linux-kernel - Re: [RFC 3/4] x86/signal/64: Re-add support for SS in the 64-bit signal context

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Message-ID: <20151014170146.GU2048@uranus>
Date:	Wed, 14 Oct 2015 20:01:46 +0300
From:	Cyrill Gorcunov <gorcunov@...il.com>
To:	Stas Sergeev <stsp@...t.ru>
Cc:	Andy Lutomirski <luto@...nel.org>, x86@...nel.org,
	linux-kernel@...r.kernel.org, Brian Gerst <brgerst@...il.com>,
	Denys Vlasenko <dvlasenk@...hat.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Borislav Petkov <bp@...en8.de>,
	Pavel Emelyanov <xemul@...allels.com>
Subject: Re: [RFC 3/4] x86/signal/64: Re-add support for SS in the 64-bit
 signal context

On Wed, Oct 14, 2015 at 07:57:02PM +0300, Stas Sergeev wrote:
...
> > correct? This should work for us. Stas, mind to refresh my memory,
> > which ss value doesmu setups here?
>
> Nothing.
> Older dosemus didn't care about touching __pad0, so
> whatever kernel saves there, is still there, even when
> dosemu needs another value.
> The problem starts to happen IIRC when dosemu invalidates
> the LDT entry that was previously saved by the kernel as an SS.
> IIRC this was causing the SIGSEGV right from sigreturn().
> It is actually a bit annoying to have such bad code in kernel
> only for the sake of the older dosemu.

I see. Thanks a huge for info!
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