Copy the register context before calling StackWalk64

base/debug/stack_trace_win.cc

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "base/debug/stack_trace.h"
 
 #include <windows.h>
 #include <dbghelp.h>
 
 #include <iostream>
@@ skipping 204 matching lines @@
 }
 
 #if defined(COMPILER_MSVC)
 #pragma optimize("", on)
 #endif
 
 StackTrace::StackTrace(EXCEPTION_POINTERS* exception_pointers) {
   InitTrace(exception_pointers->ContextRecord);
 }
 
-StackTrace::StackTrace(CONTEXT* context) {
+StackTrace::StackTrace(const CONTEXT* context) {
   InitTrace(context);
 }
 
-void StackTrace::InitTrace(CONTEXT* context_record) {
+void StackTrace::InitTrace(const CONTEXT* context_record) {
+  // StackWalk64 modifies the register context in place, so we have to copy it
+  // so that downstream exception handlers get the right context.  The incoming
+  // context may have had more register state (YMM, etc) than we need to unwind
+  // the stack. Typically StackWalk64 only needs integer and control registers.
+  CONTEXT context_copy;
+  memcpy(&context_copy, context_record, sizeof(context_copy));
+  context_copy.ContextFlags = CONTEXT_INTEGER | CONTEXT_CONTROL;
+
   // When walking an exception stack, we need to use StackWalk64().
   count_ = 0;
   // Initialize stack walking.
   STACKFRAME64 stack_frame;
   memset(&stack_frame, 0, sizeof(stack_frame));
 #if defined(_WIN64)
   int machine_type = IMAGE_FILE_MACHINE_AMD64;
   stack_frame.AddrPC.Offset = context_record->Rip;
   stack_frame.AddrFrame.Offset = context_record->Rbp;
   stack_frame.AddrStack.Offset = context_record->Rsp;
 #else
   int machine_type = IMAGE_FILE_MACHINE_I386;
   stack_frame.AddrPC.Offset = context_record->Eip;
   stack_frame.AddrFrame.Offset = context_record->Ebp;
   stack_frame.AddrStack.Offset = context_record->Esp;
 #endif
   stack_frame.AddrPC.Mode = AddrModeFlat;
   stack_frame.AddrFrame.Mode = AddrModeFlat;
   stack_frame.AddrStack.Mode = AddrModeFlat;
   while (StackWalk64(machine_type,
                      GetCurrentProcess(),
                      GetCurrentThread(),
                      &stack_frame,
-                     context_record,
+                     &context_copy,
                      NULL,
                      &SymFunctionTableAccess64,
                      &SymGetModuleBase64,
                      NULL) &&
          count_ < arraysize(trace_)) {
     trace_[count_++] = reinterpret_cast<void*>(stack_frame.AddrPC.Offset);
   }
 
   for (size_t i = count_; i < arraysize(trace_); ++i)
     trace_[i] = NULL;
@@ skipping 12 matching lines @@
       (*os) << "\t" << trace_[i] << "\n";
     }
   } else {
     (*os) << "Backtrace:\n";
     context->OutputTraceToStream(trace_, count_, os);
   }
 }
 
 }  // namespace debug
 }  // namespace base