sysdeps/unix/sysv/linux/system.c

   1 /* Copyright (C) 2002, 2003, 2005 Free Software Foundation, Inc.
   2    This file is part of the GNU C Library.
   3
   4    The GNU C Library is free software; you can redistribute it and/or
   5    modify it under the terms of the GNU Lesser General Public
   6    License as published by the Free Software Foundation; either
   7    version 2.1 of the License, or (at your option) any later version.
   8
   9    The GNU C Library is distributed in the hope that it will be useful,
  10    but WITHOUT ANY WARRANTY; without even the implied warranty of
  11    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  12    Lesser General Public License for more details.
  13
  14    You should have received a copy of the GNU Lesser General Public
  15    License along with the GNU C Library; if not, write to the Free
  16    Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
  17    02111-1307 USA.  */
  18
  19 #include <sched.h>
  20 #include <signal.h>
  21 #include <string.h>     /* For the real memset prototype.  */
  22 #include <sysdep.h>
  23 #include <unistd.h>
  24 #include <sys/wait.h>
  25 #include <bits/libc-lock.h>
  26 #include <kernel-features.h>
  27
  28 /* We have to and actually can handle cancelable system().  The big
  29    problem: we have to kill the child process if necessary.  To do
  30    this a cleanup handler has to be registered and is has to be able
  31    to find the PID of the child.  The main problem is to reliable have
  32    the PID when needed.  It is not necessary for the parent thread to
  33    return.  It might still be in the kernel when the cancellation
  34    request comes.  Therefore we have to use the clone() calls ability
  35    to have the kernel write the PID into the user-level variable.  */
  36 #if defined __ASSUME_CLONE_THREAD_FLAGS && !defined FORK
  37 # define FORK() \
  38   INLINE_SYSCALL (clone, 3, CLONE_PARENT_SETTID | SIGCHLD, 0, &pid)
  39 #endif
  40
  41 #ifdef _LIBC_REENTRANT
  42 static void cancel_handler (void *arg);
  43
  44 # define CLEANUP_HANDLER \
  45   __libc_cleanup_region_start (1, cancel_handler, &pid)
  46
  47 # define CLEANUP_RESET \
  48   __libc_cleanup_region_end (0)
  49 #endif
  50
  51
  52 /* Linux has waitpid(), so override the generic unix version.  */
  53 #include <sysdeps/posix/system.c>
  54
  55
  56 #ifdef _LIBC_REENTRANT
  57 /* The cancellation handler.  */
  58 static void
  59 cancel_handler (void *arg)
  60 {
  61   pid_t child = *(pid_t *) arg;
  62
  63   INTERNAL_SYSCALL_DECL (err);
  64   INTERNAL_SYSCALL (kill, err, 2, child, SIGKILL);
  65
  66   TEMP_FAILURE_RETRY (__waitpid (child, NULL, 0));
  67
  68   DO_LOCK ();
  69
  70   if (SUB_REF () == 0)
  71     {
  72       (void) __sigaction (SIGQUIT, &quit, (struct sigaction *) NULL);
  73       (void) __sigaction (SIGINT, &intr, (struct sigaction *) NULL);
  74     }
  75
  76   DO_UNLOCK ();
  77 }
  78 #endif