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

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

[Song Liu]

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@canonical.com>
Cc: Joe Perches <joe@perches.com>
Signed-off-by: Song Liu <songliubraving@fb.com>

---
Changes v1 => v2:
  1. Add function exclude_global_initialisers() to keep the code clean.
---
 scripts/checkpatch.pl | 12 +++++++++++-
 1 file changed, 11 insertions(+), 1 deletion(-)

diff --git a/scripts/checkpatch.pl b/scripts/checkpatch.pl
index 1afe3af1cc097..c46a3d2713062 100755
--- 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/ ||
+		$realfile =~ /.bpf.c$/;
+}
+
 sub process {
 	my $filename = shift;
 
@@ -4323,7 +4332,8 @@ sub process {
 		}
 
 # check for global initialisers.
-		if ($line =~ /^\+$Type\s*$Ident(?:\s+$Modifier)*\s*=\s*($zero_initializer)\s*;/) {
+		if ($line =~ /^\+$Type\s*$Ident(?:\s+$Modifier)*\s*=\s*($zero_initializer)\s*;/ &&
+		    !exclude_global_initialisers($realfile)) {
 			if (ERROR("GLOBAL_INITIALISERS",
 				  "do not initialise globals to $1\n" . $herecurr) &&
 			    $fix) {
-- 
2.24.1

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

[Joe Perches]

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@canonical.com>
> Cc: Joe Perches <joe@perches.com>
> Signed-off-by: Song Liu <songliubraving@fb.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@^tools/testing/selftests/bpf/progs/.*\.c@ ||
		$realfile =~ m@^samples/bpf/.*_kern\.c@ ||

> +		$realfile =~ /.bpf.c$/;

And lastly, is this pattern meant to escape the periods?
I presume so, but if not, the leading period isn't useful.

Maybe:
		$realfile =~ m@/bpf/.*\.bpf\.c$@;

$ 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

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

[Song Liu]

> On Feb 9, 2021, at 9:24 AM, Joe Perches <joe@perches.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@canonical.com>
>> Cc: Joe Perches <joe@perches.com>
>> Signed-off-by: Song Liu <songliubraving@fb.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@^tools/testing/selftests/bpf/progs/.*\.c@ ||
> 		$realfile =~ m@^samples/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:
> 		$realfile =~ m@/bpf/.*\.bpf\.c$@;

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
> 
>