Qing Zhao <qing.z...@oracle.com> writes: >> On Sep 22, 2020, at 1:35 PM, H.J. Lu <hjl.to...@gmail.com> wrote: >> On Tue, Sep 22, 2020 at 11:25 AM Qing Zhao <qing.z...@oracle.com >> <mailto:qing.z...@oracle.com>> wrote: >>>> On Sep 22, 2020, at 11:31 AM, Richard Sandiford >>>> <richard.sandif...@arm.com> wrote: >>>> Taking each in turn: what is the reason for not clearing mask registers? >>>> And what is the reason for not clearing mm0-7? In each case, is it a >>>> performance or a correctness issue? >>> >>> Could you please provide more information on the above questions? (Why we >>> exclude mask registers and mm0-7 registers from ALL on x86?) >>> >> >> No particular reason. You can add them. > > Okay, thanks. > > Then I guess that the reason we didn’t zero mask registers and mm0-7 > registers on x86 is mainly for the performance consideration. > There might not be too much benefit for mitigating ROP attack if we zero > these additional registers, but we will got much more performance overhead. > > What’s you opinion, Richard?
Dropping them is fine with me FWIW. That seems like a natural use for the new hook: drop zeroing that isn't actively wrong, but isn't likely to be useful either. Thanks, Richard
