bool
UnwindAssemblyInstEmulation::GetNonCallSiteUnwindPlanFromAssembly (AddressRange& range, 
                                                                   Thread& thread, 
                                                                   UnwindPlan& unwind_plan)
{
    if (range.GetByteSize() > 0 && 
        range.GetBaseAddress().IsValid() &&
        m_inst_emulator_ap.get())
    {
     
        // The instruction emulation subclass setup the unwind plan for the
        // first instruction.
        m_inst_emulator_ap->CreateFunctionEntryUnwind (unwind_plan);

        // CreateFunctionEntryUnwind should have created the first row. If it
        // doesn't, then we are done.
        if (unwind_plan.GetRowCount() == 0)
            return false;
        
        ExecutionContext exe_ctx;
        thread.CalculateExecutionContext(exe_ctx);
        const bool prefer_file_cache = true;
        DisassemblerSP disasm_sp (Disassembler::DisassembleRange (m_arch,
                                                                  NULL,
                                                                  NULL,
                                                                  exe_ctx,
                                                                  range,
                                                                  prefer_file_cache));
        
        Log *log(GetLogIfAllCategoriesSet (LIBLLDB_LOG_UNWIND));

        if (disasm_sp)
        {
            
            m_range_ptr = ⦥
            m_thread_ptr = &thread;
            m_unwind_plan_ptr = &unwind_plan;

            const uint32_t addr_byte_size = m_arch.GetAddressByteSize();
            const bool show_address = true;
            const bool show_bytes = true;
            m_inst_emulator_ap->GetRegisterInfo (unwind_plan.GetRegisterKind(), 
                                                 unwind_plan.GetInitialCFARegister(), 
                                                 m_cfa_reg_info);
            
            m_fp_is_cfa = false;
            m_register_values.clear();
            m_pushed_regs.clear();

            // Initialize the CFA with a known value. In the 32 bit case
            // it will be 0x80000000, and in the 64 bit case 0x8000000000000000.
            // We use the address byte size to be safe for any future address sizes
            m_initial_sp = (1ull << ((addr_byte_size * 8) - 1));
            RegisterValue cfa_reg_value;
            cfa_reg_value.SetUInt (m_initial_sp, m_cfa_reg_info.byte_size);
            SetRegisterValue (m_cfa_reg_info, cfa_reg_value);

            const InstructionList &inst_list = disasm_sp->GetInstructionList ();
            const size_t num_instructions = inst_list.GetSize();

            if (num_instructions > 0)
            {
                Instruction *inst = inst_list.GetInstructionAtIndex (0).get();
                const lldb::addr_t base_addr = inst->GetAddress().GetFileAddress();

                // Map for storing the unwind plan row and the value of the registers at a given offset.
                // When we see a forward branch we add a new entry to this map with the actual unwind plan
                // row and register context for the target address of the branch as the current data have
                // to be valid for the target address of the branch too if we are in the same function.
                std::map<lldb::addr_t, std::pair<UnwindPlan::RowSP, RegisterValueMap>> saved_unwind_states;

                // Make a copy of the current instruction Row and save it in m_curr_row
                // so we can add updates as we process the instructions.  
                UnwindPlan::RowSP last_row = unwind_plan.GetLastRow();
                UnwindPlan::Row *newrow = new UnwindPlan::Row;
                if (last_row.get())
                    *newrow = *last_row.get();
                m_curr_row.reset(newrow);

                // Add the initial state to the save list with offset 0.
                saved_unwind_states.insert({0, {last_row, m_register_values}});

                // cache the pc register number (in whatever register numbering this UnwindPlan uses) for
                // quick reference during instruction parsing.
                uint32_t pc_reg_num = LLDB_INVALID_REGNUM;
                RegisterInfo pc_reg_info;
                if (m_inst_emulator_ap->GetRegisterInfo (eRegisterKindGeneric, LLDB_REGNUM_GENERIC_PC, pc_reg_info))
                    pc_reg_num = pc_reg_info.kinds[unwind_plan.GetRegisterKind()];
                else
                    pc_reg_num = LLDB_INVALID_REGNUM;

