[PATCH] x86_64: Pass -32 to the assembler when compiling the 32bit vsyscall pages

This quietens warnings and actually fixes a bug.  The unwind tables would
come out wrong without -32, causing pthread cancellation during them to
crash in the gcc runtime.

The problem seems to only happen with newer binutils (it doesn't happen
with 2.16.91.0.2 but happens wit 2.16.91.0.5)

Thanks to David Altobelli <david.altobelli@hp.com> and Brian Baker
<Brian.B@hp.com> for test case and initial analysis.
Signed-off-by: NAndi Kleen <ak@suse.de>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

arch/x86_64/ia32/Makefile

@@ -27,5 +27,5 @@ $(obj)/vsyscall-sysenter.so $(obj)/vsyscall-syscall.so: \
 $(obj)/vsyscall-%.so: $(src)/vsyscall.lds $(obj)/vsyscall-%.o FORCE
 	$(call if_changed,syscall)
 
-AFLAGS_vsyscall-sysenter.o = -m32
-AFLAGS_vsyscall-syscall.o = -m32
+AFLAGS_vsyscall-sysenter.o = -m32 -Wa,-32
+AFLAGS_vsyscall-syscall.o = -m32 -Wa,-32