linux-kernel - [PATCH] checkpatch: add warning for avoiding .L prefix symbols in assembly files

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Date:   Wed, 20 Jan 2021 12:55:47 +0530
From:   Aditya Srivastava <yashsri421@...il.com>
To:     linux-kernel@...r.kernel.org
Cc:     yashsri421@...il.com, lukas.bulwahn@...il.com,
        dwaipayanray1@...il.com, broonie@...nel.org, joe@...ches.com,
        linux-kernel-mentees@...ts.linuxfoundation.org,
        clang-built-linux@...glegroups.com
Subject: [PATCH] checkpatch: add warning for avoiding .L prefix symbols in assembly files

Local symbols prefixed with '.L' do not emit symbol table entries, as
they have special meaning for the assembler.

'.L' prefixed symbols can be used within a code region, but should be
avoided for denoting a range of code via 'SYM_*_START/END' annotations.

Add a new check to emit a warning on finding the usage of '.L' symbols
in '.S' files, if it lies within SYM_*_START/END annotation pair.

Suggested-by: Mark Brown <broonie@...nel.org>
Link: https://lore.kernel.org/lkml/20210112210154.GI4646@sirena.org.uk/
Signed-off-by: Aditya Srivastava <yashsri421@...il.com>
---
 scripts/checkpatch.pl | 22 ++++++++++++++++++++++
 1 file changed, 22 insertions(+)

diff --git a/scripts/checkpatch.pl b/scripts/checkpatch.pl
index 7030c4d6d126..858b5def61e9 100755
--- a/scripts/checkpatch.pl
+++ b/scripts/checkpatch.pl
@@ -2501,6 +2501,9 @@ sub process {
 
 	my $checklicenseline = 1;
 
+	# record SYM_*_START/END annotation pair count, for AVOID_L_PREFIX
+	my $sym_start_block = 0;
+
 	sanitise_line_reset();
 	my $line;
 	foreach my $rawline (@rawlines) {
@@ -3590,6 +3593,25 @@ sub process {
 			}
 		}
 
+# check for .L prefix local symbols in .S files
+		if ($realfile =~ /\.S$/) {
+			if ($line =~ /SYM_.*_START/ ||
+			    (defined $context_function && $context_function =~ /SYM_.*_START/)) {
+				$sym_start_block++;
+			}
+
+			if ($line=~ /\.L\S+/ &&		# line contains .L prefixed local symbol
+			    $sym_start_block > 0) {	# lies between SYM_*_START and SYM_*_END pair
+				WARN("AVOID_L_PREFIX",
+					"Avoid using '.L' prefixed local symbol names for denoting a range of code via 'SYM_*_START/END' annotations; see Documentation/asm-annotations.rst\n" . $herecurr);
+			}
+
+			if ($line =~ /SYM_.*_END/ ||
+			    (defined $context_function && $context_function =~ /SYM_.*_END/)) {
+				$sym_start_block--;
+			}
+		}
+
 # check we are in a valid source file C or perl if not then ignore this hunk
 		next if ($realfile !~ /\.(h|c|pl|dtsi|dts)$/);
 
-- 
2.17.1