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SubjectRe: [PATCH 12/23] x86, kaiser: map dynamically-allocated LDTs

* Andy Lutomirski <luto@kernel.org> wrote:

> On Tue, Oct 31, 2017 at 3:32 PM, Dave Hansen
> <dave.hansen@linux.intel.com> wrote:
> >
> > Normally, a process just has a NULL mm->context.ldt. But, we
> > have a syscall for a process to set a new one. If a process does
> > that, we need to map the new LDT.
> >
> > The original KAISER patch missed this case.
>
> Tglx suggested that we instead increase the padding at the top of the
> user address space from 4k to 64k and put the LDT there. This is a
> slight ABI break, but I'd be rather surprised if anything noticed,
> especially because the randomized vdso currently regularly lands there
> (IIRC), so any user code that explicitly uses those 60k already
> collides with the vdso.
>
> I can make this happen.

Yes, let's try that.

Thanks,

Ingo

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