[PATCH] [Fwd: RE: [Xen-ia64-devel] stack corruption creating idle domain]

[Alex Williamson <alex.williamson@xxxxxx>]

Dan,

   I'd like to see this patch from last week make it in before we forget
about it.  It's a compiler timebomb waiting to go off.  To see it on
gcc-3.4, run ski, set a break point at alloc_vcpu_struct, set the data
window to the address in r12 (sp), step over the second memset and note
that the stack has been cleared.  If we were using the stack (as I was
w/ gcc-3.3) we'd be in trouble.  Thanks,

        Alex

-------- Forwarded Message --------
From: Alex Williamson <alex.williamson@xxxxxx>
To: Tian, Kevin <kevin.tian@xxxxxxxxx>
Cc: xen-ia64-devel@xxxxxxxxxxxxxxxxxxx
Subject: RE: [Xen-ia64-devel] stack corruption creating idle domain
Date: Wed, 25 Jan 2006 10:36:49 -0700

On Wed, 2006-01-25 at 11:04 +0800, Tian, Kevin wrote:
> 
> Make sense and thanks for info. We shouldn't manipulate switch stack
> area for current running vcpu, since that area only makes sense when
> specific vcpu is de-activated. The initial stack of idle vcpu0 starts
> from point under pt_regs, and thus above memset definitely corrupts
> active stack frames. Could you try whether following change working
> for you?

Kevin,

   Yes, that seems to fix the problem, or at least avoid it.
xen-unstable.hg looks to be a bit out of date with xen-ia64-unstable.hg
in this area.  I think the patch below is effectively the same change
versus xen-unstable.hg.  Thanks,

        Alex


Signed-off-by: Alex Williamson <alex.williamson@xxxxxx>
---

diff -r aad2b2da3c8b xen/arch/ia64/xen/domain.c
--- a/xen/arch/ia64/xen/domain.c        Wed Jan 25 11:51:21 2006
+++ b/xen/arch/ia64/xen/domain.c        Wed Jan 25 04:22:50 2006
@@ -157,14 +157,14 @@
            if ((v = alloc_xenheap_pages(KERNEL_STACK_SIZE_ORDER)) == NULL)
                return NULL;
            memset(v, 0, sizeof(*v)); 
-       }
-
-       ti = alloc_thread_info(v);
-       /* Clear thread_info to clear some important fields, like
-        * preempt_count
-        */
-       memset(ti, 0, sizeof(struct thread_info));
-       init_switch_stack(v);
+
+           ti = alloc_thread_info(v);
+           /* Clear thread_info to clear some important fields, like
+            * preempt_count
+            */
+           memset(ti, 0, sizeof(struct thread_info));
+           init_switch_stack(v);
+       }
 
        if (!is_idle_domain(d)) {
            v->arch.privregs = 



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-- 
Alex Williamson                             HP Linux & Open Source Lab


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