[PATCH] ARM: Fix kernel stack offset calculations

Various places in the ARM kernel implicitly assumed that kernel
stacks are always 8K due to hard coded constants.  Replace these
constants with definitions.

Correct the allowable range of kernel stack pointer values within
the allocation.  Arrange for the entire kernel stack to be zeroed,
not just the upper 4K if CONFIG_DEBUG_STACK_USAGE is set.

Signed-off-by: Russell King <rmk@arm.linux.org.uk>

arch/arm/kernel/head.S

@@ -19,6 +19,7 @@
 #include <asm/procinfo.h>
 #include <asm/ptrace.h>
 #include <asm/constants.h>
+#include <asm/thread_info.h>
 #include <asm/system.h>
 
 #define PROCINFO_MMUFLAGS	8
@@ -131,7 +132,7 @@ __switch_data:
 	.long	processor_id			@ r4
 	.long	__machine_arch_type		@ r5
 	.long	cr_alignment			@ r6
-	.long	init_thread_union+8192		@ sp
+	.long	init_thread_union + THREAD_START_SP @ sp
 
 /*
  * The following fragment of code is executed with the MMU on, and uses