> From: Hansen, Dave > Sent: Tuesday, April 28, 2015 3:09 PM > To: Yu, Fenghua; H. Peter Anvin; Ingo Molnar; Thomas Gleixner; Mallick, Asit > K; Williamson, Glenn P > Cc: linux-kernel; x86 > Subject: Re: [PATCH Bugfix v2 2/4] x86/xsaves: Define and use > user_xstate_size for xstate size in signal context > > On 04/21/2015 09:51 PM, Fenghua Yu wrote: > > + /* > > + * Clear xcomp_bv[63] in user's xsave area header to indicate > > + * buf_fx is in standard format. > > + */ > > + xcomp_bv = xsave->xsave_hdr.xcomp_bv; > > + user_xsave = buf_fx; > > + xcomp_bv &= ~((u64)1 << 63); > > I ran in to another bug. xrestor_user() is hitting a #GP with these values: > > [ 6.258743] xrestore_user() tmp: ffff88003f813000 > [ 6.261122] XCR0: 000000000000001f > [ 6.261868] xstate_bv: 0000000000000003 > [ 6.262613] xcomp_bv: 000000000000001f > > I think it is because bit 63 is clear in xcomp_bv, but there are other bits > set in > there. > > I think the above needs to just do: > > /* > * We are uncompacting the state for the user buffer. We need > * to clear out the xcomp_bv field entirely. The uncompacted > * form of xsave/xrstor treats this field as reserved. > */ > if (__put_user(0, &user_xsave->xsave_hdr.xcomp_bv)) > return -1;
Yes, that makes sense. I will add this in v3 patchset. Thanks. -Fenghua -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
