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/*
* Copyright (c) 2022 SAP SE. All rights reserved.
* Copyright (c) 2022, Oracle and/or its affiliates. All rights reserved.
* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
*
* This code is free software; you can redistribute it and/or modify it
* under the terms of the GNU General Public License version 2 only, as
* published by the Free Software Foundation.
*
* This code is distributed in the hope that it will be useful, but WITHOUT
* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
* version 2 for more details (a copy is included in the LICENSE file that
* accompanied this code).
*
* You should have received a copy of the GNU General Public License version
* 2 along with this work; if not, write to the Free Software Foundation,
* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
*
* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
* or visit www.oracle.com if you need additional information or have any
* questions.
*
*/
#include "precompiled.hpp"
#include "runtime/safefetch.hpp"
#include "utilities/debug.hpp"
#include "utilities/globalDefinitions.hpp"
#ifdef SAFEFETCH_METHOD_SIGSETJMP
// For SafeFetch we need POSIX TLS and sigsetjmp/longjmp.
#include <setjmp.h>
#include <pthread.h>
static pthread_key_t g_jmpbuf_key;
struct InitTLSKey { InitTLSKey() { pthread_key_create(&g_jmpbuf_key, NULL); } };
static InitTLSKey g_init_tly_key;
// Handle safefetch, sigsetjmp style:
//
// If a safefetch jump had been established and the sig qualifies, we
// jump back to the established jump point (and hence out of signal handling).
//
// Note that this function will never return for safefetch faults. We just
// keep the prototype the same as other handle_safefetch() versions to keep
// caller sites simple.
bool handle_safefetch(int sig, address ignored1, void* ignored2) {
if (sig == SIGSEGV || sig == SIGBUS) {
// Retrieve jump buffer pointer from TLS. If not NULL, it means we set the
// jump buffer and this is indeed a SafeFetch fault.
// Note signal safety: pthread_getspecific is not safe for signal handler
// usage, but in practice it works and we have done this in the JVM for many
// years (via Thread::current_or_null_safe()).
sigjmp_buf* const jb = (sigjmp_buf*) pthread_getspecific(g_jmpbuf_key);
if (jb) {
siglongjmp(*jb, 1);
}
}
return false;
}
template <class T>
static bool _SafeFetchXX_internal(const T *adr, T* result) {
T n = 0;
// Set up a jump buffer. Anchor its pointer in TLS. Then read from the unsafe address.
// If that address was invalid, we fault, and in the signal handler we will jump back
// to the jump point.
sigjmp_buf jb;
if (sigsetjmp(jb, 1) != 0) {
// We faulted. Reset TLS slot, then return.
pthread_setspecific(g_jmpbuf_key, NULL);
*result = 0;
return false;
}
// Anchor jump buffer in TLS
pthread_setspecific(g_jmpbuf_key, &jb);
// unsafe access
n = *adr;
// Still here... All went well, adr was valid.
// Reset TLS slot, then return result.
pthread_setspecific(g_jmpbuf_key, NULL);
*result = n;
return true;
}
int SafeFetch32_impl(int *adr, int errValue) {
int result;
return _SafeFetchXX_internal<int>(adr, &result) ? result : errValue;
}
intptr_t SafeFetchN_impl(intptr_t *adr, intptr_t errValue) {
intptr_t result;
return _SafeFetchXX_internal<intptr_t>(adr, &result) ? result : errValue;
}
#endif // SAFEFETCH_METHOD_SIGSETJMP
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