[PATCH] PPC linuxthreads tls.h fix

[Roland McGrath]

> Sure, I realize Paul is talking about the words after the DTV pointer.
> And our thread register _doesn't_ point to the TCB, rather to the end
> of TCB + 0x7000.  Which is why the TCB size and contents are entirely
> a glibc issue for powerpc.

Ah, right!  The glibc code uses the names TLS_DTV_AT_TP (variant I) and
TLS_TCB_AT_TP (variant II), matching the two layout styles described in the
original TLS document.  PowerPC (and Alpha if it changes to be similar)
actually use a third form that is like TLS_DTV_AT_TP in that positive
offsets are used and that TLS blocks immediately follow the TCB, but due to
the TP bias is like TLS_TCB_AT_TP in that the TCB layout is private to the
implementation and its size does not affect static TLS block offsets.