;;; GNU Guix --- Functional package management for GNU
;;; Copyright © 2013 Ludovic Courtès <ludo@gnu.org>
;;;
;;; 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 <http://www.gnu.org/licenses/>.

(define-module (gnu packages linux-initrd)
  #:use-module (guix utils)
  #:use-module (guix licenses)
  #:use-module (gnu packages)
  #:use-module (gnu packages cpio)
  #:use-module (gnu packages compression)
  #:use-module (gnu packages linux)
  #:use-module ((gnu packages make-bootstrap)
                #:select (%guile-static-stripped))
  #:use-module (guix packages)
  #:use-module (guix download)
  #:use-module (guix build-system trivial))


;;; Commentary:
;;;
;;; Tools to build initial RAM disks (initrd's) for Linux-Libre, and in
;;; particular initrd's that run Guile.
;;;
;;; Code:


(define* (expression->initrd exp
                             #:key
                             (guile %guile-static-stripped)
                             (cpio cpio)
                             (gzip gzip)
                             (name "guile-initrd")
                             (system (%current-system))
                             (linux #f)
                             (linux-modules '()))
  "Return a package that contains a Linux initrd (a gzipped cpio archive)
containing GUILE and that evaluates EXP upon booting.  LINUX-MODULES is a list
of `.ko' file names to be copied from LINUX into the initrd."
  ;; TODO: Add a `modules' parameter.

  ;; General Linux overview in `Documentation/early-userspace/README' and
  ;; `Documentation/filesystems/ramfs-rootfs-initramfs.txt'.

  (define builder
    `(begin
       (use-modules (guix build utils)
                    (ice-9 pretty-print)
                    (ice-9 popen)
                    (ice-9 match)
                    (ice-9 ftw)
                    (srfi srfi-26)
                    (system base compile)
                    (rnrs bytevectors)
                    ((system foreign) #:select (sizeof)))

       (let ((guile (assoc-ref %build-inputs "guile"))
             (cpio  (string-append (assoc-ref %build-inputs "cpio")
                                   "/bin/cpio"))
             (gzip  (string-append (assoc-ref %build-inputs "gzip")
                                   "/bin/gzip"))
             (out   (assoc-ref %outputs "out")))
         (mkdir out)
         (mkdir "contents")
         (with-directory-excursion "contents"
           (copy-recursively guile ".")
           (call-with-output-file "init"
             (lambda (p)
               (format p "#!/bin/guile -ds~%!#~%" guile)
               (pretty-print ',exp p)))
           (chmod "init" #o555)
           (chmod "bin/guile" #o555)

           ;; Compile `init'.
           (let ((go-dir (format #f ".cache/guile/ccache/~a-~a-~a-~a"
                                 (effective-version)
                                 (if (eq? (native-endianness) (endianness little))
                                     "LE"
                                     "BE")
                                 (sizeof '*)
                                 (effective-version))))
             (mkdir-p go-dir)
             (compile-file "init"
                           #:opts %auto-compilation-options
                           #:output-file (string-append go-dir "/init.go")))

           (let* ((linux      (assoc-ref %build-inputs "linux"))
                  (module-dir (and linux
                                   (string-append linux "/lib/modules"))))
             (mkdir "modules")
             ,@(map (lambda (module)
                      `(match (find-files module-dir ,module)
                         ((file)
                          (format #t "copying '~a'...~%" file)
                          (copy-file file (string-append "modules/"
                                                         ,module)))
                         (()
                          (error "module not found" ,module module-dir))
                         ((_ ...)
                          (error "several modules by that name"
                                 ,module module-dir))))
                    linux-modules))

           ;; Reset the timestamps of all the files that will make it in the
           ;; initrd.
           (for-each (cut utime <> 0 0 0 0)
                     (find-files "." ".*"))

           (system* cpio "--version")
           (let ((pipe (open-pipe* OPEN_WRITE cpio "-o"
                                   "-O" (string-append out "/initrd")
                                   "-H" "newc" "--null")))
             (define print0
               (let ((len (string-length "./")))
                 (lambda (file)
                   (format pipe "~a\0" (string-drop file len)))))

             ;; Note: as per `ramfs-rootfs-initramfs.txt', always add
             ;; directory entries before the files that are inside of it: "The
             ;; Linux kernel cpio extractor won't create files in a directory
             ;; that doesn't exist, so the directory entries must go before
             ;; the files that go in those directories."
             (file-system-fold (const #t)
                               (lambda (file stat result) ; leaf
                                 (print0 file))
                               (lambda (dir stat result) ; down
                                 (unless (string=? dir ".")
                                   (print0 dir)))
                               (const #f)         ; up
                               (const #f)         ; skip
                               (const #f)
                               #f
                               ".")

