linux-kernel - Re: [PATCH v5 2/3] mm/slub, kunit: add a KUnit test for SLUB debugging functionality

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Message-ID: <CAD=R=qpH+GHcWzgZtd42uFRr8VgeQ=YMUPJnwjQadEQ_azdo0g@mail.gmail.com>
Date:   Thu, 13 May 2021 11:32:17 +0200
From:   Oliver Glitta <glittao@...il.com>
To:     Andrew Morton <akpm@...ux-foundation.org>
Cc:     Brendan Higgins <brendanhiggins@...gle.com>,
        Christoph Lameter <cl@...ux.com>,
        Pekka Enberg <penberg@...nel.org>,
        David Rientjes <rientjes@...gle.com>,
        Joonsoo Kim <iamjoonsoo.kim@....com>,
        Vlastimil Babka <vbabka@...e.cz>,
        LKML <linux-kernel@...r.kernel.org>,
        "open list:KERNEL SELFTEST FRAMEWORK" 
        <linux-kselftest@...r.kernel.org>,
        KUnit Development <kunit-dev@...glegroups.com>,
        Linux Memory Management List <linux-mm@...ck.org>,
        Marco Elver <elver@...gle.com>,
        Daniel Latypov <dlatypov@...gle.com>
Subject: Re: [PATCH v5 2/3] mm/slub, kunit: add a KUnit test for SLUB
 debugging functionality

št 13. 5. 2021 o 6:44 Andrew Morton <akpm@...ux-foundation.org> napísal(a):
>
> On Tue, 11 May 2021 17:07:33 +0200 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.
> > Tests next_pointer, first_word and clobber_50th_byte do not run
> > with KASAN option on. Because the test deliberately modifies non-allocated
> > objects.
> >
> > 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.
> >
> > ...
> >
> >  lib/slub_kunit.c  | 155 ++++++++++++++++++++++++++++++++++++++++++++++
> >  mm/slab.h         |   1 +
> >  mm/slub.c         |  46 +++++++++++++-
> >  5 files changed, 212 insertions(+), 3 deletions(-)
> >  create mode 100644 lib/slub_kunit.c
> >
> > diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
> > index 678c13967580..7723f58a9394 100644
> > --- a/lib/Kconfig.debug
> > +++ b/lib/Kconfig.debug
> > @@ -2429,6 +2429,18 @@ config BITS_TEST
> >
> >         If unsure, say N.
> >
> > +config SLUB_KUNIT_TEST
> > +     tristate "KUnit test for SLUB cache error detection" if !KUNIT_ALL_TESTS
>
> This means it can be compiled as a kernel module.  Did you runtime test the
> code as a module?
>
We tested this as a module in the previous version, but I forgot to
try it with this new one. So we didn't find this error.
Thank you for your fix.

> ERROR: modpost: "kasan_enable_current" [lib/slub_kunit.ko] undefined!
> ERROR: modpost: "kasan_disable_current" [lib/slub_kunit.ko] undefined!
>
> --- a/mm/kasan/common.c~a
> +++ a/mm/kasan/common.c
> @@ -51,11 +51,14 @@ void kasan_enable_current(void)
>  {
>         current->kasan_depth++;
>  }
> +EXPORT_SYMBOL(kasan_enable_current);
>
>  void kasan_disable_current(void)
>  {
>         current->kasan_depth--;
>  }
> +EXPORT_SYMBOL(kasan_disable_current);
> +
>  #endif /* CONFIG_KASAN_GENERIC || CONFIG_KASAN_SW_TAGS */
>
>  void __kasan_unpoison_range(const void *address, size_t size)
> _
>