x86 vDSO: reorder vdso32 code

This reorders the code in the 32-bit vDSO images to put the signal
trampolines first and __kernel_vsyscall after them.  The order does
not matter to userland, it just uses what AT_SYSINFO or e_entry
says.  Since the signal trampolines are the same size in both
versions of the vDSO, putting them first is the simplest way to get
the addresses to line up.  This makes it work to use a more compact
layout for the vDSO.

Signed-off-by: Roland McGrath <roland@redhat.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

1 files changed, 11 insertions, 10 deletions

diff --git a/arch/x86/vdso/vdso32/sysenter.S b/arch/x86/vdso/vdso32/sysenter.S
index 109bfa394eaa..902d5fc11f1b 100644
--- a/arch/x86/vdso/vdso32/sysenter.S
+++ b/arch/x86/vdso/vdso32/sysenter.S
@@ -1,11 +1,10 @@
 /*
- * Code for the vsyscall page.  This version uses the sysenter instruction.
+ * Code for the vDSO.  This version uses the sysenter instruction.
  *
- * NOTE:
- * 1) __kernel_vsyscall _must_ be first in this page.
- * 2) there are alignment constraints on this stub, see vsyscall-sigreturn.S
- *    for details.
+ * First get the common code for the sigreturn entry points.
+ * This must come first.
  */
+#include "sigreturn.S"
 
 /*
  * The caller puts arg2 in %ecx, which gets pushed. The kernel will use
@@ -23,11 +22,12 @@
  * arg6 from the stack.
  *
  * You can not use this vsyscall for the clone() syscall because the
- * three dwords on the parent stack do not get copied to the child.
+ * three words on the parent stack do not get copied to the child.
  */
         .text
         .globl __kernel_vsyscall
         .type __kernel_vsyscall,@function
+        ALIGN
 __kernel_vsyscall:
 .LSTART_vsyscall:
         push %ecx
@@ -115,7 +115,8 @@ VDSO32_SYSENTER_RETURN:	/* Symbol used by sysenter.c via vdso32-syms.h */
 .LENDFDEDLSI:
         .previous
 
-/*
- * Get the common code for the sigreturn entry points.
- */
-#include "sigreturn.S"
+        /*
+         * Emit a symbol with the size of this .eh_frame data,
+         * to verify it matches the other versions.
+         */
+VDSO32_vsyscall_eh_frame_size = (.LENDFDEDLSI-.LSTARTFRAMEDLSI)