guix/gnu/build/linux-modules.scm

;;; GNU Guix --- Functional package management for GNU
;;; Copyright © 2014, 2016, 2018, 2019, 2022 Ludovic Courtès <ludo@gnu.org>
;;; Copyright © 2017 Mathieu Othacehe <m.othacehe@gmail.com>
;;; Copyright © 2018 Danny Milosavljevic <dannym@scratchpost.org>
;;; Copyright © 2023 Tobias Geerinckx-Rice <me@tobias.gr>
;;;
;;; 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 build linux-modules)
  #:use-module (guix elf)
  #:use-module (guix glob)
  #:use-module (guix build syscalls)
  #:use-module ((guix build utils) #:select (find-files invoke))
  #:use-module (guix build union)
  #:autoload   (zlib) (call-with-gzip-input-port)
  #:use-module (rnrs io ports)
  #:use-module (rnrs bytevectors)
  #:use-module (srfi srfi-1)
  #:use-module (srfi srfi-9 gnu)
  #:use-module (srfi srfi-11)
  #:use-module (srfi srfi-26)
  #:use-module (ice-9 ftw)
  #:use-module (ice-9 vlist)
  #:use-module (ice-9 match)
  #:use-module (ice-9 rdelim)
  #:autoload   (ice-9 pretty-print) (pretty-print)
  #:export (dot-ko
            ensure-dot-ko
            module-formal-name
            module-aliases
            module-dependencies
            module-soft-dependencies
            normalize-module-name
            file-name->module-name
            find-module-file
            recursive-module-dependencies
            modules-loaded
            module-loaded?
            load-linux-module*
            load-linux-modules-from-directory

            pci-devices
            pci-device?
            pci-device-vendor
            pci-device-id
            pci-device-class
            pci-device-module-alias
            storage-pci-device?
            network-pci-device?
            display-pci-device?
            load-pci-device-database

            current-module-debugging-port

            device-module-aliases
            known-module-aliases
            matching-modules
            missing-modules

            write-module-name-database
            write-module-alias-database
            write-module-device-database

            make-linux-module-directory))

;;; Commentary:
;;;
;;; Tools to deal with Linux kernel modules.
;;;
;;; Code:

(define current-module-debugging-port
  (make-parameter (%make-void-port "w")))

(define (section-contents elf section)
  "Return the contents of SECTION in ELF as a bytevector."
  (let ((contents (make-bytevector (elf-section-size section))))
    (bytevector-copy! (elf-bytes elf) (elf-section-offset section)
                      contents 0
                      (elf-section-size section))
    contents))

(define %not-nul
  (char-set-complement (char-set #\nul)))

(define (nul-separated-string->list str)
  "Split STR at occurrences of the NUL character and return the resulting
string list."
  (string-tokenize str %not-nul))

(define (key=value->pair str)
  "Assuming STR has the form \"KEY=VALUE\", return a pair like (KEY
. \"VALUE\")."
  (let ((= (string-index str #\=)))
    (cons (string->symbol (string-take str =))
          (string-drop str (+ 1 =)))))

;; Matches kernel modules, without compression, with GZIP compression or with
;; XZ compression.
(define module-regex "\\.ko(\\.gz|\\.xz)?$")

(define (modinfo-section-contents file)
  "Return the contents of the '.modinfo' section of FILE as a list of
key/value pairs.."
  (define (get-bytevector file)
    (cond
     ((string-suffix? ".ko.gz" file)
      (let ((port (open-file file "r0")))
        (dynamic-wind
          (lambda ()
            #t)
          (lambda ()
            (call-with-gzip-input-port port get-bytevector-all))
          (lambda ()
            (close-port port)))))
     (else
      (call-with-input-file file get-bytevector-all))))

  (let* ((bv      (get-bytevector file))
         (elf     (parse-elf bv))
         (section (elf-section-by-name elf ".modinfo"))
         (modinfo (section-contents elf section)))
    (map key=value->pair
         (nul-separated-string->list (utf8->string modinfo)))))

(define %not-comma
  (char-set-complement (char-set #\,)))

