4. Known Problems

There are some known problems with the current implementation

1. If the OpenRISC 1000 Architecture supports hardware watchpoints, GDB will use them to implement hardware breakpoints and watchpoints. GDB is not perfect in handling of watchpoints. It is possible to allocate hardware watchpoints and not discover until running that sufficient watchpoints are not available. It is also possible that GDB will report watchpoints being hit spuriously. This can be down to the assembly code having additional memory accesses that are not obviously reflected in the source code.
2. The remote JTAG connection is not robust to being interrupted, or reconnecting. If the connection is lost due to error, then you must restart GDB and the target server (for example the Or1ksim architectural simulator). Moving to the Remote Serial Protocol is intended to remedy this problem in the future.
3. The OpenRISC 1000 architecture has evolved since the port of GDB 5.3 in 2001. In particular the structure of the Unit Present register has changed and the CPU Configuration register has been added. The port of GDB version 6.8 uses the current specification of the OpenRISC 1000. This means that old clients that talk to the debugger may not work. In particular the Or1ksim Architectural simulator requires a patch to work.
4. The handling of watchpoints in the Or1ksim architectural simulator was incorrect. To work with GDB 6.8, a patch is required to fix this problem. This is combined with the patch changing the structure of the Unit Present and CPU Configuration registers.
5. The OpenRISC 1000 architecture uses its General Purpose Register (GPR) 2 as a frame pointer register. However the $fp variable in GDB is not currently implemented, and will return the value of the stack pointer (GPR 1) instead.

Reports of bugs are much welcomed. Please report problems through the OpenCORES tracker at www.opencores.org/ptracker.cgi/list/or1k.

This document was generated by Jeremy Bennett on November, 12 2008 using texi2html 1.78.