diff options
Diffstat (limited to 'gnu/build/file-systems.scm')
| -rw-r--r-- | gnu/build/file-systems.scm | 126 |
1 files changed, 57 insertions, 69 deletions
diff --git a/gnu/build/file-systems.scm b/gnu/build/file-systems.scm index 431b287d0c..c121ca5f8b 100644 --- a/gnu/build/file-systems.scm +++ b/gnu/build/file-systems.scm @@ -1,5 +1,6 @@ ;;; GNU Guix --- Functional package management for GNU ;;; Copyright © 2014, 2015, 2016 Ludovic Courtès <ludo@gnu.org> +;;; Copyright © 2016 David Craven <david@craven.ch> ;;; ;;; This file is part of GNU Guix. ;;; @@ -71,67 +72,69 @@ "Bind-mount SOURCE at TARGET." (mount source target "" MS_BIND)) +(define (read-superblock device offset size magic?) + "Read a superblock of SIZE from OFFSET and DEVICE. Return the raw +superblock on success, and #f if no valid superblock was found. MAGIC? +takes a bytevector and returns #t when it's a valid superblock." + (call-with-input-file device + (lambda (port) + (seek port offset SEEK_SET) + + (let ((block (make-bytevector size))) + (match (get-bytevector-n! port block 0 (bytevector-length block)) + ((? eof-object?) + #f) + ((? number? len) + (and (= len (bytevector-length block)) + (and (magic? block) + block)))))))) + +(define (sub-bytevector bv start size) + "Return a copy of the SIZE bytes of BV starting from offset START." + (let ((result (make-bytevector size))) + (bytevector-copy! bv start result 0 size) + result)) + +(define (null-terminated-latin1->string bv) + "Return the volume name of SBLOCK as a string of at most 256 characters, or +#f if SBLOCK has no volume name." + ;; This is a Latin-1, nul-terminated string. + (let ((bytes (take-while (negate zero?) (bytevector->u8-list bv)))) + (if (null? bytes) + #f + (list->string (map integer->char bytes))))) + ;;; ;;; Ext2 file systems. ;;; +;; <http://www.nongnu.org/ext2-doc/ext2.html#DEF-SUPERBLOCK>. +;; TODO: Use "packed structs" from Guile-OpenGL or similar. + (define-syntax %ext2-endianness ;; Endianness of ext2 file systems. (identifier-syntax (endianness little))) -;; Offset in bytes of interesting parts of an ext2 superblock. See -;; <http://www.nongnu.org/ext2-doc/ext2.html#DEF-SUPERBLOCK>. -;; TODO: Use "packed structs" from Guile-OpenGL or similar. -(define-syntax %ext2-sblock-magic (identifier-syntax 56)) -(define-syntax %ext2-sblock-creator-os (identifier-syntax 72)) -(define-syntax %ext2-sblock-uuid (identifier-syntax 104)) -(define-syntax %ext2-sblock-volume-name (identifier-syntax 120)) +(define (ext2-superblock? sblock) + "Return #t when SBLOCK is an ext2 superblock." + (let ((magic (bytevector-u16-ref sblock 56 %ext2-endianness))) + (= magic #xef53))) (define (read-ext2-superblock device) "Return the raw contents of DEVICE's ext2 superblock as a bytevector, or #f if DEVICE does not contain an ext2 file system." - (define %ext2-magic - ;; The magic bytes that identify an ext2 file system. - #xef53) - - (define superblock-size - ;; Size of the interesting part of an ext2 superblock. - 264) - - (define block - ;; The superblock contents. - (make-bytevector superblock-size)) - - (call-with-input-file device - (lambda (port) - (seek port 1024 SEEK_SET) - - ;; Note: work around <http://bugs.gnu.org/17466>. - (and (eqv? superblock-size (get-bytevector-n! port block 0 - superblock-size)) - (let ((magic (bytevector-u16-ref block %ext2-sblock-magic - %ext2-endianness))) - (and (= magic %ext2-magic) - block)))))) + (read-superblock device 1024 264 ext2-superblock?)) (define (ext2-superblock-uuid sblock) "Return the UUID of ext2 superblock SBLOCK as a 16-byte bytevector." - (let ((uuid (make-bytevector 16))) - (bytevector-copy! sblock %ext2-sblock-uuid uuid 0 16) - uuid)) + (sub-bytevector sblock 104 16)) (define (ext2-superblock-volume-name sblock) "Return the volume name of SBLOCK as a string of at most 16 characters, or #f if SBLOCK has no volume name." - (let ((bv (make-bytevector 16))) - (bytevector-copy! sblock %ext2-sblock-volume-name bv 0 16) + (null-terminated-latin1->string (sub-bytevector sblock 120 16))) - ;; This is a Latin-1, nul-terminated string. - (let ((bytes (take-while (negate zero?) (bytevector->u8-list bv)))) - (if (null? bytes) - #f - (list->string (map integer->char bytes)))))) ;;; @@ -146,37 +149,22 @@ if DEVICE does not contain an ext2 file system." ;; Endianness of LUKS headers. (identifier-syntax (endianness big))) -(define-syntax %luks-header-size - ;; Size in bytes of the LUKS header, including key slots. - (identifier-syntax 592)) - -(define %luks-magic - ;; The 'LUKS_MAGIC' constant. - (u8-list->bytevector (append (map char->integer (string->list "LUKS")) - (list #xba #xbe)))) - -(define (sub-bytevector bv start size) - "Return a copy of the SIZE bytes of BV starting from offset START." - (let ((result (make-bytevector size))) - (bytevector-copy! bv start result 0 size) - result)) +(define (luks-superblock? sblock) + "Return #t when SBLOCK is a luks superblock." + (define %luks-magic + ;; The 'LUKS_MAGIC' constant. + (u8-list->bytevector (append (map char->integer (string->list "LUKS")) + (list #xba #xbe)))) + (let ((magic (sub-bytevector sblock 0 6)) + (version (bytevector-u16-ref sblock 6 %luks-endianness))) + (and (bytevector=? magic %luks-magic) + (= version 1)))) (define (read-luks-header file) "Read a LUKS header from FILE. Return the raw header on success, and #f if not valid header was found." - (call-with-input-file file - (lambda (port) - (let ((header (make-bytevector %luks-header-size))) - (match (get-bytevector-n! port header 0 (bytevector-length header)) - ((? eof-object?) - #f) - ((? number? len) - (and (= len (bytevector-length header)) - (let ((magic (sub-bytevector header 0 6)) ;XXX: inefficient - (version (bytevector-u16-ref header 6 %luks-endianness))) - (and (bytevector=? magic %luks-magic) - (= version 1) - header))))))))) + ;; Size in bytes of the LUKS header, including key slots. + (read-superblock file 0 592 luks-superblock?)) (define (luks-header-uuid header) "Return the LUKS UUID from HEADER, as a 16-byte bytevector." @@ -267,7 +255,7 @@ returns #t if that partition's volume name is LABEL." ext2-superblock-uuid bytevector=?)) -(define partition-luks-uuid-predicate +(define luks-partition-uuid-predicate (partition-predicate read-luks-header luks-header-uuid bytevector=?)) @@ -289,7 +277,7 @@ or #f if none was found." (define (find-partition-by-luks-uuid uuid) "Return the first LUKS partition whose unique identifier is UUID (a bytevector), or #f if none was found." - (and=> (find (partition-luks-uuid-predicate uuid) + (and=> (find (luks-partition-uuid-predicate uuid) (disk-partitions)) (cut string-append "/dev/" <>))) |