diff options
| -rw-r--r-- | gnu/build/file-systems.scm | 117 |
1 files changed, 116 insertions, 1 deletions
diff --git a/gnu/build/file-systems.scm b/gnu/build/file-systems.scm index 9ceb2fda4e..41e1c9e282 100644 --- a/gnu/build/file-systems.scm +++ b/gnu/build/file-systems.scm @@ -3,7 +3,7 @@ ;;; Copyright © 2016, 2017 David Craven <david@craven.ch> ;;; Copyright © 2017 Mathieu Othacehe <m.othacehe@gmail.com> ;;; Copyright © 2019 Guillaume Le Vaillant <glv@posteo.net> -;;; Copyright © 2019–2021 Tobias Geerinckx-Rice <me@tobias.gr> +;;; Copyright © 2019–2021, 2024 Tobias Geerinckx-Rice <me@tobias.gr> ;;; Copyright © 2019 David C. Trudgian <dave@trudgian.net> ;;; Copyright © 2020 Maxim Cournoyer <maxim.cournoyer@gmail.com> ;;; Copyright © 2022 Oleg Pykhalov <go.wigust@gmail.com> @@ -450,6 +450,116 @@ fix only those considered safe to repair automatically." ;;; +;;; exFAT file systems. +;;; + +;; <https://learn.microsoft.com/en-us/windows/win32/fileio/exfat-specification>. + +(define-syntax %exfat-endianness + (identifier-syntax (endianness little))) + +(define (exfat-superblock? sblock) + "Return #t when SBLOCK, a bytevector of at least length 512, is an exFAT +superblock, called main boot sector in the exFAT specification." + (and (bytevector=? (string->utf8 "EXFAT ") + (sub-bytevector sblock 3 8)) ;FileSystemName + (bytevector=? (make-bytevector 53 0) + (sub-bytevector sblock 11 53)) ;MustBeZero + (bytevector=? #vu8(#x55 #xaa) + (sub-bytevector sblock 510 2)))) ;BootSignature + +(define (exfat-bytes-per-sector-shift sblock) + (bytevector-u8-ref sblock 108)) + +(define (exfat-sectors-per-cluster-shift sblock) + (bytevector-u8-ref sblock 109)) + +(define (exfat-root-directory-offset sblock) + (let ((cluster-heap-offset (bytevector-u32-ref sblock 88 + %exfat-endianness)) + (root-directory-cluster (bytevector-u32-ref sblock 96 + %exfat-endianness))) + (define (cluster->sector cluster) + (let ((first-data-cluster 2)) + (+ cluster-heap-offset (ash (- cluster first-data-cluster) + (exfat-sectors-per-cluster-shift sblock))))) + (ash (cluster->sector root-directory-cluster) + (exfat-bytes-per-sector-shift sblock)))) + +(define (exfat-cluster-size sblock) + (ash 1 (+ (exfat-bytes-per-sector-shift sblock) + (exfat-sectors-per-cluster-shift sblock)))) + +;; exFAT stores the volume name in a directory entry with no fixed location. We +;; search an arbitrary number of entries before giving up: 128 for devices <256M +;; (4K clusters), 1024 for those <32G (32K clusters), or 4096 for others (128K). +;; It's silly but mostly matches what util-linux's libblkid does with its higher +;; arbitrary number of 10,000 tries. To match that, we'd not only have to look +;; up subsequent clusters in the FAT, but redesign this entire module not to +;; assume that all file systems have a `superblock' that both fits neatly into +;; RAM, and just happens to politely contain all the metadata we'll ever need. +(define (read-exfat-superblock+root-directory-cluster device sblock) + "Return as a bytevector the raw contents of DEVICE's exFAT `superblock' from +main boot sector up to the RootDirectoryCluster expected to contain the volume +label." + (let* ((span (+ (exfat-root-directory-offset sblock) + (exfat-cluster-size sblock)))) + (read-superblock device 0 span (const #t)))) + +(define (read-exfat-superblock device) + "Return the raw contents of DEVICE's exFAT superblock as a bytevector, or #f +if DEVICE does not contain an exFAT file system." + (and=> (read-superblock device 0 512 exfat-superblock?) + (cut read-exfat-superblock+root-directory-cluster device <>))) + +(define (exfat-superblock-volume-name sblock) + "Return as a string the volume name belonging to an exFAT file system +beginning with bytevector SBLOCK, which includes directory entries. +Return #f if no volume name was found within our arbitrary limit." + ;; Defined in section 7.3 of the exFAT specification. + (let ((root-directory (exfat-root-directory-offset sblock)) + (cluster-size (exfat-cluster-size sblock)) + (entry-size 32)) ;bytes + (let loop ((cluster-offset 0)) + (if (< cluster-offset cluster-size) + (let ((offset (+ root-directory cluster-offset))) + (match (bytevector-u8-ref sblock offset) + ((or #x00 ;end of directory + #x03) ;type 3 & not in use + #f) + (#x83 ;type 3 & in use + (let* ((length (min 11 (bytevector-u8-ref sblock (+ 1 offset)))) + (label (sub-bytevector sblock (+ 2 offset) (* 2 length)))) + (utf16->string label %exfat-endianness))) + (_ (loop (+ entry-size offset))))) + #f)))) + +(define (exfat-superblock-uuid sblock) + "Return the Volume Serial Number of exFAT superblock SBLOCK as a bytevector. +This 4-byte identifier is guaranteed to exist, unlike the optional 16-byte +Volume GUID from section 7.5 of the exFAT specification." + (sub-bytevector sblock 100 4)) + +(define (check-exfat-file-system device force? repair) + "Return the health of an unmounted exFAT file system on DEVICE. If FORCE? +is true, check the file system even if it's marked as clean. If REPAIR is +false, do not write to the file system to fix errors. If it's #t, fix all +errors. Otherwise, fix only those considered safe to repair automatically." + (match (status:exit-val + (apply system*/tty "fsck.exfat" "-sv" + `(,@(if force? '("-b") '()) + ,@(match repair + (#f '("-n")) + (#t '("-y")) + (_ '("-p"))) + ,device))) + (0 'pass) + (1 'errors-corrected) + (2 'reboot-required) + (_ 'fatal-error))) + + +;;; ;;; FAT32 file systems. ;;; @@ -937,6 +1047,8 @@ partition field reader that returned a value." bcachefs-superblock-volume-name) (partition-field-reader read-btrfs-superblock btrfs-superblock-volume-name) + (partition-field-reader read-exfat-superblock + exfat-superblock-volume-name) (partition-field-reader read-fat32-superblock fat32-superblock-volume-name) (partition-field-reader read-fat16-superblock @@ -959,6 +1071,8 @@ partition field reader that returned a value." bcachefs-superblock-external-uuid) (partition-field-reader read-btrfs-superblock btrfs-superblock-uuid) + (partition-field-reader read-exfat-superblock + exfat-superblock-uuid) (partition-field-reader read-fat32-superblock fat32-superblock-uuid) (partition-field-reader read-fat16-superblock @@ -1079,6 +1193,7 @@ an exception in such cases but perform the nearest sane action." ((string-prefix? "ext" type) check-ext2-file-system) ((string-prefix? "bcachefs" type) check-bcachefs-file-system) ((string-prefix? "btrfs" type) check-btrfs-file-system) + ((string-suffix? "exfat" type) check-exfat-file-system) ((string-suffix? "fat" type) check-fat-file-system) ((string-prefix? "jfs" type) check-jfs-file-system) ((string-prefix? "f2fs" type) check-f2fs-file-system) |