(define (module-formal-name file)
  "Return the module name of FILE as it appears in its info section.  Usually
the module name is the same as the base name of FILE, modulo hyphens and minus
the \".ko[.gz|.xz]\" extension."
  (match (assq 'name (modinfo-section-contents file))
    (('name . name) name)
    (#f #f)))

(define (module-dependencies file)
  "Return the list of modules that FILE depends on.  The returned list
contains module names, not actual file names."
  (let ((info (modinfo-section-contents file)))
    (match (assq 'depends info)
      (('depends . what)
       (string-tokenize what %not-comma)))))

(define not-softdep-whitespace
  (char-set-complement (char-set #\space #\tab)))

(define (module-soft-dependencies file)
  "Return the list of modules that can be preloaded, and then the list of
modules that can be postloaded, of the soft dependencies of module FILE."
  ;; TEXT: "pre: baz blubb foo post: bax bar"
  (define (parse-softdep text)
    (let loop ((value '())
               (tokens (string-tokenize text not-softdep-whitespace))
               (section #f))
      (match tokens
       ((token rest ...)
        (if (string=? (string-take-right token 1) ":") ; section
            (loop value rest (string-trim-both (string-drop-right token 1)))
            (loop (cons (cons section token) value) rest section)))
       (()
        value))))

  ;; Note: Multiple 'softdep sections are allowed.
  (let* ((info (modinfo-section-contents file))
         (entries (concatenate
                   (filter-map (match-lambda
                                (('softdep . value)
                                 (parse-softdep value))
                                (_ #f))
                               (modinfo-section-contents file)))))
    (let-values (((pres posts)
                  (partition (match-lambda
                              (("pre" . _) #t)
                              (("post" . _) #f))
                             entries)))
      (values (map (match-lambda
                    ((_ . value) value))
                   pres)
              (map (match-lambda
                    ((_ . value) value))
                   posts)))))

(define (module-aliases file)
  "Return the list of aliases of module FILE."
  (let ((info (modinfo-section-contents file)))
    (filter-map (match-lambda
                 (('alias . value)
                  value)
                 (_ #f))
                (modinfo-section-contents file))))

(define (strip-extension filename)
  (let ((extension (string-index filename #\.)))
    (if extension
        (string-take filename extension)
        filename)))

(define* (dot-ko name #:optional compression)
  (let ((suffix (match compression
                  ('xz   ".ko.xz")
                  ('gzip ".ko.gz")
                  (else  ".ko"))))
    (string-append name suffix)))

(define (ensure-dot-ko name compression)
  "Return NAME with a '.ko[.gz|.xz]' suffix appended, unless it already has
it."
  (if (string-contains name ".ko")
      name
      (dot-ko name compression)))

(define (normalize-module-name module)
  "Return the \"canonical\" name for MODULE, replacing hyphens with
underscores."
  ;; See 'modname_normalize' in libkmod.
  (string-map (lambda (chr)
                (case chr
                  ((#\-) #\_)
                  (else chr)))
              module))

(define (file-name->module-name file)
  "Return the module name corresponding to FILE, stripping the trailing
'.ko[.gz|.xz]' and normalizing it."
  (normalize-module-name (strip-extension (basename file))))

(define (find-module-file directory module)
  "Lookup module NAME under DIRECTORY, and return its absolute file name.
NAME can be a file name with or without '.ko', or it can be a module name.
Raise an error if it could not be found.

Module names can differ from file names in interesting ways; for instance,
module names usually (always?) use underscores as the inter-word separator,
whereas file names often, but not always, use hyphens.  Examples:
\"usb-storage.ko\", \"serpent_generic.ko\"."
  (define names
    ;; List of possible file names.  XXX: It would of course be cleaner to
    ;; have a database that maps module names to file names and vice versa,
    ;; but everyone seems to be doing hacks like this one.  Oh well!
    (delete-duplicates
     (list module
           (normalize-module-name module)
           (string-map (lambda (chr) ;converse of 'normalize-module-name'
                         (case chr
                           ((#\_) #\-)
                           (else chr)))
                       module))))

  (match (find-files directory
                     (lambda (file stat)
                       (member (strip-extension
                                (basename file)) names)))
    ((file)
     file)
    (()
     (error "kernel module not found" module directory))
    ((_ ...)
     (error "several modules by that name" module directory))))

