"Remote failure reply: E01" with FRDM-K64F

Hi,

I am using pyOCD (0.8.0) with a FRDM-K64F and CLion (2018.1) under macOS 10.13.3 for debugging.

I start the GDB Server via
pyocd-gdbserver -t k64f -o
and then start a remote GDB Session in CLion.
It stops at program entry and I can step through with (gdb) si
But when entering (gdb) continue I get the following error:
Remote failure reply: E01 in my GDB remote session.

In the terminal where the pyocd-gdbserver runs, is the following exception:
(It is always a ERROR:root:Unhandled exception in handleMsgwhich results in a TransferFaultError but it also occurs in different places.)

ERROR:root:Unhandled exception in handleMsg: 
Traceback (most recent call last):
  File "/Users/stefan/Development/pyocd/lib/python2.7/site-packages/pyOCD/gdbserver/gdbserver.py", line 413, in handleMsg
    return self.stopReasonQuery(), 0
  File "/Users/stefan/Development/pyocd/lib/python2.7/site-packages/pyOCD/gdbserver/gdbserver.py", line 540, in stopReasonQuery
    return self.createRSPPacket(self.target.getTResponse())
  File "/Users/stefan/Development/pyocd/lib/python2.7/site-packages/pyOCD/target/coresight_target.py", line 198, in getTResponse
    return self.selected_core.getTResponse(forceSignal)
  File "/Users/stefan/Development/pyocd/lib/python2.7/site-packages/pyOCD/coresight/cortex_m.py", line 871, in getTResponse
    response = 'T' + conversion.byteToHex2(self.getSignalValue())
  File "/Users/stefan/Development/pyocd/lib/python2.7/site-packages/pyOCD/coresight/cortex_m.py", line 885, in getSignalValue
    fault = self.readCoreRegister('xpsr') & 0xff
  File "/Users/stefan/Development/pyocd/lib/python2.7/site-packages/pyOCD/coresight/cortex_m.py", line 597, in readCoreRegister
    regValue = self.readCoreRegisterRaw(regIndex)
  File "/Users/stefan/Development/pyocd/lib/python2.7/site-packages/pyOCD/coresight/cortex_m.py", line 623, in readCoreRegisterRaw
    vals = self.readCoreRegistersRaw([reg])
  File "/Users/stefan/Development/pyocd/lib/python2.7/site-packages/pyOCD/coresight/cortex_m.py", line 666, in readCoreRegistersRaw
    dhcsr_val = dhcsr_cb()
  File "/Users/stefan/Development/pyocd/lib/python2.7/site-packages/pyOCD/coresight/cortex_m.py", line 405, in readMemoryCb
    return self.bp_manager.filter_memory(addr, transfer_size, result())
  File "/Users/stefan/Development/pyocd/lib/python2.7/site-packages/pyOCD/coresight/ap.py", line 160, in readMemCb
    res = result_cb()
  File "/Users/stefan/Development/pyocd/lib/python2.7/site-packages/pyOCD/coresight/dap.py", line 280, in readAPCb
    result = result_cb()
  File "/Users/stefan/Development/pyocd/lib/python2.7/site-packages/pyOCD/pyDAPAccess/dap_access_cmsis_dap.py", line 565, in read_reg_cb
    res = transfer.get_result()
  File "/Users/stefan/Development/pyocd/lib/python2.7/site-packages/pyOCD/pyDAPAccess/dap_access_cmsis_dap.py", line 116, in get_result
    self.daplink.flush()
  File "/Users/stefan/Development/pyocd/lib/python2.7/site-packages/pyOCD/pyDAPAccess/dap_access_cmsis_dap.py", line 500, in flush
    self._read_packet()
  File "/Users/stefan/Development/pyocd/lib/python2.7/site-packages/pyOCD/pyDAPAccess/dap_access_cmsis_dap.py", line 651, in _read_packet
    decoded_data = cmd.decode_data(raw_data)
  File "/Users/stefan/Development/pyocd/lib/python2.7/site-packages/pyOCD/pyDAPAccess/dap_access_cmsis_dap.py", line 333, in decode_data
    data = self._decode_transfer_data(data)
  File "/Users/stefan/Development/pyocd/lib/python2.7/site-packages/pyOCD/pyDAPAccess/dap_access_cmsis_dap.py", line 276, in _decode_transfer_data
    raise DAPAccessIntf.TransferFaultError()
TransferFaultError

Start by reproducing the failure with pyOCD 0.8.0, an FRDM-K64F, and the continue command, then trace the reported path through gdbserver.py, cortex_m.py, and dap_access_cmsis_dap.py. Determine where the TransferFaultError originates and define a reliable outcome for the GDB remote session when it occurs.