x86 vDSO: consolidate vdso32

This makes x86_64's ia32 emulation support share the sources used in the
32-bit kernel for the 32-bit vDSO and much of its setup code.

The 32-bit vDSO mapping now behaves the same on x86_64 as on native 32-bit.
The abi.syscall32 sysctl on x86_64 now takes the same values that
vm.vdso_enabled takes on the 32-bit kernel.  That is, 1 means a randomized
vDSO location, 2 means the fixed old address.  The CONFIG_COMPAT_VDSO
option is now available to make this the default setting, the same meaning
it has for the 32-bit kernel.  (This does not affect the 64-bit vDSO.)

The argument vdso32=[012] can be used on both 32-bit and 64-bit kernels to
set this paramter at boot time.  The vdso=[012] argument still does this
same thing on the 32-bit kernel.

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>
diff --git a/arch/x86/vdso/Makefile b/arch/x86/vdso/Makefile
index 1127c71..47bc276 100644
--- a/arch/x86/vdso/Makefile
+++ b/arch/x86/vdso/Makefile
@@ -15,7 +15,7 @@
 
 # files to link into kernel
 obj-$(VDSO64-y)			+= vma.o vdso.o
-obj-$(CONFIG_X86_32)		+= vdso32.o vdso32-setup.o
+obj-$(VDSO32-y)			+= vdso32.o vdso32-setup.o
 
 vobjs := $(foreach F,$(vobjs-y),$(obj)/$F)