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
David Binderman <[email protected]> writes:
> 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]
Thanks.
> 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.
It expands to:
if ((((event.attr.config >> ev_shift_sample >> 2) & ev_mask_sample >> 2) != get_mmcra_rand_samp_elig(get_reg_value(intr_regs, "MMCRA"), 4)))
Which AFAICS is valid, and does compile.
Whether it's what the author actually intended is less clear.
And the other example with & 0x3 seems obviously wrong, it expands to:
if ((((event.attr.config >> ev_shift_sample & 0x3) & ev_mask_sample & 0x3) != get_mmcra_sample_mode(get_reg_value(intr_regs, "MMCRA"), 4)))
The shift is 24, so bitwise anding it with 0x3 gets 0 which doesn't seem
likely to be what was intended.
cheers
On 2/27/23 10:56, Michael Ellerman wrote:
> David Binderman <[email protected]> writes:
>> 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]
Hi,
Thanks David for reporting it.
>
> Thanks.
>
>> 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.
>
> It expands to:
>
> if ((((event.attr.config >> ev_shift_sample >> 2) & ev_mask_sample >> 2) != get_mmcra_rand_samp_elig(get_reg_value(intr_regs, "MMCRA"), 4)))
>
> Which AFAICS is valid, and does compile.
>
> Whether it's what the author actually intended is less clear.
>
> And the other example with & 0x3 seems obviously wrong, it expands to:
>
> if ((((event.attr.config >> ev_shift_sample & 0x3) & ev_mask_sample & 0x3) != get_mmcra_sample_mode(get_reg_value(intr_regs, "MMCRA"), 4)))
>
> The shift is 24, so bitwise anding it with 0x3 gets 0 which doesn't seem
> likely to be what was intended.
>
Hi Michael,
Thanks for checking it. The intention is to check 3 bits of
rand_samp_elig field and 2 bits of rand_samp_mode field from the
sampling bits. Basically we first want to extract that sample field
using EV_CODE_EXTRACT macro and then fetch required value of
rand_samp_elig and rand_samp_mode, to compare it with MMCRA bits.
Right approach to do that would be:
FAIL_IF((EV_CODE_EXTRACT(event.attr.config, sample) >> 2) !=
get_mmcra_rand_samp_elig(get_reg_value(intr_regs, "MMCRA"), 4));
FAIL_IF((EV_CODE_EXTRACT(event.attr.config, sample) & 0x3) !=
get_mmcra_rand_samp_elig(get_reg_value(intr_regs, "MMCRA"), 4));
I will send a fix patch for same.
Thanks,
Kajol Jain
> cheers