linux-kernel - Re: Random panic in load

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Message-ID: <CA+55aFzOoJzqJ=4RVPEBfscA8oRdr5Nv7fKx9aXYw2+frkuhwA@mail.gmail.com>
Date:	Fri, 25 Jul 2014 11:29:06 -0700
From:	Linus Torvalds <torvalds@...ux-foundation.org>
To:	Steven Rostedt <rostedt@...dmis.org>
Cc:	Alexei Starovoitov <ast@...nel.org>,
	Michel Dänzer <michel@...nzer.net>,
	Jakub Jelinek <jakub@...hat.com>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Debian GCC Maintainers <debian-gcc@...ts.debian.org>,
	Debian Kernel Team <debian-kernel@...ts.debian.org>
Subject: Re: Random panic in load_balance() with 3.16-rc

On Fri, Jul 25, 2014 at 7:02 AM, Steven Rostedt <rostedt@...dmis.org> wrote:
>
> But wouldn't it be rather trivial to run a static analyzer on the final
> vmlinux to make sure there are no red zones? I mean, you would only need
> to read each function and check to make sure that the offset of rbp is
> within the change of rsp, wouldn't you?
>
> Almost seems like an objdump -rd into a perl script could do this.

I'm sure it's possible, but it sounds potentially complicated. It's
not like the function prologue is fixed, and gcc will create code
(including conditional branches etc) before the whole frame setup if
there are simple things that can be done purely with the
callee-clobbered registers etc.

Some simple pattern to make sure that the "sub $frame-size,%rsp" comes
before any accesses to (%rbp) (when frame pointers are enabled)
*might* work, but it might also end up missing things.

You want to try?

             Linus
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