[LEDE-DEV,LEDE-DEV,1/3] fstools: add exfat filesystem support

diff --git a/CMakeLists.txt b/CMakeLists.txt
index 9e855bd..8efa56a 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -24,6 +24,7 @@  ADD_LIBRARY(blkid-tiny SHARED
 		libblkid-tiny/ext.c
 		libblkid-tiny/jffs2.c
 		libblkid-tiny/vfat.c
+		libblkid-tiny/exfat.c
 		libblkid-tiny/ntfs.c
 		libblkid-tiny/hfs.c
 		libblkid-tiny/swap.c
diff --git a/libblkid-tiny/blkidP.h b/libblkid-tiny/blkidP.h
index 1ba7673..a573166 100644
--- a/libblkid-tiny/blkidP.h
+++ b/libblkid-tiny/blkidP.h
@@ -557,4 +557,16 @@  extern size_t blkid_encode_to_utf8(int enc, unsigned char *dest, size_t len,
 #define BLKID_ENC_UTF16BE	0
 #define BLKID_ENC_UTF16LE	1
 
+enum uuid_format {
+	UUID_DOS = 0,		/* 4 bytes */
+	UUID_NTFS = 1,		/* 8 bytes */
+	UUID_DCE = 2,		/* 16 bytes */
+	UUID_DCE_STRING = 3,	/* 36 bytes (VOLUME_ID_UUID_SIZE) */
+};
+
+enum endian {
+	LE = 0,
+	BE = 1
+};
+
 #endif /* _BLKID_BLKIDP_H */
diff --git a/libblkid-tiny/exfat.c b/libblkid-tiny/exfat.c
new file mode 100644
index 0000000..8e69350
--- /dev/null
+++ b/libblkid-tiny/exfat.c
@@ -0,0 +1,155 @@ 
+ /*
+ * Copyright (C) 1999 by Andries Brouwer
+ * Copyright (C) 1999, 2000, 2003 by Theodore Ts'o
+ * Copyright (C) 2001 by Andreas Dilger
+ * Copyright (C) 2004 Kay Sievers <kay.sievers@vrfy.org>
+ * Copyright (C) 2008 Karel Zak <kzak@redhat.com>
+ * Copyright (C) 2012 S-G Bergh <sgb@systemasis.org>
+ * Copyright (C) 2018 rosysong <rosysong@rosinson.com>
+ *
+ * This file may be redistributed under the terms of the
+ * GNU Lesser General Public License.
+ */
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <unistd.h>
+#include <string.h>
+#include <errno.h>
+#include <ctype.h>
+#include <stdint.h>
+
+#if 0
+#include "pt-mbr.h"
+#endif
+
+#include "superblocks.h"
+
+#define EXFAT_SB_OFFSET		0
+#define EXFAT_DIR_ENTRY_SZ	32
+#define EXFAT_MAX_DIR_ENTRIES	100
+
+struct exfat_super_block {
+/* 0x00 */	uint8_t		boot_jump[3];
+/* 0x03 */	uint8_t		fs_name[8];
+/* 0x0B */	uint8_t		must_be_zero[53];
+/* 0x40 */	uint64_t	partition_offset;
+/* 0x48 */	uint64_t	volume_length;
+/* 0x50 */	uint32_t	fat_offset;		// Sector address of 1st FAT
+/* 0x54 */	uint32_t	fat_size;		// In sectors
+/* 0x58 */	uint32_t	cluster_heap_offset;	// Sector address of Data Region
+/* 0x5C */	uint32_t	cluster_count;
+/* 0x60 */	uint32_t	root_dir;		// Cluster address of Root Directory
+/* 0x64 */	uint8_t		vol_serial_nr[4];	// Volume ID
+/* 0x68 */	uint16_t	fs_revision;		// VV.MM
+/* 0x6A */	uint16_t	vol_flags;
+/* 0x6C */	uint8_t		bytes_per_sector;	// Power of 2: 9 => 512, 12 => 4096
+/* 0x6D */	uint8_t		sectors_per_cluster;	// Power of 2
+/* 0x6E */	uint8_t		nr_of_fats;		// 2 for TexFAT
+/* 0x6F */	// ...
+} __attribute__((packed));
+
+struct exfat_dir_entry {
+/* 0x00 */	uint8_t		entry_type;
+		union {
+			struct volume_label {
+/* 0x01 */			uint8_t		char_count;		// Length of label
+/* 0x02 */			uint16_t	vol_label[11];		// UTF16 string without null termination
+/* 0x18 */			uint8_t		reserved[8];
+/* 0x20 */		} __attribute__((packed)) label;
+			struct volume_guid {
+/* 0x01 */			uint8_t		sec_count;
+/* 0x02 */			uint16_t	set_checksum;
+/* 0x04 */			uint16_t	flags;
+/* 0x06 */			uint8_t		vol_guid[16];
+/* 0x16 */			uint8_t		reserved[10];
