From: Julien Grall <jgrall@amazon.com>
There is an implicit padding of 2 bytes in struct xen_hvm_param between
the field domid and index. Make it explicit by introduce a padding
field. This can also serve as documentation.
Note that I don't think we can mandate it to be zero because a guest may
not have initialized the padding.
Signed-off-by: Julien Grall <jgrall@amazon.com>
---
xen/include/public/hvm/hvm_op.h | 1 +
1 file changed, 1 insertion(+)
diff --git a/xen/include/public/hvm/hvm_op.h b/xen/include/public/hvm/hvm_op.h
index 610e020a62..b599d3cbd0 100644
--- a/xen/include/public/hvm/hvm_op.h
+++ b/xen/include/public/hvm/hvm_op.h
@@ -32,6 +32,7 @@
#define HVMOP_get_param 1
struct xen_hvm_param {
domid_t domid; /* IN */
+ uint16_t pad;
uint32_t index; /* IN */
uint64_t value; /* IN/OUT */
};
--
2.17.1
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On 06.02.2020 16:41, Julien Grall wrote: > From: Julien Grall <jgrall@amazon.com> > > There is an implicit padding of 2 bytes in struct xen_hvm_param between > the field domid and index. Make it explicit by introduce a padding > field. This can also serve as documentation. > > Note that I don't think we can mandate it to be zero because a guest may > not have initialized the padding. Agreed - we can mandate such only at introduction, not at any later time. > Signed-off-by: Julien Grall <jgrall@amazon.com> Acked-by: Jan Beulich <jbeulich@suse.com> (I doubt this is the only missing field to make padding explicit.) Jan _______________________________________________ Xen-devel mailing list Xen-devel@lists.xenproject.org https://lists.xenproject.org/mailman/listinfo/xen-devel
Hi Jan, On 06/02/2020 15:52, Jan Beulich wrote: > On 06.02.2020 16:41, Julien Grall wrote: >> From: Julien Grall <jgrall@amazon.com> >> >> There is an implicit padding of 2 bytes in struct xen_hvm_param between >> the field domid and index. Make it explicit by introduce a padding >> field. This can also serve as documentation. >> >> Note that I don't think we can mandate it to be zero because a guest may >> not have initialized the padding. > > Agreed - we can mandate such only at introduction, not at any > later time. > >> Signed-off-by: Julien Grall <jgrall@amazon.com> > > Acked-by: Jan Beulich <jbeulich@suse.com> Thank you! > (I doubt this is the only missing field to make padding explicit.) Probably not, sadly. I stumbled accross the HVM param implicit padding while looking at liveupdating the HVM param. I guess I could use pahole to check the paddings are explicit for all the public structure. Cheers, -- Julien Grall _______________________________________________ Xen-devel mailing list Xen-devel@lists.xenproject.org https://lists.xenproject.org/mailman/listinfo/xen-devel
On Thu, Feb 06, 2020 at 03:41:18PM +0000, Julien Grall wrote: > From: Julien Grall <jgrall@amazon.com> > > There is an implicit padding of 2 bytes in struct xen_hvm_param between > the field domid and index. Make it explicit by introduce a padding > field. This can also serve as documentation. > > Note that I don't think we can mandate it to be zero because a guest may > not have initialized the padding. > > Signed-off-by: Julien Grall <jgrall@amazon.com> Acked-by: Wei Liu <wl@xen.org> _______________________________________________ Xen-devel mailing list Xen-devel@lists.xenproject.org https://lists.xenproject.org/mailman/listinfo/xen-devel
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