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
45static struct sigaction sact[NSIG]; /* saved signal handlers */
46static sigset_t jvmsigs; /* Signals used by jvm. */
47
48/* Used to synchronize the installation of signal handlers. */
49static pthread_mutex_t mutex = PTHREAD_MUTEX_INITIALIZER;
50static pthread_cond_t cond = PTHREAD_COND_INITIALIZER;
51static pthread_t tid = 0;
52
53typedef void (*sa_handler_t)(int);
54typedef void (*sa_sigaction_t)(int, siginfo_t *, void *);
55// signal_t is already defined on AIX.
56typedef sa_handler_t (*signal_like_function_t)(int, sa_handler_t);
57typedef int (*sigaction_t)(int, const struct sigaction *, struct sigaction *);
58
59static signal_like_function_t os_signal = 0; /* os's version of signal()/sigset() */
60static sigaction_t os_sigaction = 0; /* os's version of sigaction() */
61
62static bool jvm_signal_installing = false;
63static bool jvm_signal_installed = false;
64
65static 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
76static void signal_unlock() {
77  pthread_mutex_unlock(&mutex);
78}
79
80static 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
98static 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
106static 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
143sa_handler_t signal(int sig, sa_handler_t disp) {
144  return set_signal(sig, disp, false);
145}
146
147sa_handler_t sigset(int sig, sa_handler_t disp) {
148  return set_signal(sig, disp, true);
149}
150
151static 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
164int 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. */
209void JVM_begin_signal_setting() {
210  signal_lock();
211  sigemptyset(&jvmsigs);
212  jvm_signal_installing = true;
213  tid = pthread_self();
214  signal_unlock();
215}
216
217void 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
225struct 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}
232