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|
;;; GNU Guix --- Functional package management for GNU
;;; Copyright © 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 (guix build syscalls)
#:use-module (system foreign)
#:use-module (rnrs bytevectors)
#:use-module (srfi srfi-1)
#:use-module (ice-9 rdelim)
#:use-module (ice-9 match)
#:use-module (ice-9 ftw)
#:export (errno
MS_RDONLY
MS_REMOUNT
MS_BIND
MS_MOVE
mount
umount
processes))
;;; Commentary:
;;;
;;; This module provides bindings to libc's syscall wrappers. It uses the
;;; FFI, and thus requires a dynamically-linked Guile. (For statically-linked
;;; Guile, we instead apply 'guile-linux-syscalls.patch'.)
;;;
;;; Code:
(define %libc-errno-pointer
;; Glibc's 'errno' pointer.
(let ((errno-loc (dynamic-func "__errno_location" (dynamic-link))))
(and errno-loc
(let ((proc (pointer->procedure '* errno-loc '())))
(proc)))))
(define errno
(if %libc-errno-pointer
(let ((bv (pointer->bytevector %libc-errno-pointer (sizeof int))))
(lambda ()
"Return the current errno."
;; XXX: We assume that nothing changes 'errno' while we're doing all this.
;; In particular, that means that no async must be running here.
;; Use one of the fixed-size native-ref procedures because they are
;; optimized down to a single VM instruction, which reduces the risk
;; that we fiddle with 'errno' (needed on Guile 2.0.5, libc 2.11.)
(let-syntax ((ref (lambda (s)
(syntax-case s ()
((_ bv)
(case (sizeof int)
((4)
#'(bytevector-s32-native-ref bv 0))
((8)
#'(bytevector-s64-native-ref bv 0))
(else
(error "unsupported 'int' size"
(sizeof int)))))))))
(ref bv))))
(lambda () 0)))
(define (augment-mtab source target type options)
"Augment /etc/mtab with information about the given mount point."
(let ((port (open-file "/etc/mtab" "a")))
(format port "~a ~a ~a ~a 0 0~%"
source target type (or options "rw"))
(close-port port)))
(define (read-mtab port)
"Read an mtab-formatted file from PORT, returning a list of tuples."
(let loop ((result '()))
(let ((line (read-line port)))
(if (eof-object? line)
(reverse result)
(loop (cons (string-tokenize line) result))))))
(define (remove-from-mtab target)
"Remove mount point TARGET from /etc/mtab."
(define entries
(remove (match-lambda
((device mount-point type options freq passno)
(string=? target mount-point))
(_ #f))
(call-with-input-file "/etc/fstab" read-mtab)))
(call-with-output-file "/etc/fstab"
(lambda (port)
(for-each (match-lambda
((device mount-point type options freq passno)
(format port "~a ~a ~a ~a ~a ~a~%"
device mount-point type options freq passno)))
entries))))
;; Linux mount flags, from libc's <sys/mount.h>.
(define MS_RDONLY 1)
(define MS_REMOUNT 32)
(define MS_BIND 4096)
(define MS_MOVE 8192)
(define mount
(let* ((ptr (dynamic-func "mount" (dynamic-link)))
(proc (pointer->procedure int ptr `(* * * ,unsigned-long *))))
(lambda* (source target type #:optional (flags 0) options
#:key (update-mtab? #t))
"Mount device SOURCE on TARGET as a file system TYPE. Optionally, FLAGS
may be a bitwise-or of the MS_* <sys/mount.h> constants, and OPTIONS may be a
string. When FLAGS contains MS_REMOUNT, SOURCE and TYPE are ignored. When
UPDATE-MTAB? is true, update /etc/mtab. Raise a 'system-error' exception on
error."
(let ((ret (proc (if source
(string->pointer source)
%null-pointer)
(string->pointer target)
(if type
(string->pointer type)
%null-pointer)
flags
(if options
(string->pointer options)
%null-pointer)))
(err (errno)))
(unless (zero? ret)
(throw 'system-error "mount" "mount ~S on ~S: ~A"
(list source target (strerror err))
(list err)))
(when update-mtab?
(augment-mtab source target type options))))))
(define umount
(let* ((ptr (dynamic-func "umount2" (dynamic-link)))
(proc (pointer->procedure int ptr `(* ,int))))
(lambda* (target #:optional (flags 0)
#:key (update-mtab? #t))
"Unmount TARGET. Optionally FLAGS may be one of the MNT_* or UMOUNT_*
constants from <sys/mount.h>."
(let ((ret (proc (string->pointer target) flags))
(err (errno)))
(unless (zero? ret)
(throw 'system-error "umount" "~S: ~A"
(list target (strerror err))
(list err)))
(when update-mtab?
(remove-from-mtab target))))))
(define (kernel? pid)
"Return #t if PID designates a \"kernel thread\" rather than a normal
user-land process."
(let ((stat (call-with-input-file (format #f "/proc/~a/stat" pid)
(compose string-tokenize read-string))))
;; See proc.txt in Linux's documentation for the list of fields.
(match stat
((pid tcomm state ppid pgrp sid tty_nr tty_pgrp flags min_flt
cmin_flt maj_flt cmaj_flt utime stime cutime cstime
priority nice num_thread it_real_value start_time
vsize rss rsslim
(= string->number start_code) (= string->number end_code) _ ...)
;; Got this obscure trick from sysvinit's 'killall5' program.
(and (zero? start_code) (zero? end_code))))))
(define (processes)
"Return the list of live processes."
(sort (filter-map (lambda (file)
(let ((pid (string->number file)))
(and pid
(not (kernel? pid))
pid)))
(scandir "/proc"))
<))
;;; syscalls.scm ends here
|
