1 /*
2 * Copyright (c) 2001, 2015, 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 /* CopyrightVersion 1.2 */
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 <signal.h>
35 #include <dlfcn.h>
36 #include <pthread.h>
37 #include <stdio.h>
38 #include <stdlib.h>
39 #include <stdint.h>
40
41 #define bool int
42 #define true 1
43 #define false 0
44
45 static struct sigaction sact[NSIG]; /* saved signal handlers */
46 static sigset_t jvmsigs; /* Signals used by jvm. */
47
48 /* Used to synchronize the installation of signal handlers. */
49 static pthread_mutex_t mutex = PTHREAD_MUTEX_INITIALIZER;
50 static pthread_cond_t cond = PTHREAD_COND_INITIALIZER;
51 static pthread_t tid = 0;
52
53 typedef void (*sa_handler_t)(int);
54 typedef void (*sa_sigaction_t)(int, siginfo_t *, void *);
55 // signal_t is already defined on AIX.
56 typedef sa_handler_t (*signal_like_function_t)(int, sa_handler_t);
57 typedef int (*sigaction_t)(int, const struct sigaction *, struct sigaction *);
58
59 static signal_like_function_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 // Aix: call functions directly instead of dlsym'ing them.
85 os_signal = signal;
86 } else {
87 // Aix: call functions directly instead of dlsym'ing them.
88 os_signal = sigset;
89 }
90 if (os_signal == NULL) {
91 printf("%s\n", dlerror());
92 exit(0);
93 }
94 }
95 return (*os_signal)(sig, disp);
96 }
97
98 static void save_signal_handler(int sig, sa_handler_t disp) {
99 sigset_t set;
100 sact[sig].sa_handler = disp;
101 sigemptyset(&set);
102 sact[sig].sa_mask = set;
103 sact[sig].sa_flags = 0;
104 }
105
106 static sa_handler_t set_signal(int sig, sa_handler_t disp, bool is_sigset) {
107 sa_handler_t oldhandler;
108 bool sigused;
109
110 signal_lock();
111
112 sigused = sigismember(&jvmsigs, sig);
113 if (jvm_signal_installed && sigused) {
114 /* jvm has installed its signal handler for this signal. */
115 /* Save the handler. Don't really install it. */
116 oldhandler = sact[sig].sa_handler;
117 save_signal_handler(sig, disp);
118
119 signal_unlock();
120 return oldhandler;
121 } else if (jvm_signal_installing) {
122 /* jvm is installing its signal handlers. Install the new
123 * handlers and save the old ones. jvm uses sigaction().
124 * Leave the piece here just in case. */
125 oldhandler = call_os_signal(sig, disp, is_sigset);
126 save_signal_handler(sig, oldhandler);
127
128 /* Record the signals used by jvm */
129 sigaddset(&jvmsigs, sig);
130
131 signal_unlock();
132 return oldhandler;
133 } else {
134 /* jvm has no relation with this signal (yet). Install the
135 * the handler. */
136 oldhandler = call_os_signal(sig, disp, is_sigset);
137
138 signal_unlock();
139 return oldhandler;
140 }
141 }
142
143 sa_handler_t signal(int sig, sa_handler_t disp) {
144 return set_signal(sig, disp, false);
145 }
146
147 sa_handler_t sigset(int sig, sa_handler_t disp) {
148 return set_signal(sig, disp, true);
149 }
150
151 static int call_os_sigaction(int sig, const struct sigaction *act,
152 struct sigaction *oact) {
153 if (os_sigaction == NULL) {
154 // Aix: call functions directly instead of dlsym'ing them.
155 os_sigaction = sigaction;
156 if (os_sigaction == NULL) {
157 printf("%s\n", dlerror());
158 exit(0);
159 }
160 }
161 return (*os_sigaction)(sig, act, oact);
162 }
163
164 int sigaction(int sig, const struct sigaction *act, struct sigaction *oact) {
165 int res;
166 bool sigused;
167 struct sigaction oldAct;
168
169 signal_lock();
170
171 sigused = sigismember(&jvmsigs, sig);
172 if (jvm_signal_installed && sigused) {
173 /* jvm has installed its signal handler for this signal. */
174 /* Save the handler. Don't really install it. */
175 if (oact != NULL) {
176 *oact = sact[sig];
177 }
178 if (act != NULL) {
179 sact[sig] = *act;
180 }
181
182 signal_unlock();
183 return 0;
184 } else if (jvm_signal_installing) {
185 /* jvm is installing its signal handlers. Install the new
186 * handlers and save the old ones. */
187 res = call_os_sigaction(sig, act, &oldAct);
188 sact[sig] = oldAct;
189 if (oact != NULL) {
190 *oact = oldAct;
191 }
192
193 /* Record the signals used by jvm. */
194 sigaddset(&jvmsigs, sig);
195
196 signal_unlock();
197 return res;
198 } else {
199 /* jvm has no relation with this signal (yet). Install the
200 * the handler. */
201 res = call_os_sigaction(sig, act, oact);
202
203 signal_unlock();
204 return res;
205 }
206 }
207
208 /* The three functions for the jvm to call into. */
209 void JVM_begin_signal_setting() {
210 signal_lock();
211 sigemptyset(&jvmsigs);
212 jvm_signal_installing = true;
213 tid = pthread_self();
214 signal_unlock();
215 }
216
217 void JVM_end_signal_setting() {
218 signal_lock();
219 jvm_signal_installed = true;
220 jvm_signal_installing = false;
221 pthread_cond_broadcast(&cond);
222 signal_unlock();
223 }
224
225 struct sigaction *JVM_get_signal_action(int sig) {
226 /* Does race condition make sense here? */
227 if (sigismember(&jvmsigs, sig)) {
228 return &sact[sig];
229 }
230 return NULL;
231 }