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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_ppc.cc: ppc-specific stackwalker.
//
// See stackwalker_ppc.h for documentation.
//
// Author: Mark Mentovai
#include "processor/stackwalker_ppc.h"
#include "processor/minidump.h"
namespace google_airbag {
StackwalkerPPC::StackwalkerPPC(const MDRawContextPPC *context,
MemoryRegion *memory,
MinidumpModuleList *modules,
SymbolSupplier *supplier)
: Stackwalker(memory, modules, supplier),
context_(context) {
if (memory_->GetBase() + memory_->GetSize() - 1 > 0xffffffff) {
// This implementation only covers 32-bit ppc CPUs. The limits of the
// supplied stack are invalid. Mark memory_ = NULL, which will cause
// stackwalking to fail.
memory_ = NULL;
}
}
bool StackwalkerPPC::GetContextFrame(StackFrame *frame) {
if (!context_ || !memory_ || !frame)
return false;
// The stack frame and instruction pointers are stored directly in
// registers, so pull them straight out of the CPU context structure.
frame->frame_pointer = context_->gpr[1];
frame->instruction = context_->srr0;
return true;
}
bool StackwalkerPPC::GetCallerFrame(StackFrame *frame,
const StackFrames *walked_frames) {
if (!memory_ || !frame || !walked_frames)
return false;
// The stack frame and instruction pointers for previous frames are saved
// on the stack. The typical ppc calling convention is for the called
// procedure to store its return address in the calling procedure's stack
// frame at 8(%r1), and to allocate its own stack frame by decrementing %r1
// (the stack pointer) and saving the old value of %r1 at 0(%r1). Because
// the ppc has no hardware stack, there is no distinction between the
// stack pointer and frame pointer, and what is typically thought of as
// the frame pointer on an x86 is usually referred to as the stack pointer
// on a ppc.
u_int32_t last_stack_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 stack_pointer;
if (!memory_->GetMemoryAtAddress(last_stack_pointer, &stack_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 (stack_pointer <= last_stack_pointer)
return false;
u_int32_t instruction;
if (!memory_->GetMemoryAtAddress(stack_pointer + 8, &instruction))
return false;
// Mac OS X/Darwin gives 1 as the return address from the bottom-most
// frame in a stack (a thread's entry point). I haven't found any
// documentation on this, but 0 or 1 would be bogus return addresses,
// so check for them here and return false (end of stack) when they're
// hit to avoid having a phantom frame.
if (instruction <= 1)
return false;
frame->frame_pointer = stack_pointer;
frame->instruction = instruction;
return true;
}
} // namespace google_airbag
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