volume_id: add exFAT detection

function                                             old     new   delta
volume_id_probe_exfat                                  -     294    +294

Signed-off-by: S-G Bergh <sgb@systemasis.org>
Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>

5 files changed, 145 insertions, 0 deletions

diff --git a/util-linux/Config.src b/util-linux/Config.src
index 3355e9729..e4516ddb7 100644
--- a/util-linux/Config.src
+++ b/util-linux/Config.src
@@ -734,6 +734,15 @@ config FEATURE_VOLUMEID_FAT
         help
           TODO
 
+config FEATURE_VOLUMEID_EXFAT
+        bool "exFAT filesystem"
+        default y
+        depends on VOLUMEID
+        help
+          exFAT (extended FAT) is a proprietary file system designed especially
+          for flash drives. It has many features from NTFS, but with less
+          overhead. exFAT is used on most SDXC cards for consumer electronics.
+
 config FEATURE_VOLUMEID_HFS
         bool "hfs filesystem"
         default y
diff --git a/util-linux/volume_id/Kbuild.src b/util-linux/volume_id/Kbuild.src
index 39a2d8cf4..759fdaae5 100644
--- a/util-linux/volume_id/Kbuild.src
+++ b/util-linux/volume_id/Kbuild.src
@@ -33,6 +33,7 @@ lib-$(CONFIG_FEATURE_VOLUMEID_LINUXSWAP)        += linux_swap.o
 ### lib-$(CONFIG_FEATURE_VOLUMEID_MSDOS)            += msdos.o
 lib-$(CONFIG_FEATURE_VOLUMEID_NILFS)            += nilfs.o
 lib-$(CONFIG_FEATURE_VOLUMEID_NTFS)             += ntfs.o
+lib-$(CONFIG_FEATURE_VOLUMEID_EXFAT)            += exfat.o
 lib-$(CONFIG_FEATURE_VOLUMEID_REISERFS)         += reiserfs.o
 lib-$(CONFIG_FEATURE_VOLUMEID_UDF)              += udf.o
 ### lib-$(CONFIG_FEATURE_VOLUMEID_UFS)              += ufs.o
diff --git a/util-linux/volume_id/exfat.c b/util-linux/volume_id/exfat.c
new file mode 100644
index 000000000..a38a8916d
--- /dev/null
+++ b/util-linux/volume_id/exfat.c
@@ -0,0 +1,130 @@
+/*
+ * volume_id - reads filesystem label and uuid
+ *
+ * Copyright (C) 2012 S-G Bergh <sgb@systemasis.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 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 */      // ...
+} 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 */              } 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 */              } PACKED guid;
+                } PACKED type;
+} PACKED;
+
+int FAST_FUNC volume_id_probe_exfat(struct volume_id *id /*,uint64_t off*/)
+{
+        struct exfat_super_block *sb;
+        struct exfat_dir_entry *de;
+        unsigned        sector_sz;
+        unsigned        cluster_sz;
+        uint64_t        root_dir_off;
+        unsigned        count;
+        unsigned        need_lbl_guid;
+
+        // Primary super block
+        dbg("exFAT: probing at offset 0x%x", EXFAT_SB_OFFSET);
+        sb = volume_id_get_buffer(id, EXFAT_SB_OFFSET, sizeof(*sb));
+
+        if (!sb)
+                return -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("exFAT: sector size 0x%x bytes", sector_sz);
+        dbg("exFAT: cluster size 0x%x bytes", cluster_sz);
+        dbg("exFAT: root dir is at 0x%llx", (long long)root_dir_off);
+
+        // Use DOS uuid as fallback, if no GUID set
+        volume_id_set_uuid(id, sb->vol_serial_nr, 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 = volume_id_get_buffer(id, 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("exFAT: End of root directory reached after %u entries", count);
+                        break;
+                }
+                if (de->entry_type == 0x83) {
+                        // Volume Label Directory Entry
+                        volume_id_set_label_unicode16(id, (uint8_t *)de->type.label.vol_label,
+                                                LE, 2 * de->type.label.char_count);
+                        need_lbl_guid &= ~(1 << 0);
+                }
+                if (de->entry_type == 0xA0) {
+                        // Volume GUID Directory Entry
+                        volume_id_set_uuid(id, de->type.guid.vol_guid, UUID_DCE);
+                        need_lbl_guid &= ~(1 << 1);
+                }
+                if (!need_lbl_guid)
+                        break;
+        }
+
+        IF_FEATURE_BLKID_TYPE(id->type = "exfat";)
+        return 0;
+}
diff --git a/util-linux/volume_id/volume_id.c b/util-linux/volume_id/volume_id.c
index c1d615283..3c3c69818 100644
--- a/util-linux/volume_id/volume_id.c
+++ b/util-linux/volume_id/volume_id.c
@@ -93,6 +93,9 @@ static const probe_fptr fs1[] = {
 #if ENABLE_FEATURE_VOLUMEID_FAT
         volume_id_probe_vfat,
 #endif
+#if ENABLE_FEATURE_VOLUMEID_EXFAT
+        volume_id_probe_exfat,
+#endif
 #if ENABLE_FEATURE_VOLUMEID_MAC
         volume_id_probe_mac_partition_map,
 #endif
diff --git a/util-linux/volume_id/volume_id_internal.h b/util-linux/volume_id/volume_id_internal.h
index 1c2e0ffa6..03dc46f27 100644
--- a/util-linux/volume_id/volume_id_internal.h
+++ b/util-linux/volume_id/volume_id_internal.h
@@ -216,6 +216,8 @@ int FAST_FUNC volume_id_probe_nilfs(struct volume_id *id /*,uint64_t off*/);
 
 int FAST_FUNC volume_id_probe_ntfs(struct volume_id *id /*,uint64_t off*/);
 
+int FAST_FUNC volume_id_probe_exfat(struct volume_id *id /*,uint64_t off*/);
+
 int FAST_FUNC volume_id_probe_ocfs2(struct volume_id *id /*,uint64_t off*/);
 
 int FAST_FUNC volume_id_probe_reiserfs(struct volume_id *id /*,uint64_t off*/);