Followup to: <20020418183639.20946.qmail@science.horizon.com>
By author: linux@horizon.com
In newsgroup: linux.dev.kernel
>
> Um, people here seem to be assuming that, in the absence of MMX,
> fninit *doesn't* leak information.
>
> I thought it was well-known to just clear (set to all-ones) the
> tag register and not alter the actual floating-point registers.
>
> Thus, it seems quite feasible to reset the tag word with FLDENV and
> store out the FPU registers, even on an 80387.
>
> Isn't this the same security hole? Shouldn't there be 8 FLDZ instructions
> (or equivalent) in the processor state initialization?
>
Perhaps the right thing to do is to have a description in data of the
desired initialization state and just F[NX]RSTOR it?
-hpa
-- <hpa@transmeta.com> at work, <hpa@zytor.com> in private! "Unix gives you enough rope to shoot yourself in the foot." http://www.zytor.com/~hpa/puzzle.txt <amsp@zytor.com> - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
This archive was generated by hypermail 2b29 : Tue Apr 23 2002 - 22:00:22 EST