Thu, 24 May 2018 17:06:56 +0800
Merge
1 /*
2 * Copyright (c) 2001, 2015, 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 */
25 /* CopyrightVersion 1.2 */
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 */
33 #include <signal.h>
34 #include <dlfcn.h>
35 #include <pthread.h>
36 #include <stdio.h>
37 #include <stdlib.h>
38 #include <stdbool.h>
39 #include <string.h>
41 #define MAXSIGNUM 32
42 #define MASK(sig) ((unsigned int)1 << sig)
44 static struct sigaction sact[MAXSIGNUM]; /* saved signal handlers */
45 static unsigned int jvmsigs = 0; /* signals used by jvm */
47 static pthread_key_t reentry_flag_key;
48 static pthread_once_t reentry_key_init_once = PTHREAD_ONCE_INIT;
50 /* used to synchronize the installation of signal handlers */
51 static pthread_mutex_t mutex = PTHREAD_MUTEX_INITIALIZER;
52 static pthread_cond_t cond = PTHREAD_COND_INITIALIZER;
53 static pthread_t tid = 0;
55 typedef void (*sa_handler_t)(int);
56 typedef void (*sa_sigaction_t)(int, siginfo_t *, void *);
57 typedef sa_handler_t (*signal_t)(int, sa_handler_t);
58 typedef int (*sigaction_t)(int, const struct sigaction *, struct sigaction *);
60 static signal_t os_signal = 0; /* os's version of signal()/sigset() */
61 static sigaction_t os_sigaction = 0; /* os's version of sigaction() */
63 static bool jvm_signal_installing = false;
64 static bool jvm_signal_installed = false;
66 #define check_status(cmd) \
67 do { \
68 int status = (cmd); \
69 if (status != 0) { \
70 printf("error %s (%d) in " #cmd "\n", strerror(status), status); \
71 exit(1); \
72 } \
73 } while (0)
75 static void signal_lock() {
76 pthread_mutex_lock(&mutex);
77 /* When the jvm is installing its set of signal handlers, threads
78 * other than the jvm thread should wait */
79 if (jvm_signal_installing) {
80 if (tid != pthread_self()) {
81 pthread_cond_wait(&cond, &mutex);
82 }
83 }
84 }
86 static void signal_unlock() {
87 pthread_mutex_unlock(&mutex);
88 }
90 static void reentry_tls_init() {
91 // value for reentry_flag_key will default to NULL (false)
92 check_status(pthread_key_create(&reentry_flag_key, NULL));
93 }
95 static sa_handler_t call_os_signal(int sig, sa_handler_t disp,
96 bool is_sigset) {
97 sa_handler_t res;
99 if (os_signal == NULL) {
100 if (!is_sigset) {
101 os_signal = (signal_t)dlsym(RTLD_NEXT, "signal");
102 } else {
103 os_signal = (signal_t)dlsym(RTLD_NEXT, "sigset");
104 }
105 if (os_signal == NULL) {
106 printf("%s\n", dlerror());
107 exit(0);
108 }
109 }
110 check_status(pthread_once(&reentry_key_init_once, reentry_tls_init));
111 // set reentry_flag_key to non-NULL to show reentry
112 check_status(pthread_setspecific(reentry_flag_key, &res));
113 res = (*os_signal)(sig, disp);
114 check_status(pthread_setspecific(reentry_flag_key, NULL));
115 return res;
116 }
118 static void save_signal_handler(int sig, sa_handler_t disp) {
119 sigset_t set;
120 sact[sig].sa_handler = disp;
121 sigemptyset(&set);
122 sact[sig].sa_mask = set;
123 sact[sig].sa_flags = 0;
124 }
126 static sa_handler_t set_signal(int sig, sa_handler_t disp, bool is_sigset) {
127 sa_handler_t oldhandler;
128 bool sigused;
130 signal_lock();
132 sigused = (MASK(sig) & jvmsigs) != 0;
133 if (jvm_signal_installed && sigused) {
134 /* jvm has installed its signal handler for this signal. */
135 /* Save the handler. Don't really install it. */
136 oldhandler = sact[sig].sa_handler;
137 save_signal_handler(sig, disp);
139 signal_unlock();
140 return oldhandler;
141 } else if (jvm_signal_installing) {
142 /* jvm is installing its signal handlers. Install the new
143 * handlers and save the old ones. jvm uses sigaction().