                // cache the return address register number (in whatever register numbering this UnwindPlan uses) for
                // quick reference during instruction parsing.
                uint32_t ra_reg_num = LLDB_INVALID_REGNUM;
                RegisterInfo ra_reg_info;
                if (m_inst_emulator_ap->GetRegisterInfo (eRegisterKindGeneric, LLDB_REGNUM_GENERIC_RA, ra_reg_info))
                    ra_reg_num = ra_reg_info.kinds[unwind_plan.GetRegisterKind()];
                else
                    ra_reg_num = LLDB_INVALID_REGNUM;

                for (size_t idx=0; idx<num_instructions; ++idx)
                {
                    m_curr_row_modified = false;
                    m_forward_branch_offset = 0;

                    inst = inst_list.GetInstructionAtIndex (idx).get();
                    if (inst)
                    {
                        lldb::addr_t current_offset = inst->GetAddress().GetFileAddress() - base_addr;
                        auto it = saved_unwind_states.upper_bound(current_offset);
                        assert(it != saved_unwind_states.begin() && "Unwind row for the function entry missing");
                        --it; // Move it to the row corresponding to the current offset

                        // If the offset of m_curr_row don't match with the offset we see in saved_unwind_states
                        // then we have to update m_curr_row and m_register_values based on the saved values. It
                        // is happenning after we processed an epilogue and a return to caller instruction.
                        if (it->second.first->GetOffset() != m_curr_row->GetOffset())
                        {
                            UnwindPlan::Row *newrow = new UnwindPlan::Row;
                            *newrow = *it->second.first;
                            m_curr_row.reset(newrow);
                            m_register_values = it->second.second;;
                        }

                        if (log && log->GetVerbose ())
                        {
                            StreamString strm;
                            lldb_private::FormatEntity::Entry format;
                            FormatEntity::Parse("${frame.pc}: ", format);
                            inst->Dump(&strm, inst_list.GetMaxOpcocdeByteSize (), show_address, show_bytes, NULL, NULL, NULL, &format, 0);
                            log->PutCString (strm.GetData());
                        }

                        m_inst_emulator_ap->SetInstruction (inst->GetOpcode(), 
                                                            inst->GetAddress(), 
                                                            exe_ctx.GetTargetPtr());

                        m_inst_emulator_ap->EvaluateInstruction (eEmulateInstructionOptionIgnoreConditions);

                        // If the current instruction is a branch forward then save the current CFI information
                        // for the offset where we are branching.
                        if (m_forward_branch_offset != 0 && range.ContainsFileAddress(inst->GetAddress().GetFileAddress() + m_forward_branch_offset))
                        {
                            auto newrow = std::make_shared<UnwindPlan::Row>(*m_curr_row.get());
                            newrow->SetOffset(current_offset + m_forward_branch_offset);
                            saved_unwind_states.insert({current_offset + m_forward_branch_offset, {newrow, m_register_values}});
                            unwind_plan.InsertRow(newrow);
                        }

                        // Were there any changes to the CFI while evaluating this instruction?
                        if (m_curr_row_modified)
                        {
                            // Save the modified row if we don't already have a CFI row in the currennt address
                            if (saved_unwind_states.count(current_offset + inst->GetOpcode().GetByteSize()) == 0)
                            {
                                m_curr_row->SetOffset (current_offset + inst->GetOpcode().GetByteSize());
                                unwind_plan.InsertRow (m_curr_row);
                                saved_unwind_states.insert({current_offset + inst->GetOpcode().GetByteSize(), {m_curr_row, m_register_values}});

                                // Allocate a new Row for m_curr_row, copy the current state into it
                                UnwindPlan::Row *newrow = new UnwindPlan::Row;
                                *newrow = *m_curr_row.get();
                                m_curr_row.reset(newrow);
                            }
                        }
                    }
                }
            }
            // FIXME: The DisassemblerLLVMC has a reference cycle and won't go away if it has any active instructions.
            // I'll fix that but for now, just clear the list and it will go away nicely.
            disasm_sp->GetInstructionList().Clear();
        }
        
        if (log && log->GetVerbose ())
        {
            StreamString strm;
            lldb::addr_t base_addr = range.GetBaseAddress().GetLoadAddress(thread.CalculateTarget().get());
            strm.Printf ("Resulting unwind rows for [0x%" PRIx64 " - 0x%" PRIx64 "):", base_addr, base_addr + range.GetByteSize());
            unwind_plan.Dump(strm, &thread, base_addr);
            log->PutCString (strm.GetData());
        }
        return unwind_plan.GetRowCount() > 0;
    }
    return false;
}
예제 #2
0
bool
UnwindAssemblyInstEmulation::GetNonCallSiteUnwindPlanFromAssembly (AddressRange& range, 
                                                                   Thread& thread, 
                                                                   UnwindPlan& unwind_plan)
{
    if (range.GetByteSize() > 0 && 
        range.GetBaseAddress().IsValid() &&
        m_inst_emulator_ap.get())
    {
     
