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libblkid-tiny: add exfat superblock support
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@milecki.pl>
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Rafał Miłecki
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Feb 28, 2023
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Original file line number | Diff line number | Diff line change |
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/* | ||
* Copyright (C) 2010 Andrew Nayenko <resver@gmail.com> | ||
* | ||
* This file may be redistributed under the terms of the | ||
* GNU Lesser General Public License. | ||
*/ | ||
#include "superblocks.h" | ||
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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__)); | ||
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struct exfat_entry_label { | ||
uint8_t type; | ||
uint8_t length; | ||
uint8_t name[22]; | ||
uint8_t reserved[8]; | ||
} __attribute__((__packed__)); | ||
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#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 | ||
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#define EXFAT_ENTRY_EOD 0x00 | ||
#define EXFAT_ENTRY_LABEL 0x83 | ||
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static uint64_t block_to_offset(const struct exfat_super_block *sb, | ||
uint64_t block) | ||
{ | ||
return block << sb->BytesPerSectorShift; | ||
} | ||
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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); | ||
} | ||
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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)); | ||
} | ||
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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; | ||
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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); | ||
} | ||
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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; | ||
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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; | ||
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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); | ||
} | ||
} | ||
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return NULL; | ||
} | ||
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static int probe_exfat(blkid_probe pr, const struct blkid_idmag *mag) | ||
{ | ||
struct exfat_super_block *sb; | ||
struct exfat_entry_label *label; | ||
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sb = blkid_probe_get_sb(pr, mag, struct exfat_super_block); | ||
if (!sb || !CLUSTER_SIZE(sb)) | ||
return errno ? -errno : BLKID_PROBE_NONE; | ||
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if (le16_to_cpu(sb->BootSignature) != 0xAA55) | ||
return BLKID_PROBE_NONE; | ||
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if (memcmp(sb->JumpBoot, "\xEB\x76\x90", 3) != 0) | ||
return BLKID_PROBE_NONE; | ||
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for (size_t i = 0; i < sizeof(sb->MustBeZero); i++) | ||
if (sb->MustBeZero[i] != 0x00) | ||
return BLKID_PROBE_NONE; | ||
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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; | ||
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blkid_probe_sprintf_uuid(pr, sb->VolumeSerialNumber, 4, | ||
"%02hhX%02hhX-%02hhX%02hhX", | ||
sb->VolumeSerialNumber[3], sb->VolumeSerialNumber[2], | ||
sb->VolumeSerialNumber[1], sb->VolumeSerialNumber[0]); | ||
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blkid_probe_sprintf_version(pr, "%u.%u", | ||
sb->FileSystemRevision.vermaj, sb->FileSystemRevision.vermin); | ||
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#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 | ||
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return BLKID_PROBE_OK; | ||
} | ||
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const struct blkid_idinfo exfat_idinfo = | ||
{ | ||
.name = "exfat", | ||
.usage = BLKID_USAGE_FILESYSTEM, | ||
.probefunc = probe_exfat, | ||
.magics = | ||
{ | ||
{ .magic = "EXFAT ", .len = 8, .sboff = 3 }, | ||
{ NULL } | ||
} | ||
}; |
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