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References: <20240207-fix_sparse_errors_checksum_tests-v6-0-4caa9629705b@rivosinc.com>
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From: Geert Uytterhoeven <geert@linux-m68k.org>
Date: Mon, 12 Feb 2024 13:46:01 +0100
Message-ID: <CAMuHMdVocStpwYKJ4OzgHBWRsDUhAT73JaQ7HgaQbJK_Zo+VvA@mail.gmail.com>
Subject: Re: [PATCH v6 0/2] lib: checksum: Fix issues with checksum tests
To: Guenter Roeck <linux@roeck-us.net>
Cc: Charlie Jenkins <charlie@rivosinc.com>, David Laight <David.Laight@aculab.com>, 
	Palmer Dabbelt <palmer@dabbelt.com>, Andrew Morton <akpm@linux-foundation.org>, 
	linux-kernel@vger.kernel.org, kernel test robot <lkp@intel.com>
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Hi G=C3=BCnter,

On Sun, Feb 11, 2024 at 8:18=E2=80=AFPM Guenter Roeck <linux@roeck-us.net> =
wrote:
> On 2/7/24 16:22, Charlie Jenkins wrote:
> > The ip_fast_csum and csum_ipv6_magic tests did not have the data
> > types properly casted, and improperly misaligned data.
> >
> > Signed-off-by: Charlie Jenkins <charlie@rivosinc.com>
>
> I sorted out most of the problems with this version, but I still get:
>
>      # test_csum_ipv6_magic: ASSERTION FAILED at lib/checksum_kunit.c:513
>      Expected ( u64)csum_result =3D=3D ( u64)expected, but
>          ( u64)csum_result =3D=3D 16630 (0x40f6)
>          ( u64)expected =3D=3D 65535 (0xffff)
>      not ok 5 test_csum_ipv6_magic
>
> on m68k:q800. This is suspicious because there is no 0xffff in
> expected_csum_ipv6_magic[]. With some debugging information:
>
> ####### num_tests=3D86 i=3D84 expect array size=3D84
> ####### MAX_LEN=3D512 WORD_ALIGNMENT=3D4 magic data size=3D42
>
> That means the loop
>
>         for (int i =3D 0; i < num_tests; i++) {
>                 ...
>                 expected =3D (__force __sum16)expected_csum_ipv6_magic[i]=
;
>                 ...
>         }
>
> will access data beyond the end of the expected_csum_ipv6_magic[] array,
> possibly because m68k doesn't pad struct csum_ipv6_magic_data to 44 bytes=
.

Exactly, sizeof(struct csum_ipv6_magic_data) =3D 42 on m68k.
Hence struct csum_ipv6_magic_data needs an extra field "unsigned char pad[3=
];"
at the end.

Gr{oetje,eeting}s,

                        Geert

--=20
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k=
org

In personal conversations with technical people, I call myself a hacker. Bu=
t
when I'm talking to journalists I just say "programmer" or something like t=
hat.
                                -- Linus Torvalds