;;; GNU Guix --- Functional package management for GNU
;;; Copyright © 2018 Ludovic Courtès <ludo@gnu.org>
;;; Copyright © 2019 Mathieu Othacehe <m.othacehe@gmail.com>
;;;
;;; 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 (test-processes)
  #:use-module (guix scripts processes)
  #:use-module (guix store)
  #:use-module (guix derivations)
  #:use-module (guix packages)
  #:use-module (guix gexp)
  #:use-module ((guix utils) #:select (call-with-temporary-directory))
  #:use-module (gnu packages bootstrap)
  #:use-module (guix tests)
  #:use-module (srfi srfi-1)
  #:use-module (srfi srfi-64)
  #:use-module (rnrs bytevectors)
  #:use-module (rnrs io ports)
  #:use-module (ice-9 match)
  #:use-module (ice-9 threads))

;; When using --system argument, binfmt-misc mechanism may be used. In that
;; case, (guix script processes) won't work because:
;;
;; * ARGV0 is qemu-user and not guix-daemon.
;; * Guix-daemon won't be able to stuff client PID in ARGV1 of forked
;;   processes.
;;
;; See: https://lists.gnu.org/archive/html/bug-guix/2019-12/msg00017.html.
;;
;; If we detect that we are running with binfmt emulation, all the following
;; tests must be skipped.

(define (binfmt-misc?)
  (let ((pid (getpid))
        (cmdline (call-with-input-file "/proc/self/cmdline" get-string-all)))
    (match (primit<pre>
#include &quot;pathlocks.hh&quot;
#include &quot;util.hh&quot;

#include &lt;cerrno&gt;
#include &lt;cstdlib&gt;

#include &lt;sys/types.h&gt;
#include &lt;sys/stat.h&gt;
#include &lt;fcntl.h&gt;


namespace nix {


int openLockFile(const Path &amp; path, bool create)
{
    AutoCloseFD fd;

    fd = open(path.c_str(), O_RDWR | (create ? O_CREAT : 0), 0600);
    if (fd == -1 &amp;&amp; (create || errno != ENOENT))
        throw SysError(format(&quot;opening lock file `%1%&apos;&quot;) % path);

    closeOnExec(fd);

    return fd.borrow();
}


void deleteLockFile(const Path &amp; path, int fd)
{
    /* Get rid of the lock file.  Have to be careful not to introduce
       races.  Write a (meaningless) token to the file to indicate to
       other processes waiting on this lock that the lock is stale
       (deleted). */
    unlink(path.c_str());
    writeFull(fd, &quot;d&quot;);
    /* Note that the result of unlink() is ignored; removing the lock
       file is an optimisation, not a necessity. */
}


bool lockFile(int fd, LockType lockType, bool wait)
{
    struct flock lock;
    if (lockType == ltRead) lock.l_type = F_RDLCK;
    else if (lockType == ltWrite) lock.l_type = F_WRLCK;
    else if (lockType == ltNone) lock.l_type = F_UNLCK;
    else abort();
    lock.l_whence = SEEK_SET;
    lock.l_start = 0;
    lock.l_len = 0; /* entire file */

    if (wait) {
        while (fcntl(fd, F_SETLKW, &amp;lock) != 0) {
            checkInterrupt();
            if (errno != EINTR)
                throw SysError(format(&quot;acquiring/releasing lock&quot;));
        }
    } else {
        while (fcntl(fd, F_SETLK, &amp;lock) != 0) {
            checkInterrupt();
            if (errno == EACCES || errno == EAGAIN) return false;
            if (errno != EINTR) 
                throw SysError(format(&quot;acquiring/releasing lock&quot;));
        }
    }

    return true;
}


/* This enables us to check whether are not already holding a lock on
   a file ourselves.  POSIX locks (fcntl) suck in this respect: if we
   close a descriptor, the previous lock will be closed as well.  And
   there is no way to query whether we already have a lock (F_GETLK
   only works on locks held by other processes). */
static StringSet lockedPaths; /* !!! not thread-safe */


PathLocks::PathLocks()
    : deletePaths(false)
{
}


PathLocks::PathLocks(const PathSet &amp; paths, const string &amp; waitMsg)
    : deletePaths(false)
{
    lockPaths(paths, waitMsg);
}


bool PathLocks::lockPaths(const PathSet &amp; _paths,
    const string &amp; waitMsg, bool wait)
{
    assert(fds.empty());
    
    /* Note that `fds&apos; is built incrementally so that the destructor
       will only release those locks