+/* 0x20 */		} __attribute__((packed)) guid;
+		} __attribute__((packed)) type;
+} __attribute__((packed));
+
+static int probe_exfat(blkid_probe pr, const struct blkid_idmag *mag)
+{
+	struct exfat_super_block *sb;
+	struct exfat_dir_entry *de;
+	unsigned char *vol_label = 0;
+	unsigned char *vol_serno = NULL;
+	unsigned	sector_sz;
+	unsigned	cluster_sz;
+	uint64_t	root_dir_off;
+	unsigned	count;
+	unsigned	need_lbl_guid;
+	const char *version = "EXFAT";
+
+	// Primary super block
+	DBG(LOWPROBE, ul_debug("exFAT: probing at offset 0x%x", EXFAT_SB_OFFSET));
+	sb = blkid_probe_get_sb(pr, mag, struct exfat_super_block);
+	if (!sb)
+		return errno ? -errno : 1;
+
+	if (memcmp(sb->fs_name, "EXFAT   ", 8) != 0)
+		return -1;
+
+	sector_sz = 1 << sb->bytes_per_sector;
+	cluster_sz = sector_sz << sb->sectors_per_cluster;
+	// There are no clusters 0 and 1, so the first cluster is 2.
+	root_dir_off = (uint64_t)EXFAT_SB_OFFSET +
+		// Hmm... should we cast sector_sz/cluster_sz to uint64_t?
+		(le32_to_cpu(sb->cluster_heap_offset)) * sector_sz +
+		(le32_to_cpu(sb->root_dir) - 2) * cluster_sz;
+	DBG(LOWPROBE, ul_debug("exFAT: sector size 0x%x bytes", sector_sz));
+	DBG(LOWPROBE, ul_debug("exFAT: cluster size 0x%x bytes", cluster_sz));
+	DBG(LOWPROBE, ul_debug("exFAT: root dir is at 0x%llx", (long long)root_dir_off));
+
+	// Use DOS uuid(UUID_DOS) as fallback, if no GUID set
+	vol_serno = sb->vol_serial_nr;
+	blkid_probe_sprintf_uuid_exfat(pr, vol_serno, UUID_DOS);
+
+	// EXFAT_MAX_DIR_ENTRIES is used as a safety belt.
+	// The Root Directory may hold an unlimited number of entries,
+	// so we do not want to check all. Usually label and GUID
+	// are in the beginning, but there are no guarantees.
+	need_lbl_guid = (1 << 0) | (1 << 1);
+	for (count = 0; count < EXFAT_MAX_DIR_ENTRIES; count++) {
+		de = (struct exfat_dir_entry *)
+		blkid_probe_get_buffer(pr, root_dir_off + (count * EXFAT_DIR_ENTRY_SZ), EXFAT_DIR_ENTRY_SZ);
+		if (de == NULL)
+			break;
+		if (de->entry_type == 0x00) {
+			// End of Directory Marker
+			DBG(LOWPROBE, ul_debug("exFAT: End of root directory reached after %u entries", count));
+			break;
+		}
+		if (de->entry_type == 0x83) {
+			// Volume Label Directory Entry
+			vol_label = (unsigned char *)de->type.label.vol_label;
+			blkid_probe_set_unicode16label(pr, vol_label, LE, 2 * de->type.label.char_count);
+			need_lbl_guid &= ~(1 << 0);
+		}
+		if (de->entry_type == 0xA0) {
+			// Volume GUID Directory Entry (UUID_DCE)
+			vol_serno = de->type.guid.vol_guid;
+			blkid_probe_sprintf_uuid_exfat(pr, vol_serno, UUID_DCE);
+			need_lbl_guid &= ~(1 << 1);
+		}
+		if (!need_lbl_guid)
+			break;
+	}
+
+	if (version)
+		blkid_probe_set_version(pr, version);
+
+	return 0;
+}
+
+const struct blkid_idinfo exfat_idinfo =
+{
+	.name		= "exfat",
+	.usage		= BLKID_USAGE_FILESYSTEM,
+	.probefunc	= probe_exfat,
+	.magics		=
+	{
+		{ .magic = "EXFAT   ", .len = 8, .sboff = 0x03 },
+		{ NULL }
+	}
+};
+
diff --git a/libblkid-tiny/libblkid-tiny.c b/libblkid-tiny/libblkid-tiny.c
index f020e23..ccfaf63 100644
--- a/libblkid-tiny/libblkid-tiny.c
+++ b/libblkid-tiny/libblkid-tiny.c
@@ -121,6 +121,51 @@  int blkid_probe_set_label(blkid_probe pr, unsigned char *label, size_t len)
 	return 0;
 }
 
