From 11e19555e5693b420f32ab5cc002764ef906ad16 Mon Sep 17 00:00:00 2001 From: Ludovic Courtès Date: Thu, 22 Oct 2020 23:28:31 +0200 Subject: file-systems: Allow swap space lookup by UUID/label. * gnu/build/file-systems.scm (%linux-swap-magic, %page-size): New variables. (linux-swap-superblock?, read-linux-swap-superblock) (linux-swap-superblock-uuid, linux-swap-superblock-volume-name): New procedures. (%partition-label-readers, %partition-uuid-readers): Add them. --- gnu/build/file-systems.scm | 46 +++++++++++++++++++++++++++++++++++++++++++++- 1 file changed, 45 insertions(+), 1 deletion(-) (limited to 'gnu/build') diff --git a/gnu/build/file-systems.scm b/gnu/build/file-systems.scm index 734d648575..8ec8eac896 100644 --- a/gnu/build/file-systems.scm +++ b/gnu/build/file-systems.scm @@ -1,5 +1,5 @@ ;;; GNU Guix --- Functional package management for GNU -;;; Copyright © 2014, 2015, 2016, 2017, 2018 Ludovic Courtès +;;; Copyright © 2014, 2015, 2016, 2017, 2018, 2020 Ludovic Courtès ;;; Copyright © 2016, 2017 David Craven ;;; Copyright © 2017 Mathieu Othacehe ;;; Copyright © 2019 Guillaume Le Vaillant @@ -179,6 +179,46 @@ if DEVICE does not contain an ext2 file system." (2 'reboot-required) (_ 'fatal-error))) + +;;; +;;; Linux swap. +;;; + +;; Linux "swap space" is not a file system but it has a UUID and volume name, +;; like actual file systems, and we want to be able to look up swap partitions +;; by UUID and by label. + +(define %linux-swap-magic + (string->utf8 "SWAPSPACE2")) + +;; Like 'PAGE_SIZE' in Linux, arch/x86/include/asm/page.h. +;; XXX: This is always 4K on x86_64, i386, and ARMv7. However, on AArch64, +;; this is determined by 'CONFIG_ARM64_PAGE_SHIFT' in the kernel, which is 12 +;; by default (4K) but can be 14 or 16. +(define %page-size 4096) + +(define (linux-swap-superblock? sblock) + "Return #t when SBLOCK is an linux-swap superblock." + (and (= (bytevector-length sblock) %page-size) + (bytevector=? (sub-bytevector sblock (- %page-size 10) 10) + %linux-swap-magic))) + +(define (read-linux-swap-superblock device) + "Return the raw contents of DEVICE's linux-swap superblock as a bytevector, or #f +if DEVICE does not contain an linux-swap file system." + (read-superblock device 0 %page-size linux-swap-superblock?)) + +;; See 'union swap_header' in 'include/linux/swap.h'. + +(define (linux-swap-superblock-uuid sblock) + "Return the UUID of Linux-swap superblock SBLOCK as a 16-byte bytevector." + (sub-bytevector sblock (+ 1024 4 4 4) 16)) + +(define (linux-swap-superblock-volume-name sblock) + "Return the label of Linux-swap superblock SBLOCK as a string." + (null-terminated-latin1->string + (sub-bytevector sblock (+ 1024 4 4 4 16) 16))) + ;;; ;;; Btrfs file systems. @@ -596,6 +636,8 @@ partition field reader that returned a value." iso9660-superblock-volume-name) (partition-field-reader read-ext2-superblock ext2-superblock-volume-name) + (partition-field-reader read-linux-swap-superblock + linux-swap-superblock-volume-name) (partition-field-reader read-btrfs-superblock btrfs-superblock-volume-name) (partition-field-reader read-fat32-superblock @@ -612,6 +654,8 @@ partition field reader that returned a value." iso9660-superblock-uuid) (partition-field-reader read-ext2-superblock ext2-superblock-uuid) + (partition-field-reader read-linux-swap-superblock + linux-swap-superblock-uuid) (partition-field-reader read-btrfs-superblock btrfs-superblock-uuid) (partition-field-reader read-fat32-superblock -- cgit v1.2.3