linux-kernel - Re: situation with signals

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Message-ID: <4CC89352.7020808@tilera.com>
Date:	Wed, 27 Oct 2010 17:02:10 -0400
From:	Chris Metcalf <cmetcalf@...era.com>
To:	Arnd Bergmann <arnd@...db.de>
CC:	Al Viro <viro@...iv.linux.org.uk>, <linux-arch@...r.kernel.org>,
	<linux-kernel@...r.kernel.org>
Subject: Re: situation with signals

On 9/24/2010 9:33 AM, Arnd Bergmann wrote:
> On Friday 24 September 2010, Al Viro wrote:
>>         There are several interesting issues in arch/*/*/*signal* (besides
>> shoggoths starting to show up when one reads that code) and I'd been crawling
>> through that area for the last few weeks.  Here are more or less common
>> issues; there are really arch-specific bugs (e.g. roothole on frv that
>> used to allow reading kernel memory by setting the right sa_handler), but
>> that's a separate story.
> 
> I still plan to make a counterpart to the asm-generic headers with an
> example architecture that new architectures can copy from. Signal handling
> is one of the areas that I have very limited understanding of. Did you
> encounter any architecture that basically gets signal handling right and that
> can serve as a positive example to others?
> 
> arch/tile/kernel/signal.c was the last one that got merged and I tried
> to direct the maintainer in the right direction as much as I could, but
> there are a lot of things I didn't know about.

(Sorry for the belated reply.)

I set aside this thread to look at when I had a minute, and I believe there
is just one of the signal issues present in the tile code.  The fix is to
reset regs->fault to something other than the "syscall" fault type when
exiting from do_signal(), so I'll submit that up for 2.6.37 shortly.

Otherwise I think tile is doing things right, though I admit, the signal
support is pretty deep magic generally.
-- 
Chris Metcalf, Tilera Corp.
http://www.tilera.com
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