Summary of GDB with OpenRISC 1000

GDB is described well in its user manual, “Debugging with GDB: The GNU Source-Level Debugger”.

This manual describes how to use GDB to debug C programs cross compiled for and running on processors using the OpenRISC 1000 architecture. In general GDB does not run on the actual target, but on a separate host processor. It communicates with the target via the GDB Remote Serial Protocol (RSP).

For backwards compatibility, GDB for OpenRISC also supports the legacy custom remote protocol, which drives the JTAG interface on the OpenRISC 1000. This is provided by adding a special target, “jtag” to GDB, allowing the debugger to connect via the JTAG interface. See section Connecting to the Target.

In addition the info command is extended to allow inspection of OpenRISC 1000 Special Purpose registers, and a new command “spr” is added to set the value of a Special Purpose Register. See section OpenRISC 1000 Specific Commands.

All the normal GDB commands should work, although hardware watchpoints are not tested at present. The info registers command will show the 32 general purpose registers, while the info registers all command will add the program counter, supervision register and exception program counter register.

For those who like their debugging graphical, the gdbtui command is available (typically as or32-uclinux-gdbtui). GDB for OpenRISC 1000 can also be run under ddd as follows:

ddd --debugger=or32-uclinux-gdb --gdb

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Contributors to GDB for the OpenRISC 1000

The pantheon of contributors to GDB over the years is recorded in the main user manual, `Debugging with GDB: The GNU Source-Level Debugger”.

There is no official history of contributors to the OpenRISC 1000 version. However the current author believes the original GDB 5.0 and 5.3 ports were the work of:

Ivan Guzvinec and Johan Rydverg at OpenCores, who wrote the Binary File Descriptor library;
Alessandro Forin at Carnegie-Mellon University and Per Bothner at the University of Wisconsin who wrote the main GDB interface; and
Mark Mlinar at Cygnus Support and Chris Ziomkowski at ASICS.ws,who wrote the OpenRISC JTAG interface.

The port to GDB 6.8 is the work of Jeremy Bennett of Embecosm Limited (jeremy.bennett@embecosm.com).