linux-kernel - Re: [PATCH v4 2/3] mm/slub, kunit: add a KUnit test for SLUB debugging functionality

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Message-ID: <d31f8829-1cbd-7159-6f93-6f750fd3cbd4@suse.cz>
Date:   Thu, 15 Apr 2021 12:30:08 +0200
From:   Vlastimil Babka <vbabka@...e.cz>
To:     glittao@...il.com, brendanhiggins@...gle.com, cl@...ux.com,
        penberg@...nel.org, rientjes@...gle.com, iamjoonsoo.kim@....com,
        akpm@...ux-foundation.org
Cc:     linux-kernel@...r.kernel.org, linux-kselftest@...r.kernel.org,
        kunit-dev@...glegroups.com, linux-mm@...ck.org, elver@...gle.com,
        dlatypov@...gle.com
Subject: Re: [PATCH v4 2/3] mm/slub, kunit: add a KUnit test for SLUB
 debugging functionality

On 4/13/21 12:07 PM, glittao@...il.com wrote:
> From: Oliver Glitta <glittao@...il.com>
> 
> SLUB has resiliency_test() function which is hidden behind #ifdef
> SLUB_RESILIENCY_TEST that is not part of Kconfig, so nobody
> runs it. KUnit should be a proper replacement for it.
> 
> Try changing byte in redzone after allocation and changing
> pointer to next free node, first byte, 50th byte and redzone
> byte. Check if validation finds errors.
> 
> There are several differences from the original resiliency test:
> Tests create own caches with known state instead of corrupting
> shared kmalloc caches.
> 
> The corruption of freepointer uses correct offset, the original
> resiliency test got broken with freepointer changes.
> 
> Scratch changing random byte test, because it does not have
> meaning in this form where we need deterministic results.
> 
> Add new option CONFIG_SLUB_KUNIT_TEST in Kconfig.
> Because the test deliberatly modifies non-allocated objects, it depends on
> !KASAN which would have otherwise prevented that.
> 
> Use kunit_resource to count errors in cache and silence bug reports.
> Count error whenever slab_bug() or slab_fix() is called or when
> the count of pages is wrong.
> 
> Signed-off-by: Oliver Glitta <glittao@...il.com>

Acked-by: Vlastimil Babka <vbabka@...e.cz>

(again with a disclaimer that I'm the advisor of Oliver's student project)