1 /*
2 * Copyright (c) 2001, 2018, 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 /* This is a special library that should be loaded before libc &
27 * libthread to interpose the signal handler installation functions:
28 * sigaction(), signal(), sigset().
29 * Used for signal-chaining. See RFE 4381843.
30 */
31
32 #include <dlfcn.h>
33 #include <signal.h>
34 #include <stdio.h>
35 #include <stdlib.h>
36
37 #ifdef SOLARIS
38 #include <synch.h>
39 #include <thread.h>
40 #else
41 #include <pthread.h>
42 #endif
43
44 #if (__STDC_VERSION__ >= 199901L)
45 #include <stdbool.h>
46 #else
47 #define bool int
48 #define true 1
49 #define false 0
50 #endif
51
52 #ifndef NSIG
53 #define NSIG SIGRTMAX
54 #endif
55
56 static struct sigaction sact[NSIG]; /* saved signal handlers */
57 static sigset_t jvmsigs; /* Signals used by jvm. */
58 static __thread bool reentry = false; /* prevent reentry deadlock (per-thread) */
59
60 /* Used to synchronize the installation of signal handlers. */
61 #ifdef SOLARIS
62 static mutex_t mutex = DEFAULTMUTEX;
63 static cond_t cond = DEFAULTCV;
64 static thread_t tid = 0;
65 #else
66 static pthread_mutex_t mutex = PTHREAD_MUTEX_INITIALIZER;
67 static pthread_cond_t cond = PTHREAD_COND_INITIALIZER;
68 static pthread_t tid = 0;
69 #endif
70
71 typedef void (*sa_handler_t)(int);
72 typedef void (*sa_sigaction_t)(int, siginfo_t *, void *);
73 typedef sa_handler_t (*signal_function_t)(int, sa_handler_t);
74 typedef int (*sigaction_t)(int, const struct sigaction *, struct sigaction *);
75
76 static signal_function_t os_signal = 0; /* os's version of signal()/sigset() */
77 static sigaction_t os_sigaction = 0; /* os's version of sigaction() */
78
79 static bool jvm_signal_installing = false;
80 static bool jvm_signal_installed = false;
81
82 static void signal_lock() {
83 #ifdef SOLARIS
84 mutex_lock(&mutex);
85 #else
86 pthread_mutex_lock(&mutex);
87 #endif
88 /* When the jvm is installing its set of signal handlers, threads
89 * other than the jvm thread should wait. */
90 if (jvm_signal_installing) {
91 #ifdef SOLARIS
92 if (tid != thr_self()) {
93 cond_wait(&cond, &mutex);
94 }
95 #else
96 if (tid != pthread_self()) {
97 pthread_cond_wait(&cond, &mutex);
98 }
99 #endif
100 }
101 }
102
103 static void signal_unlock() {
104 #ifdef SOLARIS
105 mutex_unlock(&mutex);
106 #else
107 pthread_mutex_unlock(&mutex);
108 #endif
109 }
110
111 static sa_handler_t call_os_signal(int sig, sa_handler_t disp,
112 bool is_sigset) {
113 sa_handler_t res;
114
115 if (os_signal == NULL) {
116 if (!is_sigset) {
117 #ifdef AIX
118 os_signal = signal;
119 #else
120 os_signal = (signal_function_t)dlsym(RTLD_NEXT, "signal");
121 #endif
122 } else {
123 #ifdef AIX
124 os_signal = sigset;
125 #else
126 os_signal = (signal_function_t)dlsym(RTLD_NEXT, "sigset");
127 #endif
128 }
129 if (os_signal == NULL) {
130 printf("%s\n", dlerror());
131 exit(0);
132 }
133 }
134 /* On some OSes like macosx, the OS implementation of signal calls sigaction.
135 * Make sure we do not deadlock with ourself. (See JDK-8072147). */
136 reentry = true;
137 res = (*os_signal)(sig, disp);
138 reentry = false;
139 return res;
140 }
141
142 static void save_signal_handler(int sig, sa_handler_t disp, bool is_sigset) {
143 sigset_t set;
144 sact[sig].sa_handler = disp;
145 sigemptyset(&set);
146 sact[sig].sa_mask = set;
147 if (!is_sigset) {
148 #ifdef SOLARIS
149 sact[sig].sa_flags = SA_NODEFER;
150 if (sig != SIGILL && sig != SIGTRAP && sig != SIGPWR) {
151 sact[sig].sa_flags |= SA_RESETHAND;
152 }
153 #else
154 sact[sig].sa_flags = 0;
155 #endif
156 } else {
157 sact[sig].sa_flags = 0;
158 }
159 }
160
161 static sa_handler_t set_signal(int sig, sa_handler_t disp, bool is_sigset) {
162 sa_handler_t oldhandler;
163 bool sigused;
164 bool sigblocked;
165
166 signal_lock();
167
168 sigused = sigismember(&jvmsigs, sig);
169 if (jvm_signal_installed && sigused) {
170 /* jvm has installed its signal handler for this signal. */
171 /* Save the handler. Don't really install it. */
172 if (is_sigset) {
173 sigblocked = sigismember(&(sact[sig].sa_mask), sig);
174 }
175 oldhandler = sact[sig].sa_handler;
176 save_signal_handler(sig, disp, is_sigset);
177
178 #ifdef SOLARIS
179 if (is_sigset && sigblocked) {
180 /* We won't honor the SIG_HOLD request to change the signal mask */
181 oldhandler = SIG_HOLD;
182 }
183 #endif
184
185 signal_unlock();
186 return oldhandler;
187 } else if (jvm_signal_installing) {
188 /* jvm is installing its signal handlers. Install the new
189 * handlers and save the old ones. jvm uses sigaction().
