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. Oracle designates this
9 * particular file as subject to the "Classpath" exception as provided
10 * by Oracle in the LICENSE file that accompanied this code.
11 *
12 * This code is distributed in the hope that it will be useful, but WITHOUT
13 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
14 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
15 * version 2 for more details (a copy is included in the LICENSE file that
16 * accompanied this code).
17 *
18 * You should have received a copy of the GNU General Public License version
19 * 2 along with this work; if not, write to the Free Software Foundation,
20 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
21 *
22 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
23 * or visit www.oracle.com if you need additional information or have any
24 * questions.
25 *
26 */
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 "jni.h"
35
36 #ifdef SOLARIS
37 /* Our redeclarations of the system functions must not have a less
38 * restrictive linker scoping, so we have to declare them as JNIEXPORT
39 * before including signal.h */
40 #include "sys/signal.h"
41 JNIEXPORT void (*signal(int sig, void (*disp)(int)))(int);
42 JNIEXPORT void (*sigset(int sig, void (*disp)(int)))(int);
43 JNIEXPORT int sigaction(int sig, const struct sigaction *act, struct sigaction *oact);
44 #endif
45
46 #include <dlfcn.h>
47 #include <errno.h>
48 #include <pthread.h>
49 #include <signal.h>
50 #include <stdio.h>
51 #include <stdlib.h>
52 #include <string.h>
53
54 #if (__STDC_VERSION__ >= 199901L)
55 #include <stdbool.h>
56 #else
57 #define bool int
58 #define true 1
59 #define false 0
60 #endif
61
62 #ifdef SOLARIS
63 #define MAX_SIGNALS (SIGRTMAX+1)
64
65 /* On solaris, MAX_SIGNALS is a macro, not a constant, so we must allocate sact dynamically. */
66 static struct sigaction *sact = (struct sigaction *)NULL; /* saved signal handlers */
67 #else
68 #define MAX_SIGNALS NSIG
69
70 static struct sigaction sact[MAX_SIGNALS]; /* saved signal handlers */
71 #endif
72
73 static sigset_t jvmsigs; /* Signals used by jvm. */
74
75 #ifdef MACOSX
76 static __thread bool reentry = false; /* prevent reentry deadlock (per-thread) */
77 #endif
78
79 /* Used to synchronize the installation of signal handlers. */
80 static pthread_mutex_t mutex = PTHREAD_MUTEX_INITIALIZER;
81 static pthread_cond_t cond = PTHREAD_COND_INITIALIZER;
82 static pthread_t tid;
83
84 typedef void (*sa_handler_t)(int);
85 typedef void (*sa_sigaction_t)(int, siginfo_t *, void *);
86 typedef sa_handler_t (*signal_function_t)(int, sa_handler_t);
87 typedef int (*sigaction_t)(int, const struct sigaction *, struct sigaction *);
88
89 static signal_function_t os_signal = 0; /* os's version of signal()/sigset() */
90 static sigaction_t os_sigaction = 0; /* os's version of sigaction() */
91
92 static bool jvm_signal_installing = false;
93 static bool jvm_signal_installed = false;
94
95
96 /* assume called within signal_lock */
97 static void allocate_sact() {
98 #ifdef SOLARIS
99 if (sact == NULL) {
100 sact = (struct sigaction *)malloc((MAX_SIGNALS) * (size_t)sizeof(struct sigaction));
101 if (sact == NULL) {
102 printf("%s\n", "libjsig.so unable to allocate memory");
103 exit(0);
104 }
105 memset(sact, 0, (MAX_SIGNALS) * (size_t)sizeof(struct sigaction));
106 }
107 #endif
108 }
109
110 static void signal_lock() {
111 pthread_mutex_lock(&mutex);
112 /* When the jvm is installing its set of signal handlers, threads
113 * other than the jvm thread should wait. */
114 if (jvm_signal_installing) {
115 /* tid is not initialized until jvm_signal_installing is set to true. */
116 if (pthread_equal(tid, pthread_self()) == 0) {
117 do {
118 pthread_cond_wait(&cond, &mutex);
119 } while (jvm_signal_installing);
120 }
121 }
122 }
123
124 static void signal_unlock() {
125 pthread_mutex_unlock(&mutex);
126 }
127
128 static sa_handler_t call_os_signal(int sig, sa_handler_t disp,
129 bool is_sigset) {
130 sa_handler_t res;
131
132 if (os_signal == NULL) {
133 if (!is_sigset) {
134 os_signal = (signal_function_t)dlsym(RTLD_NEXT, "signal");
135 } else {
136 os_signal = (signal_function_t)dlsym(RTLD_NEXT, "sigset");
137 }
138 if (os_signal == NULL) {
139 printf("%s\n", dlerror());
140 exit(0);
141 }
142 }
143
144 #ifdef MACOSX
145 /* On macosx, the OS implementation of signal calls sigaction.
