From: Nicolas Pitre Date: Tue, 12 Aug 2008 21:10:59 +0000 (+0100) Subject: [ARM] 5196/1: fix inline asm constraints for preload X-Git-Tag: v2.6.27-rc4~54^2~7 X-Git-Url: https://err.no/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=16f719de62809e224e37c320760c3ce59098d862;p=linux-2.6 [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 Signed-off-by: Russell King --- diff --git a/arch/arm/include/asm/processor.h b/arch/arm/include/asm/processor.h index b01d5e7e3d..517a4d6ffc 100644 --- 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"); }