1 /*
2 * Copyright (c) 2001, 2015, Oracle and/or its affiliates. All rights reserved.
3 * Copyright (c) 2012, 2015 SAP SE. All rights reserved.
4 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
5 *
6 * This code is free software; you can redistribute it and/or modify it
7 * under the terms of the GNU General Public License version 2 only, as
8 * published by the Free Software Foundation.
9 *
10 * This code is distributed in the hope that it will be useful, but WITHOUT
11 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
12 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
13 * version 2 for more details (a copy is included in the LICENSE file that
14 * accompanied this code).
15 *
16 * You should have received a copy of the GNU General Public License version
17 * 2 along with this work; if not, write to the Free Software Foundation,
18 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
19 *
20 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
21 * or visit www.oracle.com if you need additional information or have any
22 * questions.
23 *
24 */
25
26 /* CopyrightVersion 1.2 */
27
28 /* This is a special library that should be loaded before libc &
29 * libthread to interpose the signal handler installation functions:
30 * sigaction(), signal(), sigset().
31 * Used for signal-chaining. See RFE 4381843.
32 */
33
34 #include <signal.h>
35 #include <dlfcn.h>
36 #include <pthread.h>
37 #include <stdio.h>
38 #include <stdlib.h>
39 #include <stdint.h>
40 #include "jni.h"
41
42 #define bool int
43 #define true 1
44 #define false 0
45
46 static struct sigaction sact[NSIG]; /* saved signal handlers */
47 static sigset_t jvmsigs; /* Signals used by jvm. */
48
49 /* Used to synchronize the installation of signal handlers. */
50 static pthread_mutex_t mutex = PTHREAD_MUTEX_INITIALIZER;
51 static pthread_cond_t cond = PTHREAD_COND_INITIALIZER;
52 static pthread_t tid = 0;
53
54 typedef void (*sa_handler_t)(int);
55 typedef void (*sa_sigaction_t)(int, siginfo_t *, void *);
56 // signal_t is already defined on AIX.
57 typedef sa_handler_t (*signal_like_function_t)(int, sa_handler_t);
58 typedef int (*sigaction_t)(int, const struct sigaction *, struct sigaction *);
59
60 static signal_like_function_t os_signal = 0; /* os's version of signal()/sigset() */
61 static sigaction_t os_sigaction = 0; /* os's version of sigaction() */
62
63 static bool jvm_signal_installing = false;
64 static bool jvm_signal_installed = false;
65
66 static void signal_lock() {
67 pthread_mutex_lock(&mutex);
68 /* When the jvm is installing its set of signal handlers, threads
69 * other than the jvm thread should wait. */
70 if (jvm_signal_installing) {
71 if (tid != pthread_self()) {
72 pthread_cond_wait(&cond, &mutex);
73 }
74 }
75 }
76
77 static void signal_unlock() {
78 pthread_mutex_unlock(&mutex);
79 }
80
81 static sa_handler_t call_os_signal(int sig, sa_handler_t disp,
82 bool is_sigset) {
83 if (os_signal == NULL) {
84 if (!is_sigset) {
85 // Aix: call functions directly instead of dlsym'ing them.
86 os_signal = signal;
87 } else {
88 // Aix: call functions directly instead of dlsym'ing them.
89 os_signal = sigset;
90 }
91 if (os_signal == NULL) {
92 printf("%s\n", dlerror());
93 exit(0);
94 }
95 }
96 return (*os_signal)(sig, disp);
97 }
98
99 static void save_signal_handler(int sig, sa_handler_t disp) {
100 sigset_t set;
101 sact[sig].sa_handler = disp;
102 sigemptyset(&set);
103 sact[sig].sa_mask = set;
104 sact[sig].sa_flags = 0;
105 }
106
107 static sa_handler_t set_signal(int sig, sa_handler_t disp, bool is_sigset) {
108 sa_handler_t oldhandler;
109 bool sigused;
110
111 signal_lock();
112
113 sigused = sigismember(&jvmsigs, sig);
114 if (jvm_signal_installed && sigused) {
115 /* jvm has installed its signal handler for this signal. */
116 /* Save the handler. Don't really install it. */
117 oldhandler = sact[sig].sa_handler;
118 save_signal_handler(sig, disp);
119
120 signal_unlock();
121 return oldhandler;
122 } else if (jvm_signal_installing) {
123 /* jvm is installing its signal handlers. Install the new
124 * handlers and save the old ones. jvm uses sigaction().