146 * Make sure we do not deadlock with ourself. (See JDK-8072147). */
147 reentry = true;
148 #endif
149
150 res = (*os_signal)(sig, disp);
151
152 #ifdef MACOSX
153 reentry = false;
154 #endif
155
156 return res;
157 }
158
159 static void save_signal_handler(int sig, sa_handler_t disp, bool is_sigset) {
160 sigset_t set;
161
162 sact[sig].sa_handler = disp;
163 sigemptyset(&set);
164 sact[sig].sa_mask = set;
165 if (!is_sigset) {
166 #ifdef SOLARIS
167 sact[sig].sa_flags = SA_NODEFER;
168 if (sig != SIGILL && sig != SIGTRAP && sig != SIGPWR) {
169 sact[sig].sa_flags |= SA_RESETHAND;
170 }
171 #else
172 sact[sig].sa_flags = 0;
173 #endif
174 } else {
175 sact[sig].sa_flags = 0;
176 }
177 }
178
179 static sa_handler_t set_signal(int sig, sa_handler_t disp, bool is_sigset) {
180 sa_handler_t oldhandler;
181 bool sigused;
182 bool sigblocked;
183
184 signal_lock();
185 allocate_sact();
186
187 sigused = sigismember(&jvmsigs, sig);
188 if (jvm_signal_installed && sigused) {
189 /* jvm has installed its signal handler for this signal. */
190 /* Save the handler. Don't really install it. */
191 if (is_sigset) {
192 sigblocked = sigismember(&(sact[sig].sa_mask), sig);
193 }
194 oldhandler = sact[sig].sa_handler;
195 save_signal_handler(sig, disp, is_sigset);
196
197 #ifdef SOLARIS
198 if (is_sigset && sigblocked) {
199 /* We won't honor the SIG_HOLD request to change the signal mask */
200 oldhandler = SIG_HOLD;
201 }
202 #endif
203
204 signal_unlock();
205 return oldhandler;
206 } else if (jvm_signal_installing) {
207 /* jvm is installing its signal handlers. Install the new
208 * handlers and save the old ones. jvm uses sigaction().
209 * Leave the piece here just in case. */
210 oldhandler = call_os_signal(sig, disp, is_sigset);
211 save_signal_handler(sig, oldhandler, is_sigset);
212
213 /* Record the signals used by jvm */
214 sigaddset(&jvmsigs, sig);
215
216 signal_unlock();
217 return oldhandler;
218 } else {
219 /* jvm has no relation with this signal (yet). Install the
220 * the handler. */
221 oldhandler = call_os_signal(sig, disp, is_sigset);
222
223 signal_unlock();
224 return oldhandler;
225 }
226 }
227
228 JNIEXPORT sa_handler_t signal(int sig, sa_handler_t disp) {
229 if (sig < 0 || sig >= MAX_SIGNALS) {
230 errno = EINVAL;
231 return SIG_ERR;
232 }
233
234 return set_signal(sig, disp, false);
235 }
236
237 JNIEXPORT sa_handler_t sigset(int sig, sa_handler_t disp) {
238 #ifdef _ALLBSD_SOURCE
239 printf("sigset() is not supported by BSD");
240 exit(0);
241 #else
242 if (sig < 0 || sig >= MAX_SIGNALS) {
243 errno = EINVAL;
244 return (sa_handler_t)-1;
245 }
246
247 return set_signal(sig, disp, true);
248 #endif
249 }
250
251 static int call_os_sigaction(int sig, const struct sigaction *act,
252 struct sigaction *oact) {
253 if (os_sigaction == NULL) {
254 os_sigaction = (sigaction_t)dlsym(RTLD_NEXT, "sigaction");
255 if (os_sigaction == NULL) {
256 printf("%s\n", dlerror());
257 exit(0);
258 }
259 }
260 return (*os_sigaction)(sig, act, oact);
261 }
262
263 JNIEXPORT int sigaction(int sig, const struct sigaction *act, struct sigaction *oact) {
264 int res;
265 bool sigused;
266 struct sigaction oldAct;
267
268 if (sig < 0 || sig >= MAX_SIGNALS) {
269 errno = EINVAL;
270 return -1;
271 }
272
273 #ifdef MACOSX
274 if (reentry) {
275 return call_os_sigaction(sig, act, oact);
276 }
277 #endif
278
279 signal_lock();
280
281 allocate_sact();
282 sigused = sigismember(&jvmsigs, sig);
283 if (jvm_signal_installed && sigused) {
284 /* jvm has installed its signal handler for this signal. */
285 /* Save the handler. Don't really install it. */
286 if (oact != NULL) {
287 *oact = sact[sig];
288 }
289 if (act != NULL) {
290 sact[sig] = *act;
291 }
292
293 signal_unlock();
294 return 0;
295 } else if (jvm_signal_installing) {
296 /* jvm is installing its signal handlers. Install the new
297 * handlers and save the old ones. */
298 res = call_os_sigaction(sig, act, &oldAct);
299 sact[sig] = oldAct;
300 if (oact != NULL) {
301 *oact = oldAct;
302 }
303
304 /* Record the signals used by jvm. */
305 sigaddset(&jvmsigs, sig);
306
307 signal_unlock();
308 return res;
309 } else {
310 /* jvm has no relation with this signal (yet). Install the
311 * the handler. */
312 res = call_os_sigaction(sig, act, oact);
313
314 signal_unlock();
315 return res;
316 }
317 }
318
319 /* The three functions for the jvm to call into. */
320 JNIEXPORT void JVM_begin_signal_setting() {
321 signal_lock();
322 sigemptyset(&jvmsigs);
323 jvm_signal_installing = true;
324 tid = pthread_self();
325 signal_unlock();
326 }
327
328 JNIEXPORT void JVM_end_signal_setting() {
329 signal_lock();
330 jvm_signal_installed = true;
331 jvm_signal_installing = false;
332 pthread_cond_broadcast(&cond);
333 signal_unlock();
334 }
335
336 JNIEXPORT struct sigaction *JVM_get_signal_action(int sig) {
337 allocate_sact();
338 /* Does race condition make sense here? */
339 if (sigismember(&jvmsigs, sig)) {
340 return &sact[sig];
341 }
342 return NULL;
343 }