;;; GNU Guix --- Functional package management for GNU ;;; Copyright © 2013, 2014, 2015, 2016 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 (gnu build linux-boot) #:use-module (rnrs io ports) #:use-module (system repl error-handling) #: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) #:use-module (gnu build linux-modules) #:use-module (gnu build file-systems) #:export (mount-essential-file-systems linux-command-line find-long-option make-essential-device-nodes configure-qemu-networking bind-mount 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 /dev, /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 "dev")) (mkdir (scope "dev"))) (mount "none" (scope "dev") "devtmpfs") (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))) '("/dev" "/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 (find-long-option option arguments) "Find OPTION among ARGUMENTS, where OPTION is something like \"--load\". Return the value associated with OPTION, or #f on failure." (let ((opt (string-append option "="))) (and=> (find (cut string-prefix? opt <>) arguments) (lambda (arg) (substring arg (+ 1 (string-index arg #\=))))))) (define* (make-disk-device-nodes base major #:optional (minor 0)) "Make the block device nodes around BASE (something like \"/root/dev/sda\") with the given MAJOR number, starting with MINOR." (mknod base 'block-special #o644 (device-number major minor)) (let loop ((i 1)) (when (< i 16) (mknod (string-append base (number->string i)) 'block-special #o644 (device-number major (+ minor i))) (loop (+ i 1))))) (define* (make-essential-device-nodes #:key (root "/")) "Make essential device nodes under ROOT/dev." ;; The hand-made devtmpfs/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. (make-disk-device-nodes (scope "dev/sda") 8) (make-disk-device-nodes (scope "dev/sdb") 8 16) (make-disk-device-nodes (scope "dev/sdc") 8 32) (make-disk-device-nodes (scope "dev/sdd") 8 48) ;; SCSI CD-ROM devices (aka. "/dev/sr0" etc.). (mknod (scope "dev/scd0") 'block-special #o644 (device-number 11 0)) (mknod (scope "dev/scd1") 'block-special #o644 (device-number 11 1)) ;; The virtio (para-virtualized) block devices, as supported by QEMU/KVM. (make-disk-device-nodes (scope "dev/vda") 252) ;; 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)) ;; System console. This node is magically created by the kernel on the ;; initrd's root, so don't try to create it in that case. (unless (string=? root "/") (mknod (scope "dev/console") 'char-special #o600 (device-number 5 1))) ;; 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))))) ;; Serial line. (mknod (scope "dev/ttyS0") 'char-special #o660 (device-number 4 64)) ;; 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")) ;; Loopback devices. (let loop ((i 0)) (when (< i 8) (mknod (scope (string-append "dev/loop" (number->string i))) 'block-special #o660 (device-number 7 i)) (loop (+ 1 i)))) ;; 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)) ;; Hello! We used to create /etc/resolv.conf here, with "nameserver ;; 10.0.2.3\n". However, with Linux-libre 3.16, we're getting ENOSPC. ;; And since it's actually unnecessary, it's gone. (logand (network-interface-flags sock interface) IFF_UP))) (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 (pidof program) "Return the PID of the first presumed instance of PROGRAM." (let ((program (basename program))) (find (lambda (pid) (let ((exe (format #f "/proc/~a/exe" pid))) (and=> (false-if-exception (readlink exe)) (compose (cut string=? program <>) basename)))) (filter-map string->number (scandir "/proc"))))) (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." (define (mark-as-not-killable pid) ;; Tell the 'user-processes' shepherd service that PID must be kept alive ;; when shutting down. (mkdir-p "/root/etc/shepherd") (let ((port (open-file "/root/etc/shepherd/do-not-kill" "a"))) (chmod port #o600) (write pid port) (newline port) (close-port port))) (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. (mkdir-p "/rw-root/dev") (mount "none" "/rw-root/dev" "devtmpfs") ;; Make /root a union of the tmpfs and the actual root. Use ;; 'max_files' to set a high RLIMIT_NOFILE for the unionfs process ;; itself. Failing to do that, we quickly run out of file ;; descriptors; see . (unless (zero? (system* unionfs "-o" "cow,allow_other,use_ino,suid,dev,max_files=65536" "/rw-root=RW:/real-root=RO" "/root")) (error "unionfs failed")) ;; Make sure unionfs remains alive till the end. Because ;; 'fuse_daemonize' doesn't tell the PID of the forked daemon, we ;; have to resort to 'pidof' here. (mark-as-not-killable (pidof unionfs))) (begin (check-file-system root type) (mount root "/root" type))) ;; Make sure /root/etc/mtab is a symlink to /proc/self/mounts. (false-if-exception (delete-file "/root/etc/mtab")) (symlink "/proc/self/mounts" "/root/etc/mtab")) (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 '()) linux-module-directory qemu-guest-networking? volatile-root? pre-mount (mounts '())) "This procedure is meant to be called from an initrd. Boot a system by first loading LINUX-MODULES (a list of module names) from LINUX-MODULE-DIRECTORY, then setting up QEMU guest networking if QEMU-GUEST-NETWORKING? is true, calling PRE-MOUNT, 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 VOLATILE-ROOT? is true, the root file system is writable but any changes to it are lost." (define root-mount-point? (match-lambda ((device _ "/" _ ...) #t) (_ #f))) (define root-fs-type (or (any (match-lambda ((device _ "/" type _ ...) type) (_ #f)) mounts) "ext4")) (define (lookup-module name) (string-append linux-module-directory "/" (ensure-dot-ko name))) (display "Welcome, this is GNU's early boot Guile.\n") (display "Use '--repl' for an initrd REPL.\n\n") (call-with-error-handling (lambda () (mount-essential-file-systems) (let* ((args (linux-command-line)) (to-load (find-long-option "--load" args)) (root (find-long-option "--root" args))) (when (member "--repl" args) (start-repl)) (display "loading kernel modules...\n") (for-each (cut load-linux-module* <> #:lookup-module lookup-module) (map lookup-module linux-modules)) (when qemu-guest-networking? (unless (configure-qemu-networking) (display "network interface is DOWN\n"))) ;; Prepare the real root file system under /root. (unless (file-exists? "/root") (mkdir "/root")) (when (procedure? pre-mount) ;; Do whatever actions are needed before mounting the root file ;; system--e.g., installing device mappings. Error out when the ;; return value is false. (unless (pre-mount) (error "pre-mount actions failed"))) (if root (mount-root-file-system (canonicalize-device-spec root) root-fs-type #:volatile-root? volatile-root?) (mount "none" "/root" "tmpfs")) ;; Mount the specified file systems. (for-each mount-file-system (remove root-mount-point? mounts)) (if to-load (begin (switch-root "/root") (format #t "loading '~a'...\n" to-load) (primitive-load to-load) (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