[RFA] gdbserver fetch/store registers problem on s390x

[Ulrich Weigand]

Hi Daniel,

> When you access the acrs, it looks like we are actually peeking/poking
> two of them at once.  I didn't see any sign of the "rest must be
> zeroed" you mentioned.  Is this in code not currently contributed to
> kernel.org?

OK, this only applies to the FPC register.  For the ACRs we're indeed
always transferring two at the same time, except when trying to read
the last one (%a15), in which case we get zeros in the low word on
peeking, and on poking the low word is ignored.

> In the current code the ACR we want to be poking at is the
> low-memory-address end of the buffer, i.e. leftmost in a big endian
> system (which all supported s390 appears to be).  Is that right?

Yes, that's correct.

> This is unfortunate... it means I need another target knob, since the
> PPC64 FPSCR is definitively in the rightmost 32 bits of the ptrace
> xfer.

Hmm ...


Mit freundlichen Gruessen / Best Regards

Ulrich Weigand

--
  Dr. Ulrich Weigand
  Linux for S/390 Design & Development
  IBM Deutschland Entwicklung GmbH, Schoenaicher Str. 220, 71032 Boeblingen
  Phone: +49-7031/16-3727   ---   Email: Ulrich.Weigand@de.ibm.com