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2b778ceb | 1 | /* Copyright (C) 1991-2021 Free Software Foundation, Inc. |
993b3242 UD |
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 | |
41bdb6e2 AJ |
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. | |
993b3242 UD |
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 | |
41bdb6e2 | 12 | Lesser General Public License for more details. |
993b3242 | 13 | |
41bdb6e2 | 14 | You should have received a copy of the GNU Lesser General Public |
59ba27a6 | 15 | License along with the GNU C Library; if not, see |
5a82c748 | 16 | <https://www.gnu.org/licenses/>. */ |
28f540f4 | 17 | |
918bd861 UD |
18 | #include <errno.h> |
19 | #include <signal.h> | |
28f540f4 RM |
20 | #include <stdlib.h> |
21 | #include <unistd.h> | |
5fb7fc96 AZ |
22 | #include <sigsetops.h> |
23 | #include <spawn.h> | |
24 | #include <pthread.h> | |
28f540f4 | 25 | #include <sys/types.h> |
918bd861 | 26 | #include <sys/wait.h> |
5fb7fc96 | 27 | #include <stdio.h> |
28f540f4 | 28 | |
5fb7fc96 AZ |
29 | #include <libc-lock.h> |
30 | #include <not-errno.h> | |
31 | #include <not-cancel.h> | |
32 | #include <internal-signals.h> | |
28f540f4 | 33 | |
28f540f4 RM |
34 | #define SHELL_PATH "/bin/sh" /* Path of the shell. */ |
35 | #define SHELL_NAME "sh" /* Name to give it. */ | |
36 | ||
918bd861 | 37 | |
5fb7fc96 AZ |
38 | /* This system implementation aims to be thread-safe, which requires to |
39 | restore the signal dispositions for SIGINT and SIGQUIT correctly and to | |
40 | deal with cancellation by terminating the child process. | |
41 | ||
42 | The signal disposition restoration on the single-thread case is | |
43 | straighfoward. For multithreaded case, a reference-counter with a lock | |
44 | is used, so the first thread will set the SIGINT/SIGQUIT dispositions and | |
45 | last thread will restore them. | |
46 | ||
47 | Cancellation handling is done with thread cancellation clean-up handlers | |
48 | on waitpid call. */ | |
49 | ||
918bd861 UD |
50 | #ifdef _LIBC_REENTRANT |
51 | static struct sigaction intr, quit; | |
52 | static int sa_refcntr; | |
53 | __libc_lock_define_initialized (static, lock); | |
54 | ||
55 | # define DO_LOCK() __libc_lock_lock (lock) | |
56 | # define DO_UNLOCK() __libc_lock_unlock (lock) | |
57 | # define INIT_LOCK() ({ __libc_lock_init (lock); sa_refcntr = 0; }) | |
58 | # define ADD_REF() sa_refcntr++ | |
59 | # define SUB_REF() --sa_refcntr | |
60 | #else | |
61 | # define DO_LOCK() | |
62 | # define DO_UNLOCK() | |
63 | # define INIT_LOCK() | |
43cd9933 | 64 | # define ADD_REF() 0 |
918bd861 UD |
65 | # define SUB_REF() 0 |
66 | #endif | |
67 | ||
68 | ||
5fb7fc96 AZ |
69 | #if defined(_LIBC_REENTRANT) && defined(SIGCANCEL) |
70 | struct cancel_handler_args | |
71 | { | |
72 | struct sigaction *quit; | |
73 | struct sigaction *intr; | |
74 | pid_t pid; | |
75 | }; | |
76 | ||
77 | static void | |
78 | cancel_handler (void *arg) | |
79 | { | |
80 | struct cancel_handler_args *args = (struct cancel_handler_args *) (arg); | |
81 | ||
82 | __kill_noerrno (args->pid, SIGKILL); | |
83 | ||
478f7078 AZ |
84 | int state; |
85 | __libc_ptf_call (__pthread_setcancelstate, | |
86 | (PTHREAD_CANCEL_DISABLE, &state), 0); | |
87 | TEMP_FAILURE_RETRY (__waitpid (args->pid, NULL, 0)); | |
88 | __libc_ptf_call (__pthread_setcancelstate, (state, NULL), 0); | |
5fb7fc96 AZ |
89 | |
90 | DO_LOCK (); | |
91 | if (SUB_REF () == 0) | |
92 | { | |
93 | __sigaction (SIGQUIT, args->quit, NULL); | |
94 | __sigaction (SIGINT, args->intr, NULL); | |
95 | } | |
96 | DO_UNLOCK (); | |
97 | } | |
98 | #endif | |
99 | ||
28f540f4 | 100 | /* Execute LINE as a shell command, returning its status. */ |
a585ba22 RM |
101 | static int |
102 | do_system (const char *line) | |
28f540f4 | 103 | { |
f09542c5 AZ |
104 | int status = -1; |
105 | int ret; | |
28f540f4 | 106 | pid_t pid; |
918bd861 UD |
107 | struct sigaction sa; |
