From b367cdba0cc3e2de4237ca74f31043141deda892 Mon Sep 17 00:00:00 2001 From: Konrad Rzeszutek Wilk Date: Tue, 24 Nov 2015 02:54:45 +0000 Subject: [PATCH 3/5] netbsd/ring: Add 'barrier' to provide an compiler barrier. We need an mechanism to disable the compiler from generating to much optimization. Using the 'barrier' macro will make the compiler not optimize variables past the 'barrier' (as in, re-use the registers or only read part of a value from a memory). This is part of XSA155. Signed-off-by: Konrad Rzeszutek Wilk --- arch/xen/include/xen-public/io/ring.h | 2 ++ 1 file changed, 2 insertions(+) diff --git a/arch/xen/include/xen-public/io/ring.h b/arch/xen/include/xen-public/io/ring.h index 316bceb..5278d06 100644 --- a/arch/xen/include/xen-public/io/ring.h +++ b/arch/xen/include/xen-public/io/ring.h @@ -35,6 +35,7 @@ #define xen_mb() mb() #define xen_rmb() rmb() #define xen_wmb() wmb() +#define barrier() __asm__ __volatile__("": : :"memory") #endif #endif @@ -42,6 +43,7 @@ #define xen_mb() x86_mfence() #define xen_rmb() x86_lfence() #define xen_wmb() x86_sfence() +#define barrier() __asm__ __volatile__("": : :"memory") #endif typedef unsigned int RING_IDX; -- 2.5.2