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

[PATCH] 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>
---
 scripts/checkpatch.pl | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/scripts/checkpatch.pl b/scripts/checkpatch.pl
index 1afe3af1cc097..24d1856187651 100755
--- 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/ &&
+		    $realfile !~ /.bpf.c$/) {
 			if (ERROR("GLOBAL_INITIALISERS",
 				  "do not initialise globals to $1\n" . $herecurr) &&
 			    $fix) {
-- 
2.24.1

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

[Joe Perches]

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))


>  			if (ERROR("GLOBAL_INITIALISERS",
>  				  "do not initialise globals to $1\n" . $herecurr) &&
>  			    $fix) {

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

[Joe Perches]

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:

Another possible option is simply to add --ignore=GLOBAL_INITIALISERS
to the checkpatch command line for these files.

> 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/ &&
> +		    $realfile !~ /.bpf.c$/) {
>  			if (ERROR("GLOBAL_INITIALISERS",
>  				  "do not initialise globals to $1\n" . $herecurr) &&
>  			    $fix) {

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

[Song Liu]

> On Feb 8, 2021, at 10:29 PM, Joe Perches <joe@perches.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