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 <signal.h>
34 #include <dlfcn.h>
35 #include <pthread.h>
36 #include <stdio.h>
37 #include <stdlib.h>
38
39 #define bool int
40 #define true 1
41 #define false 0
42
43 #define MAXSIGNUM 32
44 #define MASK(sig) ((unsigned int)1 << sig)
45
46 static struct sigaction sact[MAXSIGNUM]; /* saved signal handlers */
47 static unsigned int jvmsigs = 0; /* signals used by jvm */
48
49 /* used to synchronize the installation of signal handlers */
50 static pthread_mutex_t mutex = PTHREAD_MUTEX_INITIALIZER;
51 static pthread_cond_t cond = PTHREAD_COND_INITIALIZER;
52 static pthread_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 static void signal_lock() {
66 pthread_mutex_lock(&mutex);
67 /* When the jvm is installing its set of signal handlers, threads
68 * other than the jvm thread should wait */
69 if (jvm_signal_installing) {
70 if (tid != pthread_self()) {
71 pthread_cond_wait(&cond, &mutex);
72 }
73 }
74 }
75
76 static void signal_unlock() {
77 pthread_mutex_unlock(&mutex);
78 }
79
80 static sa_handler_t call_os_signal(int sig, sa_handler_t disp,
81 bool is_sigset) {
82 if (os_signal == NULL) {
83 if (!is_sigset) {
84 os_signal = (signal_t)dlsym(RTLD_NEXT, "signal");
85 } else {
86 os_signal = (signal_t)dlsym(RTLD_NEXT, "sigset");
87 }
88 if (os_signal == NULL) {
89 printf("%s\n", dlerror());
90 exit(0);
91 }
92 }
93 return (*os_signal)(sig, disp);
94 }
95
96 static void save_signal_handler(int sig, sa_handler_t disp) {
97 sigset_t set;
98 sact[sig].sa_handler = disp;
99 sigemptyset(&set);
100 sact[sig].sa_mask = set;
101 sact[sig].sa_flags = 0;
102 }
103
104 static sa_handler_t set_signal(int sig, sa_handler_t disp, bool is_sigset) {
105 sa_handler_t oldhandler;
106 bool sigused;
107
108 signal_lock();
109
110 sigused = (MASK(sig) & jvmsigs) != 0;
111 if (jvm_signal_installed && sigused) {
112 /* jvm has installed its signal handler for this signal. */
113 /* Save the handler. Don't really install it. */
114 oldhandler = sact[sig].sa_handler;
115 save_signal_handler(sig, disp);
116
117 signal_unlock();
118 return oldhandler;
119 } else if (jvm_signal_installing) {
120 /* jvm is installing its signal handlers. Install the new
121 * handlers and save the old ones. jvm uses sigaction().
122 * Leave the piece here just in case. */
123 oldhandler = call_os_signal(sig, disp, is_sigset);
124 save_signal_handler(sig, oldhandler);
125
126 /* Record the signals used by jvm */
127 jvmsigs |= MASK(sig);
128
129 signal_unlock();
130 return oldhandler;
131 } else {
132 /* jvm has no relation with this signal (yet). Install the
133 * the handler. */
134 oldhandler = call_os_signal(sig, disp, is_sigset);
135
136 signal_unlock();
137 return oldhandler;
138 }
139 }
140
141 sa_handler_t signal(int sig, sa_handler_t disp) {
142 return set_signal(sig, disp, false);
143 }
144
145 sa_handler_t sigset(int sig, sa_handler_t disp) {
146 return set_signal(sig, disp, true);
147 }
148
149 static int call_os_sigaction(int sig, const struct sigaction *act,
150 struct sigaction *oact) {
151 if (os_sigaction == NULL) {
152 os_sigaction = (sigaction_t)dlsym(RTLD_NEXT, "sigaction");
153 if (os_sigaction == NULL) {
154 printf("%s\n", dlerror());
155 exit(0);
156 }
157 }
158 return (*os_sigaction)(sig, act, oact);
159 }
160
161 int sigaction(int sig, const struct sigaction *act, struct sigaction *oact) {
162 int res;
163 bool sigused;
164 struct sigaction oldAct;
165
166 signal_lock();
167
168 sigused = (MASK(sig) & jvmsigs) != 0;
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 (oact != NULL) {
173 *oact = sact[sig];
174 }
175 if (act != NULL) {
176 sact[sig] = *act;
177 }
178
179 signal_unlock();
180 return 0;
181 } else if (jvm_signal_installing) {
182 /* jvm is installing its signal handlers. Install the new
183 * handlers and save the old ones. */
184 res = call_os_sigaction(sig, act, &oldAct);
185 sact[sig] = oldAct;
186 if (oact != NULL) {
187 *oact = oldAct;
188 }
189
190 /* Record the signals used by jvm */
191 jvmsigs |= MASK(sig);
192
193 signal_unlock();
194 return res;
195 } else {
196 /* jvm has no relation with this signal (yet). Install the
197 * the handler. */
198 res = call_os_sigaction(sig, act, oact);
199
200 signal_unlock();
201 return res;
202 }
203 }
204
205 /* The three functions for the jvm to call into */
206 void JVM_begin_signal_setting() {
207 signal_lock();
208 jvm_signal_installing = true;
209 tid = pthread_self();
210 signal_unlock();
211 }
212
213 void JVM_end_signal_setting() {
214 signal_lock();
215 jvm_signal_installed = true;
216 jvm_signal_installing = false;
217 pthread_cond_broadcast(&cond);
218 signal_unlock();
219 }
220
221 struct sigaction *JVM_get_signal_action(int sig) {
222 /* Does race condition make sense here? */
223 if ((MASK(sig) & jvmsigs) != 0) {
224 return &sact[sig];
225 }
226 return NULL;
227 }