Messages in this thread | | | Date | Sat, 10 Feb 2001 10:09:41 +0100 | From | Manfred Spraul <> | Subject | Re: [beta patch] SSE copy_page() / clear_page() |
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Doug Ledford wrote: > > > I have this strong suspicion that your kernel will lock up in a bad way > > of you have somebody do something like divide by zero without actually > > touching a single FP instruction after the divide (so that the error has > > happened, but has not yet been raised as an exception). > > Or much worse, let the kernel mix-and-match SSE and MMX optimized routines > without doing full saves of the FPU on SSE routines, which leads to FPU saves > in MMX routines with kernel data in the SSE registers, which then shows up > when the app touches those SSE registers and you get use space corruption. My > code to handle this type of situation was *very* complex, and I don't think I > ever got it quite perfectly right without simply imposing a rule that the > kernel could never use both SSE and MMX instructions on the same CPU. >
I don't see that problem: * sse_{copy,clear}_page() restore the sse registers before returning. * the fpu saves into current->thread.i387.f{,x}save never happen from interrupts.
How can kernel sse values end up in user space? I'm sure I overlook something, but what?
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