linux-kernel - Re: [PATCH v12 08/11] arm64/kasan: add and use kasan_map

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Message-ID: <0ae84532-8dcb-10aa-9d69-79d7025b089e@virtuozzo.com>
Date:   Wed, 18 Oct 2017 19:55:02 +0300
From:   Andrey Ryabinin <aryabinin@...tuozzo.com>
To:     Pavel Tatashin <pasha.tatashin@...cle.com>,
        linux-kernel@...r.kernel.org, sparclinux@...r.kernel.org,
        linux-mm@...ck.org, linuxppc-dev@...ts.ozlabs.org,
        linux-s390@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        x86@...nel.org, kasan-dev@...glegroups.com, borntraeger@...ibm.com,
        heiko.carstens@...ibm.com, davem@...emloft.net,
        willy@...radead.org, mhocko@...nel.org, ard.biesheuvel@...aro.org,
        mark.rutland@....com, will.deacon@....com, catalin.marinas@....com,
        sam@...nborg.org, mgorman@...hsingularity.net,
        akpm@...ux-foundation.org, steven.sistare@...cle.com,
        daniel.m.jordan@...cle.com, bob.picco@...cle.com
Subject: Re: [PATCH v12 08/11] arm64/kasan: add and use kasan_map_populate()

On 10/13/2017 08:32 PM, Pavel Tatashin wrote:
> During early boot, kasan uses vmemmap_populate() to establish its shadow
> memory. But, that interface is intended for struct pages use.
> 
> Because of the current project, vmemmap won't be zeroed during allocation,
> but kasan expects that memory to be zeroed. We are adding a new
> kasan_map_populate() function to resolve this difference.
> 
> Therefore, we must use a new interface to allocate and map kasan shadow
> memory, that also zeroes memory for us.
> 

What's the point of this patch? We have "arm64: kasan: Avoid using vmemmap_populate to initialise shadow"
which does the right thing and basically reverts this patch.
This patch as intermediate step looks absolutely useless. We can just avoid vemmap_populate() right away.

> Signed-off-by: Pavel Tatashin <pasha.tatashin@...cle.com>
> ---
>  arch/arm64/mm/kasan_init.c | 72 ++++++++++++++++++++++++++++++++++++++++++----
>  1 file changed, 66 insertions(+), 6 deletions(-)
> 
> diff --git a/arch/arm64/mm/kasan_init.c b/arch/arm64/mm/kasan_init.c
> index 81f03959a4ab..cb4af2951c90 100644
> --- a/arch/arm64/mm/kasan_init.c
> +++ b/arch/arm64/mm/kasan_init.c
> @@ -28,6 +28,66 @@
>