linux-kernel - Re: [PATCH v2] mm/memblock: skip kmemleak for kasan

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Message-ID: <20181129170016.GD22027@arrakis.emea.arm.com>
Date:   Thu, 29 Nov 2018 17:00:16 +0000
From:   Catalin Marinas <catalin.marinas@....com>
To:     Qian Cai <cai@....us>
Cc:     akpm@...ux-foundation.org, mhocko@...e.com,
        rppt@...ux.vnet.ibm.com, aryabinin@...tuozzo.com,
        glider@...gle.com, dvyukov@...gle.com, kasan-dev@...glegroups.com,
        linux-mm@...ck.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] mm/memblock: skip kmemleak for kasan_init()

On Wed, Nov 28, 2018 at 05:08:45PM -0500, Qian Cai wrote:
> Kmemleak does not play well with KASAN (tested on both HPE Apollo 70 and
> Huawei TaiShan 2280 aarch64 servers).
> 
> After calling start_kernel()->setup_arch()->kasan_init(), kmemleak early
> log buffer went from something like 280 to 260000 which caused kmemleak
> disabled and crash dump memory reservation failed. The multitude of
> kmemleak_alloc() calls is from nested loops while KASAN is setting up
> full memory mappings, so let early kmemleak allocations skip those
> memblock_alloc_internal() calls came from kasan_init() given that those
> early KASAN memory mappings should not reference to other memory.
> Hence, no kmemleak false positives.
> 
> kasan_init
>   kasan_map_populate [1]
>     kasan_pgd_populate [2]
>       kasan_pud_populate [3]
>         kasan_pmd_populate [4]
>           kasan_pte_populate [5]
>             kasan_alloc_zeroed_page
>               memblock_alloc_try_nid
>                 memblock_alloc_internal
>                   kmemleak_alloc
> 
> [1] for_each_memblock(memory, reg)
> [2] while (pgdp++, addr = next, addr != end)
> [3] while (pudp++, addr = next, addr != end && pud_none(READ_ONCE(*pudp)))
> [4] while (pmdp++, addr = next, addr != end && pmd_none(READ_ONCE(*pmdp)))
> [5] while (ptep++, addr = next, addr != end && pte_none(READ_ONCE(*ptep)))
> 
> Signed-off-by: Qian Cai <cai@....us>

Acked-by: Catalin Marinas <catalin.marinas@....com>

(for both the kmemleak and arm64 changes)