linux-kernel - Re: [PATCH] Revert "sh: Handle calling csum

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Date: Mon, 25 Mar 2024 08:35:27 -0700
From: Guenter Roeck <linux@...ck-us.net>
To: John Paul Adrian Glaubitz <glaubitz@...sik.fu-berlin.de>
Cc: Yoshinori Sato <ysato@...rs.sourceforge.jp>,
	Rich Felker <dalias@...c.org>, linux-sh@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] Revert "sh: Handle calling csum_partial with misaligned
 data"

On Mon, Mar 25, 2024 at 08:39:39AM +0100, John Paul Adrian Glaubitz wrote:
> Hi Guenter,
> 
> On Sun, 2024-03-24 at 16:18 -0700, Guenter Roeck wrote:
> > This reverts commit cadc4e1a2b4d20d0cc0e81f2c6ba0588775e54e5.
> > 
> > Commit cadc4e1a2b4d ("sh: Handle calling csum_partial with misaligned
> > data") causes bad checksum calculations on unaligned data. Reverting
> > it fixes the problem.
> > 
> >     # Subtest: checksum
> >     # module: checksum_kunit
> >     1..5
> >     # test_csum_fixed_random_inputs: ASSERTION FAILED at lib/checksum_kunit.c:500
> >     Expected ( u64)result == ( u64)expec, but
> >         ( u64)result == 53378 (0xd082)
> >         ( u64)expec == 33488 (0x82d0)
> >     # test_csum_fixed_random_inputs: pass:0 fail:1 skip:0 total:1
> >     not ok 1 test_csum_fixed_random_inputs
> >     # test_csum_all_carry_inputs: ASSERTION FAILED at lib/checksum_kunit.c:525
> >     Expected ( u64)result == ( u64)expec, but
> >         ( u64)result == 65281 (0xff01)
> >         ( u64)expec == 65280 (0xff00)
> >     # test_csum_all_carry_inputs: pass:0 fail:1 skip:0 total:1
> >     not ok 2 test_csum_all_carry_inputs
> >     # test_csum_no_carry_inputs: ASSERTION FAILED at lib/checksum_kunit.c:573
> >     Expected ( u64)result == ( u64)expec, but
> >         ( u64)result == 65535 (0xffff)
> >         ( u64)expec == 65534 (0xfffe)
> >     # test_csum_no_carry_inputs: pass:0 fail:1 skip:0 total:1
> >     not ok 3 test_csum_no_carry_inputs
> >     # test_ip_fast_csum: pass:1 fail:0 skip:0 total:1
> >     ok 4 test_ip_fast_csum
> >     # test_csum_ipv6_magic: pass:1 fail:0 skip:0 total:1
> >     ok 5 test_csum_ipv6_magic
> >  # checksum: pass:2 fail:3 skip:0 total:5
> >  # Totals: pass:2 fail:3 skip:0 total:5
> > not ok 22 checksum
> 
> Can you tell me how the tests are run so I can try to verify this on real hardware?
> 

Please also see
https://lore.kernel.org/lkml/0a0fbbd8-17dd-4f4c-9513-f3ac9749890b@roeck-us.net/t/
where I reported the problem a while ago. I didn't see a fix, so I figured
I'd submit a revert, following the logic that non-optimized code is better
than buggy code. Obviously a real fix would be preferrable, but I don't
understand sh4 assembler well enough to understand what is happening.

Thanks,
Guenter