Re: [PATCH v4 0/4] x86: sigcontext fixes, again

From: Borislav Petkov
Date: Tue Feb 16 2016 - 05:23:35 EST


On Mon, Feb 15, 2016 at 06:38:12PM -0800, Andy Lutomirski wrote:
> This is take 2 at fixing x86 64-bit signals wrt SS. After a lot of
> thought, this is not controlled by any flags -- I would much prefer
> to avoid opt-in behavior. Instead, it just tries hard to avoid
> triggering the cases that break DOSEMU.
>
> Stas, this now seems to pass the test you sent me. It works with
> stock dosemu2 (I haven't tested classic dosemu because I can't get it
> to work regardless). It also works with a patched dosemu2 that bypasses
> the userspace trampoline:
>
> https://github.com/amluto/dosemu2/commit/571b4d08dc885b7a133e444a2ad23e0d21366206
>
> With this applied, all of the x86 selftests pass on x86_64. That
> wasn't the case before -- ldt_gdt_64 was broken.
>
> This is a bit risky, and another option would be to do nothing at
> all. Then we'd disable the problematic self-tests (sigh), and
> DOSEMU and similar tools will be stuck using gross hacks even on new
> kernels.
>
> Changes from v3:
> - Comment fixes from Borislav.
> - Improve AR_xyz comments to better match SDM. (Borislav, is this good?)

Yep, nice.

Thanks!

--
Regards/Gruss,
Boris.

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