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
46static struct sigaction *sact = (struct sigaction *)NULL; /* saved signal handlers */
47static sigset_t jvmsigs;
48
49/* used to synchronize the installation of signal handlers */
50static mutex_t mutex = DEFAULTMUTEX;
51static cond_t cond = DEFAULTCV;
52static thread_t tid = 0;
53
54typedef void (*sa_handler_t)(int);
55typedef void (*sa_sigaction_t)(int, siginfo_t *, void *);
56typedef sa_handler_t (*signal_t)(int, sa_handler_t);
57typedef int (*sigaction_t)(int, const struct sigaction *, struct sigaction *);
58
59static signal_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
65
66/* assume called within signal_lock */
67static 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
83static 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
94static void signal_unlock() {
95  mutex_unlock(&mutex);
96}
97
98static 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
114static 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
132static 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
179sa_handler_t signal(int sig, sa_handler_t disp) {
180  return set_signal(sig, disp, false);
181}
182
183sa_handler_t sigset(int sig, sa_handler_t disp) {
184  return set_signal(sig, disp, true);
185}
186
187static 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
199int 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 */
245void JVM_begin_signal_setting() {
246  signal_lock();
247  jvm_signal_installing = true;
248  tid = thr_self();
249  signal_unlock();
250}
251
252void 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
260struct 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
271int JVM_get_libjsig_version() {
272  return JSIG_VERSION_1_4_1;
273}
274