sysdeps/posix/system.c

   1 /* Copyright (C) 1991-2014 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, see
  16    <http://www.gnu.org/licenses/>.  */
  17
  18 #include <errno.h>
  19 #include <signal.h>
  20 #include <stddef.h>
  21 #include <stdlib.h>
  22 #include <unistd.h>
  23 #include <sys/types.h>
  24 #include <sys/wait.h>
  25 #include <bits/libc-lock.h>
  26 #include <sysdep-cancel.h>
  27
  28
  29 #define SHELL_PATH      "/bin/sh"       /* Path of the shell.  */
  30 #define SHELL_NAME      "sh"            /* Name to give it.  */
  31
  32
  33 #ifdef _LIBC_REENTRANT
  34 static struct sigaction intr, quit;
  35 static int sa_refcntr;
  36 __libc_lock_define_initialized (static, lock);
  37
  38 # define DO_LOCK() __libc_lock_lock (lock)
  39 # define DO_UNLOCK() __libc_lock_unlock (lock)
  40 # define INIT_LOCK() ({ __libc_lock_init (lock); sa_refcntr = 0; })
  41 # define ADD_REF() sa_refcntr++
  42 # define SUB_REF() --sa_refcntr
  43 #else
  44 # define DO_LOCK()
  45 # define DO_UNLOCK()
  46 # define INIT_LOCK()
  47 # define ADD_REF() 0
  48 # define SUB_REF() 0
  49 #endif
  50
  51
  52 /* Execute LINE as a shell command, returning its status.  */
  53 static int
  54 do_system (const char *line)
  55 {
  56   int status, save;
  57   pid_t pid;
  58   struct sigaction sa;
  59 #ifndef _LIBC_REENTRANT
  60   struct sigaction intr, quit;
  61 #endif
  62   sigset_t omask;
  63
  64   sa.sa_handler = SIG_IGN;
  65   sa.sa_flags = 0;
  66   __sigemptyset (&sa.sa_mask);
  67
  68   DO_LOCK ();
  69   if (ADD_REF () == 0)
  70     {
  71       if (__sigaction (SIGINT, &sa, &intr) < 0)
  72         {
  73           (void) SUB_REF ();
  74           goto out;
  75         }
  76       if (__sigaction (SIGQUIT, &sa, &quit) < 0)
  77         {
  78           save = errno;
  79           (void) SUB_REF ();
  80           goto out_restore_sigint;
  81         }
  82     }
  83   DO_UNLOCK ();
  84
  85   /* We reuse the bitmap in the 'sa' structure.  */
  86   __sigaddset (&sa.sa_mask, SIGCHLD);
  87   save = errno;
  88   if (__sigprocmask (SIG_BLOCK, &sa.sa_mask, &omask) < 0)
  89     {
  90 #ifndef _LIBC
  91       if (errno == ENOSYS)
  92         __set_errno (save);
  93       else
  94 #endif
  95         {
  96           DO_LOCK ();
  97           if (SUB_REF () == 0)
  98             {
  99               save = errno;
 100               (void) __sigaction (SIGQUIT, &quit, (struct sigaction *) NULL);
 101             out_restore_sigint:
 102               (void) __sigaction (SIGINT, &intr, (struct sigaction *) NULL);
 103               __set_errno (save);
 104             }
 105         out:
 106           DO_UNLOCK ();
 107           return -1;
 108         }
 109     }
 110
 111 #ifdef CLEANUP_HANDLER
 112   CLEANUP_HANDLER;
 113 #endif
 114
 115 #ifdef FORK
 116   pid = FORK ();
 117 #else
 118   pid = __fork ();
 119 #endif
 120   if (pid == (pid_t) 0)
 121     {
 122       /* Child side.  */
 123       const char *new_argv[4];
 124       new_argv[0] = SHELL_NAME;
 125       new_argv[1] = "-c";
 126       new_argv[2] = line;
 127       new_argv[3] = NULL;
 128
 129       /* Restore the signals.  */
 130       (void) __sigaction (SIGINT, &intr, (struct sigaction *) NULL);
 131       (void) __sigaction (SIGQUIT, &quit, (struct sigaction *) NULL);
 132       (void) __sigprocmask (SIG_SETMASK, &omask, (sigset_t *) NULL);
 133       INIT_LOCK ();
 134
 135       /* Exec the shell.  */
 136       (void) __execve (SHELL_PATH, (char *const *) new_argv, __environ);
 137       _exit (127);
 138     }
 139   else if (pid < (pid_t) 0)
 140     /* The fork failed.  */
 141     status = -1;
 142   else
 143     /* Parent side.  */
 144     {
 145       /* Note the system() is a cancellation point.  But since we call
 146          waitpid() which itself is a cancellation point we do not
 147          have to do anything here.  */
 148       if (TEMP_FAILURE_RETRY (__waitpid (pid, &status, 0)) != pid)
 149         status = -1;
 150     }
 151
 152 #ifdef CLEANUP_HANDLER
 153   CLEANUP_RESET;
 154 #endif
 155
 156   save = errno;
 157   DO_LOCK ();
 158   if ((SUB_REF () == 0
 159        && (__sigaction (SIGINT, &intr, (struct sigaction *) NULL)
 160            | __sigaction (SIGQUIT, &quit, (struct sigaction *) NULL)) != 0)
 161       || __sigprocmask (SIG_SETMASK, &omask, (sigset_t *) NULL) != 0)
 162     {
 163 #ifndef _LIBC
 164       /* glibc cannot be used on systems without waitpid.  */
 165       if (errno == ENOSYS)
 166         __set_errno (save);
 167       else
 168 #endif
 169         status = -1;
 170     }
 171   DO_UNLOCK ();
 172
 173   return status;
 174 }
 175
 176 int
 177 __libc_system (const char *line)
 178 {
 179   if (line == NULL)
 180     /* Check that we have a command processor available.  It might
 181        not be available after a chroot(), for example.  */
 182     return do_system ("exit 0") == 0;
 183
 184   if (SINGLE_THREAD_P)
 185     return do_system (line);
 186
 187   int oldtype = LIBC_CANCEL_ASYNC ();
 188
 189   int result = do_system (line);
 190
 191   LIBC_CANCEL_RESET (oldtype);
 192
 193   return result;
 194 }
 195 weak_alias (__libc_system, system)