(define* (recursive-module-dependencies files
                                        #:key (lookup-module dot-ko))
  "Return the topologically-sorted list of file names of the modules depended
on by FILES, recursively.  File names of modules are determined by applying
LOOKUP-MODULE to the module name."
  (let loop ((files   files)
             (result  '())
             (visited vlist-null))
    (match files
      (()
       (delete-duplicates (reverse result)))
      ((head . tail)
       (let* ((visited? (vhash-assoc head visited))
              (deps     (if visited?
                            '()
                            (map lookup-module (module-dependencies head))))
              (visited  (if visited?
                            visited
                            (vhash-cons head #t visited))))
         (loop (append deps tail)
               (append result deps) visited))))))

(define %not-newline
  (char-set-complement (char-set #\newline)))

(define (modules-loaded)
  "Return the list of names of currently loaded Linux modules."
  (let* ((contents (call-with-input-file "/proc/modules"
                     get-string-all))
         (lines    (string-tokenize contents %not-newline)))
    (match (map string-tokenize lines)
      (((modules . _) ...)
       modules))))

(define (module-black-list)
  "Return the black list of modules that must not be loaded.  This black list
is specified using 'modprobe.blacklist=MODULE1,MODULE2,...' on the kernel
command line; it is honored by libkmod for users that pass
'KMOD_PROBE_APPLY_BLACKLIST', which includes 'modprobe --use-blacklist' and
udev."
  (define parameter
    "modprobe.blacklist=")

  (let ((command (call-with-input-file "/proc/cmdline"
                   get-string-all)))
    (append-map (lambda (arg)
                  (if (string-prefix? parameter arg)
                      (string-tokenize (string-drop arg (string-length parameter))
                                       %not-comma)
                      '()))
                (string-tokenize command))))

(define (module-loaded? module)
  "Return #t if MODULE is already loaded.  MODULE must be a Linux module name,
not a file name."
  (member module (modules-loaded)))

(define* (load-linux-module* file
                             #:key
                             (recursive? #t)
                             (lookup-module dot-ko)
                             (black-list (module-black-list)))
  "Load Linux module from FILE, the name of a '.ko[.gz|.xz]' file; return true
on success, false otherwise.  When RECURSIVE? is true, load its dependencies
first (à la 'modprobe'.)  The actual files containing modules depended on are
obtained by calling LOOKUP-MODULE with the module name.  Modules whose name
appears in BLACK-LIST are not loaded."
  (define (black-listed? module)
    (let ((result (member module black-list)))
      (when result
        (format (current-module-debugging-port)
                "not loading module '~a' because it's black-listed~%"
                module))
      result))

  (define (load-dependencies file)
    (let ((dependencies (module-dependencies file)))
      (every (cut load-linux-module* <>
                  #:lookup-module lookup-module
                  #:black-list black-list)
             (map lookup-module dependencies))))

  (and (not (black-listed? (file-name->module-name file)))
       (or (not recursive?)
           (load-dependencies file))
       (let ((fd #f))
         (format (current-module-debugging-port)
                 "loading Linux module from '~a'...~%" file)

         (catch 'system-error
           (lambda ()
             (set! fd (open-fdes file O_RDONLY))
             (load-linux-module/fd fd)
             (close-fdes fd)
             #t)
           (lambda args
             (when fd (close-fdes fd))
             (let ((errno (system-error-errno args)))
               (or (and recursive?      ; we're operating in ‘modprobe’ style
                        (member errno
                                (list EEXIST    ; already loaded
                                      EINVAL))) ; unsupported by hardware
                   (apply throw args))))))))

(define (load-linux-modules-from-directory modules directory)
  "Load MODULES and their dependencies from DIRECTORY, a directory containing
the '.ko' files.  The '.ko' suffix is automatically added to MODULES if
needed."
  (define module-name->file-name
    (module-name-lookup directory))

  (for-each (lambda (module)
              (when (file-exists? module)
                (load-linux-module* module
                                    #:lookup-module module-name->file-name)))
            (map module-name->file-name modules)))


;;;
;;; Device modules.
;;;