        // The the instruction emulation subclass setup the unwind plan for the
        // first instruction.
        m_inst_emulator_ap->CreateFunctionEntryUnwind (unwind_plan);

        // CreateFunctionEntryUnwind should have created the first row. If it
        // doesn't, then we are done.
        if (unwind_plan.GetRowCount() == 0)
            return false;
        
        ExecutionContext exe_ctx;
        thread.CalculateExecutionContext(exe_ctx);
        DisassemblerSP disasm_sp (Disassembler::DisassembleRange (m_arch,
                                                                  NULL,
                                                                  exe_ctx,
                                                                  range));
        
        LogSP log(GetLogIfAllCategoriesSet (LIBLLDB_LOG_UNWIND));

        if (disasm_sp)
        {
            
            m_range_ptr = &range;
            m_thread_ptr = &thread;
            m_unwind_plan_ptr = &unwind_plan;

            const uint32_t addr_byte_size = m_arch.GetAddressByteSize();
            const bool show_address = true;
            const bool show_bytes = true;
            const bool raw = false;
            // Initialize the CFA with a known value. In the 32 bit case
            // it will be 0x80000000, and in the 64 bit case 0x8000000000000000.
            // We use the address byte size to be safe for any future addresss sizes
            m_inst_emulator_ap->GetRegisterInfo (unwind_plan.GetRegisterKind(), 
                                                 unwind_plan.GetInitialCFARegister(), 
                                                 m_cfa_reg_info);
            
            m_fp_is_cfa = false;
            m_register_values.clear();
            m_pushed_regs.clear();

            m_initial_sp = (1ull << ((addr_byte_size * 8) - 1));
            RegisterValue cfa_reg_value;
            cfa_reg_value.SetUInt (m_initial_sp, m_cfa_reg_info.byte_size);
            SetRegisterValue (m_cfa_reg_info, cfa_reg_value);
                
            const InstructionList &inst_list = disasm_sp->GetInstructionList ();
            const size_t num_instructions = inst_list.GetSize();
            if (num_instructions > 0)
            {
                Instruction *inst = inst_list.GetInstructionAtIndex (0).get();
                const addr_t base_addr = inst->GetAddress().GetFileAddress();
                // Initialize the current row with the one row that was created
                // from the CreateFunctionEntryUnwind call above...
                m_curr_row = unwind_plan.GetLastRow();

                for (size_t idx=0; idx<num_instructions; ++idx)
                {
                    inst = inst_list.GetInstructionAtIndex (idx).get();
                    if (inst)
                    {

                        if (log && log->GetVerbose ())
                        {
                            StreamString strm;
                            inst->Dump(&strm, inst_list.GetMaxOpcocdeByteSize (), show_address, show_bytes, &exe_ctx, raw);
                            log->PutCString (strm.GetData());
                        }

                        m_inst_emulator_ap->SetInstruction (inst->GetOpcode(), 
                                                            inst->GetAddress(), 
                                                            exe_ctx.GetTargetPtr());

                        m_inst_emulator_ap->EvaluateInstruction (eEmulateInstructionOptionIgnoreConditions);
                        
                        if (unwind_plan.GetLastRow() != m_curr_row)
                        {
                            // Be sure to not edit the offset unless our row has changed
                            // so that the "!=" call above doesn't trigger every time
                            m_curr_row.SetOffset (inst->GetAddress().GetFileAddress() + inst->GetOpcode().GetByteSize() - base_addr);
                            // Append the new row
                            unwind_plan.AppendRow (m_curr_row);
                        }
                    }
                }
            }
        }
        
