ARM: 8078/1: get rid of hardcoded assumptions about kernel stack size

Changing kernel stack size on arm is not as simple as it should be:
1) THREAD_SIZE macro doesn't respect PAGE_SIZE and THREAD_SIZE_ORDER
2) stack size is hardcoded in get_thread_info macro

This patch fixes it by calculating THREAD_SIZE and thread_info address
taking into account PAGE_SIZE and THREAD_SIZE_ORDER.

Now changing stack size becomes simply changing THREAD_SIZE_ORDER.

Signed-off-by: Andrey Ryabinin <a.ryabinin@samsung.com>
Acked-by: Nicolas Pitre <nico@linaro.org>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>

arch/arm/include/asm/assembler.h

@@ -24,6 +24,8 @@
 #include <asm/domain.h>
 #include <asm/opcodes-virt.h>
 #include <asm/asm-offsets.h>
+#include <asm/page.h>
+#include <asm/thread_info.h>
 
 #define IOMEM(x)	(x)
 
@@ -179,10 +181,10 @@
  * Get current thread_info.
  */
 	.macro	get_thread_info, rd
- ARM(	mov	\rd, sp, lsr #13	)
+ ARM(	mov	\rd, sp, lsr #THREAD_SIZE_ORDER + PAGE_SHIFT	)
  THUMB(	mov	\rd, sp			)
- THUMB(	lsr	\rd, \rd, #13		)
-	mov	\rd, \rd, lsl #13
+ THUMB(	lsr	\rd, \rd, #THREAD_SIZE_ORDER + PAGE_SHIFT	)
+	mov	\rd, \rd, lsl #THREAD_SIZE_ORDER + PAGE_SHIFT
 	.endm
 
 /*

arch/arm/include/asm/thread_info.h

@@ -14,9 +14,10 @@
 
 #include <linux/compiler.h>
 #include <asm/fpstate.h>
+#include <asm/page.h>
 
 #define THREAD_SIZE_ORDER	1
-#define THREAD_SIZE		8192
+#define THREAD_SIZE		(PAGE_SIZE << THREAD_SIZE_ORDER)
 #define THREAD_START_SP		(THREAD_SIZE - 8)
 
 #ifndef __ASSEMBLY__