;; Copied from (guix utils).  FIXME: Factorize.
(define (readlink* file)
  "Call 'readlink' until the result is not a symlink."
  (define %max-symlink-depth 50)

  (let loop ((file  file)
             (depth 0))
    (define (absolute target)
      (if (absolute-file-name? target)
          target
          (string-append (dirname file) "/" target)))

    (if (>= depth %max-symlink-depth)
        file
        (call-with-values
            (lambda ()
              (catch 'system-error
                (lambda ()
                  (values #t (readlink file)))
                (lambda args
                  (let ((errno (system-error-errno args)))
                    (if (or (= errno EINVAL))
                        (values #f file)
                        (apply throw args))))))
          (lambda (success? target)
            (if success?
                (loop (absolute target) (+ depth 1))
                file))))))

;; See 'major' and 'minor' in <sys/sysmacros.h>.

(define (stat->device-major st)
  (ash (logand #xfff00 (stat:rdev st)) -8))

(define (stat->device-minor st)
  (logand #xff (stat:rdev st)))

(define %not-slash
  (char-set-complement (char-set #\/)))

(define (read-uevent port)
  "Read a /sys 'uevent' file from PORT and return an alist where each car is a
key such as 'MAJOR or 'DEVTYPE and each cdr is the corresponding value."
  (let loop ((result '()))
    (match (read-line port)
      ((? eof-object?)
       (reverse result))
      (line
       (loop (cons (key=value->pair line) result))))))

;; PCI device known to the Linux kernel.
(define-immutable-record-type <pci-device>
  (pci-device vendor device class module-alias)
  pci-device?
  (vendor       pci-device-vendor)                ;integer
  (device       pci-device-id)                    ;integer
  (class        pci-device-class)                 ;integer
  (module-alias pci-device-module-alias))         ;string | #f

(define (pci-device-class-predicate mask bits)
  (lambda (device)
    "Return true if DEVICE has the chosen class."
    (= (logand mask (pci-device-class device)) bits)))

(define storage-pci-device?                   ;"Mass storage controller" class
  (pci-device-class-predicate #xff0000 #x010000))
(define network-pci-device?                       ;"Network controller" class
  (pci-device-class-predicate #xff0000 #x020000))
(define display-pci-device?                       ;"Display controller" class
  (pci-device-class-predicate #xff0000 #x030000))

(define (pci-devices)
  "Return the list of PCI devices of the system (<pci-device> records)."
  (define (read-hex port)
    (let ((line (read-line port)))
      (and (string? line)
           (string-prefix? "0x" line)
           (string->number (string-drop line 2) 16))))

  (filter-map (lambda (directory)
                (define properties
                  (call-with-input-file (string-append directory "/uevent")
                    read-uevent))
                (define vendor
                  (call-with-input-file (string-append directory "/vendor")
                    read-hex))
                (define device
                  (call-with-input-file (string-append directory "/device")
                    read-hex))
                (define class
                  (call-with-input-file (string-append directory "/class")
                    read-hex))

                (pci-device vendor device class
                            (assq-ref properties 'MODALIAS)))
              (find-files "/sys/bus/pci/devices"
                          #:stat lstat)))

(define (read-pci-device-database port)
  "Parse the 'pci.ids' database that ships with the pciutils package and is
maintained at <https://pci-ids.ucw.cz/>."
  (define (comment? str)
    (string-prefix? "#" (string-trim str)))
  (define (blank? str)
    (string-null? (string-trim-both str)))
  (define (device? str)
    (eqv? #\tab (string-ref str 0)))
  (define (subvendor? str)
    (string-prefix? "\t\t" str))
  (define (class? str)
    (string-prefix? "C " str))
  (define (parse-id-line str)
    (let* ((str   (string-trim-both str))
           (space (string-index str char-set:whitespace)))
      (values (string->number (string-take str space) 16)
              (string-trim (string-drop str (+ 1 space))))))
  (define (finish vendor vendor-id devices table)
    (fold (lambda (device table)
            (match device
              ((device-id . name)
               (vhash-consv (logior (ash vendor-id 16) device-id)
                            (cons vendor name)
                            table))))
          table
          devices))

