linux-kernel - Re: [PATCH v7 0/4] KASAN for arm64

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Date:	Tue, 17 Nov 2015 18:47:08 +0300
From:	Andrey Ryabinin <aryabinin@...tuozzo.com>
To:	"Suzuki K. Poulose" <Suzuki.Poulose@....com>
CC:	Catalin Marinas <catalin.marinas@....com>,
	Will Deacon <will.deacon@....com>,
	<linux-arm-kernel@...ts.infradead.org>,
	Yury <yury.norov@...il.com>,
	Alexey Klimov <klimov.linux@...il.com>,
	Arnd Bergmann <arnd@...db.de>, <linux-mm@...ck.org>,
	Andrey Konovalov <andreyknvl@...gle.com>,
	Linus Walleij <linus.walleij@...aro.org>,
	Ard Biesheuvel <ard.biesheuvel@...aro.org>,
	<linux-kernel@...r.kernel.org>,
	kasan-dev <kasan-dev@...glegroups.com>,
	David Keitel <dkeitel@...eaurora.org>,
	Alexander Potapenko <glider@...gle.com>,
	Dmitry Vyukov <dvyukov@...gle.com>
Subject: Re: [PATCH v7 0/4] KASAN for arm64



On 11/17/2015 05:58 PM, Suzuki K. Poulose wrote:
> On 16/11/15 15:34, Andrey Ryabinin wrote:
>> On 11/16/2015 02:16 PM, Suzuki K. Poulose wrote:
>>> On 13/10/15 09:34, Catalin Marinas wrote:
>>>> On Mon, Oct 12, 2015 at 06:52:56PM +0300, Andrey Ryabinin wrote:
> 
>>> Hi,
>>>
>>> I get the following failure with KASAN + 16K_PAGES + 48BIT_VA, with 4.4-rc1:
>>>
>>>
>>> arch/arm64/mm/kasan_init.c: In function ‘kasan_early_init’:
>>> include/linux/compiler.h:484:38: error: call to ‘__compiletime_assert_95’ declared with attribute error: BUILD_BUG_ON failed: !IS_ALIGNED(KASAN_SHADOW_END, PGDIR_SIZE)
>>>    _compiletime_assert(condition, msg, __compiletime_assert_, __LINE__)
>>>                                        ^
> 
> ...
> 
>>
>> Yes, it's really needed, because some code relies on this (e.g.  clear_pgs() and kasan_init()).
>> But it should be possible to get rid of this requirement.
> 
> And the other important point I missed mentioning was that, my tool chain doesn't
> support KASAN. But still the KASAN support files are still compiled and generates
> the above error. Shouldn't we disable it at build time if we detect that compiler
> doesn't support it ? Something like we do for LSE_ATOMICS.
> 

We should either add proper Kconfig dependency for now, or just make it work.


From: Andrey Ryabinin <aryabinin@...tuozzo.com>
Subject: [PATCH] arm64: KASAN depends on !(ARM64_16K_PAGES && ARM64_VA_BITS_48)

On KASAN + 16K_PAGES + 48BIT_VA
 arch/arm64/mm/kasan_init.c: In function ‘kasan_early_init’:
 include/linux/compiler.h:484:38: error: call to ‘__compiletime_assert_95’ declared with attribute error: BUILD_BUG_ON failed: !IS_ALIGNED(KASAN_SHADOW_END, PGDIR_SIZE)
    _compiletime_assert(condition, msg, __compiletime_assert_, __LINE__)

Currently KASAN will not work on 16K_PAGES and 48BIT_VA, so
forbid such configuration to avoid above build failure.

Reported-by: Suzuki K. Poulose <Suzuki.Poulose@....com>
Signed-off-by: Andrey Ryabinin <aryabinin@...tuozzo.com>
---
 arch/arm64/Kconfig | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
index 9ac16a4..bf7de69 100644
--- a/arch/arm64/Kconfig
+++ b/arch/arm64/Kconfig
@@ -49,7 +49,7 @@ config ARM64
 	select HAVE_ARCH_AUDITSYSCALL
 	select HAVE_ARCH_BITREVERSE
 	select HAVE_ARCH_JUMP_LABEL
-	select HAVE_ARCH_KASAN if SPARSEMEM_VMEMMAP
+	select HAVE_ARCH_KASAN if SPARSEMEM_VMEMMAP && !(ARM64_16K_PAGES && ARM64_VA_BITS_48)
 	select HAVE_ARCH_KGDB
 	select HAVE_ARCH_SECCOMP_FILTER
 	select HAVE_ARCH_TRACEHOOK
-- 
2.4.10

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