[PATCH fstools] libblkid-tiny: add exfat superblock support
Rafał Miłecki
zajec5 at gmail.com
Thu Feb 23 10:26:14 PST 2023
From: Rafał Miłecki <rafal at milecki.pl>
exFAT became very popular over last years and also well supported with
Linux kernel driver and macOS support. It's commonly used for USB
drivers. Port a simple support for it from util-linux / libblkid.
Signed-off-by: Rafał Miłecki <rafal at milecki.pl>
---
CMakeLists.txt | 1 +
libblkid-tiny/exfat.c | 175 ++++++++++++++++++++++++++++++++++
libblkid-tiny/libblkid-tiny.c | 1 +
libblkid-tiny/superblocks.h | 1 +
4 files changed, 178 insertions(+)
create mode 100644 libblkid-tiny/exfat.c
diff --git a/CMakeLists.txt b/CMakeLists.txt
index 9a87979..3421fec 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -25,6 +25,7 @@ ADD_LIBRARY(blkid-tiny SHARED
libblkid-tiny/libblkid-tiny.c
libblkid-tiny/mkdev.c
libblkid-tiny/probe.c
+ libblkid-tiny/exfat.c
libblkid-tiny/ext.c
libblkid-tiny/jffs2.c
libblkid-tiny/vfat.c
diff --git a/libblkid-tiny/exfat.c b/libblkid-tiny/exfat.c
new file mode 100644
index 0000000..85d6f82
--- /dev/null
+++ b/libblkid-tiny/exfat.c
@@ -0,0 +1,175 @@
+/*
+ * Copyright (C) 2010 Andrew Nayenko <resver at gmail.com>
+ *
+ * This file may be redistributed under the terms of the
+ * GNU Lesser General Public License.
+ */
+#include "superblocks.h"
+
+struct exfat_super_block {
+ uint8_t JumpBoot[3];
+ uint8_t FileSystemName[8];
+ uint8_t MustBeZero[53];
+ uint64_t PartitionOffset;
+ uint64_t VolumeLength;
+ uint32_t FatOffset;
+ uint32_t FatLength;
+ uint32_t ClusterHeapOffset;
+ uint32_t ClusterCount;
+ uint32_t FirstClusterOfRootDirectory;
+ uint8_t VolumeSerialNumber[4];
+ struct {
+ uint8_t vermin;
+ uint8_t vermaj;
+ } FileSystemRevision;
+ uint16_t VolumeFlags;
+ uint8_t BytesPerSectorShift;
+ uint8_t SectorsPerClusterShift;
+ uint8_t NumberOfFats;
+ uint8_t DriveSelect;
+ uint8_t PercentInUse;
+ uint8_t Reserved[7];
+ uint8_t BootCode[390];
+ uint16_t BootSignature;
+} __attribute__((__packed__));
+
+struct exfat_entry_label {
+ uint8_t type;
+ uint8_t length;
+ uint8_t name[22];
+ uint8_t reserved[8];
+} __attribute__((__packed__));
+
+#define BLOCK_SIZE(sb) ((sb)->BytesPerSectorShift < 32 ? (1u << (sb)->BytesPerSectorShift) : 0)
+#define CLUSTER_SIZE(sb) ((sb)->SectorsPerClusterShift < 32 ? (BLOCK_SIZE(sb) << (sb)->SectorsPerClusterShift) : 0)
+#define EXFAT_FIRST_DATA_CLUSTER 2
+#define EXFAT_LAST_DATA_CLUSTER 0xffffff6
+#define EXFAT_ENTRY_SIZE 32
+
+#define EXFAT_ENTRY_EOD 0x00
+#define EXFAT_ENTRY_LABEL 0x83
+
+static uint64_t block_to_offset(const struct exfat_super_block *sb,
+ uint64_t block)
+{
+ return block << sb->BytesPerSectorShift;
+}
+
+static uint64_t cluster_to_block(const struct exfat_super_block *sb,
+ uint32_t cluster)
+{
+ return le32_to_cpu(sb->ClusterHeapOffset) +
+ ((uint64_t) (cluster - EXFAT_FIRST_DATA_CLUSTER)
+ << sb->SectorsPerClusterShift);
+}
+
+static uint64_t cluster_to_offset(const struct exfat_super_block *sb,
+ uint32_t cluster)
+{
+ return block_to_offset(sb, cluster_to_block(sb, cluster));
+}
+
+static uint32_t next_cluster(blkid_probe pr,
+ const struct exfat_super_block *sb, uint32_t cluster)
+{
+ uint32_t *nextp, next;
+ uint64_t fat_offset;
+
+ fat_offset = block_to_offset(sb, le32_to_cpu(sb->FatOffset))
+ + (uint64_t) cluster * sizeof(cluster);
+ nextp = (uint32_t *) blkid_probe_get_buffer(pr, fat_offset,
+ sizeof(uint32_t));
+ if (!nextp)
+ return 0;
