[PATCH 3/3] ntdll: For Mac 64-bit, poke NtCurrentTeb()->ThreadLocalStoragePointer to the corresponding offset from %gs.

[Ken Thomases]

On Jul 27, 2016, at 11:06 AM, Sebastian Lackner <sebastian at fds-team.de> wrote:
> 
> On 27.07.2016 17:42, Ken Thomases wrote:
>> 64-bit Windows apps have hard-coded accesses to %gs:0x58 baked into them.  They
>> need to find the ThreadLocalStoragePointer 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.
>> Slot 11 (offset 0x58) is currently used for the implementation of the ttyname()
>> system library function.  We do not anticipate that Wine or any of the system
>> libraries or frameworks it uses will call ttyname().  Furthermore, Apple has
>> made it so that future releases of macOS will no longer use that slot.  So, we
>> hijack it for our purposes.
>> 
>> Signed-off-by: Ken Thomases <ken at codeweavers.com>
>> ---
>> dlls/ntdll/loader.c        | 11 +++++++-
>> dlls/ntdll/signal_x86_64.c | 62 ++++++++++++++++++++++++++++++++++++++++++++++
>> 2 files changed, 72 insertions(+), 1 deletion(-)
> 
> I'm not sure if I correctly understand the purpose of this patch. If you have to
> set %gs:0x58 to some specific value, why not just use an assembly instruction for that?
> 

alloc_tls_slot() is setting ThreadLocalStoragePointer for all threads, not just the current one.

-Ken