  (let loop ((table vlist-null)
             (vendor-id #f)
             (vendor #f)
             (devices '()))
    (match (read-line port)
      ((? eof-object?)
       (let ((table (if (and vendor vendor-id)
                        (finish vendor vendor-id devices table)
                        table)))
         (lambda (vendor device)
           (match (vhash-assv (logior (ash vendor 16) device) table)
             (#f
              (values #f #f))
             ((_ . (vendor . name))
              (values vendor name))))))
      ((? comment?)
       (loop table vendor-id vendor devices))
      ((? blank?)
       (loop table vendor-id vendor devices))
      ((? subvendor?)                             ;currently ignored
       (loop table vendor-id vendor devices))
      ((? class?)                                 ;currently ignored
       (loop table vendor-id vendor devices))
      ((? device? line)
       (let-values (((id name) (parse-id-line line)))
         (loop table vendor-id vendor
               (if (and vendor-id vendor)         ;class or device?
                   (alist-cons id name devices)
                   devices))))
      (line
       (let ((table (if (and vendor vendor-id)
                        (finish vendor vendor-id devices table)
                        table)))
         (let-values (((vendor-id vendor) (parse-id-line line)))
           (loop table vendor-id vendor '())))))))

(define (load-pci-device-database file)
  "Read the 'pci.ids' database at FILE (get it from the pciutils package or
from <https://pci-ids.ucw.cz/>) and return a lookup procedure that takes a PCI
vendor ID and a device ID (two integers) and returns the vendor name and
device name as two values."
  (let ((port (open-file file "r0")))
    (call-with-gzip-input-port port
      read-pci-device-database)))

(define (device-module-aliases device)
  "Return the list of module aliases required by DEVICE, a /dev file name, as
in this example:

  (device-module-aliases \"/dev/sda\")
  => (\"scsi:t-0x00\" \"pci:v00008086d00009D03sv0000103Csd000080FAbc01sc06i01\")

The modules corresponding to these aliases can then be found using
'matching-modules'."
  ;; The approach is adapted from
  ;; <https://unix.stackexchange.com/questions/97676/how-to-find-the-driver-module-associated-with-a-device-on-linux>.
  (let* ((st        (stat device))
         (type      (stat:type st))
         (major     (stat->device-major st))
         (minor     (stat->device-minor st))
         (sys-name  (string-append "/sys/dev/"
                                   (case type
                                     ((block-special) "block")
                                     ((char-special)  "char")
                                     (else (symbol->string type)))
                                   "/" (number->string major) ":"
                                   (number->string minor)))
         (directory (canonicalize-path (readlink* sys-name))))
    (let loop ((components (string-tokenize directory %not-slash))
               (aliases    '()))
      (match components
        (("sys" "devices" _)
         (reverse aliases))
        ((head ... _)
         (let ((uevent (string-append (string-join components "/" 'prefix)
                                      "/uevent")))
           (if (file-exists? uevent)
               (let ((props (call-with-input-file uevent read-uevent)))
                 (match (assq-ref props 'MODALIAS)
                   (#f    (loop head aliases))
                   (alias (loop head (cons alias aliases)))))
               (loop head aliases))))))))

(define (read-module-aliases port)
  "Read from PORT data in the Linux 'modules.alias' file format.  Return a
list of alias/module pairs where each alias is a glob pattern as like the
result of:

  (string->compiled-sglob \"scsi:t-0x01*\")

and each module is a module name like \"snd_hda_intel\"."
  (define (comment? str)
    (string-prefix? "#" str))

  (define (tokenize str)
    ;; Lines have the form "alias ALIAS MODULE", where ALIAS can contain
    ;; whitespace.  This is why we don't use 'string-tokenize'.
    (let* ((str   (string-trim-both str))
           (left  (string-index str #\space))
           (right (string-rindex str #\space)))
      (list (string-take str left)
            (string-trim-both (substring str left right))
            (string-trim-both (string-drop str right)))))

  (let loop ((aliases '()))
    (match (read-line port)
      ((? eof-object?)
       (reverse aliases))
      ((? comment?)
       (loop aliases))
      (line
       (match (tokenize line)
         (("alias" alias module)
          (loop (alist-cons (string->compiled-sglob alias) module
                            aliases)))
         (()                                      ;empty line
          (loop aliases)))))))

