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: <CALCETrWmsL2=qMxYvG=qQGmy-9ita7ne2WL-vZTR7tPPh+OtUQ@mail.gmail.com>
Date:	Sun, 18 Oct 2015 09:36:08 -0700
From:	Andy Lutomirski <luto@...capital.net>
To:	Stas Sergeev <stsp@...t.ru>
Cc:	Denys Vlasenko <dvlasenk@...hat.com>,
	Pavel Emelyanov <xemul@...allels.com>,
	Borislav Petkov <bp@...en8.de>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Cyrill Gorcunov <gorcunov@...il.com>,
	Brian Gerst <brgerst@...il.com>, X86 ML <x86@...nel.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>
Subject: Re: [RFC 3/4] x86/signal/64: Re-add support for SS in the 64-bit
 signal context

On Sun, Oct 18, 2015 at 9:29 AM, Stas Sergeev <stsp@...t.ru> wrote:
> 18.10.2015 19:12, Andy Lutomirski пишет:
>>
>> On Sun, Oct 18, 2015 at 6:36 AM, Stas Sergeev <stsp@...t.ru> wrote:
>>>
>>> 15.10.2015 00:41, Andy Lutomirski пишет:
>>>>>
>>>>> If this my
>>>>> understanding is correct and the flag is just an indication rather
>>>>> than a requested action, perhaps the name should be different,
>>>>> e.g. UC_SIG_FROM_32BIT or the like?
>>>>> Anyway, this is minor. :)
>>>>> I'll try to test the patch within a few days, thanks for you time!
>>>>
>>>> No problem.  Thanks for being willing to test!
>>>
>>> Hello Andy, I am unlucky at testing this.
>>> dosemu doesn't even start for me on the git kernels.
>>> After a half day of debugging, it seems the kernel forgets
>>> to fill in the "err" field in the sigcontext struct when
>>> page fault occurs. That confuses the dosemu's instruction
>>> decoder.
>>> Does this ring any bells?
>>
>> No, but I can reproduce it on some kernels.  Let me see if I can fix it,
>> too.
>
> Thanks!
> You should really consider adding dosemu as your test-case.
> It feels very unhappy on all recent kernels. I was getting hard
> lock-ups under different circumstances (when starting windows,
> for example). But fedora-packaged kernels are quite good, as of
> yet. I fear the problems will soon populate to them too.

I'll work on that.  It's a lot easier to have a packaged set of tests
that say yes/no, though, and it's handy when those tests are fully
open-source and easy to run (DOSEMU, in contrast, requires the
annoyingly impossible-to-compile freedos stuff iirc, and the
interesting bits need other test programs).  In any case, I'll add a
self-test for the
err thing once I figure out what's going on.

--Andy

-- 
Andy Lutomirski
AMA Capital Management, LLC
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