster_count 0x%x", cluster_count);
+
+	if (cluster_count < FAT12_MAX) {
+		strcpy(id->type_version, "FAT12");
+	} else if (cluster_count < FAT16_MAX) {
+		strcpy(id->type_version, "FAT16");
+	} else {
+		strcpy(id->type_version, "FAT32");
+		goto fat32;
+	}
+
+	/* the label may be an attribute in the root directory */
+	root_start = (reserved + fat_size) * sector_size;
+	dbg("root dir start 0x%llx", (unsigned long long) root_start);
+	root_dir_entries = le16_to_cpu(vs->dir_entries);
+	dbg("expected entries 0x%x", root_dir_entries);
+
+	buf_size = root_dir_entries * sizeof(struct vfat_dir_entry);
+	buf = volume_id_get_buffer(id, off + root_start, buf_size);
+	if (buf == NULL)
+		goto found;
+
+	dir = (struct vfat_dir_entry*) buf;
+
+	label = get_attr_volume_id(dir, root_dir_entries);
+
+	vs = volume_id_get_buffer(id, off, 0x200);
+	if (vs == NULL)
+		return -1;
+
+	if (label != NULL && memcmp(label, "NO NAME    ", 11) != 0) {
+		volume_id_set_label_raw(id, label, 11);
+		volume_id_set_label_string(id, label, 11);
+	} else if (memcmp(vs->type.fat.label, "NO NAME    ", 11) != 0) {
+		volume_id_set_label_raw(id, vs->type.fat.label, 11);
+		volume_id_set_label_string(id, vs->type.fat.label, 11);
+	}
+	volume_id_set_uuid(id, vs->type.fat.serno, UUID_DOS);
+	goto found;
+
+ fat32:
+	/* FAT32 root dir is a cluster chain like any other directory */
+	buf_size = vs->sectors_per_cluster * sector_size;
+	root_cluster = le32_to_cpu(vs->type.fat32.root_cluster);
+	dbg("root dir cluster %u", root_cluster);
+	start_data_sect = reserved + fat_size;
+
+	next = root_cluster;
+	maxloop = 100;
+	while (--maxloop) {
+		uint32_t next_sect_off;
+		uint64_t next_off;
+		uint64_t fat_entry_off;
+		int count;
+
+		dbg("next cluster %u", next);
+		next_sect_off = (next - 2) * vs->sectors_per_cluster;
+		next_off = (start_data_sect + next_sect_off) * sector_size;
+		dbg("cluster offset 0x%llx", (unsigned long long) next_off);
+
+		/* get cluster */
+		buf = volume_id_get_buffer(id, off + next_off, buf_size);
+		if (buf == NULL)
+			goto found;
+
+		dir = (struct vfat_dir_entry*) buf;
+		count = buf_size / sizeof(struct vfat_dir_entry);
+		dbg("expected entries 0x%x", count);
+
+		label = get_attr_volume_id(dir, count);
+		if (label)
+			break;
+
+		/* get FAT entry */
+		fat_entry_off = (reserved * sector_size) + (next * sizeof(uint32_t));
+		buf = volume_id_get_buffer(id, off + fat_entry_off, buf_size);
+		if (buf == NULL)
+			goto found;
+
+		/* set next cluster */
+		next = le32_to_cpu(*((uint32_t *) buf) & 0x0fffffff);
+		if (next == 0)
+			break;
+	}
+	if (maxloop == 0)
+		dbg("reached maximum follow count of root cluster chain, give up");
+
+	vs = volume_id_get_buffer(id, off, 0x200);
+	if (vs == NULL)
+		return -1;
+
+	if (label != NULL && memcmp(label, "NO NAME    ", 11) != 0) {
+		volume_id_set_label_raw(id, label, 11);
+		volume_id_set_label_string(id, label, 11);
+	} else if (memcmp(vs->type.fat32.label, "NO NAME    ", 11) != 0) {
+		volume_id_set_label_raw(id, vs->type.fat32.label, 11);
+		volume_id_set_label_string(id, vs->type.fat32.label, 11);
+	}
+	volume_id_set_uuid(id, vs->type.fat32.serno, UUID_DOS);
+
+ found:
+	volume_id_set_usage(id, VOLUME_ID_FILESYSTEM);
+	id->type = "vfat";
+
+	return 0;
+}