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Re: [RFA 5/8] New port: TI C6x: gdb port

On Thu, 4 Aug 2011, Pedro Alves wrote:

> > Won't GDB need a list of how the register names correspond to DWARF 
> > register numbers (which are allocated for all these registers) somewhere?
> AFAICS, gdbserver only exposes A0-A15, CSR, PC, A16-A31
> B16-B31, TSR, ILC, RILC, so I assumed all other registers would be
> system dependent non general purpose control registers, but it's
> probably then that they are only not "user space" registers, and will
> be acessible by bare metal probes/stubs?  Linux programs won't access
> those, right?  I now browsed the ABI's dwarf section and I got that
> impression.

I expect most of them are bare metal only - and I don't suppose they are 
particularly likely to appear in debug info either, but GDB may as well 
know the numbers since they are assigned.

Some of the others *can* however be read/written from userspace (the 
documentation of the MVC instruction gives details, for the documented 
control registers).  (The default in the ABI is for control registers to 
be caller-save.)

Looking at the list of control registers, I'd think that at least AMR, 
GFPGFR, GPLYA, GPLYB, FADCR, FAUCR, FMCR, SSR are plausibly relevant to 
userspace - userspace code using inline assembly or intrinsics, anyway - 
and ought to be available from gdbserver (which might of course require 
kernel changes to expose them to ptrace).

Joseph S. Myers

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