;;; GNU Guix --- Functional package management for GNU
;;; Copyright © 2013, 2014 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 system linux-initrd)
  #:use-module (guix monads)
  #:use-module (guix gexp)
  #:use-module (guix utils)
  #:use-module ((guix store)
                #:select (%store-prefix))
  #:use-module ((guix derivations)
                #:select (derivation->output-path))
  #:use-module (gnu packages cpio)
  #:use-module (gnu packages compression)
  #:use-module (gnu packages linux)
  #:use-module (gnu packages guile)
  #:use-module ((gnu packages make-bootstrap)
                #:select (%guile-static-stripped))
  #:use-module (ice-9 match)
  #:use-module (ice-9 regex)
  #:export (expression->initrd
            qemu-initrd
            gnu-system-initrd))


;;; 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))
                             (modules '())
                             (to-copy '())
                             (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.  TO-COPY is a
list of additional derivations or packages to copy to the initrd.  MODULES is
a list of Guile module names to be embedded in the initrd."

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

  (define (string->regexp str)
    ;; Return a regexp that matches STR exactly.
    (string-append "^" (regexp-quote str) "$"))

  (mlet* %store-monad ((source   (imported-modules modules))
                       (compiled (compiled-modules modules)))
    (define builder
      ;; TODO: Move most of this code to (guix build linux-initrd).
      #~(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 ((cpio    (string-append #$cpio "/bin/cpio"))
                (gzip    (string-append #$gzip "/bin/gzip"))
                (modules #$source)
                (gos     #$compiled)
                (scm-dir (string-append "share/guile/" (effective-version)))
                (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 #$output)
            (mkdir "contents")
            (with-directory-excursion "contents"
              (copy-recursively #$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)

              ;; Copy Guile modules.
              (chmod scm-dir #o777)
              (copy-recursively modules scm-dir
                                #:follow-symlinks? #t)
              (copy-recursively gos (string-append "lib/guile/"
                                                   (effective-version) "/ccache")
                                #:follow-symlinks? #t)

              ;; Compile `init'.
              (mkdir-p go-dir)
              (set! %load-path (cons modules %load-path))
              (set! %load-compiled-path (cons gos %load-compiled-path))
              (compile-file "init"
                            #:opts %auto-compilation-options
                            #:output-file (string-append go-dir "/init.go"))

              ;; Copy Linux modules.
              (let* ((linux      #$linux)
                     (module-dir (and linux
                                      (string-append linux "/lib/modules"))))
                (mkdir "modules")
                #$@(map (lambda (module)
                          #~(match (find-files module-dir
                                               #$(string->regexp module))
                              ((file)
                               (format #t "copying '~a'...~%" file)
                               (copy-file file (string-append "modules/"
                                                              #$module)))
                              (()
                               (error "module not found" #$module module-dir))
                              ((_ ...)
                               (error "several modules by that name"
                                      #$module module-dir))))
                        linux-modules))

              (let ((store   #$(string-append "." (%store-prefix)))
                    (to-copy '#$to-copy))
                (unless (null? to-copy)
                  (mkdir-p store))
                ;; XXX: Should we do export-references-graph?
                (for-each (lambda (input)
                            (let ((target
                                   (string-append store "/"
                                                  (basename input))))
                              (copy-recursively input target)))
                          to-copy))

              ;; 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 #$output "/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 #$output
                       (and (zero? (system* gzip "--best" "initrd"))
                            (rename-file "initrd.gz" "initrd")))))))))

   (gexp->derivation name builder
                     #:modules '((guix build utils)))))

(define* (qemu-initrd #:key
                      guile-modules-in-chroot?
                      volatile-root?
                      (mounts `((cifs "/store" ,(%store-prefix))
                                (cifs "/xchg" "/xchg"))))
  "Return a monadic derivation that builds an initrd for use in a QEMU guest
where the store is shared with the host.  MOUNTS is a list of file systems to
be mounted atop the root file system, where each item has the form:

    (FILE-SYSTEM-TYPE SOURCE TARGET)

When GUILE-MODULES-IN-CHROOT? is true, make core Guile modules available in
the new root.  This is necessary is the file specified as '--load' needs
access to these modules (which is the case if it wants to even just print an
exception and backtrace!).

When VOLATILE-ROOT? is true, the root file system is writable but any changes
to it are lost."
  (define cifs-modules
    ;; Modules needed to mount CIFS file systems.
    '("md4.ko" "ecb.ko" "cifs.ko"))

  (define virtio-9p-modules
    ;; Modules for the 9p paravirtualized file system.
    '("9pnet.ko" "9p.ko" "9pnet_virtio.ko"))

  (define linux-modules
    ;; Modules added to the initrd and loaded from the initrd.
    `("virtio.ko" "virtio_ring.ko" "virtio_pci.ko"
      "virtio_balloon.ko" "virtio_blk.ko" "virtio_net.ko"
      ,@(if (assoc-ref mounts 'cifs)
            cifs-modules
            '())
      ,@(if (assoc-ref mounts '9p)
            virtio-9p-modules
            '())
      ,@(if volatile-root?
            '("fuse.ko")
            '())))

  (expression->initrd
   #~(begin
       (use-modules (guix build linux-initrd)
                    (srfi srfi-26))

       (boot-system #:mounts '#$mounts
                    #:linux-modules '#$linux-modules
                    #:qemu-guest-networking? #t
                    #:guile-modules-in-chroot? '#$guile-modules-in-chroot?
                    #:unionfs (and=> #$(and volatile-root? unionfs-fuse/static)
                                     (cut string-append <> "/bin/unionfs"))
                    #:volatile-root? '#$volatile-root?))
   #:name "qemu-initrd"
   #:modules '((guix build utils)
               (guix build linux-initrd))
   #:to-copy (if volatile-root?
                 (list unionfs-fuse/static)
                 '())
   #:linux linux-libre
   #:linux-modules linux-modules))

(define (gnu-system-initrd)
  "Initrd for the GNU system itself, with nothing QEMU-specific."
  (qemu-initrd #:guile-modules-in-chroot? #f
               #:mounts '()))

;;; linux-initrd.scm ends here
