linux-kernel - Re: [PATCH v3 00/13] Kernel address sanitizer

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Message-ID: <CACT4Y+Y0fzbs4DPt3n30R33cYqXEZ8E86tzCfzL6RUE9f+-r=w@mail.gmail.com>
Date:	Fri, 26 Sep 2014 10:07:04 -0700
From:	Dmitry Vyukov <dvyukov@...gle.com>
To:	Sasha Levin <sasha.levin@...cle.com>
Cc:	Andrey Ryabinin <a.ryabinin@...sung.com>,
	LKML <linux-kernel@...r.kernel.org>,
	Konstantin Serebryany <kcc@...gle.com>,
	Dmitry Chernenkov <dmitryc@...gle.com>,
	Andrey Konovalov <adech.fo@...il.com>,
	Yuri Gribov <tetra2005@...il.com>,
	Konstantin Khlebnikov <koct9i@...il.com>,
	Michal Marek <mmarek@...e.cz>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	Christoph Lameter <cl@...ux.com>,
	Pekka Enberg <penberg@...nel.org>,
	David Rientjes <rientjes@...gle.com>,
	Joonsoo Kim <iamjoonsoo.kim@....com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Dave Hansen <dave.hansen@...el.com>,
	Andi Kleen <andi@...stfloor.org>,
	Vegard Nossum <vegard.nossum@...il.com>,
	"H. Peter Anvin" <hpa@...or.com>, linux-kbuild@...r.kernel.org,
	x86@...nel.org, linux-mm@...ck.org,
	Randy Dunlap <rdunlap@...radead.org>,
	Peter Zijlstra <peterz@...radead.org>,
	Alexander Viro <viro@...iv.linux.org.uk>,
	Dave Jones <davej@...hat.com>
Subject: Re: [PATCH v3 00/13] Kernel address sanitizer - runtime memory debugger.

On Fri, Sep 26, 2014 at 10:01 AM, Sasha Levin <sasha.levin@...cle.com> wrote:
> On 09/24/2014 08:43 AM, Andrey Ryabinin wrote:
>> Hi.
>>
>> This is a third iteration of kerenel address sanitizer (KASan).
>>
>> KASan is a runtime memory debugger designed to find use-after-free
>> and out-of-bounds bugs.
>>
>> Currently KASAN supported only for x86_64 architecture and requires kernel
>> to be build with SLUB allocator.
>> KASAN uses compile-time instrumentation for checking every memory access, therefore you
>> will need a fresh GCC >= v5.0.0.
>
> Hi Andrey,
>
> I tried this patchset, with the latest gcc, and I'm seeing the following:
>
> arch/x86/kernel/head.o: In function `_GLOBAL__sub_I_00099_0_reserve_ebda_region':
> /home/sasha/linux-next/arch/x86/kernel/head.c:71: undefined reference to `__asan_init_v4'
> init/built-in.o: In function `_GLOBAL__sub_I_00099_0___ksymtab_system_state':
> /home/sasha/linux-next/init/main.c:1034: undefined reference to `__asan_init_v4'
> init/built-in.o: In function `_GLOBAL__sub_I_00099_0_init_uts_ns':
> /home/sasha/linux-next/init/version.c:50: undefined reference to `__asan_init_v4'
> init/built-in.o: In function `_GLOBAL__sub_I_00099_0_root_mountflags':
> /home/sasha/linux-next/init/do_mounts.c:638: undefined reference to `__asan_init_v4'
> init/built-in.o: In function `_GLOBAL__sub_I_00099_0_rd_prompt':
> /home/sasha/linux-next/init/do_mounts_rd.c:361: undefined reference to `__asan_init_v4'
> init/built-in.o:/home/sasha/linux-next/init/do_mounts_md.c:312: more undefined references to `__asan_init_v4' follow
>
>
> What am I missing?


Emission of __asan_init_vx needs to be disabled when
-fsanitize=kernel-address. Our kernel does not boot with them at all.
It probably hits some limit for something that can be increased. But I
don't want to investigate what that limit is, as __asan_init is not
needed for kasan at all.
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