        if (log && log->GetVerbose ())
        {
            StreamString strm;
            lldb::addr_t base_addr = range.GetBaseAddress().GetLoadAddress(&thread.GetProcess().GetTarget());
            strm.Printf ("Resulting unwind rows for [0x%llx - 0x%llx):", base_addr, base_addr + range.GetByteSize());
            unwind_plan.Dump(strm, &thread, base_addr);
            log->PutCString (strm.GetData());
        }
        return unwind_plan.GetRowCount() > 0;
    }
    return false;
}
예제 #3
0
bool UnwindAssemblyInstEmulation::GetNonCallSiteUnwindPlanFromAssembly(
    AddressRange &range, uint8_t *opcode_data, size_t opcode_size,
    UnwindPlan &unwind_plan) {
  if (opcode_data == nullptr || opcode_size == 0)
    return false;

  if (range.GetByteSize() > 0 && range.GetBaseAddress().IsValid() &&
      m_inst_emulator_ap.get()) {

    // The instruction emulation subclass setup the unwind plan for the
    // first instruction.
    m_inst_emulator_ap->CreateFunctionEntryUnwind(unwind_plan);

    // CreateFunctionEntryUnwind should have created the first row. If it
    // doesn't, then we are done.
    if (unwind_plan.GetRowCount() == 0)
      return false;

    const bool prefer_file_cache = true;
    DisassemblerSP disasm_sp(Disassembler::DisassembleBytes(
        m_arch, NULL, NULL, range.GetBaseAddress(), opcode_data, opcode_size,
        99999, prefer_file_cache));

    Log *log(GetLogIfAllCategoriesSet(LIBLLDB_LOG_UNWIND));

    if (disasm_sp) {

      m_range_ptr = &range;
      m_unwind_plan_ptr = &unwind_plan;

      const uint32_t addr_byte_size = m_arch.GetAddressByteSize();
      const bool show_address = true;
      const bool show_bytes = true;
      m_inst_emulator_ap->GetRegisterInfo(unwind_plan.GetRegisterKind(),
                                          unwind_plan.GetInitialCFARegister(),
                                          m_cfa_reg_info);

      m_fp_is_cfa = false;
      m_register_values.clear();
      m_pushed_regs.clear();

      // Initialize the CFA with a known value. In the 32 bit case
      // it will be 0x80000000, and in the 64 bit case 0x8000000000000000.
      // We use the address byte size to be safe for any future address sizes
      m_initial_sp = (1ull << ((addr_byte_size * 8) - 1));
      RegisterValue cfa_reg_value;
      cfa_reg_value.SetUInt(m_initial_sp, m_cfa_reg_info.byte_size);
      SetRegisterValue(m_cfa_reg_info, cfa_reg_value);

      const InstructionList &inst_list = disasm_sp->GetInstructionList();
      const size_t num_instructions = inst_list.GetSize();

      if (num_instructions > 0) {
        Instruction *inst = inst_list.GetInstructionAtIndex(0).get();
        const lldb::addr_t base_addr = inst->GetAddress().GetFileAddress();

        // Map for storing the unwind plan row and the value of the registers at
        // a given offset.
        // When we see a forward branch we add a new entry to this map with the
        // actual unwind plan
        // row and register context for the target address of the branch as the
        // current data have
        // to be valid for the target address of the branch too if we are in the
        // same function.
        std::map<lldb::addr_t, std::pair<UnwindPlan::RowSP, RegisterValueMap>>
            saved_unwind_states;

        // Make a copy of the current instruction Row and save it in m_curr_row
        // so we can add updates as we process the instructions.
        UnwindPlan::RowSP last_row = unwind_plan.GetLastRow();
        UnwindPlan::Row *newrow = new UnwindPlan::Row;
        if (last_row.get())
          *newrow = *last_row.get();
        m_curr_row.reset(newrow);

        // Add the initial state to the save list with offset 0.
        saved_unwind_states.insert({0, {last_row, m_register_values}});

        // cache the pc register number (in whatever register numbering this
        // UnwindPlan uses) for
        // quick reference during instruction parsing.
        RegisterInfo pc_reg_info;
        m_inst_emulator_ap->GetRegisterInfo(
            eRegisterKindGeneric, LLDB_REGNUM_GENERIC_PC, pc_reg_info);

        // cache the return address register number (in whatever register
        // numbering this UnwindPlan uses) for
        // quick reference during instruction parsing.
        RegisterInfo ra_reg_info;
        m_inst_emulator_ap->GetRegisterInfo(
            eRegisterKindGeneric, LLDB_REGNUM_GENERIC_RA, ra_reg_info);

