Re: [PATCH] linux-2.5.43_vsyscall_A0

Pavel Machek
2002-10-26T10:26:49Z

Hi!

> > > Since no one really brought up any issues with the code itself
> > > (correct me if I'm wrong), here is the i386 vsyscall gettimeofday port
> > > I sent last night, synced up and ready for integration.
> >
> > This vsyscall implementation breaks UML. Any app that's run inside UML
> > that uses vsyscalls will get the host's vsyscalls rather than the UML
> > vsyscalls.
>
> Ugh.
>
> Guess you'll have some problems then with UML on x86-64, which always uses
> vgettimeofday. But it's only used for gettimeofday() currently, perhaps it's
> not that bad when the UML child runs with the host's time.

Well, if you want to use UML for time shifting (pretty common use,
AFAICS)...

> I guess it would be possible to add some support for UML
> to map own code over the vsyscall reserved locations. UML would need
> to use the syscalls then. But it'll be likely ugly.

I guess this is the right solution. [Or UML could simply unmap that
area and handle the faults...].
Pavel
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