linux-kernel - Re: [PATCH v2] checkpatch: do not apply "initialise globals to 0" check to BPF progs

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Message-ID: <9A955431-E33F-4AEB-8D3F-74032E55CA0A@fb.com>
Date:   Tue, 9 Feb 2021 18:24:42 +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 v2] checkpatch: do not apply "initialise globals to 0"
 check to BPF progs



> On Feb 9, 2021, at 9:24 AM, Joe Perches <joe@...ches.com> wrote:
> 
> On Tue, 2021-02-09 at 09:00 -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:
>> 
>> Cc: Andy Whitcroft <apw@...onical.com>
>> Cc: Joe Perches <joe@...ches.com>
>> Signed-off-by: Song Liu <songliubraving@...com>
>> 
>> ---
>> Changes v1 => v2:
>>   1. Add function exclude_global_initialisers() to keep the code clean.
> 
> thanks.  trivia and a question:
> 
>> diff --git a/scripts/checkpatch.pl b/scripts/checkpatch.pl
> []
>> @@ -2428,6 +2428,15 @@ sub get_raw_comment {
>>  	return $comment;
>>  }
>> 
>> +sub exclude_global_initialisers {
>> +	my ($realfile) = @_;
>> +
>> +	# Do not check for BPF programs (tools/testing/selftests/bpf/progs/*.c, samples/bpf/*_kern.c, *.bpf.c).
>> +	return $realfile =~ /^tools\/testing\/selftests\/bpf\/progs\/.*\.c/ ||
>> +		$realfile =~ /^samples\/bpf\/.*_kern.c/ ||
> 
> The checkpatch convention commonly used for $realfile comparisons
> to file patterns with directory paths is m@...@
> 
> 	return $realfile =~ m@...ols/testing/selftests/bpf/progs/.*\.c@ ||
> 		$realfile =~ m@...mples/bpf/.*_kern\.c@ ||

Will fix. 

> 
>> +		$realfile =~ /.bpf.c$/;
> 
> And lastly, is this pattern meant to escape the periods?
> I presume so, but if not, the leading period isn't useful.
> 
> Maybe:
> 		$realfile =~ m@...f/.*\.bpf\.c$@;

Exactly! Will fix in v3. 

Thanks,
Song

> 
> $ git ls-files | grep "\.bpf\.c$"
> kernel/bpf/preload/iterators/iterators.bpf.c
> tools/bpf/bpftool/skeleton/pid_iter.bpf.c
> tools/bpf/bpftool/skeleton/profiler.bpf.c
> tools/bpf/runqslower/runqslower.bpf.c
> 
> vs
> 
> $ git ls-files | grep ".bpf.c$"
> drivers/net/hyperv/netvsc_bpf.c
> drivers/net/netdevsim/bpf.c
> kernel/bpf/preload/iterators/iterators.bpf.c
> lib/test_bpf.c
> net/core/lwt_bpf.c
> net/ipv4/tcp_bpf.c
> net/ipv4/udp_bpf.c
> net/netfilter/xt_bpf.c
> net/sched/act_bpf.c
> net/sched/cls_bpf.c
> samples/bpf/test_lwt_bpf.c
> tools/bpf/bpftool/skeleton/pid_iter.bpf.c
> tools/bpf/bpftool/skeleton/profiler.bpf.c
> tools/bpf/runqslower/runqslower.bpf.c
> tools/build/feature/test-bpf.c
> tools/build/feature/test-libbpf.c
> tools/lib/bpf/bpf.c
> tools/lib/bpf/libbpf.c
> tools/perf/tests/bpf.c
> tools/testing/selftests/bpf/prog_tests/fexit_bpf2bpf.c
> tools/testing/selftests/bpf/prog_tests/xdp_bpf2bpf.c
> tools/testing/selftests/bpf/progs/fexit_bpf2bpf.c
> tools/testing/selftests/bpf/progs/test_xdp_bpf2bpf.c
> tools/testing/selftests/net/reuseport_bpf.c
> tools/testing/selftests/seccomp/seccomp_bpf.c
> 
>