[ARM] 5196/1: fix inline asm constraints for preload

With gcc 4.3 and later, a pointer that has already been dereferenced is
assumed not to be null since it should have caused a segmentation fault
otherwise, hence any subsequent test against NULL is optimized away.

Current inline asm constraint used in the implementation of prefetch()
makes gcc believe that the pointer is dereferenced even though the PLD
instruction does not load any data and does not cause a segmentation
fault on null pointers, which causes all sorts of interesting results
when reaching the end of a linked lists for example.

Let's use a better constraint to properly represent the actual usage of
the pointer value.

Problem reported by Chris Steel.

Signed-off-by: Nicolas Pitre <nico@marvell.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>

diff --git a/arch/arm/include/asm/processor.h b/arch/arm/include/asm/processor.h
index b01d5e7e3d5abb4a5632c1b677764310c81db243..517a4d6ffc74b791691a3a2f65099bb6352e5e64 100644 (file)
--- a/arch/arm/include/asm/processor.h
+++ b/arch/arm/include/asm/processor.h
@@ -112,9 +112,9 @@ extern int kernel_thread(int (*fn)(void *), void *arg, unsigned long flags);
 static inline void prefetch(const void *ptr)
 {
        __asm__ __volatile__(
-               "pld\t%0"
+               "pld\t%a0"
                :
-               : "o" (*(char *)ptr)
+               : "p" (ptr)
                : "cc");
 }