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 "jvm_solaris.h"
41
42 #define bool int
43 #define true 1
44 #define false 0
45
46 static struct sigaction *sact = (struct sigaction *)NULL; /* saved signal handlers */
47 static sigset_t jvmsigs;
48
49 /* used to synchronize the installation of signal handlers */
50 static mutex_t mutex = DEFAULTMUTEX;
51 static cond_t cond = DEFAULTCV;
52 static thread_t tid = 0;
53
54 typedef void (*sa_handler_t)(int);
55 typedef void (*sa_sigaction_t)(int, siginfo_t *, void *);
56 typedef sa_handler_t (*signal_t)(int, sa_handler_t);
57 typedef int (*sigaction_t)(int, const struct sigaction *, struct sigaction *);
58
59 static signal_t os_signal = 0; /* os's version of signal()/sigset() */
60 static sigaction_t os_sigaction = 0; /* os's version of sigaction() */
61
62 static bool jvm_signal_installing = false;
63 static bool jvm_signal_installed = false;
64
65
66 /* assume called within signal_lock */
67 static void allocate_sact() {
68 size_t maxsignum;
69 maxsignum = SIGRTMAX;
70 if (sact == NULL) {
71 sact = (struct sigaction *)malloc((maxsignum+1) * (size_t)sizeof(struct sigaction));
72 memset(sact, 0, (maxsignum+1) * (size_t)sizeof(struct sigaction));
73 }
74
75 if (sact == NULL) {
76 printf("%s\n", "libjsig.so unable to allocate memory");
77 exit(0);
78 }
79
80 sigemptyset(&jvmsigs);
81 }
82
83 static void signal_lock() {
84 mutex_lock(&mutex);
85 /* When the jvm is installing its set of signal handlers, threads
86 * other than the jvm thread should wait */
87 if (jvm_signal_installing) {
88 if (tid != thr_self()) {
89 cond_wait(&cond, &mutex);
90 }
91 }
92 }
93
94 static void signal_unlock() {
95 mutex_unlock(&mutex);
96 }
97
98 static sa_handler_t call_os_signal(int sig, sa_handler_t disp,
99 bool is_sigset) {
100 if (os_signal == NULL) {
101 if (!is_sigset) {
102 os_signal = (signal_t)dlsym(RTLD_NEXT, "signal");
103 } else {
104 os_signal = (signal_t)dlsym(RTLD_NEXT, "sigset");
105 }
106 if (os_signal == NULL) {
107 printf("%s\n", dlerror());
108 exit(0);
109 }
110 }
111 return (*os_signal)(sig, disp);
112 }
113
114 static void save_signal_handler(int sig, sa_handler_t disp, bool is_sigset) {
115 sigset_t set;
116 if (sact == NULL) {
117 allocate_sact();
118 }
119 sact[sig].sa_handler = disp;
120 sigemptyset(&set);
121 sact[sig].sa_mask = set;
122 if (!is_sigset) {
123 sact[sig].sa_flags = SA_NODEFER;
124 if (sig != SIGILL && sig != SIGTRAP && sig != SIGPWR) {
125 sact[sig].sa_flags |= SA_RESETHAND;
126 }
127 } else {
128 sact[sig].sa_flags = 0;
129 }
130 }
131
132 static sa_handler_t set_signal(int sig, sa_handler_t disp, bool is_sigset) {
133 sa_handler_t oldhandler;
134 bool sigblocked;
135
136 signal_lock();
137 if (sact == NULL) {
138 allocate_sact();
139 }
140
141 if (jvm_signal_installed && sigismember(&jvmsigs, sig)) {
142 /* jvm has installed its signal handler for this signal. */
143 /* Save the handler. Don't really install it. */
144 if (is_sigset) {
145 /* We won't honor the SIG_HOLD request to change the signal mask */
146 sigblocked = sigismember(&(sact[sig].sa_mask), sig);
147 }
148 oldhandler = sact[sig].sa_handler;
149 save_signal_handler(sig, disp, is_sigset);
150
151 if (is_sigset && sigblocked) {
152 oldhandler = SIG_HOLD;
153 }
154
155 signal_unlock();
156 return oldhandler;
157 } else if (jvm_signal_installing) {
158 /* jvm is installing its signal handlers. Install the new
159 * handlers and save the old ones. jvm uses sigaction().
