Messages in this thread | | | From | Thomas Gleixner <> | Subject | Re: [patch 08/41] x86/fpu: Restrict fpstate sanitizing to legacy components | Date | Fri, 11 Jun 2021 22:33:20 +0200 |
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On Fri, Jun 11 2021 at 12:18, Andy Lutomirski wrote: > On 6/11/21 12:03 PM, Andy Lutomirski wrote: >> On 6/11/21 9:15 AM, Thomas Gleixner wrote: >> Does this result in the mxcsr_mask and mxcsr fields being correct? >> There is a silly number of special cases there.
Let me stare at that.
> The SDM says, in a footnote in XRSTOR: > > There is an exception if RFBM[1] = 0 and RFBM[2] = 1. In this case, the > standard form of XRSTOR will load MXCSR from memory, even though MXCSR > is part of state component 1 — SSE. The compacted form of XRSTOR does > not make this exception. > > which makes me think that this code has a bug. Also, the code is > manifest nonsense for a different reason: > > if (!FP) > memset(the whole damn thing, 0); > > if (!SSE) > memset(just part of it, 0); > > which means that, if the FP bit is clear but the SSE bit is set, this > thing will clobber the SSE state. > > This code is garbage. So is the architecture that gave rise to this code.
No argument about that :)
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