linux-kernel - Re: [PATCH] checkpatch: do not apply "initialise globals to 0" check to BPF progs

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Message-ID: <A8E7D663-AD18-49CE-BC3A-E0D7AC9049FD@fb.com>
Date:   Tue, 9 Feb 2021 16:47:38 +0000
From:   Song Liu <songliubraving@...com>
To:     Joe Perches <joe@...ches.com>
CC:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "bpf@...r.kernel.org" <bpf@...r.kernel.org>,
        Andy Whitcroft <apw@...onical.com>
Subject: Re: [PATCH] checkpatch: do not apply "initialise globals to 0" check
 to BPF progs



> On Feb 8, 2021, at 10:29 PM, Joe Perches <joe@...ches.com> wrote:
> 
> On Mon, 2021-02-08 at 15:40 -0800, Song Liu wrote:
>> BPF programs explicitly initialise global variables to 0 to make sure
>> clang (v10 or older) do not put the variables in the common section.
>> Skip "initialise globals to 0" check for BPF programs to elimiate error
>> messages like:
>> 
>>     ERROR: do not initialise globals to 0
>>     #19: FILE: samples/bpf/tracex1_kern.c:21:
> []
>> diff --git a/scripts/checkpatch.pl b/scripts/checkpatch.pl
> []
>> @@ -4323,7 +4323,11 @@ sub process {
>>  		}
>>  
>> 
>>  # check for global initialisers.
>> -		if ($line =~ /^\+$Type\s*$Ident(?:\s+$Modifier)*\s*=\s*($zero_initializer)\s*;/) {
>> +# Do not apply to BPF programs (tools/testing/selftests/bpf/progs/*.c, samples/bpf/*_kern.c, *.bpf.c).
>> +		if ($line =~ /^\+$Type\s*$Ident(?:\s+$Modifier)*\s*=\s*($zero_initializer)\s*;/ &&
>> +		    $realfile !~ /^tools\/testing\/selftests\/bpf\/progs\/.*\.c/ &&
>> +		    $realfile !~ /^samples\/bpf\/.*_kern.c/ &&
>> +		    $realfile !~ /.bpf.c$/) {
> 
> probably better to make this a function so when additional files are
> added it'd be easier to update this and it will not look as complex.
> 
> 		if ($line =~ /.../ &&
> 		    !exclude_global_initialisers($realfile))

Good point! I will make this a function in v2. 

--ignore is not ideal, because it is common for a BPF test/sample patch
to have both BPF code and user space code. Adding --ignore will skip the
check for user space code. 

Thanks,
Song