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

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Date:	Sun, 18 Oct 2015 19:43:48 +0300
From:	Stas Sergeev <stsp@...t.ru>
To:	Andy Lutomirski <luto@...capital.net>
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

18.10.2015 19:36, Andy Lutomirski пишет:
> 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.
I meant just a local test-case on your PC. :)
It can't be a part of an automated test-suit of course.
But after changing anything in vm86 or signal handling,
running dosemu will never hurt, as it is probably the
most rigorous test-case for them. I deduce that based
on its breakage frequency with the kernel updates.
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