arch: personality independent stack top

New arch macro STACK_TOP_MAX it gives the larges valid stack address for the
architecture in question.

It differs from STACK_TOP in that it will not distinguish between
personalities but will always return the largest possible address.

This is used to create the initial stack on execve, which we will move down to
the proper location once the binfmt code has figured out where that is.

Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Ollie Wild <aaw@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/include/asm-ia64/ustack.h b/include/asm-ia64/ustack.h
index a349467..504167c 100644
--- a/include/asm-ia64/ustack.h
+++ b/include/asm-ia64/ustack.h
@@ -11,6 +11,7 @@
 /* The absolute hard limit for stack size is 1/2 of the mappable space in the region */
 #define MAX_USER_STACK_SIZE	(RGN_MAP_LIMIT/2)
 #define STACK_TOP		(0x6000000000000000UL + RGN_MAP_LIMIT)
+#define STACK_TOP_MAX		STACK_TOP
 #endif
 
 /* Make a default stack size of 2GiB */