uml: fix stub address calculations

The calculation of CONFIG_STUB_CODE and CONFIG_STUB_DATA didn't take into
account anything but 3G/1G and 2G/2G, leaving the other vmsplits out in the
cold.

I'd rather not duplicate the four known host vmsplit cases for each of these
symbols.  I'd also like to calculate them based on the highest userspace
address.

The Kconfig language seems not to allow calculation of hex constants, so I
moved this to as-layout.h.  CONFIG_STUB_CODE, CONFIG_STUB_DATA, and
CONFIG_STUB_START are now gone.  In their place are STUB_CODE, STUB_DATA, and
STUB_START in as-layout.h.

i386 and x86_64 seem to differ as to whether an unadorned constant is an int
or a long, so I cast them to unsigned long so they can be printed
consistently.  However, they are also used in stub.S, where C types don't work
so well.  So, there are ASM_ versions of these constants for use in stub.S.  I
also ifdef-ed the non-asm-friendly portion of as-layout.h.

With this in place, most of the rest of this patch is changing CONFIG_STUB_*
to STUB_*, except in stub.S, where they are changed to ASM_STUB_*.

defconfig has the old symbols deleted.

I also print these addresses out in case there is any problem mapping them on
the host.

The two stub.S files had some trailing whitespace, so that is cleaned up here.

[akpm@linux-foundation.org: coding-style fixes]
Signed-off-by: Jeff Dike <jdike@linux.intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/arch/um/Kconfig.x86_64 b/arch/um/Kconfig.x86_64
index f60e9e5..d632e9a 100644
--- a/arch/um/Kconfig.x86_64
+++ b/arch/um/Kconfig.x86_64
@@ -17,24 +17,12 @@
 
 config TOP_ADDR
  	hex
-	default 0x80000000
+	default 0x7fc0000000
 
 config 3_LEVEL_PGTABLES
        bool
        default y
 
-config STUB_CODE
-	hex
-	default 0x7fbfffe000
-
-config STUB_DATA
-	hex
-	default 0x7fbffff000
-
-config STUB_START
-	hex
-	default STUB_CODE
-
 config ARCH_HAS_SC_SIGNALS
 	bool
 	default n