__tls_get_addr interface question.

[Martin Schwidefsky]

Hi,
we - that is Ulrich Weigand my myself - have started working on the
TLS support for s390/s390x. I've done a preliminary binutils patch
which seems to work. This version uses the standard IA-32 calling
convention to __tls_get_addr. Now Ulrich came up with an idea
how to improve the instruction sequences but this requires two
changes to __tls_get_addr:
1) __tls_get_addr would be called with the got offset of a tls_index
   structure located in the got instead of a pointer to the tls_index
   structure. 
2) __tls_get_addr is to return the offset to the TCB of the variable
   the tls_index refers to instead of the address.
With these two changes we could improve the code quality for
TLS accesses quite a bit.
The question now is: can we have a s390/s390x version of
__tls_get_addr with these changes without breaking anything?

blue skies,
  Martin.