        // The architecture dependent condition code of the last processed
        // instruction.
        EmulateInstruction::InstructionCondition last_condition =
            EmulateInstruction::UnconditionalCondition;
        lldb::addr_t condition_block_start_offset = 0;

        for (size_t idx = 0; idx < num_instructions; ++idx) {
          m_curr_row_modified = false;
          m_forward_branch_offset = 0;

          inst = inst_list.GetInstructionAtIndex(idx).get();
          if (inst) {
            lldb::addr_t current_offset =
                inst->GetAddress().GetFileAddress() - base_addr;
            auto it = saved_unwind_states.upper_bound(current_offset);
            assert(it != saved_unwind_states.begin() &&
                   "Unwind row for the function entry missing");
            --it; // Move it to the row corresponding to the current offset

            // If the offset of m_curr_row don't match with the offset we see in
            // saved_unwind_states
            // then we have to update m_curr_row and m_register_values based on
            // the saved values. It
            // is happenning after we processed an epilogue and a return to
            // caller instruction.
            if (it->second.first->GetOffset() != m_curr_row->GetOffset()) {
              UnwindPlan::Row *newrow = new UnwindPlan::Row;
              *newrow = *it->second.first;
              m_curr_row.reset(newrow);
              m_register_values = it->second.second;
            }

            m_inst_emulator_ap->SetInstruction(inst->GetOpcode(),
                                               inst->GetAddress(), nullptr);

            if (last_condition !=
                m_inst_emulator_ap->GetInstructionCondition()) {
              if (m_inst_emulator_ap->GetInstructionCondition() !=
                      EmulateInstruction::UnconditionalCondition &&
                  saved_unwind_states.count(current_offset) == 0) {
                // If we don't have a saved row for the current offset then save
                // our
                // current state because we will have to restore it after the
                // conditional block.
                auto new_row =
                    std::make_shared<UnwindPlan::Row>(*m_curr_row.get());
                saved_unwind_states.insert(
                    {current_offset, {new_row, m_register_values}});
              }

              // If the last instruction was conditional with a different
              // condition
              // then the then current condition then restore the condition.
              if (last_condition !=
                  EmulateInstruction::UnconditionalCondition) {
                const auto &saved_state =
                    saved_unwind_states.at(condition_block_start_offset);
                m_curr_row =
                    std::make_shared<UnwindPlan::Row>(*saved_state.first);
                m_curr_row->SetOffset(current_offset);
                m_register_values = saved_state.second;
                bool replace_existing =
                    true; // The last instruction might already
                          // created a row for this offset and
                          // we want to overwrite it.
                unwind_plan.InsertRow(
                    std::make_shared<UnwindPlan::Row>(*m_curr_row),
                    replace_existing);
              }

              // We are starting a new conditional block at the catual offset
              condition_block_start_offset = current_offset;
            }

            if (log && log->GetVerbose()) {
              StreamString strm;
              lldb_private::FormatEntity::Entry format;
              FormatEntity::Parse("${frame.pc}: ", format);
              inst->Dump(&strm, inst_list.GetMaxOpcocdeByteSize(), show_address,
                         show_bytes, NULL, NULL, NULL, &format, 0);
              log->PutString(strm.GetString());
            }

            last_condition = m_inst_emulator_ap->GetInstructionCondition();

            m_inst_emulator_ap->EvaluateInstruction(
                eEmulateInstructionOptionIgnoreConditions);

            // If the current instruction is a branch forward then save the
            // current CFI information
            // for the offset where we are branching.
            if (m_forward_branch_offset != 0 &&
                range.ContainsFileAddress(inst->GetAddress().GetFileAddress() +
                                          m_forward_branch_offset)) {
              auto newrow =
                  std::make_shared<UnwindPlan::Row>(*m_curr_row.get());
              newrow->SetOffset(current_offset + m_forward_branch_offset);
              saved_unwind_states.insert(
                  {current_offset + m_forward_branch_offset,
                   {newrow, m_register_values}});
              unwind_plan.InsertRow(newrow);
            }

