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

[Lukas Bulwahn]

On Mon, Jan 18, 2021 at 3:44 PM Aditya Srivastava <yashsri421 at gmail.com> wrote:
>
> 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

to emit a warning

> in '.S' files, if it lies within SYM_*_START/END annotation pair.
>
> Suggested-by: Mark Brown <bro... at kernel.org>

Hmm, that is not an email?

Did you test running it on the patch that introduced the bug initially
which then led to the overall discussion I pointed out to you?

Lukas

> Link: https://lore.kernel.org/lkml/20210112210154.GI4646@sirena.org.uk/
> Signed-off-by: Aditya Srivastava <yashsri421 at gmail.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
>