             (and (zero? (close-pipe pipe))
                  (with-directory-excursion out
                    (and (zero? (system* gzip "--best" "initrd"))
                         (rename-file "initrd.gz" "initrd")))))))))

  (let ((name* name))
    (package
      (name name*)
      (version "0")
      (source #f)
      (build-system trivial-build-system)
      (arguments `(#:modules ((guix build utils))
                   #:builder ,builder))
      (inputs `(("guile" ,guile)
                ("cpio" ,cpio)
                ("gzip" ,gzip)
                ,@(if linux
                      `(("linux" ,linux))
                      '())))
      (synopsis "An initial RAM disk (initrd) for the Linux kernel")
      (description
       "An initial RAM disk (initrd), really a gzipped cpio archive, for use by
the Linux kernel.")
      (license gpl3+)
      (home-page "http://www.gnu.org/software/guix/"))))

(define-public qemu-initrd
  (expression->initrd
   '(begin
      (use-modules (rnrs io ports)
                   (srfi srfi-1)
                   (srfi srfi-26)
                   (ice-9 match)
                   ((system foreign) #:select (string->pointer))
                   ((system base compile) #:select (compile-file)))

      (display "Welcome, this is GNU/Guile!\n")
      (display "Use '--repl' for an initrd REPL.\n\n")

      (mkdir "/proc")
      (mount "none" "/proc" "proc")

      (mkdir "/sys")
      (mount "none" "/sys" "sysfs")

      (let* ((command (string-trim-both
                       (call-with-input-file "/proc/cmdline"
                         get-string-all)))
             (args    (string-split command char-set:blank))
             (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)
          ((@ (system repl repl) start-repl)))

        (let ((slurp (lambda (module)
                       (call-with-input-file
                           (string-append "/modules/" module)
                         get-bytevector-all))))
          (display "loading CIFS and companion modules...\n")
          (for-each (compose load-linux-module slurp)
                    (list "md4.ko" "ecb.ko" "cifs.ko")))

        ;; See net/slirp.c for default QEMU networking values.
        (display "configuring network...\n")
        (let* ((sock    (socket AF_INET SOCK_STREAM 0))
               (address (make-socket-address AF_INET
                                             (inet-pton AF_INET
                                                        "10.0.2.10")
                                             0))
               (flags   (network-interface-flags sock "eth0")))
          (set-network-interface-address sock "eth0" address)
          (set-network-interface-flags sock "eth0"
                                       (logior flags IFF_UP))
          (if (logand (network-interface-flags sock "eth0") IFF_UP)
              (display "network interface is up\n")
              (display "network interface is DOWN\n"))

          (mkdir "/etc")
          (call-with-output-file "/etc/resolv.conf"
            (lambda (p)
              (display "nameserver 10.0.2.3\n" p)))
          (sleep 1))

        ;; Prepare the real root file system under /root.
        (unless (file-exists? "/root")
          (mkdir "/root"))
        (if root
            (mount root "/root" "ext3")
            (mount "none" "/root" "tmpfs"))
        (mkdir "/root/proc")
        (mount "none" "/root/proc" "proc")
        (mkdir "/root/sys")
        (mount "none" "/root/sys" "sysfs")
        (mkdir "/root/xchg")
        (mkdir "/root/nix")
        (mkdir "/root/nix/store")

        (mkdir "/root/dev")
        (let ((makedev (lambda (major minor)
                         (+ (* major 256) minor))))
          (mknod "/root/dev/null" 'char-special #o666 (makedev 1 3))
          (mknod "/root/dev/zero" 'char-special #o666 (makedev 1 5)))

        ;; Mount the host's store and exchange directory.
        (display "mounting QEMU's SMB shares...\n")
        (let ((server "10.0.2.4"))
          (mount (string-append "//" server "/store") "/root/nix/store" "cifs" 0
                 (string->pointer "guest,sec=none"))
          (mount (string-append "//" server "/xchg") "/root/xchg" "cifs" 0
                 (string->pointer "guest,sec=none")))

        (if to-load
            (begin
              (format #t "loading boot file '~a'...\n" to-load)
              (compile-file (string-append "/root/" to-load)
                            #:output-file "/root/loader.go"
                            #:opts %auto-compilation-options)
              (match (primitive-fork)
                (0
                 (chroot "/root")
                 (load-compiled "/loader.go"))
                (pid
                 (format #t "boot file loaded under PID ~a~%" pid)
                 (let ((status (waitpid pid)))
                   (reboot)))))
            (begin
              (display "no boot file passed via '--load'\n")
              (display "entering a warm and cozy REPL\n")
              ((@ (system repl repl) start-repl))))))
   #:name "qemu-initrd"
   #:linux linux-libre
   #:linux-modules '("cifs.ko" "md4.ko" "ecb.ko")))

;;; linux-initrd.scm ends here
