linux-kernel - Possible bug in linux-6.2/tools/testing/selftests/powerpc/pmu/sampling_tests/mmcra_thresh_marked_sample

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Date:   Fri, 24 Feb 2023 14:32:09 +0000
From:   David Binderman <dcb314@...mail.com>
To:     "mpe@...erman.id.au" <mpe@...erman.id.au>,
        "npiggin@...il.com" <npiggin@...il.com>,
        "christophe.leroy@...roup.eu" <christophe.leroy@...roup.eu>,
        "shuah@...nel.org" <shuah@...nel.org>,
        "linuxppc-dev@...ts.ozlabs.org" <linuxppc-dev@...ts.ozlabs.org>,
        "linux-kselftest@...r.kernel.org" <linux-kselftest@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Possible bug in
 linux-6.2/tools/testing/selftests/powerpc/pmu/sampling_tests/mmcra_thresh_marked_sample_test.c

Hello there,

I ran the static analyser cppcheck over the linux-6.2 source code and got this:

linux-6.2/tools/testing/selftests/powerpc/pmu/sampling_tests/mmcra_thresh_marked_sample_test.c:68:10: style: Same expression '0x3' found multiple times in chain of '&' operators. [duplicateExpression]

Source code is

    FAIL_IF(EV_CODE_EXTRACT(event.attr.config, sample & 0x3) !=
            get_mmcra_sample_mode(get_reg_value(intr_regs, "MMCRA"), 4));

but

#define EV_CODE_EXTRACT(x, y)   \
    ((x >> ev_shift_##y) & ev_mask_##y)

Given the token pasting, I very much doubt an expression like "sample & 0x3"
will work correctly. Same thing on the line above 

    FAIL_IF(EV_CODE_EXTRACT(event.attr.config, sample >> 2) !=
            get_mmcra_rand_samp_elig(get_reg_value(intr_regs, "MMCRA"), 4));

"sample >> 2" doesn't look like a valid token to me.

Regards

David Binderman