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.

diff --git a/ChangeLog b/ChangeLog
index 4ac339664a9dd214b326ea2ffd7ddce5154eafe4..f56f9f6920a978174425956e8f906f5364b5ad7a 100644 (file)
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,7 @@
+2013-12-04  Ulrich Weigand  <Ulrich.Weigand@de.ibm.com>
+
+       * sysdeps/powerpc/tls.h (tcbhead_t): Add __private_ss field.
+
 2013-12-04  Alan Modra  <amodra@gmail.com>
 
        * elf/elf.h (R_PPC64_TLSGD, R_PPC64_TLSLD, R_PPC64_TOCSAVE): Define.

diff --git a/nptl/sysdeps/powerpc/tls.h b/nptl/sysdeps/powerpc/tls.h
index 8e0ada6bfabacd46c4b294d8f1938db089fc5e9d..c21c0271ef980942d06a5a1356ca9719bead3295 100644 (file)
--- a/nptl/sysdeps/powerpc/tls.h
+++ b/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;