linux-kernel - Re: [PATCH v6 1/1] x86_64: fix KASan shadow region page tables

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Date:	Fri, 19 Jun 2015 16:00:51 +0200
From:	Ingo Molnar <mingo@...nel.org>
To:	Andrey Ryabinin <a.ryabinin@...sung.com>
Cc:	Borislav Petkov <bp@...en8.de>,
	Alexander Popov <alpopov@...ecurity.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	"H. Peter Anvin" <hpa@...or.com>,
	Andrey Konovalov <adech.fo@...il.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Andy Lutomirski <luto@...nel.org>,
	Alexander Kuleshov <kuleshovmail@...il.com>,
	Denys Vlasenko <dvlasenk@...hat.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Kees Cook <keescook@...omium.org>, x86@...nel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v6 1/1] x86_64: fix KASan shadow region page tables


* Andrey Ryabinin <a.ryabinin@...sung.com> wrote:

> On 06/19/2015 03:06 PM, Borislav Petkov wrote:
> > On Fri, Jun 19, 2015 at 02:49:19PM +0300, Andrey Ryabinin wrote:
> >> I guess that AMD cpus is more strict (unlike Intel) about violation
> >> of reserved/unused bits in page table entries. Please, try with this
> >> patch.
> > 
> > With that the guest boots.
> > 
> 
> Great! Thanks.
> 
> > How do I check whether KASan actually works? I don't see any note in
> > dmesg or some file named "*kasan*" in sysfs...
> > 
> 
> kasan will print report in dmesg whant it will find anything.

It should also printk a one line message at bootup, so that people can be sure 
they are running a KASan-enabled kernel.

> To make sure that it works you could try to load testing module (CONFIG_TEST_KASAN).
> This module has bugs that kasan should catch.

That's a way too obscure mechanism just to determine whether the right kernel 
config was booted. Please add a printk(), ok?

Thanks,

	Ingo
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