94 lines
2.6 KiB
C++
94 lines
2.6 KiB
C++
/*
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* SignalSafeUnwind.cpp
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*
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* This source file is part of the FoundationDB open source project
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*
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* Copyright 2013-2018 Apple Inc. and the FoundationDB project authors
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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#include "flow/SignalSafeUnwind.h"
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int64_t dl_iterate_phdr_calls = 0;
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#ifdef __linux__
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#include <link.h>
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#include <mutex>
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static bool phdr_cache_initialized = false;
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static std::vector< std::vector<uint8_t> > phdr_cache;
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static int (*chain_dl_iterate_phdr)(
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int (*callback) (struct dl_phdr_info *info, size_t size, void *data),
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void *data) = nullptr;
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static int phdr_cache_add( struct dl_phdr_info *info, size_t size, void *data ) {
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phdr_cache.push_back( std::vector<uint8_t>((uint8_t*)info, (uint8_t*)info + size) );
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return 0;
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}
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static void initChain() {
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static std::once_flag flag;
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// Ensure that chain_dl_iterate_phdr points to the "real" function that we are overriding
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std::call_once(flag, [](){ *(void**)&chain_dl_iterate_phdr = dlsym(RTLD_NEXT, "dl_iterate_phdr"); });
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if (!chain_dl_iterate_phdr) {
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criticalError(FDB_EXIT_ERROR, "SignalSafeUnwindError", "Unable to find dl_iterate_phdr symbol");
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}
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}
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void initSignalSafeUnwind() {
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initChain();
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phdr_cache.clear();
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if (chain_dl_iterate_phdr(&phdr_cache_add, 0))
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criticalError(FDB_EXIT_ERROR, "DLIterateError", "dl_iterate_phdr error");
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phdr_cache_initialized = true;
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}
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// This overrides the function in libc!
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extern "C" int dl_iterate_phdr(
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int (*callback) (struct dl_phdr_info *info, size_t size, void *data),
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void *data)
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{
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interlockedIncrement64(&dl_iterate_phdr_calls);
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if (phdr_cache_initialized)
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{
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// This path should be async signal safe
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for(int i=0; i<phdr_cache.size(); i++)
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{
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int r = callback( (struct dl_phdr_info*)&phdr_cache[i][0], phdr_cache[i].size(), data );
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if (r!=0)
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return r;
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}
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return 0;
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} else {
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// This path is NOT async signal safe, and serves until and unless initSignalSafeUnwind() is called
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initChain();
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setProfilingEnabled(0);
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int result = chain_dl_iterate_phdr(callback, data);
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setProfilingEnabled(1);
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return result;
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}
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}
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#else // __linux__
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void initSignalSafeUnwind() {}
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#endif |