linux-kernel - Re: [PATCH v2 5/5] arm64: add KASan support

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Date:	Fri, 17 Jul 2015 16:13:07 +0300
From:	Andrey Ryabinin <a.ryabinin@...sung.com>
To:	Catalin Marinas <catalin.marinas@....com>
Cc:	Arnd Bergmann <arnd@...db.de>,
	David Keitel <dkeitel@...eaurora.org>,
	Will Deacon <will.deacon@....com>,
	linux-kernel@...r.kernel.org, linux-mm@...ck.org,
	Alexander Potapenko <glider@...gle.com>,
	Dmitry Vyukov <dvyukov@...gle.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH v2 5/5] arm64: add KASan support

On 07/16/2015 07:03 PM, Catalin Marinas wrote:
> On Thu, Jul 16, 2015 at 06:30:11PM +0300, Andrey Ryabinin wrote:
>>
>> I think this may work, if pud_none(*pud) will be replaced with !pud_val(*pud).
>> We can't use pud_none() because with 2-level page tables it's always false, so
>> we will never go down to pmd level where swapper_pg_dir populated.
> 
> The reason I used "do ... while" vs "while" or "for" is so that it gets
> down to the pmd level. The iteration over pgd is always done in the top
> loop via pgd_addr_end while the loops for missing levels (nopud, nopmd)
> are always a single iteration whether we check for pud_none or not. But
> when the level is present, we avoid looping when !pud_none().
> 

Right, dunno what I was thinking.
It seems to work. Lightly tested with every possible CONFIG_PGTABLE_LEVELS.
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