/* Test the lock upgrade path in tst-pututxline.

   Copyright (C) 2019 Free Software Foundation, Inc.

   This file is part of the GNU C Library.

   The GNU C Library is free software; you can redistribute it and/or

   modify it under the terms of the GNU Lesser General Public License as

   published by the Free Software Foundation; either version 2.1 of the

   License, or (at your option) any later version.

   The GNU C Library 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

   Lesser General Public License for more details.

   You should have received a copy of the GNU Lesser General Public

   License along with the GNU C Library; see the file COPYING.LIB.  If

   not, see <http://www.gnu.org/licenses/>.  */

/* pututxline upgrades the read lock on the file to a write lock.

   This test verifies that if the lock upgrade fails, the utmp

   subsystem remains in a consistent state, so that pututxline can be

   called again.  */

#include <errno.h>

#include <fcntl.h>

#include <stdlib.h>

#include <support/check.h>

#include <support/namespace.h>

#include <support/support.h>

#include <support/temp_file.h>

#include <support/xthread.h>

#include <support/xunistd.h>

#include <unistd.h>

#include <utmp.h>

#include <utmpx.h>

/* Path to the temporary utmp file.   */

static char *path;

/* Used to synchronize the subprocesses.  The barrier itself is

   allocated in shared memory.  */

static pthread_barrier_t *barrier;

/* Use pututxline to write an entry for PID.  */

static struct utmpx *

write_entry (pid_t pid)

{

  struct utmpx ut =

    {

     .ut_type = LOGIN_PROCESS,

     .ut_id = "1",

     .ut_user = "root",

     .ut_pid = pid,

     .ut_line = "entry",

     .ut_host = "localhost",

    };

  return pututxline (&ut);

}

/* Create the initial entry in a subprocess, so that the utmp

   subsystem in the original process is not disturbed.  */

static void

subprocess_create_entry (void *closure)

{

  TEST_COMPARE (utmpname (path), 0);

  TEST_VERIFY (write_entry (101) != NULL);

}

/* Acquire an advisory read lock on PATH.  */

__attribute__ ((noreturn)) static void

subprocess_lock_file (void)

{

  int fd = xopen (path, O_RDONLY, 0);

  struct flock64 fl =

    {

     .l_type = F_RDLCK,

     fl.l_whence = SEEK_SET,

    };

  TEST_COMPARE (fcntl64 (fd, F_SETLKW, &fl), 0);

  /* Signal to the main process that the lock has been acquired.  */

  xpthread_barrier_wait (barrier);

  /* Wait for the unlock request from the main process.  */

  xpthread_barrier_wait (barrier);

  /* Implicitly unlock the file.  */

  xclose (fd);

  /* Overwrite the existing entry.  */

  TEST_COMPARE (utmpname (path), 0);

  errno = 0;

  setutxent ();

  TEST_COMPARE (errno, 0);

  TEST_VERIFY (write_entry (102) != NULL);

  errno = 0;

  endutxent ();

  TEST_COMPARE (errno, 0);

  _exit (0);

}

static int

do_test (void)

{

  xclose (create_temp_file ("tst-pututxline-lockfail-", &path));

  {

    pthread_barrierattr_t attr;

    xpthread_barrierattr_init (&attr);

    xpthread_barrierattr_setpshared (&attr, PTHREAD_SCOPE_PROCESS);

    barrier = support_shared_allocate (sizeof (*barrier));

    xpthread_barrier_init (barrier, &attr, 2);

    xpthread_barrierattr_destroy (&attr);

  }

  /* Write the initial entry.  */

  support_isolate_in_subprocess (subprocess_create_entry, NULL);

  pid_t locker_pid = xfork ();

  if (locker_pid == 0)

    subprocess_lock_file ();

  /* Wait for the file locking to complete.  */

  xpthread_barrier_wait (barrier);

  /* Try to add another entry.  This attempt will fail, with EINTR or

     EAGAIN.  */

  TEST_COMPARE (utmpname (path), 0);

  TEST_VERIFY (write_entry (102) == NULL);

  if (errno != EINTR)

    TEST_COMPARE (errno, EAGAIN);

  /* Signal the subprocess to overwrite the entry.  */

  xpthread_barrier_wait (barrier);

  /* Wait for write and unlock to complete.  */

  {

    int status;

    xwaitpid (locker_pid, &status, 0);

    TEST_COMPARE (status, 0);

  }

  /* The file is no longer locked, so this operation will succeed.  */

  TEST_VERIFY (write_entry (103) != NULL);

  errno = 0;

  endutxent ();

  TEST_COMPARE (errno, 0);

  /* Check that there is just one entry with the expected contents.

     If pututxline becomes desynchronized internally, the entry is not

     overwritten (bug 24902).  */

  errno = 0;

  setutxent ();

  TEST_COMPARE (errno, 0);

  struct utmpx *ut = getutxent ();

  TEST_VERIFY_EXIT (ut != NULL);

  TEST_COMPARE (ut->ut_type, LOGIN_PROCESS);

  TEST_COMPARE_STRING (ut->ut_id, "1");

  TEST_COMPARE_STRING (ut->ut_user, "root");

  TEST_COMPARE (ut->ut_pid, 103);

  TEST_COMPARE_STRING (ut->ut_line, "entry");

  TEST_COMPARE_STRING (ut->ut_host, "localhost");

  TEST_VERIFY (getutxent () == NULL);

  errno = 0;

  endutxent ();

  TEST_COMPARE (errno, 0);

  xpthread_barrier_destroy (barrier);

  support_shared_free (barrier);

  free (path);

  return 0;

}

#include <support/test-driver.c>