;;; GNU Guix --- Functional package management for GNU ;;; Copyright © 2013, 2014 Ludovic Courtès ;;; ;;; This file is part of GNU Guix. ;;; ;;; GNU Guix is free software; you can redistribute it and/or modify it ;;; under the terms of the GNU General Public License as published by ;;; the Free Software Foundation; either version 3 of the License, or (at ;;; your option) any later version. ;;; ;;; GNU Guix is distributed in the hope that it will be useful, but ;;; WITHOUT ANY WARRANTY; without even the implied warranty of ;;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the ;;; GNU General Public License for more details. ;;; ;;; You should have received a copy of the GNU General Public License ;;; along with GNU Guix. If not, see . (define-module (guix build linux-initrd) #:use-module (rnrs io ports) #:use-module (system foreign) #:autoload (system repl repl) (start-repl) #:autoload (system base compile) (compile-file) #:use-module (srfi srfi-1) #:use-module (srfi srfi-26) #:use-module (ice-9 match) #:use-module (ice-9 ftw) #:use-module (guix build utils) #:export (mount-essential-file-systems linux-command-line make-essential-device-nodes configure-qemu-networking check-file-system mount-file-system bind-mount load-linux-module* device-number boot-system)) ;;; Commentary: ;;; ;;; Utility procedures useful in a Linux initial RAM disk (initrd). Note that ;;; many of these use procedures not yet available in vanilla Guile (`mount', ;;; `load-linux-module', etc.); these are provided by a Guile patch used in ;;; the GNU distribution. ;;; ;;; Code: (define* (mount-essential-file-systems #:key (root "/")) "Mount /proc and /sys under ROOT." (define (scope dir) (string-append root (if (string-suffix? "/" root) "" "/") dir)) (unless (file-exists? (scope "proc")) (mkdir (scope "proc"))) (mount "none" (scope "proc") "proc") (unless (file-exists? (scope "sys")) (mkdir (scope "sys"))) (mount "none" (scope "sys") "sysfs")) (define (move-essential-file-systems root) "Move currently mounted essential file systems to ROOT." (for-each (lambda (dir) (let ((target (string-append root dir))) (unless (file-exists? target) (mkdir target)) (mount dir target "" MS_MOVE))) '("/proc" "/sys"))) (define (linux-command-line) "Return the Linux kernel command line as a list of strings." (string-tokenize (call-with-input-file "/proc/cmdline" get-string-all))) (define* (make-essential-device-nodes #:key (root "/")) "Make essential device nodes under ROOT/dev." ;; The hand-made udev! (define (scope dir) (string-append root (if (string-suffix? "/" root) "" "/") dir)) (unless (file-exists? (scope "dev")) (mkdir (scope "dev"))) ;; Make the device nodes for SCSI disks. (mknod (scope "dev/sda") 'block-special #o644 (device-number 8 0)) (mknod (scope "dev/sda1") 'block-special #o644 (device-number 8 1)) (mknod (scope "dev/sda2") 'block-special #o644 (device-number 8 2)) ;; The virtio (para-virtualized) block devices, as supported by QEMU/KVM. (mknod (scope "dev/vda") 'block-special #o644 (device-number 252 0)) (mknod (scope "dev/vda1") 'block-special #o644 (device-number 252 1)) (mknod (scope "dev/vda2") 'block-special #o644 (device-number 252 2)) ;; Memory (used by Xorg's VESA driver.) (mknod (scope "dev/mem") 'char-special #o640 (device-number 1 1)) (mknod (scope "dev/kmem") 'char-special #o640 (device-number 1 2)) ;; Inputs (used by Xorg.) (unless (file-exists? (scope "dev/input")) (mkdir (scope "dev/input"))) (mknod (scope "dev/input/mice") 'char-special #o640 (device-number 13 63)) (mknod (scope "dev/input/mouse0") 'char-special #o640 (device-number 13 32)) (mknod (scope "dev/input/event0") 'char-special #o640 (device-number 13 64)) ;; TTYs. (mknod (scope "dev/tty") 'char-special #o600 (device-number 5 0)) (chmod (scope "dev/tty") #o666) (let loop ((n 0)) (and (< n 50) (let ((name (format #f "dev/tty~a" n))) (mknod (scope name) 'char-special #o600 (device-number 4 n)) (loop (+ 1 n))))) ;; Pseudo ttys. (mknod (scope "dev/ptmx") 'char-special #o666 (device-number 5 2)) (chmod (scope "dev/ptmx") #o666) ;; Create /dev/pts; it will be mounted later, at boot time. (unless (file-exists? (scope "dev/pts")) (mkdir (scope "dev/pts"))) ;; Rendez-vous point for syslogd. (mknod (scope "dev/log") 'socket #o666 0) (mknod (scope "dev/kmsg") 'char-special #o600 (device-number 1 11)) ;; Other useful nodes, notably relied on by guix-daemon. (for-each (match-lambda ((file major minor) (mknod (scope file) 'char-special #o666 (device-number major minor)) (chmod (scope file) #o666))) '(("dev/null" 1 3) ("dev/zero" 1 5) ("dev/full" 1 7) ("dev/random" 1 8) ("dev/urandom" 1 9))) (symlink "/proc/self/fd" (scope "dev/fd")) (symlink "/proc/self/fd/0" (scope "dev/stdin")) (symlink "/proc/self/fd/1" (scope "dev/stdout")) (symlink "/proc/self/fd/2" (scope "dev/stderr")) ;; File systems in user space (FUSE). (mknod (scope "dev/fuse") 'char-special #o666 (device-number 10 229))) (define %host-qemu-ipv4-address (inet-pton AF_INET "10.0.2.10")) (define* (configure-qemu-networking #:optional (interface "eth0")) "Setup the INTERFACE network interface and /etc/resolv.conf according to QEMU's default networking settings (see net/slirp.c in QEMU for default networking values.) Return #t if INTERFACE is up, #f otherwise." (display "configuring QEMU networking...