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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 "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 {
// 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__)
struct UnwindHelper : public TLSData {
static constexpr const char* kTlsKey = "UnwindHelper::kTlsKey";
explicit UnwindHelper(size_t max_depth)
: memory_(unwindstack::Memory::CreateProcessMemory(getpid())),
jit_(memory_),
dex_(memory_),
unwinder_(max_depth, &maps_, memory_) {
CHECK(maps_.Parse());
unwinder_.SetJitDebug(&jit_, unwindstack::Regs::CurrentArch());
unwinder_.SetDexFiles(&dex_, unwindstack::Regs::CurrentArch());
unwinder_.SetResolveNames(false);
unwindstack::Elf::SetCachingEnabled(true);
}
// Reparse process mmaps to detect newly loaded libraries.
bool Reparse() { return maps_.Reparse(); }
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_;
std::shared_ptr<unwindstack::Memory> memory_;
unwindstack::JitDebug jit_;
unwindstack::DexFiles dex_;
unwindstack::Unwinder unwinder_;
};
void BacktraceCollector::Collect() {
if (!CollectImpl()) {
// Reparse process mmaps to detect newly loaded libraries and retry.
UnwindHelper::Get(Thread::Current(), max_depth_)->Reparse();
if (!CollectImpl()) {
// Failed to unwind stack. Ignore for now.
}
}
}
bool BacktraceCollector::CollectImpl() {
unwindstack::Unwinder* unwinder = UnwindHelper::Get(Thread::Current(), max_depth_)->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);
// Expected early end: Instrumentation breaks unwinding (b/138296821).
size_t align = GetInstructionSetAlignment(kRuntimeISA);
if (RoundUp(it->pc, align) == reinterpret_cast<uintptr_t>(GetQuickInstrumentationExitPc())) {
return true;
}
}
}
if (unwinder->LastErrorCode() == unwindstack::ERROR_INVALID_MAP) {
return false;
}
return true;
}
#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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