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/*
* Copyright (C) 2018 The Android Open Source Project
*
* 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 "backtrace_helper.h"
#if defined(__linux__)
#include <sys/types.h>
#include <unistd.h>
#include <iomanip>
#include "unwindstack/Regs.h"
#include "unwindstack/RegsGetLocal.h"
#include "unwindstack/Memory.h"
#include "unwindstack/Unwinder.h"
#include "base/bit_utils.h"
#include "entrypoints/runtime_asm_entrypoints.h"
#include "thread-inl.h"
#else
// For UNUSED
#include "base/macros.h"
#endif
namespace art HIDDEN {
// We only really support libunwindstack on linux which is unfortunate but since this is only for
// gcstress this isn't a huge deal.
#if defined(__linux__)
// Strict integrity check of the backtrace:
// All methods must have a name, all the way to "main".
static constexpr bool kStrictUnwindChecks = false;
struct UnwindHelper : public TLSData {
static constexpr const char* kTlsKey = "UnwindHelper::kTlsKey";
explicit UnwindHelper(size_t max_depth)
: arch_(unwindstack::Regs::CurrentArch()),
memory_(unwindstack::Memory::CreateProcessMemoryThreadCached(getpid())),
jit_(unwindstack::CreateJitDebug(arch_, memory_)),
dex_(unwindstack::CreateDexFiles(arch_, memory_)),
unwinder_(max_depth, &maps_, memory_) {
CHECK(maps_.Parse());
unwinder_.SetArch(arch_);
unwinder_.SetJitDebug(jit_.get());
unwinder_.SetDexFiles(dex_.get());
unwinder_.SetResolveNames(kStrictUnwindChecks);
unwindstack::Elf::SetCachingEnabled(true);
}
// Reparse process mmaps to detect newly loaded libraries.
bool Reparse(bool* any_changed) { return maps_.Reparse(any_changed); }
static UnwindHelper* Get(Thread* self, size_t max_depth) {
UnwindHelper* tls = reinterpret_cast<UnwindHelper*>(self->GetCustomTLS(kTlsKey));
if (tls == nullptr) {
tls = new UnwindHelper(max_depth);
self->SetCustomTLS(kTlsKey, tls);
}
return tls;
}
unwindstack::Unwinder* Unwinder() { return &unwinder_; }
private:
unwindstack::LocalUpdatableMaps maps_;
unwindstack::ArchEnum arch_;
std::shared_ptr<unwindstack::Memory> memory_;
std::unique_ptr<unwindstack::JitDebug> jit_;
std::unique_ptr<unwindstack::DexFiles> dex_;
unwindstack::Unwinder unwinder_;
};
void BacktraceCollector::Collect() {
unwindstack::Unwinder* unwinder = UnwindHelper::Get(Thread::Current(), max_depth_)->Unwinder();
if (!CollectImpl(unwinder)) {
// Reparse process mmaps to detect newly loaded libraries and retry,
// but only if any maps changed (we don't want to hide racy failures).
bool any_changed;
UnwindHelper::Get(Thread::Current(), max_depth_)->Reparse(&any_changed);
if (!any_changed || !CollectImpl(unwinder)) {
if (kStrictUnwindChecks) {
std::vector<unwindstack::FrameData>& frames = unwinder->frames();
LOG(ERROR) << "Failed to unwind stack (error " << unwinder->LastErrorCodeString() << "):";
std::string prev_name;
for (auto& frame : frames) {
if (frame.map_info != nullptr) {
std::string full_name = frame.map_info->GetFullName();
if (prev_name != full_name) {
LOG(ERROR) << " in " << full_name;
}
prev_name = full_name;
} else {
prev_name = "";
}
LOG(ERROR) << " pc " << std::setw(8) << std::setfill('0') << std::hex <<
frame.rel_pc << " " << frame.function_name.c_str();
}
LOG(FATAL);
}
}
}
}
bool BacktraceCollector::CollectImpl(unwindstack::Unwinder* unwinder) {
std::unique_ptr<unwindstack::Regs> regs(unwindstack::Regs::CreateFromLocal());
RegsGetLocal(regs.get());
unwinder->SetRegs(regs.get());
unwinder->Unwind();
num_frames_ = 0;
if (unwinder->NumFrames() > skip_count_) {
for (auto it = unwinder->frames().begin() + skip_count_; it != unwinder->frames().end(); ++it) {
CHECK_LT(num_frames_, max_depth_);
out_frames_[num_frames_++] = static_cast<uintptr_t>(it->pc);
if (kStrictUnwindChecks) {
if (it->function_name.empty()) {
return false;
}
if (it->function_name == "main" ||
it->function_name == "start_thread" ||
it->function_name == "__start_thread") {
return true;
}
}
}
}
unwindstack::ErrorCode error = unwinder->LastErrorCode();
return error == unwindstack::ERROR_NONE || error == unwindstack::ERROR_MAX_FRAMES_EXCEEDED;
}
#else
#pragma clang diagnostic push
#pragma clang diagnostic warning "-W#warnings"
#warning "Backtrace collector is not implemented. GCStress cannot be used."
#pragma clang diagnostic pop
// We only have an implementation for linux. On other plaforms just return nothing. This is not
// really correct but we only use this for hashing and gcstress so it's not too big a deal.
void BacktraceCollector::Collect() {
UNUSED(skip_count_);
UNUSED(out_frames_);
UNUSED(max_depth_);
num_frames_ = 0;
}
#endif
} // namespace art
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