linux-kernel - Re: [PATCH v6 0/6] KASAN for arm64

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Date:	Fri, 9 Oct 2015 12:32:18 +0300
From:	Andrey Ryabinin <ryabinin.a.a@...il.com>
To:	Catalin Marinas <catalin.marinas@....com>
Cc:	Ard Biesheuvel <ard.biesheuvel@...aro.org>,
	Mark Rutland <mark.rutland@....com>,
	"linux-efi@...r.kernel.org" <linux-efi@...r.kernel.org>,
	Arnd Bergmann <arnd@...db.de>, Yury <yury.norov@...il.com>,
	"linux-mm@...ck.org" <linux-mm@...ck.org>,
	Linus Walleij <linus.walleij@...aro.org>,
	Mark Salter <msalter@...hat.com>,
	Will Deacon <will.deacon@....com>,
	LKML <linux-kernel@...r.kernel.org>,
	Alexey Klimov <klimov.linux@...il.com>,
	Alexander Potapenko <glider@...gle.com>,
	Dmitry Vyukov <dvyukov@...gle.com>,
	Andrey Konovalov <andreyknvl@...gle.com>,
	David Keitel <dkeitel@...eaurora.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	Matt Fleming <matt.fleming@...el.com>
Subject: Re: [PATCH v6 0/6] KASAN for arm64

On 10/08/2015 07:07 PM, Andrey Ryabinin wrote:
> 2015-10-08 18:11 GMT+03:00 Catalin Marinas <catalin.marinas@....com>:
>> On Thu, Oct 08, 2015 at 02:09:26PM +0200, Ard Biesheuvel wrote:
>>> On 8 October 2015 at 13:23, Andrey Ryabinin <ryabinin.a.a@...il.com> wrote:
>>>> On 10/08/2015 02:11 PM, Mark Rutland wrote:
>>>>> On Thu, Oct 08, 2015 at 01:36:09PM +0300, Andrey Ryabinin wrote:
>>>>>> 2015-10-07 13:04 GMT+03:00 Catalin Marinas <catalin.marinas@....com>:
>>>>>>> On Thu, Sep 17, 2015 at 12:38:06PM +0300, Andrey Ryabinin wrote:
>>>>>>>> As usual patches available in git
>>>>>>>>       git://github.com/aryabinin/linux.git kasan/arm64v6
>>>>>>>>
>>>>>>>> Changes since v5:
>>>>>>>>  - Rebase on top of 4.3-rc1
>>>>>>>>  - Fixed EFI boot.
>>>>>>>>  - Updated Doc/features/KASAN.
>>>>>>>
>>>>>>> I tried to merge these patches (apart from the x86 one which is already
>>>>>>> merged) but it still doesn't boot on Juno as an EFI application.
>>>>>>>
>>>>>>
>>>>>> 4.3-rc1 was ok and 4.3-rc4 is not. Break caused by 0ce3cc008ec04
>>>>>> ("arm64/efi: Fix boot crash by not padding between EFI_MEMORY_RUNTIME
>>>>>> regions")
>>>>>> It introduced sort() call in efi_get_virtmap().
>>>>>> sort() is generic kernel function and it's instrumented, so we crash
>>>>>> when KASAN tries to access shadow in sort().
>>>>>
>>>>> I believe this is solved by Ard's stub isolation series [1,2], which
>>>>> will build a stub-specific copy of sort() and various other functions
>>>>> (see the arm-deps in [2]).
>>>>>
>>>>> So long as the stub is not built with ASAN, that should work.
>>>>
>>>> Thanks, this should help, as we already build the stub without ASAN instrumentation.
>>>
>>> Indeed. I did not mention instrumentation in the commit log for those
>>> patches, but obviously, something like KASAN instrumentation cannot be
>>> tolerated in the stub since it makes assumptions about the memory
>>> layout
>>
>> I'll review your latest EFI stub isolation patches and try Kasan again
>> on top (most likely tomorrow).
> 
> You'd better wait for v7, because kasan patches will need some adjustment.
> Since stub is isolated,  we need to handle memcpy vs __memcpy stuff the same
> way as we do in x86. Now we also need to #undef memset/memcpy/memmove in ARM64
> (just like this was done for x86).
> 

Hm, I was wrong, we don't need that.

I thought the EFI stub isolation patches create a copy of mem*() functions in the stub,
but they are just create aliases with __efistub_ prefix.

We only need to create some more aliases for KASAN.
The following patch on top of the EFI stub isolation series works for me.


Signed-off-by: Andrey Ryabinin <ryabinin.a.a@...il.com>
---
 arch/arm64/kernel/image.h | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/arch/arm64/kernel/image.h b/arch/arm64/kernel/image.h
index e083af0..6eb8fee 100644
--- a/arch/arm64/kernel/image.h
+++ b/arch/arm64/kernel/image.h
@@ -80,6 +80,12 @@ __efistub_strcmp		= __pi_strcmp;
 __efistub_strncmp		= __pi_strncmp;
 __efistub___flush_dcache_area	= __pi___flush_dcache_area;
 
+#ifdef CONFIG_KASAN
+__efistub___memcpy		= __pi_memcpy;
+__efistub___memmove		= __pi_memmove;
+__efistub___memset		= __pi_memset;
+#endif
+
 __efistub__text			= _text;
 __efistub__end			= _end;
 __efistub__edata		= _edata;
-- 
2.4.9






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