Thread (11 messages) 11 messages, 3 authors, 2021-01-19

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

From: Dwaipayan Ray <dwaipayanray1@gmail.com>
Date: 2021-01-16 12:43:49

On Sat, Jan 16, 2021 at 5:52 PM Aditya Srivastava [off-list ref] wrote:
quoted hunk ↗ jump to hunk
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 warning on finding the usage of '.L' symbols
in '.S' files.

Suggested-by: Mark Brown <broonie@kernel.org>
Link: https://lore.kernel.org/lkml/20210112210154.GI4646@sirena.org.uk/ (local)
Signed-off-by: Aditya Srivastava <redacted>
---
 scripts/checkpatch.pl | 6 ++++++
 1 file changed, 6 insertions(+)
diff --git a/scripts/checkpatch.pl b/scripts/checkpatch.pl
index 7030c4d6d126..87d96a039e64 100755
--- a/scripts/checkpatch.pl
+++ b/scripts/checkpatch.pl
@@ -3590,6 +3590,12 @@ sub process {
                        }
                }

+# check for .L prefix local symbols in .S files
+               if ($realfile =~ /\.S$/ && $line =~ /\.L\S+/) {
+                       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" . $herecurr);
+               }
+
 # check we are in a valid source file C or perl if not then ignore this hunk
                next if ($realfile !~ /\.(h|c|pl|dtsi|dts)$/);

--
2.17.1
From an earlier conversation:
  So basically, you can use an .L symbol *inside* a function or a code
  segment, you just can't use the .L symbol to contain the code using a
  SYM_*_START/END annotation pair.
So this check warns on all uses of the .L prefix
I think that might be incorrect.

Thanks,
Dwaipayan.
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