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 JNIEXPORT sa_handler_t JNICALL
181 signal(int sig, sa_handler_t disp) {
182 return set_signal(sig, disp, false);
183 }
184
185 JNIEXPORT sa_handler_t JNICALL
186 sigset(int sig, sa_handler_t disp) {
187 return set_signal(sig, disp, true);
188 }
189
190 static int call_os_sigaction(int sig, const struct sigaction *act,
191 struct sigaction *oact) {
192 if (os_sigaction == NULL) {
193 os_sigaction = (sigaction_t)dlsym(RTLD_NEXT, "sigaction");
194 if (os_sigaction == NULL) {
195 printf("%s\n", dlerror());
196 exit(0);
197 }
198 }
199 return (*os_sigaction)(sig, act, oact);
200 }
201
202 JNIEXPORT int JNICALL
203 sigaction(int sig, const struct sigaction *act, struct sigaction *oact) {
204 int res;
205 struct sigaction oldAct;
206
207 signal_lock();
208
209 if (sact == NULL ) {
210 allocate_sact();
211 }
212 if (jvm_signal_installed && sigismember(&jvmsigs, sig)) {
213 /* jvm has installed its signal handler for this signal. */
214 /* Save the handler. Don't really install it. */
215 if (oact != NULL) {
216 *oact = sact[sig];
217 }
218 if (act != NULL) {
219 sact[sig] = *act;
220 }
221
222 signal_unlock();
223 return 0;
224 } else if (jvm_signal_installing) {
225 /* jvm is installing its signal handlers. Install the new
226 * handlers and save the old ones. */
227 res = call_os_sigaction(sig, act, &oldAct);
228 sact[sig] = oldAct;
229 if (oact != NULL) {
230 *oact = oldAct;
231 }
232
233 /* Record the signals used by jvm */
234 sigaddset(&jvmsigs, sig);
235
236 signal_unlock();
237 return res;
238 } else {
239 /* jvm has no relation with this signal (yet). Install the
240 * the handler. */
241 res = call_os_sigaction(sig, act, oact);
242
243 signal_unlock();
244 return res;
245 }
246 }
247
248 /* The four functions for the jvm to call into */
249 JNIEXPORT void JNICALL
250 JVM_begin_signal_setting() {
251 signal_lock();
252 jvm_signal_installing = true;
253 tid = thr_self();
254 signal_unlock();
255 }
256
257 JNIEXPORT void JNICALL
258 JVM_end_signal_setting() {
259 signal_lock();
260 jvm_signal_installed = true;
261 jvm_signal_installing = false;
262 cond_broadcast(&cond);
263 signal_unlock();
264 }
265
266 JNIEXPORT struct sigaction * JNICALL
267 JVM_get_signal_action(int sig) {
268 if (sact == NULL) {
269 allocate_sact();
270 }
271 /* Does race condition make sense here? */
272 if (sigismember(&jvmsigs, sig)) {
273 return &sact[sig];
274 }
275 return NULL;
276 }
277
278 JNIEXPORT int JNICALL
279 JVM_get_libjsig_version() {
280 return JSIG_VERSION_1_4_1;
281 }