[PATCH 1/2] x86_64: Use __seg_fs qualifier to cast access to TCB in THREAD_GSCOPE_RESET_FLAG()

[Uros Bizjak]

Use the __seg_fs named address space qualifier to cast access to the
gscope_flag in the TCB as a %fs: prefixed address.  This enables the
use of the "m" operand constraint, which informs the compiler about
memory access in the inline assembly.

Signed-off-by: Uros Bizjak <ubizjak@gmail.com>
Cc: H.J.Lu <hjl.tools@gmail.com>
Cc: Florian Weimer <fweimer@redhat.com>
Cc: Carlos O'Donell <carlos@redhat.com>
---
 sysdeps/x86_64/nptl/tls.h | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/sysdeps/x86_64/nptl/tls.h b/sysdeps/x86_64/nptl/tls.h
index 683f8bfdfc..cf41430050 100644
--- a/sysdeps/x86_64/nptl/tls.h
+++ b/sysdeps/x86_64/nptl/tls.h
@@ -201,9 +201,10 @@ _Static_assert (offsetof (tcbhead_t, __glibc_unused2) == 0x80,
 # define THREAD_GSCOPE_RESET_FLAG() \
   do									      \
     { int __res;							      \
-      asm volatile ("xchgl %0, %%fs:%P1"				      \
+      asm volatile ("xchgl %1, %0"					      \
 		    : "=r" (__res)					      \
-		    : "i" (offsetof (struct pthread, header.gscope_flag)),    \
+		    : "m" (*(int __seg_fs *)				      \
+			   offsetof (struct pthread, header.gscope_flag)),    \
 		      "0" (THREAD_GSCOPE_FLAG_UNUSED));			      \
       if (__res == THREAD_GSCOPE_FLAG_WAIT)				      \
 	lll_futex_wake (&THREAD_SELF->header.gscope_flag, 1, LLL_PRIVATE);    \
-- 
2.51.0