1 /*
2 * Copyright (c) 2001, 2010, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 *
5 * This code is free software; you can redistribute it and/or modify it
6 * under the terms of the GNU General Public License version 2 only, as
7 * published by the Free Software Foundation.
8 *
9 * This code is distributed in the hope that it will be useful, but WITHOUT
10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
12 * version 2 for more details (a copy is included in the LICENSE file that
13 * accompanied this code).
14 *
15 * You should have received a copy of the GNU General Public License version
16 * 2 along with this work; if not, write to the Free Software Foundation,
17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
18 *
19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
20 * or visit www.oracle.com if you need additional information or have any
21 * questions.
22 *
23 */
24
25 /* CopyrightVersion 1.2 */
26
27 /* This is a special library that should be loaded before libc &
28 * libthread to interpose the signal handler installation functions:
29 * sigaction(), signal(), sigset().
30 * Used for signal-chaining. See RFE 4381843.
31 */
32
33 #include <stdlib.h>
34 #include <stdio.h>
35 #include <string.h>
36 #include <signal.h>
37 #include <dlfcn.h>
38 #include <thread.h>
39 #include <synch.h>
40 #include "jni.h"
41 #include "jvm_md.h"
42
43 #define bool int
44 #define true 1
45 #define false 0
46
47 static struct sigaction *sact = (struct sigaction *)NULL; /* saved signal handlers */
48 static sigset_t jvmsigs;
49
50 /* used to synchronize the installation of signal handlers */
51 static mutex_t mutex = DEFAULTMUTEX;
52 static cond_t cond = DEFAULTCV;
53 static thread_t tid = 0;
54
55 typedef void (*sa_handler_t)(int);
56 typedef void (*sa_sigaction_t)(int, siginfo_t *, void *);
57 typedef sa_handler_t (*signal_t)(int, sa_handler_t);
58 typedef int (*sigaction_t)(int, const struct sigaction *, struct sigaction *);
59
60 static signal_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
67 /* assume called within signal_lock */
68 static void allocate_sact() {
69 size_t maxsignum;
70 maxsignum = SIGRTMAX;
71 if (sact == NULL) {
72 sact = (struct sigaction *)malloc((maxsignum+1) * (size_t)sizeof(struct sigaction));
73 memset(sact, 0, (maxsignum+1) * (size_t)sizeof(struct sigaction));
74 }
75
76 if (sact == NULL) {
77 printf("%s\n", "libjsig.so unable to allocate memory");
78 exit(0);
79 }
80
81 sigemptyset(&jvmsigs);
82 }
83
84 static void signal_lock() {
85 mutex_lock(&mutex);
86 /* When the jvm is installing its set of signal handlers, threads
87 * other than the jvm thread should wait */
88 if (jvm_signal_installing) {
89 if (tid != thr_self()) {
90 cond_wait(&cond, &mutex);
91 }
92 }
93 }
94
95 static void signal_unlock() {
96 mutex_unlock(&mutex);
97 }
98
99 static sa_handler_t call_os_signal(int sig, sa_handler_t disp,
100 bool is_sigset) {
101 if (os_signal == NULL) {
102 if (!is_sigset) {
103 os_signal = (signal_t)dlsym(RTLD_NEXT, "signal");
104 } else {
105 os_signal = (signal_t)dlsym(RTLD_NEXT, "sigset");
106 }
107 if (os_signal == NULL) {
108 printf("%s\n", dlerror());
109 exit(0);
110 }
111 }
112 return (*os_signal)(sig, disp);
113 }
114
115 static void save_signal_handler(int sig, sa_handler_t disp, bool is_sigset) {
116 sigset_t set;
117 if (sact == NULL) {
118 allocate_sact();
119 }
120 sact[sig].sa_handler = disp;
121 sigemptyset(&set);
122 sact[sig].sa_mask = set;
123 if (!is_sigset) {
124 sact[sig].sa_flags = SA_NODEFER;
125 if (sig != SIGILL && sig != SIGTRAP && sig != SIGPWR) {
126 sact[sig].sa_flags |= SA_RESETHAND;
127 }
128 } else {
129 sact[sig].sa_flags = 0;
130 }
131 }
132
133 static sa_handler_t set_signal(int sig, sa_handler_t disp, bool is_sigset) {
134 sa_handler_t oldhandler;
135 bool sigblocked;
136
137 signal_lock();
138 if (sact == NULL) {
139 allocate_sact();
140 }
141
142 if (jvm_signal_installed && sigismember(&jvmsigs, sig)) {
143 /* jvm has installed its signal handler for this signal. */
144 /* Save the handler. Don't really install it. */
145 if (is_sigset) {
146 /* We won't honor the SIG_HOLD request to change the signal mask */
147 sigblocked = sigismember(&(sact[sig].sa_mask), sig);
148 }
149 oldhandler = sact[sig].sa_handler;
150 save_signal_handler(sig, disp, is_sigset);
151
152 if (is_sigset && sigblocked) {
153 oldhandler = SIG_HOLD;
154 }
155
156 signal_unlock();
157 return oldhandler;
158 } else if (jvm_signal_installing) {
159 /* jvm is installing its signal handlers. Install the new
160 * handlers and save the old ones. jvm uses sigaction().
