xen: arm: correct use of find_next_bit

find_next_bit takes a "const unsigned long *" but forcing a cast of an
"uint32_t *" throws away the alignment constraints and ends up causing an
alignment fault on arm64 if the input happened to be 4 but not 8 byte aligned.

Instead of casting use a temporary variable of the right type.

I've had a look around for similar constructs and the only thing I found was
maintenance_interrupt which cases a uint64_t down to an unsigned long, which
although perhaps not best advised is safe I think.

This was observed with the AArch64 Linaro toolchain 2013.12 but I think that
is just coincidental due to subtle changes to the stack layout etc.

Reported-by: Fu Wei <fu.wei@linaro.org>
Signed-off-by: Ian Campbell <ian.campbell@citrix.com>
Acked-by: Julien Grall <julien.grall@linaro.org>

diff --git a/xen/arch/arm/vgic.c b/xen/arch/arm/vgic.c
index 90e97074eec36e163d11f3a38aabf69ced103e06..553411d3e178c5aca60254ff0e3eb784781d4864 100644 (file)
--- a/xen/arch/arm/vgic.c
+++ b/xen/arch/arm/vgic.c
@@ -362,11 +362,12 @@ read_as_zero:
 
 static void vgic_disable_irqs(struct vcpu *v, uint32_t r, int n)
 {
+    const unsigned long mask = r;
     struct pending_irq *p;
     unsigned int irq;
     int i = 0;
 
-    while ( (i = find_next_bit((const long unsigned int *) &r, 32, i)) < 32 ) {
+    while ( (i = find_next_bit(&mask, 32, i)) < 32 ) {
         irq = i + (32 * n);
         p = irq_to_pending(v, irq);
         clear_bit(GIC_IRQ_GUEST_ENABLED, &p->status);
@@ -379,11 +380,12 @@ static void vgic_disable_irqs(struct vcpu *v, uint32_t r, int n)
 
 static void vgic_enable_irqs(struct vcpu *v, uint32_t r, int n)
 {
+    const unsigned long mask = r;
     struct pending_irq *p;
     unsigned int irq;
     int i = 0;
 
-    while ( (i = find_next_bit((const long unsigned int *) &r, 32, i)) < 32 ) {
+    while ( (i = find_next_bit(&mask, 32, i)) < 32 ) {
         irq = i + (32 * n);
         p = irq_to_pending(v, irq);
         set_bit(GIC_IRQ_GUEST_ENABLED, &p->status);