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Date: Tue, 16 Feb 2016 11:23:28 +0100
From: Borislav Petkov <bp@alien8.de>
To: Andy Lutomirski <luto@kernel.org>
Cc: x86@kernel.org, Denys Vlasenko <dvlasenk@redhat.com>,
        Stas Sergeev <stsp@list.ru>, Cyrill Gorcunov <gorcunov@gmail.com>,
        Pavel Emelyanov <xemul@parallels.com>, Brian Gerst <brgerst@gmail.com>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        Linus Torvalds <torvalds@linux-foundation.org>,
        Oleg Nesterov <oleg@redhat.com>
Subject: Re: [PATCH v4 0/4] x86: sigcontext fixes, again
Message-ID: <20160216102328.GB3902@pd.tnic>
References: <cover.1455589976.git.luto@kernel.org>
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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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