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[PATCH] PowerPC64: Add __private_ss field to TCB header


the TCB header on Intel contains a field __private_ss that is used
to efficiently implement the -fsplit-stack GCC feature.

In order to prepare for a possible future implementation of that
feature on powerpc64, we'd like to reserve a similar field in
the TCB header as well.  (It would be good if this went in with
or before the ELFv2 patches to ensure that this field will be
available always in the ELFv2 environment.)

The field needs to be added at the front of tcbhead_t structure
to avoid changing the ABI; see the recent discussion when adding
the EBB fields.

Tested on powerpc64-linux and powerpc64le-linux.

OK for mainline?



2013-11-12  Ulrich Weigand  <>

	* sysdeps/powerpc/tls.h (tcbhead_t): Add __private_ss field.

Index: glibc/nptl/sysdeps/powerpc/tls.h
--- glibc.orig/nptl/sysdeps/powerpc/tls.h
+++ glibc/nptl/sysdeps/powerpc/tls.h
@@ -61,6 +61,8 @@ typedef union dtv
    are private.  */
 typedef struct
+  /* GCC split stack support.  */
+  void *__private_ss;
   /* Reservation for the Event-Based Branching ABI.  */
   uintptr_t ebb_handler;
   uintptr_t ebb_ctx_pointer;
  Dr. Ulrich Weigand
  GNU/Linux compilers and toolchain

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