Re: [PATCH] x86, kasan: add KASAN checks to atomic operations

From: Peter Zijlstra <peterz@infradead.org>
To: Mark Rutland <mark.rutland@arm.com>
Cc: Dmitry Vyukov <dvyukov@google.com>,
	Andrew Morton <akpm@linux-foundation.org>,
	Andrey Ryabinin <aryabinin@virtuozzo.com>,
	Ingo Molnar <mingo@redhat.com>,
	kasan-dev <kasan-dev@googlegroups.com>,
	"linux-mm@kvack.org" <linux-mm@kvack.org>,
	LKML <linux-kernel@vger.kernel.org>,
	"x86@kernel.org" <x86@kernel.org>,
	will.deacon@arm.com
Subject: Re: [PATCH] x86, kasan: add KASAN checks to atomic operations
Date: Mon, 6 Mar 2017 21:35:00 +0100	[thread overview]
Message-ID: <20170306203500.GR6500@twins.programming.kicks-ass.net> (raw)
In-Reply-To: <20170306162018.GC18519@leverpostej>

On Mon, Mar 06, 2017 at 04:20:18PM +0000, Mark Rutland wrote:
> > >> So the problem is doing load/stores from asm bits, and GCC
> > >> (traditionally) doesn't try and interpret APP asm bits.
> > >>
> > >> However, could we not write a GCC plugin that does exactly that?
> > >> Something that interprets the APP asm bits and generates these KASAN
> > >> bits that go with it?

> I don't think there's much you'll be able to do within the compiler,
> assuming you mean to derive this from the asm block inputs and outputs.

Nah, I was thinking about a full asm interpreter.

> Those can hide address-generation (e.g. with per-cpu stuff), which the
> compiler may erroneously be detected as racing.
> 
> Those may also take fake inputs (e.g. the sp input to arm64's
> __my_cpu_offset()) which may confuse matters.
> 
> Parsing the assembly itself will be *extremely* painful due to the way
> that's set up for run-time patching.

Argh, yah, completely forgot about all that alternative and similar
nonsense :/