+int blkid_probe_set_unicode16(char *str, size_t len, const unsigned char *buf, enum endian endianess, size_t count)
+{
+	unsigned i, j;
+	unsigned c;
+
+	j = 0;
+	for (i = 0; i + 2 <= count; i += 2) {
+		if (endianess == LE)
+			c = (buf[i+1] << 8) | buf[i];
+		else
+			c = (buf[i] << 8) | buf[i+1];
+		if (c == 0)
+			break;
+		if (j+1 >= len)
+			break;
+		if (c < 0x80) {
+			/* 0xxxxxxx */
+		} else {
+			unsigned char topbits = 0xc0;
+			if (j+2 >= len)
+				break;
+			if (c < 0x800) {
+				/* 110yyyxx 10xxxxxx */
+			} else {
+				if (j+3 >= len)
+					break;
+				/* 1110yyyy 10yyyyxx 10xxxxxx */
+				str[j++] = (unsigned char) (0xe0 | (c >> 12));
+				topbits = 0x80;
+			}
+			str[j++] = (unsigned char) (topbits | ((c >> 6) & 0x3f));
+			c = 0x80 | (c & 0x3f);
+		}
+		str[j++] = (unsigned char) c;
+	}
+	str[j] = '\0';
+
+	return j;
+}
+
+int blkid_probe_set_unicode16label(blkid_probe pr, unsigned char *label, enum endian endianess, size_t len)
+{
+	return blkid_probe_set_unicode16(pr->label, sizeof(pr->label), label, endianess, len);
+}
+
 int blkid_probe_set_uuid_as(blkid_probe pr, unsigned char *uuid, const char *name)
 {
 	short unsigned int*u = (short unsigned int*) uuid;
@@ -135,6 +180,47 @@  int blkid_probe_set_uuid_as(blkid_probe pr, unsigned char *uuid, const char *nam
 	return 0;
 }
 
+int blkid_probe_sprintf_uuid_exfat(blkid_probe pr, unsigned char *buf, enum uuid_format format)
+{
+	unsigned i;
+	unsigned count = 4 << format;
+
+	/* if set, create string in the same format, the native platform uses */
+	for (i = 0; i < count; i++)
+		if (buf[i] != 0)
+			goto set;
+
+	/* all bytes are zero, leave it empty ("") */
+	return 0;
+
+set:
+	switch (format) {
+	case UUID_DOS:
+		blkid_probe_sprintf_uuid(pr, buf, count, "%02X%02X-%02X%02X",
+			buf[3], buf[2], buf[1], buf[0]);
+		break;
+	case UUID_NTFS:
+		blkid_probe_sprintf_uuid(pr, buf, count, "%02X%02X%02X%02X%02X%02X%02X%02X",
+			buf[7], buf[6], buf[5], buf[4],
+			buf[3], buf[2], buf[1], buf[0]);
+		break;
+	case UUID_DCE:
+		blkid_probe_sprintf_uuid(pr, buf, count,
+			"%02x%02x%02x%02x-%02x%02x-%02x%02x-%02x%02x-%02x%02x%02x%02x%02x%02x",
+			buf[0], buf[1], buf[2], buf[3],
+			buf[4], buf[5], buf[6], buf[7],
+			buf[8], buf[9], buf[10], buf[11],
+			buf[12], buf[13], buf[14], buf[15]);
+		break;
+	case UUID_DCE_STRING:
+		memcpy(pr->uuid, buf, count);
+		pr->uuid[count] = '\0';
+		break;
+	}
+
+	return count;
+}
+
 int blkid_probe_set_uuid(blkid_probe pr, unsigned char *uuid)
 {
 	return blkid_probe_set_uuid_as(pr, uuid, NULL);
@@ -155,6 +241,7 @@  int blkid_probe_sprintf_uuid(blkid_probe pr, unsigned char *uuid,
 static const struct blkid_idinfo *idinfos[] =
 {
 	&vfat_idinfo,
+	&exfat_idinfo,
 	&swsuspend_idinfo,
 	&swap_idinfo,
 	&ext4dev_idinfo,
diff --git a/libblkid-tiny/superblocks.h b/libblkid-tiny/superblocks.h
index cde8a40..85c61f7 100644
--- a/libblkid-tiny/superblocks.h
+++ b/libblkid-tiny/superblocks.h
@@ -88,9 +88,15 @@  extern int blkid_probe_sprintf_version(blkid_probe pr, const char *fmt, ...)
 extern int blkid_probe_set_label(blkid_probe pr, unsigned char *label, size_t len);
 extern int blkid_probe_set_utf8label(blkid_probe pr, unsigned char *label,
                 size_t len, int enc);
+extern int blkid_probe_set_unicode16(char *str, size_t len, const unsigned char *buf,
+                enum endian endianess, size_t count);
+extern int blkid_probe_set_unicode16label(blkid_probe pr, unsigned char *label,
+                enum endian endianess, size_t len);
 extern int blkid_probe_sprintf_uuid(blkid_probe pr, unsigned char *uuid,
                 size_t len, const char *fmt, ...)
 		__attribute__ ((__format__ (__printf__, 4, 5)));
+extern int blkid_probe_sprintf_uuid_exfat(blkid_probe pr, unsigned char *buf,
+                enum uuid_format format);
 extern int blkid_probe_strncpy_uuid(blkid_probe pr, unsigned char *str, size_t len);
 
 extern int blkid_probe_set_uuid(blkid_probe pr, unsigned char *uuid);