161 * Leave the piece here just in case. */
162 oldhandler = call_os_signal(sig, disp, is_sigset);
163 save_signal_handler(sig, oldhandler, is_sigset);
164
165 /* Record the signals used by jvm */
166 sigaddset(&jvmsigs, sig);
167
168 signal_unlock();
169 return oldhandler;
170 } else {
171 /* jvm has no relation with this signal (yet). Install the
172 * the handler. */
173 oldhandler = call_os_signal(sig, disp, is_sigset);
174
175 signal_unlock();
176 return oldhandler;
177 }
178 }
179
180 sa_handler_t signal(int sig, sa_handler_t disp) {
181 return set_signal(sig, disp, false);
182 }
183
184 sa_handler_t sigset(int sig, sa_handler_t disp) {
185 return set_signal(sig, disp, true);
186 }
187
188 static int call_os_sigaction(int sig, const struct sigaction *act,
189 struct sigaction *oact) {
190 if (os_sigaction == NULL) {
191 os_sigaction = (sigaction_t)dlsym(RTLD_NEXT, "sigaction");
192 if (os_sigaction == NULL) {
193 printf("%s\n", dlerror());
194 exit(0);
195 }
196 }
197 return (*os_sigaction)(sig, act, oact);
198 }
199
200 int sigaction(int sig, const struct sigaction *act, struct sigaction *oact) {
201 int res;
202 struct sigaction oldAct;
203
204 signal_lock();
205
206 if (sact == NULL ) {
207 allocate_sact();
208 }
209 if (jvm_signal_installed && sigismember(&jvmsigs, sig)) {
210 /* jvm has installed its signal handler for this signal. */
211 /* Save the handler. Don't really install it. */
212 if (oact != NULL) {
213 *oact = sact[sig];
214 }
215 if (act != NULL) {
216 sact[sig] = *act;
217 }
218
219 signal_unlock();
220 return 0;
221 } else if (jvm_signal_installing) {
222 /* jvm is installing its signal handlers. Install the new
223 * handlers and save the old ones. */
224 res = call_os_sigaction(sig, act, &oldAct);
225 sact[sig] = oldAct;
226 if (oact != NULL) {
227 *oact = oldAct;
228 }
229
230 /* Record the signals used by jvm */
231 sigaddset(&jvmsigs, sig);
232
233 signal_unlock();
234 return res;
235 } else {
236 /* jvm has no relation with this signal (yet). Install the
237 * the handler. */
238 res = call_os_sigaction(sig, act, oact);
239
240 signal_unlock();
241 return res;
242 }
243 }
244
245 /* The four functions for the jvm to call into */
246 JNIEXPORT void JNICALL
247 JVM_begin_signal_setting() {
248 signal_lock();
249 jvm_signal_installing = true;
250 tid = thr_self();
251 signal_unlock();
252 }
253
254 JNIEXPORT void JNICALL
255 JVM_end_signal_setting() {
256 signal_lock();
257 jvm_signal_installed = true;
258 jvm_signal_installing = false;
259 cond_broadcast(&cond);
260 signal_unlock();
261 }
262
263 JNIEXPORT struct sigaction * JNICALL
264 JVM_get_signal_action(int sig) {
265 if (sact == NULL) {
266 allocate_sact();
267 }
268 /* Does race condition make sense here? */
269 if (sigismember(&jvmsigs, sig)) {
270 return &sact[sig];
271 }
272 return NULL;
273 }
274
275 JNIEXPORT int JNICALL
276 JVM_get_libjsig_version() {
277 return JSIG_VERSION_1_4_1;
278 }