sysdeps/posix/system.c

   1 /* Copyright (C) 1991-2000, 2002, 2003 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 #ifndef HAVE_GNU_LD
  31 #define __environ       environ
  32 #endif
  33
  34 #define SHELL_PATH      "/bin/sh"       /* Path of the shell.  */
  35 #define SHELL_NAME      "sh"            /* Name to give it.  */
  36
  37
  38 #ifdef _LIBC_REENTRANT
  39 static struct sigaction intr, quit;
  40 static int sa_refcntr;
  41 __libc_lock_define_initialized (static, lock);
  42
  43 # define DO_LOCK() __libc_lock_lock (lock)
  44 # define DO_UNLOCK() __libc_lock_unlock (lock)
  45 # define INIT_LOCK() ({ __libc_lock_init (lock); sa_refcntr = 0; })
  46 # define ADD_REF() sa_refcntr++
  47 # define SUB_REF() --sa_refcntr
  48 #else
  49 # define DO_LOCK()
  50 # define DO_UNLOCK()
  51 # define INIT_LOCK()
  52 # define ADD_REF() 0
  53 # define SUB_REF() 0
  54 #endif
  55
  56
  57 /* Execute LINE as a shell command, returning its status.  */
  58 static int
  59 do_system (const char *line)
  60 {
  61   int status, save;
  62   pid_t pid;
  63   struct sigaction sa;
  64 #ifndef _LIBC_REENTRANT
  65   struct sigaction intr, quit;
  66 #endif
  67   sigset_t omask;
  68
  69   sa.sa_handler = SIG_IGN;
  70   sa.sa_flags = 0;
  71   __sigemptyset (&sa.sa_mask);
  72
  73   DO_LOCK ();
  74   if (ADD_REF () == 0)
  75     {
  76       if (__sigaction (SIGINT, &sa, &intr) < 0)
  77         {
  78           SUB_REF ();
  79           goto out;
  80         }
  81       if (__sigaction (SIGQUIT, &sa, &quit) < 0)
  82         {
  83           save = errno;
  84           SUB_REF ();
  85           goto out_restore_sigint;
  86         }
  87     }
  88   DO_UNLOCK ();
  89
  90   /* We reuse the bitmap in the 'sa' structure.  */
  91   __sigaddset (&sa.sa_mask, SIGCHLD);
  92   save = errno;
  93   if (__sigprocmask (SIG_BLOCK, &sa.sa_mask, &omask) < 0)
  94     {
  95 #ifndef _LIBC
  96       if (errno == ENOSYS)
  97         __set_errno (save);
  98       else
  99 #endif
 100         {
 101           DO_LOCK ();
 102           if (SUB_REF () == 0)
 103             {
 104               save = errno;
 105               (void) __sigaction (SIGQUIT, &quit, (struct sigaction *) NULL);
 106             out_restore_sigint:
 107               (void) __sigaction (SIGINT, &intr, (struct sigaction *) NULL);
 108               __set_errno (save);
 109             }
 110         out:
 111           DO_UNLOCK ();
 112           return -1;
 113         }
 114     }
 115
 116 #ifdef CLEANUP_HANDLER
 117   CLEANUP_HANDLER;
 118 #endif
 119
 120 #ifdef FORK
 121   pid = FORK ();
 122 #else
 123   pid = __fork ();
 124 #endif
 125   if (pid == (pid_t) 0)
 126     {
 127       /* Child side.  */
 128       const char *new_argv[4];
 129       new_argv[0] = SHELL_NAME;
 130       new_argv[1] = "-c";
 131       new_argv[2] = line;
 132       new_argv[3] = NULL;
 133
 134       /* Restore the signals.  */
 135       (void) __sigaction (SIGINT, &intr, (struct sigaction *) NULL);
 136       (void) __sigaction (SIGQUIT, &quit, (struct sigaction *) NULL);
 137       (void) __sigprocmask (SIG_SETMASK, &omask, (sigset_t *) NULL);
 138       INIT_LOCK ();
 139
 140       /* Exec the shell.  */
 141       (void) __execve (SHELL_PATH, (char *const *) new_argv, __environ);
 142       _exit (127);
 143     }
 144   else if (pid < (pid_t) 0)
 145     /* The fork failed.  */
 146     status = -1;
 147   else
 148     /* Parent side.  */
 149     {
 150 #ifdef  NO_WAITPID
 151       pid_t child;
 152       do
 153         {
 154           child = __wait (&status);
 155           if (child <= -1 && errno != EINTR)
 156             {
 157               status = -1;
 158               break;
 159             }
 160           /* Note that pid cannot be <= -1 and therefore the loop continues
 161              when __wait returned with EINTR.  */
 162         }
 163       while (child != pid);
 164 #else
 165       /* Note the system() is a cancellation point.  But since we call
 166          waitpid() which itself is a cancellation point we do not
 167          have to do anything here.  */
 168       if (TEMP_FAILURE_RETRY (__waitpid (pid, &status, 0)) != pid)
 169         status = -1;
 170 #endif
 171     }
 172
 173 #ifdef CLEANUP_HANDLER
 174   CLEANUP_RESET;
 175 #endif
 176
 177   save = errno;
 178   DO_LOCK ();
 179   if ((SUB_REF () == 0
 180        && (__sigaction (SIGINT, &intr, (struct sigaction *) NULL)
 181            | __sigaction (SIGQUIT, &quit, (struct sigaction *) NULL)) != 0)
 182       || __sigprocmask (SIG_SETMASK, &omask, (sigset_t *) NULL) != 0)
 183     {
 184 #ifndef _LIBC
 185       /* glibc cannot be used on systems without waitpid.  */
 186       if (errno == ENOSYS)
 187         __set_errno (save);
 188       else
 189 #endif
 190         status = -1;
 191     }
 192   DO_UNLOCK ();
 193
 194   return status;
 195 }
 196
 197 int
 198 __libc_system (const char *line)
 199 {
 200   if (line == NULL)
 201     /* Check that we have a command processor available.  It might
 202        not be available after a chroot(), for example.  */
 203     return do_system ("exit 0") == 0;
 204
 205   if (SINGLE_THREAD_P)
 206     return do_system (line);
 207
 208   int oldtype = LIBC_CANCEL_ASYNC ();
 209
 210   int result = do_system (line);
 211
 212   LIBC_CANCEL_RESET (oldtype);
 213
 214   return result;
 215 }
 216 weak_alias (__libc_system, system)