jdk

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/*
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 * Copyright (c) 2017, 2023, Oracle and/or its affiliates. All rights reserved.
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 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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 *
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 * This code is free software; you can redistribute it and/or modify it
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 * under the terms of the GNU General Public License version 2 only, as
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 * published by the Free Software Foundation.
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 *
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 * This code is distributed in the hope that it will be useful, but WITHOUT
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 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
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 * version 2 for more details (a copy is included in the LICENSE file that
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 * accompanied this code).
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 *
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 * You should have received a copy of the GNU General Public License version
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 * 2 along with this work; if not, write to the Free Software Foundation,
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 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
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 *
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 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
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 * or visit www.oracle.com if you need additional information or have any
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 * questions.
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 *
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 */
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#include "precompiled.hpp"
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#include "runtime/thread.hpp"
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#include "runtime/threadCrashProtection.hpp"
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Thread* ThreadCrashProtection::_protected_thread = nullptr;
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ThreadCrashProtection* ThreadCrashProtection::_crash_protection = nullptr;
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ThreadCrashProtection::ThreadCrashProtection() {
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  _protected_thread = Thread::current();
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  assert(_protected_thread->is_JfrSampler_thread(), "should be JFRSampler");
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}
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/*
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 * See the caveats for this class in threadCrashProtection_posix.hpp
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 * Protects the callback call so that SIGSEGV / SIGBUS jumps back into this
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 * method and returns false. If none of the signals are raised, returns true.
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 * The callback is supposed to provide the method that should be protected.
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 */
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bool ThreadCrashProtection::call(CrashProtectionCallback& cb) {
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  sigset_t saved_sig_mask;
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  // we cannot rely on sigsetjmp/siglongjmp to save/restore the signal mask
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  // since on at least some systems (OS X) siglongjmp will restore the mask
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  // for the process, not the thread
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  pthread_sigmask(0, nullptr, &saved_sig_mask);
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  if (sigsetjmp(_jmpbuf, 0) == 0) {
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    // make sure we can see in the signal handler that we have crash protection
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    // installed
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    _crash_protection = this;
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    cb.call();
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    // and clear the crash protection
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    _crash_protection = nullptr;
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    _protected_thread = nullptr;
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    return true;
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  }
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  // this happens when we siglongjmp() back
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  pthread_sigmask(SIG_SETMASK, &saved_sig_mask, nullptr);
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  _crash_protection = nullptr;
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  _protected_thread = nullptr;
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  return false;
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}
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void ThreadCrashProtection::restore() {
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  assert(_crash_protection != nullptr, "must have crash protection");
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  siglongjmp(_jmpbuf, 1);
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}
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void ThreadCrashProtection::check_crash_protection(int sig,
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    Thread* thread) {
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  if (thread != nullptr &&
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      thread == _protected_thread &&
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      _crash_protection != nullptr) {
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    if (sig == SIGSEGV || sig == SIGBUS) {
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      _crash_protection->restore();
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    }
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  }
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}
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