144 * Leave the piece here just in case. */
145 oldhandler = call_os_signal(sig, disp, is_sigset);
146 save_signal_handler(sig, oldhandler);
148 /* Record the signals used by jvm */
149 jvmsigs |= MASK(sig);
151 signal_unlock();
152 return oldhandler;
153 } else {
154 /* jvm has no relation with this signal (yet). Install the
155 * the handler. */
156 oldhandler = call_os_signal(sig, disp, is_sigset);
158 signal_unlock();
159 return oldhandler;
160 }
161 }
163 sa_handler_t signal(int sig, sa_handler_t disp) {
164 return set_signal(sig, disp, false);
165 }
167 sa_handler_t sigset(int sig, sa_handler_t disp) {
168 printf("sigset() is not supported by BSD");
169 exit(0);
170 }
172 static int call_os_sigaction(int sig, const struct sigaction *act,
173 struct sigaction *oact) {
174 if (os_sigaction == NULL) {
175 os_sigaction = (sigaction_t)dlsym(RTLD_NEXT, "sigaction");
176 if (os_sigaction == NULL) {
177 printf("%s\n", dlerror());
178 exit(0);
179 }
180 }
181 return (*os_sigaction)(sig, act, oact);
182 }
184 int sigaction(int sig, const struct sigaction *act, struct sigaction *oact) {
185 int res;
186 bool sigused;
187 struct sigaction oldAct;
189 check_status(pthread_once(&reentry_key_init_once, reentry_tls_init));
190 if (pthread_getspecific(reentry_flag_key) != NULL) {
191 return call_os_sigaction(sig, act, oact);
192 }
194 signal_lock();
196 sigused = (MASK(sig) & jvmsigs) != 0;
197 if (jvm_signal_installed && sigused) {
198 /* jvm has installed its signal handler for this signal. */
199 /* Save the handler. Don't really install it. */
200 if (oact != NULL) {
201 *oact = sact[sig];
202 }
203 if (act != NULL) {
204 sact[sig] = *act;
205 }
207 signal_unlock();
208 return 0;
209 } else if (jvm_signal_installing) {
210 /* jvm is installing its signal handlers. Install the new
211 * handlers and save the old ones. */
212 res = call_os_sigaction(sig, act, &oldAct);
213 sact[sig] = oldAct;
214 if (oact != NULL) {
215 *oact = oldAct;
216 }
218 /* Record the signals used by jvm */
219 jvmsigs |= MASK(sig);
221 signal_unlock();
222 return res;
223 } else {
224 /* jvm has no relation with this signal (yet). Install the
225 * the handler. */
226 res = call_os_sigaction(sig, act, oact);
228 signal_unlock();
229 return res;
230 }
231 }
233 /* The three functions for the jvm to call into */
234 void JVM_begin_signal_setting() {
235 signal_lock();
236 jvm_signal_installing = true;
237 tid = pthread_self();
238 signal_unlock();
239 }
241 void JVM_end_signal_setting() {
242 signal_lock();
243 jvm_signal_installed = true;
244 jvm_signal_installing = false;
245 pthread_cond_broadcast(&cond);
246 signal_unlock();
247 }
249 struct sigaction *JVM_get_signal_action(int sig) {
250 /* Does race condition make sense here? */
251 if ((MASK(sig) & jvmsigs) != 0) {
252 return &sact[sig];
253 }
254 return NULL;
255 }