Re: [Xen-devel] [PATCH 4/6] x86/boot: Clean up l?_bootmap[] construction

[Jan Beulich <jbeulich@xxxxxxxx>]

On 08.01.2020 17:15, Andrew Cooper wrote:
> On 08/01/2020 11:38, Jan Beulich wrote:
>> As said - I'm going to try to not stand in the way of you re-
>> arranging this, but
>> - the new code should not break silently when (in particular)
>>   l2_bootmap[] changes
> 
> What practical changes do you think could be done here?  I can't spot
> any which would be helpful.
> 
> A BUILD_BUG_ON() doesn't work.  The most likely case for something going
> wrong here is an edit to x86_64.S and no equivalent edit to page.h,
> which a BUILD_BUG_ON() wouldn't spot.  head.S similarly has no useful
> protections which could be added.

Well, the fundamental assumption is that the .S files and the
C declaration of l?_bootmap[] are kept in sync. No BUILD_BUG_ON()
can cover a mistake made there. But rather than using the literal
4 as you did, an ARRAY_SIZE() construct should be usable to either
replace it, or amend it with a BUILD_BUG_ON().

Jan

_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxxxxxxxxx
https://lists.xenproject.org/mailman/listinfo/xen-devel