fstyp(8): Detect exFAT filesystems

Simply detect the exFAT filesystem name in the Volume Boot Record
(superblock).

PR:		214908
Reported by:	<vermaden at interia.pl>

usr.sbin/fstyp/Makefile

@@ -3,7 +3,7 @@
 .include <src.opts.mk>
 
 PROG=	fstyp
-SRCS=	cd9660.c ext2fs.c fstyp.c geli.c msdosfs.c ntfs.c ufs.c
+SRCS=	cd9660.c exfat.c ext2fs.c fstyp.c geli.c msdosfs.c ntfs.c ufs.c
 
 .if ${MK_ZFS} != "no"
 SRCS +=	zfs.c

usr.sbin/fstyp/exfat.c

@@ -0,0 +1,77 @@
+/*
+ * Copyright (c) 2017 Conrad Meyer <cem@FreeBSD.org>
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
+ * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+ * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+ * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ */
+
+#include <sys/cdefs.h>
+__FBSDID("$FreeBSD$");
+
+#include <stdint.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+
+#include "fstyp.h"
+
+struct exfat_vbr {
+	char		ev_jmp[3];
+	char		ev_fsname[8];
+	char		ev_zeros[53];
+	uint64_t	ev_part_offset;
+	uint64_t	ev_vol_length;
+	uint32_t	ev_fat_offset;
+	uint32_t	ev_fat_length;
+	uint32_t	ev_cluster_offset;
+	uint32_t	ev_cluster_count;
+	uint32_t	ev_rootdir_cluster;
+	uint32_t	ev_vol_serial;
+	uint16_t	ev_fs_revision;
+	uint16_t	ev_vol_flags;
+	uint8_t		ev_log_bytes_per_sect;
+	uint8_t		ev_log_sect_per_clust;
+	uint8_t		ev_num_fats;
+	uint8_t		ev_drive_sel;
+	uint8_t		ev_percent_used;
+} __packed;
+
+int
+fstyp_exfat(FILE *fp, char *label, size_t size)
+{
+	struct exfat_vbr *ev;
+
+	ev = (struct exfat_vbr *)read_buf(fp, 0, 512);
+	if (ev == NULL || strncmp(ev->ev_fsname, "EXFAT   ", 8) != 0)
+		goto fail;
+
+	/*
+	 * Reading the volume label requires walking the root directory to look
+	 * for a special label file.  Left as an exercise for the reader.
+	 */
+	free(ev);
+	return (0);
+
+fail:
+	free(ev);
+	return (1);
+}

usr.sbin/fstyp/fstyp.8

@@ -27,7 +27,7 @@
 .\"
 .\" $FreeBSD$
 .\"
-.Dd February 28, 2016
+.Dd January 12, 2017
 .Dt FSTYP 8
 .Os
 .Sh NAME
@@ -43,7 +43,7 @@
 The
 .Nm
 utility is used to determine the filesystem type on a given device.
-It can recognize ISO-9660, Ext2, FAT, NTFS, and UFS filesystems.
+It can recognize ISO-9660, exFAT, Ext2, FAT, NTFS, and UFS filesystems.
 When the
 .Fl u
 flag is specified,
@@ -61,6 +61,8 @@ as, respectively:
 .It
 cd9660
 .It
+exfat
+.It
 ext2fs
 .It
 geli

usr.sbin/fstyp/fstyp.c

@@ -57,6 +57,7 @@ static struct {
 	bool		unmountable;
 } fstypes[] = {
 	{ "cd9660", &fstyp_cd9660, false },
+	{ "exfat", &fstyp_exfat, true },
 	{ "ext2fs", &fstyp_ext2fs, false },
 	{ "geli", &fstyp_geli, true },
 	{ "msdosfs", &fstyp_msdosfs, false },

usr.sbin/fstyp/fstyp.h

@@ -39,6 +39,7 @@ char	*checked_strdup(const char *s);
 void	rtrim(char *label, size_t size);
 
 int	fstyp_cd9660(FILE *fp, char *label, size_t size);
+int	fstyp_exfat(FILE *fp, char *label, size_t size);
 int	fstyp_ext2fs(FILE *fp, char *label, size_t size);
 int	fstyp_geli(FILE *fp, char *label, size_t size);
 int	fstyp_msdosfs(FILE *fp, char *label, size_t size);