[PATCH] ntdll: On Mac, use the Mach API as preferred approach to get a thread's GS.base.

[Ken Thomases]

The previous technique was a gross hack peeking at the internals of the pthreads
implementation.

Signed-off-by: Ken Thomases 
---
 dlls/ntdll/signal_x86_64.c | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/dlls/ntdll/signal_x86_64.c b/dlls/ntdll/signal_x86_64.c
index 5eca0432a06..e76e5be6aad 100644
--- a/dlls/ntdll/signal_x86_64.c
+++ b/dlls/ntdll/signal_x86_64.c
@@ -3204,9 +3204,18 @@ void signal_free_thread( TEB *teb )
  */
 static void *mac_thread_gsbase(void)
 {
+    struct thread_identifier_info tiinfo;
+    unsigned int info_count = THREAD_IDENTIFIER_INFO_COUNT;
     static int gsbase_offset = -1;
     void *ret;

+    kern_return_t kr = thread_info(mach_thread_self(), THREAD_IDENTIFIER_INFO, (thread_identifier_info_t) &tiinfo, &info_count);
+    if (kr == KERN_SUCCESS)
+    {
+        TRACE("pthread_self() %p thread ID %lx gsbase %lx\n", pthread_self(), tiinfo.thread_id, tiinfo.thread_handle);
+        return (void*)tiinfo.thread_handle;
+    }
+
     if (gsbase_offset < 0)
     {
         /* Search for the array of TLS slots within the pthread data structure.