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// Copyright (c) 2010 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 "google_breakpad/processor/call_stack.h"
#include "google_breakpad/processor/memory_region.h"
#include "google_breakpad/processor/stack_frame_cpu.h"
#include "processor/logging.h"
namespace google_breakpad {
StackwalkerPPC::StackwalkerPPC(const SystemInfo *system_info,
const MDRawContextPPC *context,
MemoryRegion *memory,
const CodeModules *modules,
SymbolSupplier *supplier,
SourceLineResolverInterface *resolver)
: Stackwalker(system_info, memory, modules, supplier, resolver),
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.
BPLOG(ERROR) << "Memory out of range for stackwalking: " <<
HexString(memory_->GetBase()) << "+" <<
HexString(memory_->GetSize());
memory_ = NULL;
}
}
StackFrame* StackwalkerPPC::GetContextFrame() {
if (!context_ || !memory_) {
BPLOG(ERROR) << "Can't get context frame without context or memory";
return NULL;
}
StackFramePPC *frame = new StackFramePPC();
// The instruction pointer is stored directly in a register, so pull it
// straight out of the CPU context structure.
frame->context = *context_;
frame->context_validity = StackFramePPC::CONTEXT_VALID_ALL;
frame->trust = StackFrame::FRAME_TRUST_CONTEXT;
frame->instruction = frame->context.srr0;
return frame;
}
StackFrame* StackwalkerPPC::GetCallerFrame(const CallStack *stack) {
if (!memory_ || !stack) {
BPLOG(ERROR) << "Can't get caller frame without memory or stack";
return NULL;
}
// The 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.
StackFramePPC *last_frame = static_cast<StackFramePPC*>(
stack->frames()->back());
// 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.
u_int32_t stack_pointer;
if (!memory_->GetMemoryAtAddress(last_frame->context.gpr[1],
&stack_pointer) ||
stack_pointer <= last_frame->context.gpr[1]) {
return NULL;
}
// 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.
u_int32_t instruction;
if (!memory_->GetMemoryAtAddress(stack_pointer + 8, &instruction) ||
instruction <= 1) {
return NULL;
}
StackFramePPC *frame = new StackFramePPC();
frame->context = last_frame->context;
frame->context.srr0 = instruction;
frame->context.gpr[1] = stack_pointer;
frame->context_validity = StackFramePPC::CONTEXT_VALID_SRR0 |
StackFramePPC::CONTEXT_VALID_GPR1;
frame->trust = StackFrame::FRAME_TRUST_FP;
// frame->context.srr0 is the return address, which is one instruction
// past the branch that caused us to arrive at the callee. Set
// frame_ppc->instruction to four less than that. Since all ppc
// instructions are 4 bytes wide, this is the address of the branch
// instruction. This allows source line information to match up with the
// line that contains a function call. Callers that require the exact
// return address value may access the context.srr0 field of StackFramePPC.
frame->instruction = frame->context.srr0 - 4;
return frame;
}
} // namespace google_breakpad
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