foundationdb/flow/SignalSafeUnwind.cpp

87 lines
2.7 KiB
C++

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