125 * Leave the piece here just in case. */
126 oldhandler = call_os_signal(sig, disp, is_sigset);
127 save_signal_handler(sig, oldhandler);
128
129 /* Record the signals used by jvm */
130 sigaddset(&jvmsigs, sig);
131
132 signal_unlock();
133 return oldhandler;
134 } else {
135 /* jvm has no relation with this signal (yet). Install the
136 * the handler. */
137 oldhandler = call_os_signal(sig, disp, is_sigset);
138
139 signal_unlock();
140 return oldhandler;
141 }
142 }
143
144 JNIEXPORT sa_handler_t JNICALL
145 signal(int sig, sa_handler_t disp) {
146 return set_signal(sig, disp, false);
147 }
148
149 JNIEXPORT sa_handler_t JNICALL
150 sigset(int sig, sa_handler_t disp) {
151 return set_signal(sig, disp, true);
152 }
153
154 static int call_os_sigaction(int sig, const struct sigaction *act,
155 struct sigaction *oact) {
156 if (os_sigaction == NULL) {
157 // Aix: call functions directly instead of dlsym'ing them.
158 os_sigaction = sigaction;
159 if (os_sigaction == NULL) {
160 printf("%s\n", dlerror());
161 exit(0);
162 }
163 }
164 return (*os_sigaction)(sig, act, oact);
165 }
166
167 JNIEXPORT int JNICALL
168 sigaction(int sig, const struct sigaction *act, struct sigaction *oact) {
169 int res;
170 bool sigused;
171 struct sigaction oldAct;
172
173 signal_lock();
174
175 sigused = sigismember(&jvmsigs, sig);
176 if (jvm_signal_installed && sigused) {
177 /* jvm has installed its signal handler for this signal. */
178 /* Save the handler. Don't really install it. */
179 if (oact != NULL) {
180 *oact = sact[sig];
181 }
182 if (act != NULL) {
183 sact[sig] = *act;
184 }
185
186 signal_unlock();
187 return 0;
188 } else if (jvm_signal_installing) {
189 /* jvm is installing its signal handlers. Install the new
190 * handlers and save the old ones. */
191 res = call_os_sigaction(sig, act, &oldAct);
192 sact[sig] = oldAct;
193 if (oact != NULL) {
194 *oact = oldAct;
195 }
196
197 /* Record the signals used by jvm. */
198 sigaddset(&jvmsigs, sig);
199
200 signal_unlock();
201 return res;
202 } else {
203 /* jvm has no relation with this signal (yet). Install the
204 * the handler. */
205 res = call_os_sigaction(sig, act, oact);
206
207 signal_unlock();
208 return res;
209 }
210 }
211
212 /* The three functions for the jvm to call into. */
213 JNIEXPORT void JNICALL
214 JVM_begin_signal_setting() {
215 signal_lock();
216 sigemptyset(&jvmsigs);
217 jvm_signal_installing = true;
218 tid = pthread_self();
219 signal_unlock();
220 }
221
222 JNIEXPORT void JNICALL
223 JVM_end_signal_setting() {
224 signal_lock();
225 jvm_signal_installed = true;
226 jvm_signal_installing = false;
227 pthread_cond_broadcast(&cond);
228 signal_unlock();
229 }
230
231 JNIEXPORT struct sigaction * JNICALL
232 JVM_get_signal_action(int sig) {
233 /* Does race condition make sense here? */
234 if (sigismember(&jvmsigs, sig)) {
235 return &sact[sig];
236 }
237 return NULL;
238 }