            // Were there any changes to the CFI while evaluating this
            // instruction?
            if (m_curr_row_modified) {
              // Save the modified row if we don't already have a CFI row in the
              // currennt address
              if (saved_unwind_states.count(
                      current_offset + inst->GetOpcode().GetByteSize()) == 0) {
                m_curr_row->SetOffset(current_offset +
                                      inst->GetOpcode().GetByteSize());
                unwind_plan.InsertRow(m_curr_row);
                saved_unwind_states.insert(
                    {current_offset + inst->GetOpcode().GetByteSize(),
                     {m_curr_row, m_register_values}});

                // Allocate a new Row for m_curr_row, copy the current state
                // into it
                UnwindPlan::Row *newrow = new UnwindPlan::Row;
                *newrow = *m_curr_row.get();
                m_curr_row.reset(newrow);
              }
            }
          }
        }
      }
    }

    if (log && log->GetVerbose()) {
      StreamString strm;
      lldb::addr_t base_addr = range.GetBaseAddress().GetFileAddress();
      strm.Printf("Resulting unwind rows for [0x%" PRIx64 " - 0x%" PRIx64 "):",
                  base_addr, base_addr + range.GetByteSize());
      unwind_plan.Dump(strm, nullptr, base_addr);
      log->PutString(strm.GetString());
    }
    return unwind_plan.GetRowCount() > 0;
  }
  return false;
}
bool
UnwindAssemblyInstEmulation::GetNonCallSiteUnwindPlanFromAssembly (AddressRange& range, 
                                                                   Thread& thread, 
                                                                   UnwindPlan& unwind_plan)
{
    if (range.GetByteSize() > 0 && 
        range.GetBaseAddress().IsValid() &&
        m_inst_emulator_ap.get())
    {
     
        // The instruction emulation subclass setup the unwind plan for the
        // first instruction.
        m_inst_emulator_ap->CreateFunctionEntryUnwind (unwind_plan);

        // CreateFunctionEntryUnwind should have created the first row. If it
        // doesn't, then we are done.
        if (unwind_plan.GetRowCount() == 0)
            return false;
        
        ExecutionContext exe_ctx;
        thread.CalculateExecutionContext(exe_ctx);
        const bool prefer_file_cache = true;
        DisassemblerSP disasm_sp (Disassembler::DisassembleRange (m_arch,
                                                                  NULL,
                                                                  NULL,
                                                                  exe_ctx,
                                                                  range,
                                                                  prefer_file_cache));
        
        Log *log(GetLogIfAllCategoriesSet (LIBLLDB_LOG_UNWIND));

        if (disasm_sp)
        {
            
            m_range_ptr = &range;
            m_thread_ptr = &thread;
            m_unwind_plan_ptr = &unwind_plan;

            const uint32_t addr_byte_size = m_arch.GetAddressByteSize();
            const bool show_address = true;
            const bool show_bytes = true;
            m_inst_emulator_ap->GetRegisterInfo (unwind_plan.GetRegisterKind(), 
                                                 unwind_plan.GetInitialCFARegister(), 
                                                 m_cfa_reg_info);
            
            m_fp_is_cfa = false;
            m_register_values.clear();
            m_pushed_regs.clear();

            // Initialize the CFA with a known value. In the 32 bit case
            // it will be 0x80000000, and in the 64 bit case 0x8000000000000000.
            // We use the address byte size to be safe for any future address sizes
            m_initial_sp = (1ull << ((addr_byte_size * 8) - 1));
            RegisterValue cfa_reg_value;
            cfa_reg_value.SetUInt (m_initial_sp, m_cfa_reg_info.byte_size);
            SetRegisterValue (m_cfa_reg_info, cfa_reg_value);

            const InstructionList &inst_list = disasm_sp->GetInstructionList ();
            const size_t num_instructions = inst_list.GetSize();

            if (num_instructions > 0)
            {
                Instruction *inst = inst_list.GetInstructionAtIndex (0).get();
                const addr_t base_addr = inst->GetAddress().GetFileAddress();

                // Make a copy of the current instruction Row and save it in m_curr_row
                // so we can add updates as we process the instructions.  
                UnwindPlan::RowSP last_row = unwind_plan.GetLastRow();
                UnwindPlan::Row *newrow = new UnwindPlan::Row;
                if (last_row.get())
                    *newrow = *last_row.get();
                m_curr_row.reset(newrow);

