netdev - Re: [PATCH] selftests/bpf: fix warning comparing pointer to 0

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Date:   Fri, 23 Apr 2021 19:57:22 +0800
From:   Abaci Robot <abaci@...ux.alibaba.com>
To:     Daniel Borkmann <daniel@...earbox.net>,
        Jiapeng Chong <jiapeng.chong@...ux.alibaba.com>
Cc:     linux-kselftest@...r.kernel.org, netdev@...r.kernel.org,
        bpf@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] selftests/bpf: fix warning comparing pointer to 0

在 2021/4/23 上午5:56, Daniel Borkmann 写道:
> On 4/22/21 12:00 PM, Jiapeng Chong wrote:
>> Fix the following coccicheck warning:
>>
>> ./tools/testing/selftests/bpf/progs/fentry_test.c:76:15-16: WARNING
>> comparing pointer to 0.
>>
>> Reported-by: Abaci Robot <abaci@...ux.alibaba.com>
>> Signed-off-by: Jiapeng Chong <jiapeng.chong@...ux.alibaba.com>
> 
> How many more of those 'comparing pointer to 0' patches do you have?
> Right now we already merged the following with similar trivial pattern:
> 
> - ebda107e5f222a086c83ddf6d1ab1da97dd15810
> - a9c80b03e586fd3819089fbd33c38fb65ad5e00c
> - 04ea63e34a2ee85cfd38578b3fc97b2d4c9dd573
> 
> Given they don't really 'fix' anything, I would like to reduce such
> patch cleanup churn on the bpf tree. Please _consolidate_ all other
> such occurrences into a _single_ patch for BPF selftests, and resubmit.
> 
> Thanks!
> 
>> ---
>>   tools/testing/selftests/bpf/progs/fentry_test.c | 2 +-
>>   1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/tools/testing/selftests/bpf/progs/fentry_test.c 
>> b/tools/testing/selftests/bpf/progs/fentry_test.c
>> index 52a550d..d4247d6 100644
>> --- a/tools/testing/selftests/bpf/progs/fentry_test.c
>> +++ b/tools/testing/selftests/bpf/progs/fentry_test.c
>> @@ -73,7 +73,7 @@ int BPF_PROG(test7, struct bpf_fentry_test_t *arg)
>>   SEC("fentry/bpf_fentry_test8")
>>   int BPF_PROG(test8, struct bpf_fentry_test_t *arg)
>>   {
>> -    if (arg->a == 0)
>> +    if (!arg->a)
>>           test8_result = 1;
>>       return 0;
>>   }
>>

Hi,

Thanks for your reply.

TLDR:
1. Now all this kind of warning in tools/testing/selftests/bpf/progs/ 
were reported and discussed except this one.
2. We might not do scanning and check reports on 
tools/testing/selftests/bpf/progs/ in the future, because some 
contributors want the progs to stay as close as possible to the way they 
were written. 
(https://patchwork.kernel.org/project/linux-kselftest/patch/1618307549-78149-1-git-send-email-yang.lee@linux.alibaba.com/)


Details:

We have checked the recent linux master (commit: 
16fc44d6387e260f4932e9248b985837324705d8), and the related reports and 
their current status is shown as follows:

./tools/testing/selftests/bpf/progs/fentry_test.c:67:12-13: WARNING 
comparing pointer to 0
(not appear in the bpf-next branch)


./tools/testing/selftests/bpf/progs/fentry_test.c:76:15-16: WARNING 
comparing pointer to 0
(the above patch try to eliminate it)


./tools/testing/selftests/bpf/progs/fexit_test.c:68:12-13: WARNING 
comparing pointer to 0
./tools/testing/selftests/bpf/progs/fexit_test.c:77:15-16: WARNING 
comparing pointer to 0
(eliminated in 
https://kernel.source.codeaurora.cn/pub/scm/linux/kernel/git/next/linux-next.git/commit/?id=ebda107e5f222a086c83ddf6d1ab1da97dd15810)

./tools/testing/selftests/bpf/progs/profiler.inc.h:364:18-22: WARNING 
comparing pointer to 0
./tools/testing/selftests/bpf/progs/profiler.inc.h:364:18-22: WARNING 
comparing pointer to 0, suggest !E
./tools/testing/selftests/bpf/progs/profiler.inc.h:537:23-27: WARNING 
comparing pointer to 0
./tools/testing/selftests/bpf/progs/profiler.inc.h:537:23-27: WARNING 
comparing pointer to 0, suggest !E
./tools/testing/selftests/bpf/progs/profiler.inc.h:544:21-25: WARNING 
comparing pointer to 0
./tools/testing/selftests/bpf/progs/profiler.inc.h:544:21-25: WARNING 
comparing pointer to 0, suggest !E
./tools/testing/selftests/bpf/progs/profiler.inc.h:692:29-33: WARNING 
comparing pointer to 0
./tools/testing/selftests/bpf/progs/profiler.inc.h:770:13-17: WARNING 
comparing pointer to 0
(Discussed in 
https://patchwork.kernel.org/project/linux-kselftest/patch/1618307549-78149-1-git-send-email-yang.lee@linux.alibaba.com/)

./tools/testing/selftests/bpf/progs/test_global_func10.c:17:12-13: 
WARNING comparing pointer to 0
(cleanup in 
https://kernel.source.codeaurora.cn/pub/scm/linux/kernel/git/next/linux-next.git/commit/?id=04ea63e34a2ee85cfd38578b3fc97b2d4c9dd573)

Thanks.