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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 "common/logging.h"

 namespace google_breakpad {

 StackwalkerPPC::StackwalkerPPC(const SystemInfo* system_info,

                                const MDRawContextPPC* context,

                                MemoryRegion* memory,

                                const CodeModules* modules,

                                StackFrameSymbolizer* resolver_helper)

     : Stackwalker(system_info, memory, modules, resolver_helper),

       context_(context) {

   if (memory_ && 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_) {

     BPLOG(ERROR) << "Can't get context frame without context";

     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,

                                            bool stack_scan_allowed) {

   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.

   uint32_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.

   uint32_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