+ memcpy(&next, nextp, sizeof(next));
+ return le32_to_cpu(next);
+}
+
+static struct exfat_entry_label *find_label(blkid_probe pr,
+ const struct exfat_super_block *sb)
+{
+ uint32_t cluster = le32_to_cpu(sb->FirstClusterOfRootDirectory);
+ uint64_t offset = cluster_to_offset(sb, cluster);
+ uint8_t *entry;
+ const size_t max_iter = 10000;
+ size_t i = 0;
+
+ for (; i < max_iter; i++) {
+ entry = (uint8_t *) blkid_probe_get_buffer(pr, offset,
+ EXFAT_ENTRY_SIZE);
+ if (!entry)
+ return NULL;
+ if (entry[0] == EXFAT_ENTRY_EOD)
+ return NULL;
+ if (entry[0] == EXFAT_ENTRY_LABEL)
+ return (struct exfat_entry_label *) entry;
+
+ offset += EXFAT_ENTRY_SIZE;
+ if (CLUSTER_SIZE(sb) && (offset % CLUSTER_SIZE(sb)) == 0) {
+ cluster = next_cluster(pr, sb, cluster);
+ if (cluster < EXFAT_FIRST_DATA_CLUSTER)
+ return NULL;
+ if (cluster > EXFAT_LAST_DATA_CLUSTER)
+ return NULL;
+ offset = cluster_to_offset(sb, cluster);
+ }
+ }
+
+ return NULL;
+}
+
+static int probe_exfat(blkid_probe pr, const struct blkid_idmag *mag)
+{
+ struct exfat_super_block *sb;
+ struct exfat_entry_label *label;
+
+ sb = blkid_probe_get_sb(pr, mag, struct exfat_super_block);
+ if (!sb || !CLUSTER_SIZE(sb))
+ return errno ? -errno : BLKID_PROBE_NONE;
+
+ if (le16_to_cpu(sb->BootSignature) != 0xAA55)
+ return BLKID_PROBE_NONE;
+
+ if (memcmp(sb->JumpBoot, "\xEB\x76\x90", 3) != 0)
+ return BLKID_PROBE_NONE;
+
+ for (size_t i = 0; i < sizeof(sb->MustBeZero); i++)
+ if (sb->MustBeZero[i] != 0x00)
+ return BLKID_PROBE_NONE;
+
+ label = find_label(pr, sb);
+ if (label)
+ blkid_probe_set_utf8label(pr, label->name,
+ min((size_t) label->length * 2, sizeof(label->name)),
+ BLKID_ENC_UTF16LE);
+ else if (errno)
+ return -errno;
+
+ blkid_probe_sprintf_uuid(pr, sb->VolumeSerialNumber, 4,
+ "%02hhX%02hhX-%02hhX%02hhX",
+ sb->VolumeSerialNumber[3], sb->VolumeSerialNumber[2],
+ sb->VolumeSerialNumber[1], sb->VolumeSerialNumber[0]);
+
+ blkid_probe_sprintf_version(pr, "%u.%u",
+ sb->FileSystemRevision.vermaj, sb->FileSystemRevision.vermin);
+
+#if 0
+ blkid_probe_set_fsblocksize(pr, BLOCK_SIZE(sb));
+ blkid_probe_set_block_size(pr, BLOCK_SIZE(sb));
+ blkid_probe_set_fssize(pr, BLOCK_SIZE(sb) * le64_to_cpu(sb->VolumeLength));
+#endif
+
+ return BLKID_PROBE_OK;
+}
+
+const struct blkid_idinfo exfat_idinfo =
+{
+ .name = "exfat",
+ .usage = BLKID_USAGE_FILESYSTEM,
+ .probefunc = probe_exfat,
+ .magics =
+ {
+ { .magic = "EXFAT ", .len = 8, .sboff = 3 },
+ { NULL }
+ }
+};
diff --git a/libblkid-tiny/libblkid-tiny.c b/libblkid-tiny/libblkid-tiny.c
index 8520f8a..9e67439 100644
--- a/libblkid-tiny/libblkid-tiny.c
+++ b/libblkid-tiny/libblkid-tiny.c
@@ -174,6 +174,7 @@ static const struct blkid_idinfo *idinfos[] =
&vfat_idinfo,
&swsuspend_idinfo,
&swap_idinfo,
+ &exfat_idinfo,
&ext4dev_idinfo,
&ext4_idinfo,
&ext3_idinfo,
diff --git a/libblkid-tiny/superblocks.h b/libblkid-tiny/superblocks.h
index ade2ae0..66053e6 100644
--- a/libblkid-tiny/superblocks.h
+++ b/libblkid-tiny/superblocks.h
@@ -22,6 +22,7 @@ extern const struct blkid_idinfo pdcraid_idinfo;
extern const struct blkid_idinfo silraid_idinfo;
extern const struct blkid_idinfo viaraid_idinfo;
extern const struct blkid_idinfo linuxraid_idinfo;
+extern const struct blkid_idinfo exfat_idinfo;
extern const struct blkid_idinfo ext4dev_idinfo;
extern const struct blkid_idinfo ext4_idinfo;
extern const struct blkid_idinfo ext3_idinfo;
--
2.34.1
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