linux-kernel - Re: [PATCH v3] checkpatch: add warning for avoiding .L prefix symbols in assembly files

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Date:   Mon, 25 Jan 2021 10:15:49 -0800
From:   Nick Desaulniers <ndesaulniers@...gle.com>
To:     Joe Perches <joe@...ches.com>
Cc:     Aditya Srivastava <yashsri421@...il.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Lukas Bulwahn <lukas.bulwahn@...il.com>,
        dwaipayanray1@...il.com, Mark Brown <broonie@...nel.org>,
        Josh Poimboeuf <jpoimboe@...hat.com>,
        linux-kernel-mentees@...ts.linuxfoundation.org,
        clang-built-linux <clang-built-linux@...glegroups.com>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v3] checkpatch: add warning for avoiding .L prefix symbols
 in assembly files

On Sat, Jan 23, 2021 at 1:01 PM Joe Perches <joe@...ches.com> wrote:
>
> 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@...nel.org>
> > Link: https://lore.kernel.org/lkml/20210112210154.GI4646@sirena.org.uk
> > Signed-off-by: Aditya Srivastava <yashsri421@...il.com>
>
> Acked-by: Joe Perches <joe@...ches.com>

Acked-by: Nick Desaulniers <ndesaulniers@...gle.com>

Thanks for the patch Aditya!

>
> > ---
> > * 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)$/);
> >
> >
>
>


-- 
Thanks,
~Nick Desaulniers