1/* Copyright (C) 1991-2016 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 <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
34static struct sigaction intr, quit;
35static 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. */
53static int
54do_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
176int
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 return do_system (line);
185}
186weak_alias (__libc_system, system)
187