                // Once we've seen the initial prologue instructions complete, save a
                // copy of the CFI at that point into prologue_completed_row for possible
                // use later.
                int instructions_since_last_prologue_insn = 0;     // # of insns since last CFI was update

                bool reinstate_prologue_next_instruction = false;  // Next iteration, re-install the prologue row of CFI

                bool last_instruction_restored_return_addr_reg = false;  // re-install the prologue row of CFI if the next instruction is a branch immediate

                bool return_address_register_has_been_saved = false; // if we've seen the ra register get saved yet

                UnwindPlan::RowSP prologue_completed_row;          // copy of prologue row of CFI

                // cache the pc register number (in whatever register numbering this UnwindPlan uses) for
                // quick reference during instruction parsing.
                uint32_t pc_reg_num = LLDB_INVALID_REGNUM;
                RegisterInfo pc_reg_info;
                if (m_inst_emulator_ap->GetRegisterInfo (eRegisterKindGeneric, LLDB_REGNUM_GENERIC_PC, pc_reg_info))
                    pc_reg_num = pc_reg_info.kinds[unwind_plan.GetRegisterKind()];
                else
                    pc_reg_num = LLDB_INVALID_REGNUM;

                // cache the return address register number (in whatever register numbering this UnwindPlan uses) for
                // quick reference during instruction parsing.
                uint32_t ra_reg_num = LLDB_INVALID_REGNUM;
                RegisterInfo ra_reg_info;
                if (m_inst_emulator_ap->GetRegisterInfo (eRegisterKindGeneric, LLDB_REGNUM_GENERIC_RA, ra_reg_info))
                    ra_reg_num = ra_reg_info.kinds[unwind_plan.GetRegisterKind()];
                else
                    ra_reg_num = LLDB_INVALID_REGNUM;

                for (size_t idx=0; idx<num_instructions; ++idx)
                {
                    m_curr_row_modified = false;
                    m_curr_insn_restored_a_register = false;
                    inst = inst_list.GetInstructionAtIndex (idx).get();
                    if (inst)
                    {
                        if (log && log->GetVerbose ())
                        {
                            StreamString strm;
                            inst->Dump(&strm, inst_list.GetMaxOpcocdeByteSize (), show_address, show_bytes, NULL);
                            log->PutCString (strm.GetData());
                        }

                        m_inst_emulator_ap->SetInstruction (inst->GetOpcode(), 
                                                            inst->GetAddress(), 
                                                            exe_ctx.GetTargetPtr());

                        m_inst_emulator_ap->EvaluateInstruction (eEmulateInstructionOptionIgnoreConditions);

                        // Were there any changes to the CFI while evaluating this instruction?
                        if (m_curr_row_modified)
                        {
                            reinstate_prologue_next_instruction = false;
                            m_curr_row->SetOffset (inst->GetAddress().GetFileAddress() + inst->GetOpcode().GetByteSize() - base_addr);
                            // Append the new row
                            unwind_plan.AppendRow (m_curr_row);

                            // Allocate a new Row for m_curr_row, copy the current state into it
                            UnwindPlan::Row *newrow = new UnwindPlan::Row;
                            *newrow = *m_curr_row.get();
                            m_curr_row.reset(newrow);

                            // If m_curr_insn_restored_a_register == true, we're looking at an epilogue instruction.
                            // Set instructions_since_last_prologue_insn to a very high number so we don't append 
                            // any of these epilogue instructions to our prologue_complete row.
                            if (m_curr_insn_restored_a_register == false && instructions_since_last_prologue_insn < 8)
                              instructions_since_last_prologue_insn = 0;
                            else
                              instructions_since_last_prologue_insn = 99;

                            UnwindPlan::Row::RegisterLocation pc_regloc;
                            UnwindPlan::Row::RegisterLocation ra_regloc;

                            // While parsing the instructions of this function, if we've ever
                            // seen the return address register (aka lr on arm) in a non-IsSame() state,
                            // it has been saved on the stack.  If it's ever back to IsSame(), we've
                            // executed an epilogue.
                            if (ra_reg_num != LLDB_INVALID_REGNUM
                                && m_curr_row->GetRegisterInfo (ra_reg_num, ra_regloc)
                                && !ra_regloc.IsSame())
                            {
                                return_address_register_has_been_saved = true;
                            }

