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92 lines
3.5 KiB
92 lines
3.5 KiB
4 months ago
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/*
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* Copyright (C) 2020 The Android Open Source Project
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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 "gwp_asan/common.h"
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#include "gwp_asan/optional/backtrace.h"
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#include "gwp_asan/optional/segv_handler.h"
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#include <unwindstack/LocalUnwinder.h>
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#include <unwindstack/Unwinder.h>
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namespace {
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// In reality, on Android, we use two separate unwinders. GWP-ASan internally
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// uses a fast, frame-pointer unwinder for allocation/deallocation stack traces
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// (android_unsafe_frame_pointer_chase, provided by bionic libc). When a process
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// crashes, debuggerd unwinds the access trace using libunwindstack, which is a
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// slow CFI-based unwinder. We don't split the unwinders in the test harness,
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// and frame-pointer unwinding doesn't work properly though a signal handler, so
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// we opt to use libunwindstack in this test. This has the effect that we get
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// potentially more detailed stack frames in the allocation/deallocation traces
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// (as we don't use the production unwinder), but that's fine for test-only.
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size_t BacktraceUnwindstack(uintptr_t *TraceBuffer, size_t Size) {
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unwindstack::LocalUnwinder unwinder;
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if (!unwinder.Init()) {
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return 0;
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}
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std::vector<unwindstack::LocalFrameData> frames;
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if (!unwinder.Unwind(&frames, Size)) {
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return 0;
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}
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for (const auto &frame : frames) {
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*TraceBuffer = frame.pc;
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TraceBuffer++;
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}
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return frames.size();
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}
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// We don't need any custom handling for the Segv backtrace - the unwindstack
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// unwinder has no problems with unwinding through a signal handler.
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size_t SegvBacktrace(uintptr_t *TraceBuffer, size_t Size, void * /*Context*/) {
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return BacktraceUnwindstack(TraceBuffer, Size);
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}
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// This function is a good mimic as to what's happening in the out-of-process
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// tombstone daemon (see debuggerd for more information). In our case, we want
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// to provide symbolized backtraces during ***testing only*** here. This
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// function called from a signal handler, and is extraordinarily not
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// signal-safe, but works for our purposes.
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void PrintBacktraceUnwindstack(uintptr_t *TraceBuffer, size_t TraceLength,
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gwp_asan::Printf_t Print) {
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unwindstack::UnwinderFromPid unwinder(
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gwp_asan::AllocationMetadata::kMaxTraceLengthToCollect, getpid());
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unwinder.SetRegs(unwindstack::Regs::CreateFromLocal());
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if (!unwinder.Init()) {
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Print(" Unable to init unwinder: %s\n", unwinder.LastErrorCodeString());
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return;
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}
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for (size_t i = 0; i < TraceLength; ++i) {
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unwindstack::FrameData frame_data =
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unwinder.BuildFrameFromPcOnly(TraceBuffer[i]);
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frame_data.num = i;
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Print(" %s\n", unwinder.FormatFrame(frame_data).c_str());
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}
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}
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} // anonymous namespace
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namespace gwp_asan {
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namespace backtrace {
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options::Backtrace_t getBacktraceFunction() { return BacktraceUnwindstack; }
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PrintBacktrace_t getPrintBacktraceFunction() {
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return PrintBacktraceUnwindstack;
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}
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SegvBacktrace_t getSegvBacktraceFunction() { return SegvBacktrace; }
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} // namespace backtrace
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} // namespace gwp_asan
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