[PATCH] kconfig: add kconfig-sym-check static checker

[PATCH] kconfig: add kconfig-sym-check static checker

[Andrew Jones]

Add 'make kconfig-sym-check', a static checker that finds Kconfig
symbols referenced in expressions (select, depends on, default, etc.)
but never defined via config/menuconfig anywhere in the tree. New
dangling symbols are reported as errors (exit 1) unless they are
listed in an exclusion file, e.g.

 KCONFIG_SYM_CHECK_EXCLUDES=sym-check-excludes make kconfig-sym-check

The checker also warns about uppercase N/Y/M used as tristate literal
values following the same logic as checkpatch.

This new static checker is the script used for [1] with a few
improvements to avoid some false positives.

Link: https://bugzilla.kernel.org/show_bug.cgi?id=216748 [1]
Signed-off-by: Andrew Jones <andrew.jones@linux.dev>
---
 Makefile                             |  7 ++-
 scripts/kconfig/kconfig-sym-check.pl | 93 ++++++++++++++++++++++++++++
 2 files changed, 99 insertions(+), 1 deletion(-)
 create mode 100755 scripts/kconfig/kconfig-sym-check.pl

diff --git a/Makefile b/Makefile
index fc2d94aafb45..5a0a9f9d6169 100644
--- a/Makefile
+++ b/Makefile
@@ -293,6 +293,7 @@ version_h := include/generated/uapi/linux/version.h
 clean-targets := %clean mrproper cleandocs
 no-dot-config-targets := $(clean-targets) \
 			 cscope gtags TAGS tags help% %docs check% coccicheck \
+			 kconfig-sym-check \
 			 $(version_h) headers headers_% archheaders archscripts \
 			 %asm-generic kernelversion %src-pkg dt_binding_check \
 			 outputmakefile rustavailable rustfmt rustfmtcheck \
@@ -1806,6 +1807,7 @@ help:
 	@echo  '  includecheck    - Check for duplicate included header files'
 	@echo  '  headerdep       - Detect inclusion cycles in headers'
 	@echo  '  coccicheck      - Check with Coccinelle'
+	@echo  '  kconfig-sym-check - Check for dangling Kconfig symbol references'
 	@echo  '  clang-analyzer  - Check with clang static analyzer'
 	@echo  '  clang-tidy      - Check with clang-tidy'
 	@echo  ''
@@ -2227,7 +2229,7 @@ endif
 # Scripts to check various things for consistency
 # ---------------------------------------------------------------------------
 
-PHONY += includecheck versioncheck coccicheck
+PHONY += includecheck versioncheck coccicheck kconfig-sym-check
 
 includecheck:
 	find $(srctree)/* $(RCS_FIND_IGNORE) \
@@ -2242,6 +2244,9 @@ versioncheck:
 coccicheck:
 	$(Q)$(BASH) $(srctree)/scripts/$@
 
+kconfig-sym-check:
+	$(Q)cd $(srctree) && $(PERL) scripts/kconfig/kconfig-sym-check.pl $(KCONFIG_SYM_CHECK_EXCLUDES)
+
 PHONY += checkstack kernelrelease kernelversion image_name
 
 # UML needs a little special treatment here.  It wants to use the host
diff --git a/scripts/kconfig/kconfig-sym-check.pl b/scripts/kconfig/kconfig-sym-check.pl
new file mode 100755
index 000000000000..a6907e585962
--- /dev/null
+++ b/scripts/kconfig/kconfig-sym-check.pl
@@ -0,0 +1,93 @@
+#!/usr/bin/env perl
+# SPDX-License-Identifier: GPL-2.0
+
+use warnings;
+use strict;
+
+my $kconfig_sym_check_excludes = undef;
+$kconfig_sym_check_excludes = $ARGV[0] if (defined $ARGV[0]);
+
+my @files = `git ls-files '*Kconfig*'`;
+my %configs = ();
+my %refs = ();
+
+foreach my $file (<@files>) {
+	open F, $file or die "Cannot open $file: $!";
+
+	my $help = 0;
+	my $help_level;
+	my $level;
+
+	while (<F>) {
+		chomp;
+
+		next if /^\s*$/;
+		next if /^\s*#/;
+
+		/^(\s*)/;
+		$level = length $1;
+
+		if ($help && $level < $help_level) {
+			$help = 0;
+		}
+
+		next if ($help);
+
+		if (/^\s*(help|\-\-\-help\-\-\-)$/) {
+			$help = 1;
+			$_ = <F>;
+			/^(\s*)/;
+			$help_level = length $1;
+			next;
+		}
+
+		if (/^\s*(config|menuconfig)\s+([a-zA-Z0-9_]+)\s*(#.*)?$/) {
+			$configs{$2}++;
+			next;
+		}
+
+		my $comment_idx = index $_, "#";
+		if ($comment_idx != -1) {
+			$_ = substr $_, 0, $comment_idx;
+		}
+
+		if (/^\s*(default|def_bool|def_tristate|select|depends\s+on|imply|visible\s+if|range|if)\s+(.+)\s*$/) {
+			my $s = $2;
+			$s =~ s/\$\(.*\)//g;
+			$s =~ s/'[^']*'//g;
+			$s =~ s/"[^"]*"//g;
+			$s =~ s/%%[^%]*%%//g;
+			my @syms = split /[^a-zA-Z0-9_]+/, $s;
+			map {
+				$refs{$_}++ if (/[a-zA-Z]/ && $_ ne "if" && $_ ne "y" && $_ ne "n" && $_ ne "m" && !(/^0[xX]/ && !/[g-wy-zG-WY-Z]/));
+			} @syms
+		}
+	}
+
+	close F;
+}
+
+my %known_syms = ();
+if (defined $kconfig_sym_check_excludes) {
+	my $file = $kconfig_sym_check_excludes;
+	open F, $file or die "Cannot open $file: $!";
+	while (<F>) {
+		chomp;
+		next if /^\s*$/;
+		next if /^\s*#/;
+		$known_syms{$1}++ if (/^\s*([a-zA-Z0-9_]+)\s*(#.*)?$/);
+	}
+}
+
+my $ret = 0;
+foreach my $k (sort keys %refs) {
+	next if (exists $configs{$k} || exists $known_syms{$k});
+
+	print "$k";
+	print " - warning: '$k' is probably not what you want; Kconfig tristate literals are always lowercase ('n', 'y', 'm')" if ($k eq "N" || $k eq "Y" || $k eq "M");
+	print "\n";
+
+	$ret = 1;
+}
+
+exit $ret;
-- 
2.43.0