\n") (let* ((sock (socket AF_INET SOCK_STREAM 0)) (address (make-socket-address AF_INET %host-qemu-ipv4-address 0)) (flags (network-interface-flags sock interface))) (set-network-interface-address sock interface address) (set-network-interface-flags sock interface (logior flags IFF_UP)) (unless (file-exists? "/etc") (mkdir "/etc")) (call-with-output-file "/etc/resolv.conf" (lambda (p) (display "nameserver 10.0.2.3\n" p))) (logand (network-interface-flags sock interface) IFF_UP))) ;; Linux mount flags, from libc's . (define MS_RDONLY 1) (define MS_BIND 4096) (define MS_MOVE 8192) (define (bind-mount source target) "Bind-mount SOURCE at TARGET." (mount source target "" MS_BIND)) (define (load-linux-module* file) "Load Linux module from FILE, the name of a `.ko' file." (define (slurp module) (call-with-input-file file get-bytevector-all)) (load-linux-module (slurp file))) (define (device-number major minor) "Return the device number for the device with MAJOR and MINOR, for use as the last argument of `mknod'." (+ (* major 256) minor)) (define* (mount-root-file-system root type #:key volatile-root? (unionfs "unionfs")) "Mount the root file system of type TYPE at device ROOT. If VOLATILE-ROOT? is true, mount ROOT read-only and make it a union with a writable tmpfs using UNIONFS." (catch #t (lambda () (if volatile-root? (begin (mkdir-p "/real-root") (mount root "/real-root" type MS_RDONLY) (mkdir-p "/rw-root") (mount "none" "/rw-root" "tmpfs") ;; We want read-write /dev nodes. (make-essential-device-nodes #:root "/rw-root") ;; Make /root a union of the tmpfs and the actual root. (unless (zero? (system* unionfs "-o" "cow,allow_other,use_ino,suid,dev" "/rw-root=RW:/real-root=RO" "/root")) (error "unionfs failed"))) (begin (check-file-system root type) (mount root "/root" type)))) (lambda args (format (current-error-port) "exception while mounting '~a': ~s~%" root args) (start-repl))) (copy-file "/proc/mounts" "/root/etc/mtab")) (define (check-file-system device type) "Run a file system check of TYPE on DEVICE." (define fsck (string-append "fsck." type)) (let ((status (system* fsck "-v" "-p" device))) (match (status:exit-val status) (0 #t) (1 (format (current-error-port) "'~a' corrected errors on ~a; continuing~%" fsck device)) (2 (format (current-error-port) "'~a' corrected errors on ~a; rebooting~%" fsck device) (sleep 3) (reboot)) (code (format (current-error-port) "'~a' exited with code ~a on ~a; spawning REPL~%" fsck code device) (start-repl))))) (define* (mount-file-system spec #:key (root "/root")) "Mount the file system described by SPEC under ROOT. SPEC must have the form: (DEVICE MOUNT-POINT TYPE (FLAGS ...) OPTIONS CHECK?) DEVICE, MOUNT-POINT, and TYPE must be strings; OPTIONS can be a string or #f; FLAGS must be a list of symbols. CHECK? is a Boolean indicating whether to run a file system check." (define flags->bit-mask (match-lambda (('read-only rest ...) (or MS_RDONLY (flags->bit-mask rest))) (('bind-mount rest ...) (or MS_BIND (flags->bit-mask rest))) (() 0))) (match spec ((source mount-point type (flags ...) options check?) (let ((mount-point (string-append root "/" mount-point))) (when check? (check-file-system source type)) (mkdir-p mount-point) (mount source mount-point type (flags->bit-mask flags) (if options (string->pointer options) %null-pointer)) ;; Update /etc/mtab. (mkdir-p (string-append root "/etc")) (let ((port (open-file (string-append root "/etc/mtab") "a"))) (format port "~a ~a ~a ~a 0 0~%" source mount-point type options) (close-port port)))))) (define (switch-root root) "Switch to ROOT as the root file system, in a way similar to what util-linux' switch_root(8) does." (move-essential-file-systems root) (chdir root) ;; Since we're about to 'rm -rf /', try to make sure we're on an initrd. ;; TODO: Use 'statfs' to check the fs type, like klibc does. (when (or (not (file-exists? "/init")) (directory-exists? "/home")) (format (current-error-port) "The root file system is probably not an initrd; \ bailing out.