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

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:

Link: https://lkml.kernel.org/r/20210209211954.490077-1-songliubraving@fb.com
Signed-off-by: Song Liu <songliubraving@fb.com>
Acked-by: Joe Perches <joe@perches.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/scripts/checkpatch.pl b/scripts/checkpatch.pl
index 75c9331..df8b23d 100755 (executable)
--- a/scripts/checkpatch.pl
+++ b/scripts/checkpatch.pl
@@ -2453,6 +2453,15 @@ 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 $realfile =~ m@^tools/testing/selftests/bpf/progs/.*\.c$@ ||
+               $realfile =~ m@^samples/bpf/.*_kern\.c$@ ||
+               $realfile =~ m@/bpf/.*\.bpf\.c$@;
+}
+
 sub process {
        my $filename = shift;
 
@@ -4358,7 +4367,8 @@ 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) {