1// Copyright 2017 The Abseil Authors. 2// 3// Licensed under the Apache License, Version 2.0 (the "License"); 4// you may not use this file except in compliance with the License. 5// You may obtain a copy of the License at 6// 7// https://www.apache.org/licenses/LICENSE-2.0 8// 9// Unless required by applicable law or agreed to in writing, software 10// distributed under the License is distributed on an "AS IS" BASIS, 11// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 12// See the License for the specific language governing permissions and 13// limitations under the License. 14// 15// Produces a stack trace for Windows. Normally, one could use 16// stacktrace_x86-inl.h or stacktrace_x86_64-inl.h -- and indeed, that 17// should work for binaries compiled using MSVC in "debug" mode. 18// However, in "release" mode, Windows uses frame-pointer 19// optimization, which makes getting a stack trace very difficult. 20// 21// There are several approaches one can take. One is to use Windows 22// intrinsics like StackWalk64. These can work, but have restrictions 23// on how successful they can be. Another attempt is to write a 24// version of stacktrace_x86-inl.h that has heuristic support for 25// dealing with FPO, similar to what WinDbg does (see 26// http://www.nynaeve.net/?p=97). There are (non-working) examples of 27// these approaches, complete with TODOs, in stacktrace_win32-inl.h#1 28// 29// The solution we've ended up doing is to call the undocumented 30// windows function RtlCaptureStackBackTrace, which probably doesn't 31// work with FPO but at least is fast, and doesn't require a symbol 32// server. 33// 34// This code is inspired by a patch from David Vitek: 35// https://code.google.com/p/google-perftools/issues/detail?id=83 36 37#ifndef ABSL_DEBUGGING_INTERNAL_STACKTRACE_WIN32_INL_H_ 38#define ABSL_DEBUGGING_INTERNAL_STACKTRACE_WIN32_INL_H_ 39 40#include <windows.h> // for GetProcAddress and GetModuleHandle 41#include <cassert> 42 43typedef USHORT NTAPI RtlCaptureStackBackTrace_Function( 44 IN ULONG frames_to_skip, 45 IN ULONG frames_to_capture, 46 OUT PVOID *backtrace, 47 OUT PULONG backtrace_hash); 48 49// It is not possible to load RtlCaptureStackBackTrace at static init time in 50// UWP. CaptureStackBackTrace is the public version of RtlCaptureStackBackTrace 51#if WINAPI_FAMILY_PARTITION(WINAPI_PARTITION_APP) && \ 52 !WINAPI_FAMILY_PARTITION(WINAPI_PARTITION_DESKTOP) 53static RtlCaptureStackBackTrace_Function* const RtlCaptureStackBackTrace_fn = 54 &::CaptureStackBackTrace; 55#else 56// Load the function we need at static init time, where we don't have 57// to worry about someone else holding the loader's lock. 58static RtlCaptureStackBackTrace_Function* const RtlCaptureStackBackTrace_fn = 59 (RtlCaptureStackBackTrace_Function*)GetProcAddress( 60 GetModuleHandleA("ntdll.dll"), "RtlCaptureStackBackTrace"); 61#endif // WINAPI_PARTITION_APP && !WINAPI_PARTITION_DESKTOP 62 63template <bool IS_STACK_FRAMES, bool IS_WITH_CONTEXT> 64static int UnwindImpl(void** result, int* sizes, int max_depth, int skip_count, 65 const void*, int* min_dropped_frames) { 66 int n = 0; 67 if (!RtlCaptureStackBackTrace_fn) { 68 // can't find a stacktrace with no function to call 69 } else { 70 n = (int)RtlCaptureStackBackTrace_fn(skip_count + 2, max_depth, result, 0); 71 } 72 if (IS_STACK_FRAMES) { 73 // No implementation for finding out the stack frame sizes yet. 74 memset(sizes, 0, sizeof(*sizes) * n); 75 } 76 if (min_dropped_frames != nullptr) { 77 // Not implemented. 78 *min_dropped_frames = 0; 79 } 80 return n; 81} 82 83namespace absl { 84ABSL_NAMESPACE_BEGIN 85namespace debugging_internal { 86bool StackTraceWorksForTest() { 87 return false; 88} 89} // namespace debugging_internal 90ABSL_NAMESPACE_END 91} // namespace absl 92 93#endif // ABSL_DEBUGGING_INTERNAL_STACKTRACE_WIN32_INL_H_ 94