Re: [Xen-devel] [PATCH] xen: only clobber multicall elements without error

[Ian Jackson <ian.jackson@xxxxxxxxxx>]

Juergen Gross writes ("Re: [PATCH] xen: only clobber multicall elements without 
error"):
> On 26/11/2018 15:54, Ian Jackson wrote:
> > Maybe they could be clobbered losslessly ?  Eg, by xoring with 0xaa or
> > something.
> 
> This would be rather hacky: I'd need to find out if clobbering was
> performed or not and the way of clobbering would be kind of an interface
> which I guess we'd like to avoid.

You can bake the precise method of clobbering into your kernel
debugging dump stuff, along with a mechanism which guesses whether
things have been clobbered, so long as you don't go utterly wrong if
your guesses are wrong.

Since after all Xen doesn't guarantee to preserve the arguments at
all, and therefore you mustn't rely on it anyway.

This seems fine for a debug dump mechanism - debug dump mechanisms are
generally best effort anyway.

Ian.

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