Howto: GDB Remote Serial Protocol

Writing a RSP Server

Embecosm Application Note EAN 4
Issue 2, November 2008.

This application note is aimed at engineers writing a GDB Remote Serial Protocol Server for the first time.

The GNU Debugger software distribution includes a User Guide which documents the GDB Remote Serial Protocol for communicating with remote targets. The distribution also includes "stub" code for use by those implementing their own RSP server.

However, the stub code has not been modified for several years, and is now out of step with the GDB code base. The User Guide provides a valuable reference to the protocol, it does not provide the "big picture" and in the absence of up to date stub code can provide little help to the implementer of a RSP server for a new target.

This application note provides practical advice to supplement the GDB User Guide for engineers writing a GDB RSP server. It is based on the author's experience implementing the first RSP server to support GDB 6.8 on the OpenRISC 1000 architecture, and includes practical examples from that work.

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This application note is licensed under a Creative Commons Attribution 2.0 License.

The GDB Remote Serial Interface described in this application note is supported by the latest version of Or1ksim, the OpenRISC 1000 architectural simulator, and GDB 6.8 for the OpenRISC 1000. Or1ksim is available free and open source from www.opencores.org. The OpenRISC 1000 version of GDB 6.8 is provided as a code patch to the standard GDB 6.8 source. It is available as a free download in Embecosm Software Package ESP 3, GDB 6.8 for the OpenRISC 1000 Tool Chain.