108 | #ifndef _LIBC_REENTRANT | |
109 | struct sigaction intr, quit; | |
110 | #endif | |
71302f5f | 111 | sigset_t omask; |
5fb7fc96 | 112 | sigset_t reset; |
28f540f4 | 113 | |
28f540f4 RM |
114 | sa.sa_handler = SIG_IGN; |
115 | sa.sa_flags = 0; | |
116 | __sigemptyset (&sa.sa_mask); | |
117 | ||
918bd861 UD |
118 | DO_LOCK (); |
119 | if (ADD_REF () == 0) | |
28f540f4 | 120 | { |
5fb7fc96 AZ |
121 | /* sigaction can not fail with SIGINT/SIGQUIT used with SIG_IGN. */ |
122 | __sigaction (SIGINT, &sa, &intr); | |
123 | __sigaction (SIGQUIT, &sa, &quit); | |
28f540f4 | 124 | } |
918bd861 | 125 | DO_UNLOCK (); |
28f540f4 | 126 | |
71302f5f | 127 | __sigaddset (&sa.sa_mask, SIGCHLD); |
5fb7fc96 AZ |
128 | /* sigprocmask can not fail with SIG_BLOCK used with valid input |
129 | arguments. */ | |
130 | __sigprocmask (SIG_BLOCK, &sa.sa_mask, &omask); | |
131 | ||
132 | __sigemptyset (&reset); | |
133 | if (intr.sa_handler != SIG_IGN) | |
134 | __sigaddset(&reset, SIGINT); | |
135 | if (quit.sa_handler != SIG_IGN) | |
136 | __sigaddset(&reset, SIGQUIT); | |
137 | ||
138 | posix_spawnattr_t spawn_attr; | |
139 | /* None of the posix_spawnattr_* function returns an error, including | |
140 | posix_spawnattr_setflags for the follow specific usage (using valid | |
141 | flags). */ | |
142 | __posix_spawnattr_init (&spawn_attr); | |
143 | __posix_spawnattr_setsigmask (&spawn_attr, &omask); | |
144 | __posix_spawnattr_setsigdefault (&spawn_attr, &reset); | |
145 | __posix_spawnattr_setflags (&spawn_attr, | |
146 | POSIX_SPAWN_SETSIGDEF | POSIX_SPAWN_SETSIGMASK); | |
147 | ||
f09542c5 AZ |
148 | ret = __posix_spawn (&pid, SHELL_PATH, 0, &spawn_attr, |
149 | (char *const[]){ (char *) SHELL_NAME, | |
150 | (char *) "-c", | |
151 | (char *) line, NULL }, | |
152 | __environ); | |
5fb7fc96 AZ |
153 | __posix_spawnattr_destroy (&spawn_attr); |
154 | ||
f09542c5 | 155 | if (ret == 0) |
28f540f4 | 156 | { |
5fb7fc96 AZ |
157 | /* Cancellation results in cleanup handlers running as exceptions in |
158 | the block where they were installed, so it is safe to reference | |
159 | stack variable allocate in the broader scope. */ | |
160 | #if defined(_LIBC_REENTRANT) && defined(SIGCANCEL) | |
161 | struct cancel_handler_args cancel_args = | |
162 | { | |
163 | .quit = &quit, | |
164 | .intr = &intr, | |
165 | .pid = pid | |
166 | }; | |
167 | __libc_cleanup_region_start (1, cancel_handler, &cancel_args); | |
3ca97e8f | 168 | #endif |
7a114794 UD |
169 | /* Note the system() is a cancellation point. But since we call |
170 | waitpid() which itself is a cancellation point we do not | |
171 | have to do anything here. */ | |
20f3b127 | 172 | if (TEMP_FAILURE_RETRY (__waitpid (pid, &status, 0)) != pid) |
ce40141c | 173 | status = -1; |
5fb7fc96 AZ |
174 | #if defined(_LIBC_REENTRANT) && defined(SIGCANCEL) |
175 | __libc_cleanup_region_end (0); | |
3ca97e8f | 176 | #endif |
5fb7fc96 | 177 | } |
3ca97e8f | 178 | |
918bd861 | 179 | DO_LOCK (); |
5fb7fc96 | 180 | if (SUB_REF () == 0) |
28f540f4 | 181 | { |
5fb7fc96 AZ |
182 | /* sigaction can not fail with SIGINT/SIGQUIT used with old |
183 | disposition. Same applies for sigprocmask. */ | |
184 | __sigaction (SIGINT, &intr, NULL); | |
185 | __sigaction (SIGQUIT, &quit, NULL); | |
186 | __sigprocmask (SIG_SETMASK, &omask, NULL); | |
28f540f4 | 187 | } |
918bd861 | 188 | DO_UNLOCK (); |
28f540f4 | 189 | |
f09542c5 AZ |
190 | if (ret != 0) |
191 | __set_errno (ret); | |
192 | ||
28f540f4 RM |
193 | return status; |
194 | } | |
a585ba22 RM |
195 | |
196 | int | |
197 | __libc_system (const char *line) | |
198 | { | |
199 | if (line == NULL) | |
200 | /* Check that we have a command processor available. It might | |
201 | not be available after a chroot(), for example. */ | |
202 | return do_system ("exit 0") == 0; | |
203 | ||
c4dd57c3 | 204 | return do_system (line); |
a585ba22 | 205 | } |
c4029823 | 206 | weak_alias (__libc_system, system) |