sysdeps/posix/system.c

   1 /* Copyright (C) 1991-2000,2002,2003,2005,2007 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 <errno.h>
  20 #include <signal.h>
  21 #include <stddef.h>
  22 #include <stdlib.h>
  23 #include <unistd.h>
  24 #include <sys/types.h>
  25 #include <sys/wait.h>
  26 #include <bits/libc-lock.h>
  27 #include <sysdep-cancel.h>
  28
  29
  30 #define SHELL_PATH      "/bin/sh"       /* Path of the shell.  */
  31 #define SHELL_NAME      "sh"            /* Name to give it.  */
  32
  33
  34 #ifdef _LIBC_REENTRANT
  35 static struct sigaction intr, quit;
  36 static int sa_refcntr;
  37 __libc_lock_define_initialized (static, lock);
  38
  39 # define DO_LOCK() __libc_lock_lock (lock)
  40 # define DO_UNLOCK() __libc_lock_unlock (lock)
  41 # define INIT_LOCK() ({ __libc_lock_init (lock); sa_refcntr = 0; })
  42 # define ADD_REF() sa_refcntr++
  43 # define SUB_REF() --sa_refcntr
  44 #else
  45 # define DO_LOCK()
  46 # define DO_UNLOCK()
  47 # define INIT_LOCK()
  48 # define ADD_REF() 0
  49 # define SUB_REF() 0
  50 #endif
  51
  52
  53 /* Execute LINE as a shell command, returning its status.  */
  54 static int
  55 do_system (const char *line)
  56 {
  57   int status, save;
  58   pid_t pid;
  59   struct sigaction sa;
  60 #ifndef _LIBC_REENTRANT
  61   struct sigaction intr, quit;
  62 #endif
  63   sigset_t omask;
  64
  65   sa.sa_handler = SIG_IGN;
  66   sa.sa_flags = 0;
  67   __sigemptyset (&sa.sa_mask);
  68
  69   DO_LOCK ();
  70   if (ADD_REF () == 0)
  71     {
  72       if (__sigaction (SIGINT, &sa, &intr) < 0)
  73         {
  74           SUB_REF ();
  75           goto out;
  76         }
  77       if (__sigaction (SIGQUIT, &sa, &quit) < 0)
  78         {
  79           save = errno;
  80           SUB_REF ();
  81           goto out_restore_sigint;
  82         }
  83     }
  84   DO_UNLOCK ();
  85
  86   /* We reuse the bitmap in the 'sa' structure.  */
  87   __sigaddset (&sa.sa_mask, SIGCHLD);
  88   save = errno;
  89   if (__sigprocmask (SIG_BLOCK, &sa.sa_mask, &omask) < 0)
  90     {
  91 #ifndef _LIBC
  92       if (errno == ENOSYS)
  93         __set_errno (save);
  94       else
  95 #endif
  96         {
  97           DO_LOCK ();
  98           if (SUB_REF () == 0)
  99             {
 100               save = errno;
 101               (void) __sigaction (SIGQUIT, &quit, (struct sigaction *) NULL);
 102             out_restore_sigint:
 103               (void) __sigaction (SIGINT, &intr, (struct sigaction *) NULL);
 104               __set_errno (save);
 105             }
 106         out:
 107           DO_UNLOCK ();
 108           return -1;
 109         }
 110     }
 111
 112 #ifdef CLEANUP_HANDLER
 113   CLEANUP_HANDLER;
 114 #endif
 115
 116 #ifdef FORK
 117   pid = FORK ();
 118 #else
 119   pid = __fork ();
 120 #endif
 121   if (pid == (pid_t) 0)
 122     {
 123       /* Child side.  */
 124       const char *new_argv[4];
 125       new_argv[0] = SHELL_NAME;
 126       new_argv[1] = "-c";
 127       new_argv[2] = line;
 128       new_argv[3] = NULL;
 129
 130       /* Restore the signals.  */
 131       (void) __sigaction (SIGINT, &intr, (struct sigaction *) NULL);
 132       (void) __sigaction (SIGQUIT, &quit, (struct sigaction *) NULL);
 133       (void) __sigprocmask (SIG_SETMASK, &omask, (sigset_t *) NULL);
 134       INIT_LOCK ();
 135
 136       /* Exec the shell.  */
 137       (void) __execve (SHELL_PATH, (char *const *) new_argv, __environ);
 138       _exit (127);
 139     }
 140   else if (pid < (pid_t) 0)
 141     /* The fork failed.  */
 142     status = -1;
 143   else
 144     /* Parent side.  */
 145     {
 146       /* Note the system() is a cancellation point.  But since we call
 147          waitpid() which itself is a cancellation point we do not
 148          have to do anything here.  */
 149       if (TEMP_FAILURE_RETRY (__waitpid (pid, &status, 0)) != pid)
 150         status = -1;
 151     }
 152
 153 #ifdef CLEANUP_HANDLER
 154   CLEANUP_RESET;
 155 #endif
 156
 157   save = errno;
 158   DO_LOCK ();
 159   if ((SUB_REF () == 0
 160        && (__sigaction (SIGINT, &intr, (struct sigaction *) NULL)
 161            | __sigaction (SIGQUIT, &quit, (struct sigaction *) NULL)) != 0)
 162       || __sigprocmask (SIG_SETMASK, &omask, (sigset_t *) NULL) != 0)
 163     {
 164 #ifndef _LIBC
 165       /* glibc cannot be used on systems without waitpid.  */
 166       if (errno == ENOSYS)
 167         __set_errno (save);
 168       else
 169 #endif
 170         status = -1;
 171     }
 172   DO_UNLOCK ();
 173
 174   return status;
 175 }
 176
 177 int
 178 __libc_system (const char *line)
 179 {
 180   if (line == NULL)
 181     /* Check that we have a command processor available.  It might
 182        not be available after a chroot(), for example.  */
 183     return do_system ("exit 0") == 0;
 184
 185   if (SINGLE_THREAD_P)
 186     return do_system (line);
 187
 188   int oldtype = LIBC_CANCEL_ASYNC ();
 189
 190   int result = do_system (line);
 191
 192   LIBC_CANCEL_RESET (oldtype);
 193
 194   return result;
 195 }
 196 weak_alias (__libc_system, system)