190 * Leave the piece here just in case. */
191 oldhandler = call_os_signal(sig, disp, is_sigset);
192 save_signal_handler(sig, oldhandler, is_sigset);
193
194 /* Record the signals used by jvm */
195 sigaddset(&jvmsigs, sig);
196
197 signal_unlock();
198 return oldhandler;
199 } else {
200 /* jvm has no relation with this signal (yet). Install the
201 * the handler. */
202 oldhandler = call_os_signal(sig, disp, is_sigset);
203
204 signal_unlock();
205 return oldhandler;
206 }
207 }
208
209 sa_handler_t signal(int sig, sa_handler_t disp) {
210 return set_signal(sig, disp, false);
211 }
212
213 sa_handler_t sigset(int sig, sa_handler_t disp) {
214 #ifdef _ALLBSD_SOURCE
215 printf("sigset() is not supported by BSD");
216 exit(0);
217 #else
218 return set_signal(sig, disp, true);
219 #endif
220 }
221
222 static int call_os_sigaction(int sig, const struct sigaction *act,
223 struct sigaction *oact) {
224 if (os_sigaction == NULL) {
225 #ifdef AIX
226 os_sigaction = sigaction;
227 #else
228 os_sigaction = (sigaction_t)dlsym(RTLD_NEXT, "sigaction");
229 #endif
230 if (os_sigaction == NULL) {
231 printf("%s\n", dlerror());
232 exit(0);
233 }
234 }
235 return (*os_sigaction)(sig, act, oact);
236 }
237
238 int sigaction(int sig, const struct sigaction *act, struct sigaction *oact) {
239 int res;
240 bool sigused;
241 struct sigaction oldAct;
242
243 if (reentry) {
244 return call_os_sigaction(sig, act, oact);
245 }
246
247 signal_lock();
248
249 sigused = sigismember(&jvmsigs, sig);
250 if (jvm_signal_installed && sigused) {
251 /* jvm has installed its signal handler for this signal. */
252 /* Save the handler. Don't really install it. */
253 if (oact != NULL) {
254 *oact = sact[sig];
255 }
256 if (act != NULL) {
257 sact[sig] = *act;
258 }
259
260 signal_unlock();
261 return 0;
262 } else if (jvm_signal_installing) {
263 /* jvm is installing its signal handlers. Install the new
264 * handlers and save the old ones. */
265 res = call_os_sigaction(sig, act, &oldAct);
266 sact[sig] = oldAct;
267 if (oact != NULL) {
268 *oact = oldAct;
269 }
270
271 /* Record the signals used by jvm. */
272 sigaddset(&jvmsigs, sig);
273
274 signal_unlock();
275 return res;
276 } else {
277 /* jvm has no relation with this signal (yet). Install the
278 * the handler. */
279 res = call_os_sigaction(sig, act, oact);
280
281 signal_unlock();
282 return res;
283 }
284 }
285
286 /* The three functions for the jvm to call into. */
287 void JVM_begin_signal_setting() {
288 signal_lock();
289 sigemptyset(&jvmsigs);
290 jvm_signal_installing = true;
291 #ifdef SOLARIS
292 tid = thr_self();
293 #else
294 tid = pthread_self();
295 #endif
296 signal_unlock();
297 }
298
299 void JVM_end_signal_setting() {
300 signal_lock();
301 jvm_signal_installed = true;
302 jvm_signal_installing = false;
303 #ifdef SOLARIS
304 cond_broadcast(&cond);
305 #else
306 pthread_cond_broadcast(&cond);
307 #endif
308 signal_unlock();
309 }
310
311 struct sigaction *JVM_get_signal_action(int sig) {
312 /* Does race condition make sense here? */
313 if (sigismember(&jvmsigs, sig)) {
314 return &sact[sig];
315 }
316 return NULL;
317 }