From: Eric Dumazet <eric.dumazet@gmail.com>
To: "Björn Töpel" <bjorn.topel@gmail.com>,
Netdev <netdev@vger.kernel.org>, bpf <bpf@vger.kernel.org>
Cc: Tom Herbert <tom@herbertland.com>,
linux-riscv <linux-riscv@lists.infradead.org>,
Anders Roxell <anders.roxell@gmail.com>
Subject: Re: csum_partial() on different archs (selftest/bpf)
Date: Fri, 13 Nov 2020 12:34:17 +0100 [thread overview]
Message-ID: <e23c63dd-5f90-c273-615f-d5d67991529c@gmail.com> (raw)
In-Reply-To: <CAJ+HfNiQbOcqCLxFUP2FMm5QrLXUUaj852Fxe3hn_2JNiucn6g@mail.gmail.com>
On 11/13/20 11:36 AM, Björn Töpel wrote:
> I was running the selftest/bpf on riscv, and had a closer look at one
> of the failing cases:
>
> #14/p valid read map access into a read-only array 2 FAIL retval
> 65507 != -29 (run 1/1)
>
> The test does a csum_partial() call via a BPF helper. riscv uses the
> generic implementation. arm64 uses the generic csum_partial() and fail
> in the same way [1]. arm (32-bit) has a arch specfic implementation,
> and fail in another way (FAIL retval 131042 != -29) [2].
>
> I mimicked the test case in a userland program, comparing the generic
> csum_partial() to the x86 implementation [3], and the generic and x86
> implementation does yield a different result.
>
> x86 : -29 : 0xffffffe3
> generic : 65507 : 0x0000ffe3
> arm : 131042 : 0x0001ffe2
>
> Who is correct? :-) It would be nice to get rid of this failed case...
>
There are all the same value :), they all fold to u16 0xFFE3
Maybe the test needs a fix, there is a missing folding.
>
> Thanks,
> Björn
>
>
> [1] https://qa-reports.linaro.org/lkft/linux-next-master/build/next-20201112/testrun/3430401/suite/kselftest/test/bpf.test_verifier/log
> [2] https://qa-reports.linaro.org/lkft/linux-mainline-master/build/v5.10-rc3-207-g585e5b17b92d/testrun/3432361/suite/kselftest/test/bpf.test_verifier/log
> [3] https://gist.github.com/bjoto/dc22d593aa3ac63c2c90632de5ed82e0
>
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next prev parent reply other threads:[~2020-11-13 11:34 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-11-13 10:36 csum_partial() on different archs (selftest/bpf) Björn Töpel
2020-11-13 11:34 ` Eric Dumazet [this message]
2020-11-13 13:17 ` Björn Töpel
2020-11-13 12:24 ` Jean-Philippe Brucker
2020-11-13 13:22 ` Björn Töpel
2020-11-13 14:15 ` Al Viro
2020-11-13 14:32 ` Daniel Borkmann
2020-11-13 17:28 ` Al Viro
2020-11-13 12:42 ` Al Viro
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