~%root contents: ~s~%" (scandir "/")) (force-output (current-error-port)) (exit 1)) ;; Delete files from the old root, without crossing mount points (assuming ;; there are no mount points in sub-directories.) That means we're leaving ;; the empty ROOT directory behind us, but that's OK. (let ((root-device (stat:dev (stat "/")))) (for-each (lambda (file) (unless (member file '("." "..")) (let* ((file (string-append "/" file)) (device (stat:dev (lstat file)))) (when (= device root-device) (delete-file-recursively file))))) (scandir "/"))) ;; Make ROOT the new root. (mount root "/" "" MS_MOVE) (chroot ".") (chdir "/") (when (file-exists? "/dev/console") ;; Close the standard file descriptors since they refer to the old ;; /dev/console, and reopen them. (let ((console (open-file "/dev/console" "r+b0"))) (for-each close-fdes '(0 1 2)) (dup2 (fileno console) 0) (dup2 (fileno console) 1) (dup2 (fileno console) 2) (close-port console)))) (define* (boot-system #:key (linux-modules '()) qemu-guest-networking? guile-modules-in-chroot? volatile-root? (mounts '())) "This procedure is meant to be called from an initrd. Boot a system by first loading LINUX-MODULES, then setting up QEMU guest networking if QEMU-GUEST-NETWORKING? is true, mounting the file systems specified in MOUNTS, and finally booting into the new root if any. The initrd supports kernel command-line options '--load', '--root', and '--repl'. Mount the root file system, specified by the '--root' command-line argument, if any. MOUNTS must be a list suitable for 'mount-file-system'. When GUILE-MODULES-IN-CHROOT? is true, make core Guile modules available in the new root. When VOLATILE-ROOT? is true, the root file system is writable but any changes to it are lost." (define (resolve file) ;; If FILE is a symlink to an absolute file name, resolve it as if we were ;; under /root. (let ((st (lstat file))) (if (eq? 'symlink (stat:type st)) (let ((target (readlink file))) (resolve (string-append "/root" target))) file))) (define root-mount-point? (match-lambda ((device "/" _ ...) #t) (_ #f))) (define root-fs-type (or (any (match-lambda ((device "/" type _ ...) type) (_ #f)) mounts) "ext4")) (display "Welcome, this is GNU's early boot Guile.\n") (display "Use '--repl' for an initrd REPL.\n\n") (mount-essential-file-systems) (let* ((args (linux-command-line)) (option (lambda (opt) (let ((opt (string-append opt "="))) (and=> (find (cut string-prefix? opt <>) args) (lambda (arg) (substring arg (+ 1 (string-index arg #\=)))))))) (to-load (option "--load")) (root (option "--root"))) (when (member "--repl" args) (start-repl)) (display "loading kernel modules...\n") (for-each (compose load-linux-module* (cut string-append "/modules/" <>)) linux-modules) (when qemu-guest-networking? (unless (configure-qemu-networking) (display "network interface is DOWN\n"))) ;; Make /dev nodes. (make-essential-device-nodes) ;; Prepare the real root file system under /root. (unless (file-exists? "/root") (mkdir "/root")) (if root (mount-root-file-system root root-fs-type #:volatile-root? volatile-root?) (mount "none" "/root" "tmpfs")) (unless (file-exists? "/root/dev") (mkdir "/root/dev") (make-essential-device-nodes #:root "/root")) ;; Mount the specified file systems. (for-each mount-file-system (remove root-mount-point? mounts)) (when guile-modules-in-chroot? ;; Copy the directories that contain .scm and .go files so that the ;; child process in the chroot can load modules (we would bind-mount ;; them but for some reason that fails with EINVAL -- XXX). (mkdir-p "/root/share") (mkdir-p "/root/lib") (mount "none" "/root/share" "tmpfs") (mount "none" "/root/lib" "tmpfs") (copy-recursively "/share" "/root/share" #:log (%make-void-port "w")) (copy-recursively "/lib" "/root/lib" #:log (%make-void-port "w"))) (if to-load (begin (switch-root "/root") (format #t "loading '~a'...\n" to-load) ;; Obviously this has to be done each time we boot. Do it from here ;; so that statfs(2) returns DEVPTS_SUPER_MAGIC like libc's getpt(3) ;; expects (and thus openpty(3) and its users, such as xterm.) (mount "none" "/dev/pts" "devpts") ;; TODO: Remove /lib, /share, and /loader.go. (catch #t (lambda () (primitive-load to-load)) (lambda args (format (current-error-port) "'~a' raised an exception: ~s~%" to-load args) (start-repl))) (format (current-error-port) "boot program '~a' terminated, rebooting~%" to-load) (sleep 2) (reboot)) (begin (display "no boot file passed via '--load'\n") (display "entering a warm and cozy REPL\n") (start-repl))))) ;;; linux-initrd.scm ends here