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Subject: Re: [PATCH v3] checkpatch: add warning for avoiding .L prefix
 symbols in assembly files
From:   Joe Perches <joe@perches.com>
To:     Aditya Srivastava <yashsri421@gmail.com>,
        Andrew Morton <akpm@linux-foundation.org>
Cc:     lukas.bulwahn@gmail.com, dwaipayanray1@gmail.com,
        broonie@kernel.org, ndesaulniers@google.com, jpoimboe@redhat.com,
        linux-kernel-mentees@lists.linuxfoundation.org,
        clang-built-linux@googlegroups.com, linux-kernel@vger.kernel.org
Date:   Sat, 23 Jan 2021 13:01:42 -0800
In-Reply-To: <20210123190459.9701-1-yashsri421@gmail.com>
References: <f23f4003-0017-d52a-39b9-2737e60182bb@gmail.com>
         <20210123190459.9701-1-yashsri421@gmail.com>
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On Sun, 2021-01-24 at 00:34 +0530, Aditya Srivastava wrote:
> objtool requires that all code must be contained in an ELF symbol.
> Symbol names that have a '.L' prefix 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
> for '.S' files, if it denotes range of code via SYM_*_START/END
> annotation pair.
> 
> Suggested-by: Mark Brown <broonie@kernel.org>
> Link: https://lore.kernel.org/lkml/20210112210154.GI4646@sirena.org.uk
> Signed-off-by: Aditya Srivastava <yashsri421@gmail.com>

Acked-by: Joe Perches <joe@perches.com>

> ---
> * Applies perfectly on next-20210122
> 
> Changes in v3:
> - Modify regex for SYM_*_START/END pair
> - remove check for arch/x86/entry/* and arch/x86/lib/*
> - change 'Link:' in commit message to lkml
> - Modify commit description accordingly
> 
> Changes in v2:
> - Reduce the check to only SYM_*_START/END lines
> - Reduce the check for only .S files in arch/x86/entry/* and arch/x86/lib/* as suggested by Josh and Nick
> - Modify commit message
> 
> ?scripts/checkpatch.pl | 7 +++++++
> ?1 file changed, 7 insertions(+)
> 
> diff --git a/scripts/checkpatch.pl b/scripts/checkpatch.pl
> index 7030c4d6d126..4a03326c87b6 100755
> --- a/scripts/checkpatch.pl
> +++ b/scripts/checkpatch.pl
> @@ -3590,6 +3590,13 @@ sub process {
> ?			}
> ?		}
> ?
> 
> +# check for .L prefix local symbols in .S files
> +		if ($realfile =~ /\.S$/ &&
> +		    $line =~ /^\+\s*(?:[A-Z]+_)?SYM_[A-Z]+_(?:START|END)(?:_[A-Z_]+)?\s*\(\s*\.L/) {
> +			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)$/);
> ?
>