                            // If the caller's pc is "same", we've just executed an epilogue and we return to the caller
                            // after this instruction completes executing.
                            // If there are any instructions past this, there must have been flow control over this
                            // epilogue so we'll reinstate the original prologue setup instructions.
                            if (prologue_completed_row.get()
                                && pc_reg_num != LLDB_INVALID_REGNUM 
                                && m_curr_row->GetRegisterInfo (pc_reg_num, pc_regloc)
                                && pc_regloc.IsSame())
                            {
                                if (log && log->GetVerbose())
                                    log->Printf("UnwindAssemblyInstEmulation::GetNonCallSiteUnwindPlanFromAssembly -- pc is <same>, restore prologue instructions.");
                                reinstate_prologue_next_instruction = true;
                            }
                            else if (prologue_completed_row.get()
                                     && return_address_register_has_been_saved
                                     && ra_reg_num != LLDB_INVALID_REGNUM
                                     && m_curr_row->GetRegisterInfo (ra_reg_num, ra_regloc)
                                     && ra_regloc.IsSame())
                            {
                                if (log && log->GetVerbose())
                                    log->Printf("UnwindAssemblyInstEmulation::GetNonCallSiteUnwindPlanFromAssembly -- lr is <same>, restore prologue instruction if the next instruction is a branch immediate.");
                                last_instruction_restored_return_addr_reg = true;
                            }
                        }
                        else
                        {
                            // If the previous instruction was a return-to-caller (epilogue), and we're still executing
                            // instructions in this function, there must be a code path that jumps over that epilogue.
                            // Also detect the case where we epilogue & branch imm to another function (tail-call opt)
                            // instead of a normal pop lr-into-pc exit.
                            // Reinstate the frame setup from the prologue.
                            if (reinstate_prologue_next_instruction
                                || (m_curr_insn_is_branch_immediate && last_instruction_restored_return_addr_reg))
                            {
                                if (log && log->GetVerbose())
                                    log->Printf("UnwindAssemblyInstEmulation::GetNonCallSiteUnwindPlanFromAssembly -- Reinstating prologue instruction set");
                                UnwindPlan::Row *newrow = new UnwindPlan::Row;
                                *newrow = *prologue_completed_row.get();
                                m_curr_row.reset(newrow);
                                m_curr_row->SetOffset (inst->GetAddress().GetFileAddress() + inst->GetOpcode().GetByteSize() - base_addr);
                                unwind_plan.AppendRow(m_curr_row);

                                newrow = new UnwindPlan::Row;
                                *newrow = *m_curr_row.get();
                                m_curr_row.reset(newrow);

                                reinstate_prologue_next_instruction = false;
                                last_instruction_restored_return_addr_reg = false; 
                                m_curr_insn_is_branch_immediate = false;
                            }

                            // clear both of these if either one wasn't set
                            if (last_instruction_restored_return_addr_reg)
                            {
                                last_instruction_restored_return_addr_reg = false;
                            }
                            if (m_curr_insn_is_branch_immediate)
                            {
                                m_curr_insn_is_branch_immediate = false;
                            }
 
                            // Stop updating the prologue instructions if we've seen 8 non-prologue instructions
                            // in a row.
                            if (instructions_since_last_prologue_insn++ < 8)
                            {
                                UnwindPlan::Row *newrow = new UnwindPlan::Row;
                                *newrow = *m_curr_row.get();
                                prologue_completed_row.reset(newrow);
                                if (log && log->GetVerbose())
                                    log->Printf("UnwindAssemblyInstEmulation::GetNonCallSiteUnwindPlanFromAssembly -- saving a copy of the current row as the prologue row.");
                            }
                        }
                    }
                }
            }
            // FIXME: The DisassemblerLLVMC has a reference cycle and won't go away if it has any active instructions.
            // I'll fix that but for now, just clear the list and it will go away nicely.
            disasm_sp->GetInstructionList().Clear();
        }
        
        if (log && log->GetVerbose ())
        {
            StreamString strm;
            lldb::addr_t base_addr = range.GetBaseAddress().GetLoadAddress(thread.CalculateTarget().get());
            strm.Printf ("Resulting unwind rows for [0x%" PRIx64 " - 0x%" PRIx64 "):", base_addr, base_addr + range.GetByteSize());
            unwind_plan.Dump(strm, &thread, base_addr);
            log->PutCString (strm.GetData());
        }
        return unwind_plan.GetRowCount() > 0;
    }
    return false;
}