linux-kernel - Re: [kbuild-all] Re: net/bpf/test_run.c:154:14: warning: no previous prototype for 'bpf_fentry

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Date:   Mon, 7 Jun 2021 13:39:50 +0800
From:   Rong Chen <rong.a.chen@...el.com>
To:     Yonghong Song <yhs@...com>, kernel test robot <lkp@...el.com>
Cc:     kbuild-all@...ts.01.org, linux-kernel@...r.kernel.org,
        Daniel Borkmann <daniel@...earbox.net>
Subject: Re: [kbuild-all] Re: net/bpf/test_run.c:154:14: warning: no previous
 prototype for 'bpf_fentry_test7'



On 6/4/21 11:52 PM, Yonghong Song wrote:
>
>
> On 6/4/21 12:50 AM, kernel test robot wrote:
>> Hi Yonghong,
>>
>> FYI, the error/warning still remains.
>>
>> tree: 
>> https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git 
>> master
>> head:   f88cd3fb9df228e5ce4e13ec3dbad671ddb2146e
>> commit: d923021c2ce12acb50dc7086a1bf66eed82adf6a bpf: Add tests for 
>> PTR_TO_BTF_ID vs. null comparison
>> date:   11 months ago
>> config: x86_64-rhel (attached as .config)
>> compiler: gcc-6 (Ubuntu 6.4.0-17ubuntu1) 6.4.0 20180424
>> reproduce (this is a W=1 build):
>>          # 
>> https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=d923021c2ce12acb50dc7086a1bf66eed82adf6a
>>          git remote add linus 
>> https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
>>          git fetch --no-tags linus master
>>          git checkout d923021c2ce12acb50dc7086a1bf66eed82adf6a
>>          # save the attached .config to linux build tree
>>          make W=1 ARCH=x86_64
>>
>> If you fix the issue, kindly add following tag as appropriate
>> Reported-by: kernel test robot <lkp@...el.com>
>>
>> All warnings (new ones prefixed by >>):
>>
>>     net/bpf/test_run.c:120:14: warning: no previous prototype for 
>> 'bpf_fentry_test1' [-Wmissing-prototypes]
>>      int noinline bpf_fentry_test1(int a)
>>                   ^~~~~~~~~~~~~~~~
>>     net/bpf/test_run.c:125:14: warning: no previous prototype for 
>> 'bpf_fentry_test2' [-Wmissing-prototypes]
>>      int noinline bpf_fentry_test2(int a, u64 b)
>>                   ^~~~~~~~~~~~~~~~
>>     net/bpf/test_run.c:130:14: warning: no previous prototype for 
>> 'bpf_fentry_test3' [-Wmissing-prototypes]
>>      int noinline bpf_fentry_test3(char a, int b, u64 c)
>>                   ^~~~~~~~~~~~~~~~
>>     net/bpf/test_run.c:135:14: warning: no previous prototype for 
>> 'bpf_fentry_test4' [-Wmissing-prototypes]
>>      int noinline bpf_fentry_test4(void *a, char b, int c, u64 d)
>>                   ^~~~~~~~~~~~~~~~
>>     net/bpf/test_run.c:140:14: warning: no previous prototype for 
>> 'bpf_fentry_test5' [-Wmissing-prototypes]
>>      int noinline bpf_fentry_test5(u64 a, void *b, short c, int d, 
>> u64 e)
>>                   ^~~~~~~~~~~~~~~~
>>     net/bpf/test_run.c:145:14: warning: no previous prototype for 
>> 'bpf_fentry_test6' [-Wmissing-prototypes]
>>      int noinline bpf_fentry_test6(u64 a, void *b, short c, int d, 
>> void *e, u64 f)
>>                   ^~~~~~~~~~~~~~~~
>>>> net/bpf/test_run.c:154:14: warning: no previous prototype for 
>>>> 'bpf_fentry_test7' [-Wmissing-prototypes]
>>      int noinline bpf_fentry_test7(struct bpf_fentry_test_t *arg)
>>                   ^~~~~~~~~~~~~~~~
>>>> net/bpf/test_run.c:159:14: warning: no previous prototype for 
>>>> 'bpf_fentry_test8' [-Wmissing-prototypes]
>>      int noinline bpf_fentry_test8(struct bpf_fentry_test_t *arg)
>>                   ^~~~~~~~~~~~~~~~
>>     net/bpf/test_run.c:164:14: warning: no previous prototype for 
>> 'bpf_modify_return_test' [-Wmissing-prototypes]
>>      int noinline bpf_modify_return_test(int a, int *b)
>>                   ^~~~~~~~~~~~~~~~~~~~~~
>
> I think this has been discussed earlier.
>
> In net/bpf/test_run.c, we have,
>
> __diag_push();
> __diag_ignore(GCC, 8, "-Wmissing-prototypes",
>               "Global functions as their definitions will be in 
> vmlinux BTF");
> int noinline bpf_fentry_test1(int a)
> {
>         return a + 1;
> }
> ...
>
> Unfortunately, the __diag_ignore macro only effective for gcc8 and later.
>
> So for gcc6, the above warning will be emitted. Is it possible for the 
> tool to check and ignore this error if the gcc version is less than 8?
>

Hi Yonghong,

Thanks for the advice, we'll ignore this error later.

Best Regards,
Rong Chen