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// Copyright (c) 2006, Google Inc.
// All rights reserved.
//
// Redistribution and use in source and binary forms, with or without
// modification, are permitted provided that the following conditions are
// met:
//
// * Redistributions of source code must retain the above copyright
// notice, this list of conditions and the following disclaimer.
// * Redistributions in binary form must reproduce the above
// copyright notice, this list of conditions and the following disclaimer
// in the documentation and/or other materials provided with the
// distribution.
// * Neither the name of Google Inc. nor the names of its
// contributors may be used to endorse or promote products derived from
// this software without specific prior written permission.
//
// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
// stackwalker_x86.cc: x86-specific stackwalker.
//
// See stackwalker_x86.h for documentation.
//
// Author: Mark Mentovai
#include "processor/stackwalker_x86.h"
#include "processor/minidump.h"
namespace google_airbag {
StackwalkerX86::StackwalkerX86(const MDRawContextX86 *context,
MemoryRegion *memory,
MinidumpModuleList *modules,
SymbolSupplier *supplier)
: Stackwalker(memory, modules, supplier),
context_(context) {
if (memory_->GetBase() + memory_->GetSize() - 1 > 0xffffffff) {
// The x86 is a 32-bit CPU, the limits of the supplied stack are invalid.
// Mark memory_ = NULL, which will cause stackwalking to fail.
memory_ = NULL;
}
}
bool StackwalkerX86::GetContextFrame(StackFrame *frame) {
if (!context_ || !memory_ || !frame)
return false;
// The frame and instruction pointers are stored directly in registers,
// so pull them straight out of the CPU context structure.
frame->frame_pointer = context_->ebp;
frame->instruction = context_->eip;
return true;
}
bool StackwalkerX86::GetCallerFrame(StackFrame *frame,
const StackFrames *walked_frames) {
if (!memory_ || !frame || !walked_frames)
return false;
// The frame and instruction pointers for previous frames are saved on the
// stack. The typical x86 calling convention, when frame pointers are
// present, is for the calling procedure to use CALL, which pushes the
// return address onto the stack and sets the instruction pointer (%eip)
// to the entry point of the called routine. The called routine's then
// PUSHes the calling routine's frame pointer (%ebp) onto the stack before
// copying the stack pointer (%esp) to the frame pointer (%ebp). Therefore,
// the calling procedure's frame pointer is always available by
// dereferencing the called procedure's frame pointer, and the return
// address is always available at the memory location immediately above
// the address pointed to by the called procedure's frame pointer.
// If there is no frame pointer, determining the layout of the stack is
// considerably more difficult, requiring debugging information. This
// stackwalker doesn't attempt to solve that problem (at this point).
u_int32_t last_frame_pointer = walked_frames->back().frame_pointer;
// Don't pass frame.frame_pointer or frame.instruction directly
// ReadMemory, because their types are too wide (64-bit), and we
// specifically want to read 32-bit quantities for both.
u_int32_t frame_pointer;
if (!memory_->GetMemoryAtAddress(last_frame_pointer, &frame_pointer))
return false;
// A caller frame must reside higher in memory than its callee frames.
// Anything else is an error, or an indication that we've reached the
// end of the stack.
if (frame_pointer <= last_frame_pointer)
return false;
u_int32_t instruction;
if (!memory_->GetMemoryAtAddress(last_frame_pointer + 4, &instruction))
return false;
frame->frame_pointer = frame_pointer;
frame->instruction = instruction;
return true;
}
} // namespace google_airbag
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