linux-kernel - Re: [regression] x86/signal/64: Fix SS handling for signals delivered to 64-bit programs breaks dosemu

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Message-ID: <CALCETrUwpHHORR_SB_MOPdG+0Z-+SeK9ZvPb++4s+aUcChy0AQ@mail.gmail.com>
Date:	Tue, 18 Aug 2015 15:42:00 -0700
From:	Andy Lutomirski <luto@...capital.net>
To:	Stas Sergeev <stsp@...t.ru>
Cc:	Brian Gerst <brgerst@...il.com>,
	Linux kernel <linux-kernel@...r.kernel.org>
Subject: Re: [regression] x86/signal/64: Fix SS handling for signals delivered
 to 64-bit programs breaks dosemu

On Mon, Aug 17, 2015 at 11:29 PM, Stas Sergeev <stsp@...t.ru> wrote:
> 13.08.2015 20:00, Brian Gerst пишет:
>
>> On Thu, Aug 13, 2015 at 11:43 AM, Andy Lutomirski <luto@...capital.net>
>> wrote:
>>>
>>> On Thu, Aug 13, 2015 at 8:37 AM, Linus Torvalds
>>> <torvalds@...ux-foundation.org> wrote:
>>>>
>>>> On Tue, Aug 11, 2015 at 5:17 PM, Stas Sergeev <stsp@...t.ru> wrote:
>>>>>
>>>>> I realize this patch may be good to have in general, but
>>>>> breaking userspace without a single warning is a bit
>>>>> discouraging. Seems like the old "we don't break userspace"
>>>>> rule have gone.
>>>>
>>>> That rule hasn't gone anywhere.
>>>>
>>>> Does a plain revert just fix everything? Because if so, that's the
>>>> right thing to do, and we can just re-visit this later.
>>>>
>>>> I don't understand why Andy and Ingo are even discussing this. What
>>>> the f*ck, guys?
>>>>
>>> I'm trying to fix it without reverting.  If that doesn't work, then we
>>> revert.  Yesterday, I thought I had a reasonably clean fix, but it
>>> turned out that it only solved half of the problem.
>>>
>>> If we revert, I think I need to check what will break due to the
>>> revert.  I need to check at least Wine, and we'll have to do something
>>> about all the selftests that will start failing.  I also need to check
>>> CRIU, and IIRC CRIU has started using the new sigcontext SS in new
>>> versions.
>>
>> I don't think Wine will be a problem, at least how it is currently set
>> up.  16-bit support is only in the 32-bit build.  The 64-bit build
>> only supports Win64 apps, and will call the 32-bit version (installed
>> in parallel) to run 32 and 16-bit apps.
>
> Is this also because of the lack of the proper 32/16bit support in
> a 64bit kernels? If so, dosemu's work-arounds do not look like the
> too bad thing compared to that. :)

What do you mean lack of proper 32/16 bit support?

--Andy
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