[PATCH] Fix CONFIG_COMPAT_VDSO

I wouldn't mind if CONFIG_COMPAT_VDSO went away entirely.  But if it's there,
it should work properly.  Currently it's quite haphazard: both real vma and
fixmap are mapped, both are put in the two different AT_* slots, sysenter
returns to the vma address rather than the fixmap address, and core dumps yet
are another story.

This patch makes CONFIG_COMPAT_VDSO disable the real vma and use the fixmap
area consistently.  This makes it actually compatible with what the old vdso
implementation did.

Signed-off-by: Roland McGrath <roland@redhat.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Andi Kleen <ak@suse.de>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 4 insertions, 0 deletions

diff --git a/arch/i386/kernel/entry.S b/arch/i386/kernel/entry.S
index 06461b8b715d..5e47683fc63a 100644
--- a/arch/i386/kernel/entry.S
+++ b/arch/i386/kernel/entry.S
@@ -302,12 +302,16 @@ sysenter_past_esp:
         pushl $(__USER_CS)
         CFI_ADJUST_CFA_OFFSET 4
         /*CFI_REL_OFFSET cs, 0*/
+#ifndef CONFIG_COMPAT_VDSO
         /*
          * Push current_thread_info()->sysenter_return to the stack.
          * A tiny bit of offset fixup is necessary - 4*4 means the 4 words
          * pushed above; +8 corresponds to copy_thread's esp0 setting.
          */
         pushl (TI_sysenter_return-THREAD_SIZE+8+4*4)(%esp)
+#else
+        pushl $SYSENTER_RETURN
+#endif
         CFI_ADJUST_CFA_OFFSET 4
         CFI_REL_OFFSET eip, 0