[ARM] 5340/1: fix stack placement after noexecstack changes

Commit 8ec53663 ("[ARM] Improve
non-executable support") added support for detecting non-executable
stack binaries.  One of the things it does is to make READ_IMPLIES_EXEC
be set in ->personality if we are running on a CPU that doesn't support
the XN ("Execute Never") page table bit or if we are running a binary
that needs an executable stack.

This exposed a latent bug in ARM's asm/processor.h due to which we'll
end up placing the stack at a very low address, where it will bump into
the heap on any application that uses significant amount of stack or
heap or both, causing many interesting crashes.

Fix this by testing the ADDR_LIMIT_32BIT bit in ->personality instead
of testing for equality against PER_LINUX_32BIT.
Reviewed-by: NNicolas Pitre <nico@marvell.com>
Signed-off-by: NLennert Buytenhek <buytenh@marvell.com>
Signed-off-by: NRussell King <rmk+kernel@arm.linux.org.uk>

arch/arm/include/asm/processor.h

@@ -23,7 +23,7 @@
 #include <asm/types.h>
 
 #ifdef __KERNEL__
-#define STACK_TOP	((current->personality == PER_LINUX_32BIT) ? \
+#define STACK_TOP	((current->personality & ADDR_LIMIT_32BIT) ? \
 			 TASK_SIZE : TASK_SIZE_26)
 #define STACK_TOP_MAX	TASK_SIZE
 #endif