(define (current-kernel-directory)
  "Return the directory of the currently running Linux kernel."
  (string-append (or (getenv "LINUX_MODULE_DIRECTORY")
                     "/run/booted-system/kernel/lib/modules")
                 "/" (utsname:release (uname))))

(define (current-alias-file)
  "Return the absolute file name of the default 'modules.alias' file."
  (string-append (current-kernel-directory) "/modules.alias"))

(define* (known-module-aliases #:optional (alias-file (current-alias-file)))
  "Return the list of alias/module pairs read from ALIAS-FILE.  Each alias is
actually a pattern."
  (call-with-input-file alias-file read-module-aliases))

(define* (matching-modules alias
                           #:optional (known-aliases (known-module-aliases)))
  "Return the list of modules that match ALIAS according to KNOWN-ALIASES.
ALIAS is a string like \"scsi:t-0x00\" as returned by
'device-module-aliases'."
  (filter-map (match-lambda
                ((pattern . module)
                 (and (glob-match? pattern alias)
                      module)))
              known-aliases))

(define* (missing-modules device modules-provided)
  "Assuming MODULES-PROVIDED lists kernel modules that are already
provided--e.g., in the initrd, return the list of missing kernel modules that
are required to access DEVICE."
  (define aliases
    ;; Attempt to load 'modules.alias' from the current kernel, assuming we're
    ;; on Guix System, and assuming that corresponds to the kernel we'll be
    ;; installing.
    (known-module-aliases))

  (if aliases
      (let* ((modules  (delete-duplicates
                        (append-map (cut matching-modules <> aliases)
                                    (device-module-aliases device))))

             ;; Module names (not file names) are supposed to use underscores
             ;; instead of hyphens.  MODULES is a list of module names, whereas
             ;; LINUX-MODULES is file names without '.ko', so normalize them.
             (provided (map file-name->module-name modules-provided)))
        (remove (cut member <> provided) modules))
      '()))


;;;
;;; Module databases.
;;;

(define* (module-name->file-name/guess directory name
                                       #:key compression)
  "Guess the file name corresponding to NAME, a module name.  That doesn't
always work because sometimes underscores in NAME map to hyphens (e.g.,
\"input-leds.ko\"), sometimes not (e.g., \"mac_hid.ko\").  If the module is
compressed then COMPRESSED can be set to 'xz or 'gzip, depending on the
compression type."
  (string-append directory "/" (ensure-dot-ko name compression)))

(define (module-name-lookup directory)
  "Return a one argument procedure that takes a module name (e.g.,
\"input_leds\") and returns its absolute file name (e.g.,
\"/.../input-leds.ko\")."
  (define (guess-file-name name)
    (let ((names (list
                  (module-name->file-name/guess directory name)
                  (module-name->file-name/guess directory name
                                                #:compression 'xz)
                  (module-name->file-name/guess directory name
                                                #:compression 'gzip))))
      (or (find file-exists? names)
          (first names))))

  (catch 'system-error
    (lambda ()
      (define mapping
        (call-with-input-file (string-append directory "/modules.name")
          read))

      (lambda (name)
        (or (assoc-ref mapping name)
            (guess-file-name name))))
    (lambda args
      (if (= ENOENT (system-error-errno args))
          (cut guess-file-name <>)
          (apply throw args)))))

(define (write-module-name-database directory)
  "Write a database that maps \"module names\" as they appear in the relevant
ELF section of '.ko[.gz|.xz]' files, to actual file names.  This format is
Guix-specific.  It aims to deal with inconsistent naming, in particular
hyphens vs. underscores."
  (define mapping
    (map (lambda (file)
           (match (module-formal-name file)
             (#f   (cons (strip-extension (basename file)) file))
             (name (cons name file))))
         (find-files directory module-regex)))

  (call-with-output-file (string-append directory "/modules.name")
    (lambda (port)
      (display ";; Module name to file name mapping.
;;
;; This format is Guix-specific; it is not supported by upstream Linux tools.
\n"
               port)
      (pretty-print mapping port))))