160 * Leave the piece here just in case. */
161 oldhandler = call_os_signal(sig, disp, is_sigset);
162 save_signal_handler(sig, oldhandler, is_sigset);
163
164 /* Record the signals used by jvm */
165 sigaddset(&jvmsigs, sig);
166
167 signal_unlock();
168 return oldhandler;
169 } else {
170 /* jvm has no relation with this signal (yet). Install the
171 * the handler. */
172 oldhandler = call_os_signal(sig, disp, is_sigset);
173
174 signal_unlock();
175 return oldhandler;
176 }
177 }
178
179 sa_handler_t signal(int sig, sa_handler_t disp) {
180 return set_signal(sig, disp, false);
181 }
182
183 sa_handler_t sigset(int sig, sa_handler_t disp) {
184 return set_signal(sig, disp, true);
185 }
186
187 static int call_os_sigaction(int sig, const struct sigaction *act,
188 struct sigaction *oact) {
189 if (os_sigaction == NULL) {
190 os_sigaction = (sigaction_t)dlsym(RTLD_NEXT, "sigaction");
191 if (os_sigaction == NULL) {
192 printf("%s\n", dlerror());
193 exit(0);
194 }
195 }
196 return (*os_sigaction)(sig, act, oact);
197 }
198
199 int sigaction(int sig, const struct sigaction *act, struct sigaction *oact) {
200 int res;
201 struct sigaction oldAct;
202
203 signal_lock();
204
205 if (sact == NULL ) {
206 allocate_sact();
207 }
208 if (jvm_signal_installed && sigismember(&jvmsigs, sig)) {
209 /* jvm has installed its signal handler for this signal. */
210 /* Save the handler. Don't really install it. */
211 if (oact != NULL) {
212 *oact = sact[sig];
213 }
214 if (act != NULL) {
215 sact[sig] = *act;
216 }
217
218 signal_unlock();
219 return 0;
220 } else if (jvm_signal_installing) {
221 /* jvm is installing its signal handlers. Install the new
222 * handlers and save the old ones. */
223 res = call_os_sigaction(sig, act, &oldAct);
224 sact[sig] = oldAct;
225 if (oact != NULL) {
226 *oact = oldAct;
227 }
228
229 /* Record the signals used by jvm */
230 sigaddset(&jvmsigs, sig);
231
232 signal_unlock();
233 return res;
234 } else {
235 /* jvm has no relation with this signal (yet). Install the
236 * the handler. */
237 res = call_os_sigaction(sig, act, oact);
238
239 signal_unlock();
240 return res;
241 }
242 }
243
244 /* The four functions for the jvm to call into */
245 void JVM_begin_signal_setting() {
246 signal_lock();
247 jvm_signal_installing = true;
248 tid = thr_self();
249 signal_unlock();
250 }
251
252 void JVM_end_signal_setting() {
253 signal_lock();
254 jvm_signal_installed = true;
255 jvm_signal_installing = false;
256 cond_broadcast(&cond);
257 signal_unlock();
258 }
259
260 struct sigaction *JVM_get_signal_action(int sig) {
261 if (sact == NULL) {
262 allocate_sact();
263 }
264 /* Does race condition make sense here? */
265 if (sigismember(&jvmsigs, sig)) {
266 return &sact[sig];
267 }
268 return NULL;
269 }
270
271 int JVM_get_libjsig_version() {
272 return JSIG_VERSION_1_4_1;
273 }