On 05.05.2020 13:06, Hongyan Xia wrote:
> --- a/xen/arch/x86/traps.c
> +++ b/xen/arch/x86/traps.c
> @@ -300,6 +300,7 @@ static void show_guest_stack(struct vcpu *v, const struct
> cpu_user_regs *regs)
> int i;
> unsigned long *stack, addr;
> unsigned long mask = STACK_SIZE;
> + void *stack_page = NULL;
>
> /* Avoid HVM as we don't know what the stack looks like. */
> if ( is_hvm_vcpu(v) )
> @@ -328,7 +329,7 @@ static void show_guest_stack(struct vcpu *v, const struct
> cpu_user_regs *regs)
> vcpu = maddr_get_owner(read_cr3()) == v->domain ? v : NULL;
> if ( !vcpu )
> {
> - stack = do_page_walk(v, (unsigned long)stack);
> + stack_page = stack = do_page_walk(v, (unsigned long)stack);
> if ( (unsigned long)stack < PAGE_SIZE )
> {
> printk("Inaccessible guest memory.\n");
> @@ -358,7 +359,7 @@ static void show_guest_stack(struct vcpu *v, const struct
> cpu_user_regs *regs)
> if ( mask == PAGE_SIZE )
> {
> BUILD_BUG_ON(PAGE_SIZE == STACK_SIZE);
> - unmap_domain_page(stack);
> + unmap_domain_page(stack_page);
> }
With this I think you want to change the whole construct here to
if ( stack_page )
unmap_domain_page(stack_page);
i.e. with the then no longer relevant BUILD_BUG_ON() also dropped.
What's more important though - please also fix the same issue in
compat_show_guest_stack(). Unless I'm mistaken of course, in which
case it would be nice if the description could mention why the
other similar function isn't affected.
Jan