(define (write-module-alias-database directory)
  "Traverse the '.ko[.gz|.xz]' files in DIRECTORY and create the corresponding
'modules.alias' file."
  (define aliases
    (map (lambda (file)
           (cons (file-name->module-name file) (module-aliases file)))
         (find-files directory module-regex)))

  (call-with-output-file (string-append directory "/modules.alias")
    (lambda (port)
      (display "# Aliases extracted from modules themselves.\n" port)
      (for-each (match-lambda
                  ((module . aliases)
                   (for-each (lambda (alias)
                               (format port "alias ~a ~a\n" alias module))
                             aliases)))
                aliases))))

(define (aliases->device-tuple aliases)
  "Traverse ALIASES, a list of module aliases, and search for
\"char-major-M-N\", \"block-major-M-N\", or \"devname:\" aliases.  When they
are found, return a tuple (DEVNAME TYPE MAJOR MINOR), otherwise return #f."
  (define (char/block-major? alias)
    (or (string-prefix? "char-major-" alias)
        (string-prefix? "block-major-" alias)))

  (define (char/block-major->tuple alias)
    (match (string-tokenize alias %not-dash)
      ((type "major" (= string->number major) (= string->number minor))
       (list (match type
               ("char" "c")
               ("block" "b"))
             major minor))))

  (let* ((devname     (any (lambda (alias)
                             (and (string-prefix? "devname:" alias)
                                  (string-drop alias 8)))
                           aliases))
         (major/minor (match (find char/block-major? aliases)
                        (#f #f)
                        (str (char/block-major->tuple str)))))
    (and devname major/minor
         (cons devname major/minor))))

(define %not-dash
  (char-set-complement (char-set #\-)))

(define (write-module-device-database directory)
  "Traverse the '.ko[.gz|.xz]' files in DIRECTORY and create the corresponding
'modules.devname' file.  This file contains information about modules that can
be loaded on-demand, such as file system modules."
  (define aliases
    (filter-map (lambda (file)
                  (match (aliases->device-tuple (module-aliases file))
                    (#f #f)
                    (tuple (cons (file-name->module-name file) tuple))))
                (find-files directory module-regex)))

  (call-with-output-file (string-append directory "/modules.devname")
    (lambda (port)
      (display "# Device nodes to trigger on-demand module loading.\n" port)
      (for-each (match-lambda
                  ((module devname type major minor)
                   (format port "~a ~a ~a~a:~a~%"
                           module devname type major minor)))
                aliases))))

(define (depmod version directory)
  "Given an (existing) DIRECTORY, invoke depmod on it for
kernel version VERSION."
  (let ((destination-directory (string-append directory "/lib/modules/"
                                              version))
        ;; Note: "System.map" is an input file.
        (maps-file (string-append directory "/System.map"))
        ;; Note: "Module.symvers" is an input file.
        (symvers-file (string-append directory "/Module.symvers")))
    ;; These files will be regenerated by depmod below.
    (for-each (lambda (basename)
                (when (and (string-prefix? "modules." basename)
                           ;; Note: "modules.builtin" is an input file.
                           (not (string=? "modules.builtin" basename))
                           ;; Note: "modules.order" is an input file.
                           (not (string=? "modules.order" basename)))
                  (delete-file (string-append destination-directory "/"
                                              basename))))
              (scandir destination-directory))
    (invoke "depmod"
            "-e" ; Report symbols that aren't supplied
            ;"-w" ; Warn on duplicates
            "-b" directory
            "-F" maps-file
            ;"-E" symvers-file ; using both "-E" and "-F" is not possible.
            version)))

(define (make-linux-module-directory inputs version output)
  "Create a new directory OUTPUT and ensure that the directory
OUTPUT/lib/modules/VERSION can be used as a source of Linux
kernel modules for the first kmod in PATH now to eventually
load.  Take modules to put into OUTPUT from INPUTS.

Right now that means it creates @code{modules.*.bin} which
@command{modprobe} will use to find loadable modules."
  (union-build output inputs #:create-all-directories? #t)
  (depmod version output))

;;; linux-modules.scm ends here