[PATCH 1/3] ntdll: For Mac 64-bit, poke the TEB address to %gs:0x30 and re-enable the inlining of NtCurrentTeb().

[Sebastian Lackner]

On 27.07.2016 17:42, Ken Thomases wrote:
> 64-bit Windows apps have hard-coded accesses to %gs:0x30 baked into them.  They
> need to find the TEB self pointer there.
> 
> Technically, the gsbase register and the memory it points to belong to the
> pthread implementation on macOS.  It's used for the pthread TLS implementation.
> However, study of the sources and experimentation reveal that TLS slot 6
> (offset 0x30) is not currently used.  Furthermore, Apple has promised to not
> use that slot in the future.  So, we hijack it for our purposes.
> 
> This removes the implementation of NtCurrentTeb() based on pthread_key_create()
> and pthread_set/getspecific().
> 
> Signed-off-by: Ken Thomases <ken at codeweavers.com>
> ---
>  dlls/ntdll/ntdll.spec      |  2 +-
>  dlls/ntdll/signal_x86_64.c | 34 +++-------------------------------
>  include/winnt.h            |  2 +-
>  3 files changed, 5 insertions(+), 33 deletions(-)

Nice to hear that Apple agreed to keep that slot reserved. Would it make sense to
keep the NtCurrentTeb export neverthless, for compatibility with libraries compiled
against old Wine?