Re: [PATCH] x86 page fault handler not interrupt safe

[Brian Gerst]

Nigel Gamble wrote:
> 
> On Mon, 7 May 2001, Linus Torvalds wrote:
> > On Mon, 7 May 2001, Brian Gerst wrote:
> > > This patch will still cause the user process to seg fault: The error
> > > code on the stack will not match the address in %cr2.
> >
> > You've convinced me. Good thinking. Let's do the irq thing.
> 
> I've actually seen user processes seg faulting because of this with the
> fully preemptible kernel patch applied.  The fix we used in that patch
> was to use an interrupt gate for the fault handler, then to simply
> restore the interrupt state:

Keep in mind that regs->eflags could be from user space, and could have
some undesirable flags set.  That's why I did a test/sti instead of
reloading eflags.  Plus my patch leaves interrupts disabled for the
minimum time possible.

--

                                Brian Gerst
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