MIPS stub problem

Michael Snyder msnyder@vmware.com
Tue Sep 16 18:35:00 GMT 2008

Qiu Feng wrote:
> Hi all,
> I am implementing a stub for mips. I found epc always contains the position
> of next instuction after the inserted "break", I wonder if PC client gdb
> will take it into acount? Should I manually rollback the epc to the location
> of replaced original instruction?

Hmmm.  I'm rusty here, but I don't think that's the norm
for MIPS.  What exact mips part is this?

There are two classes of processors -- those which point
to the trap instruction itself after taking a trap, and those
that point to the next instruction following the trap insn.

GDB accounts for this difference with a configuration variable
called DECR_PC_AFTER_BREAK ("decrement the PC after a breakpoint").
It's true for i386, for instance, but not normally for mips.

> Another question, does pc side GDB only read local varibles by offset of SP
> (should be $29)?

Again, my MIPS foo is rusty, but its likely that gdb may
also read local variables by offset from a frame pointer reg.

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