Re: [PATCH] kconfig: add kconfig-sym-check static checker

[Andy Shevchenko]

+Cc: Randy: FYI.

On Wed, May 13, 2026 at 04:03:29PM -0500, Andrew Jones wrote:
> Add 'make kconfig-sym-check', a static checker that finds Kconfig
> symbols referenced in expressions (select, depends on, default, etc.)
> but never defined via config/menuconfig anywhere in the tree. New
> dangling symbols are reported as errors (exit 1) unless they are
> listed in an exclusion file, e.g.
> 
>  KCONFIG_SYM_CHECK_EXCLUDES=sym-check-excludes make kconfig-sym-check
> 
> The checker also warns about uppercase N/Y/M used as tristate literal
> values following the same logic as checkpatch.
> 
> This new static checker is the script used for [1] with a few
> improvements to avoid some false positives.

Acked-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>

-- 
With Best Regards,
Andy Shevchenko

Re: [PATCH] kconfig: add kconfig-sym-check static checker

[Randy Dunlap]

On 5/13/26 2:03 PM, Andrew Jones wrote:
> Add 'make kconfig-sym-check', a static checker that finds Kconfig
> symbols referenced in expressions (select, depends on, default, etc.)
> but never defined via config/menuconfig anywhere in the tree. New
> dangling symbols are reported as errors (exit 1) unless they are
> listed in an exclusion file, e.g.
> 
>  KCONFIG_SYM_CHECK_EXCLUDES=sym-check-excludes make kconfig-sym-check
> 
> The checker also warns about uppercase N/Y/M used as tristate literal
> values following the same logic as checkpatch.
> 
> This new static checker is the script used for [1] with a few
> improvements to avoid some false positives.
> 
> Link: https://bugzilla.kernel.org/show_bug.cgi?id=216748 [1]
> Signed-off-by: Andrew Jones <andrew.jones@linux.dev>
> ---
>  Makefile                             |  7 ++-
>  scripts/kconfig/kconfig-sym-check.pl | 93 ++++++++++++++++++++++++++++
>  2 files changed, 99 insertions(+), 1 deletion(-)
>  create mode 100755 scripts/kconfig/kconfig-sym-check.pl

Acked-by: Randy Dunlap <rdunlap@infradead.org>
Tested-by: Randy Dunlap <rdunlap@infradead.org>

Thanks.

-- 
~Randy

Re: [PATCH] kconfig: add kconfig-sym-check static checker

[Nathan Chancellor]

On Wed, 13 May 2026 16:03:29 -0500, Andrew Jones <andrew.jones@linux.dev> wrote:

Hi Andrew,

> [...]
> 
> This new static checker is the script used for [1] with a few
> improvements to avoid some false positives.
> 
> Link: https://bugzilla.kernel.org/show_bug.cgi?id=216748 [1]
> Signed-off-by: Andrew Jones <andrew.jones@linux.dev>

I think something like this is reasonable, as least until kconfirm
is potentially ready for integration into the tree.

  https://lore.kernel.org/20260509203808.1142311-1-julianbraha@gmail.com/

That said, I don't know perl, so some superficial comments to follow.

>
>
> diff --git a/Makefile b/Makefile
> index e27c91ea56fc..75487383805b 100644
> --- a/Makefile
> +++ b/Makefile
> @@ -2240,6 +2242,9 @@ versioncheck:
>  coccicheck:
>  	$(Q)$(BASH) $(srctree)/scripts/$@
>  
> +kconfig-sym-check:
> +	$(Q)cd $(srctree) && $(PERL) scripts/kconfig/kconfig-sym-check.pl $(KCONFIG_SYM_CHECK_EXCLUDES)

I would prefer to avoid the 'cd $(srctree)' here.

>
> diff --git a/scripts/kconfig/kconfig-sym-check.pl b/scripts/kconfig/kconfig-sym-check.pl
> new file mode 100755
> index 000000000000..a6907e585962
> --- /dev/null
> +++ b/scripts/kconfig/kconfig-sym-check.pl
> @@ -0,0 +1,93 @@
> +#!/usr/bin/env perl
> +# SPDX-License-Identifier: GPL-2.0
> +
> +use warnings;
> +use strict;
> +
> +my $kconfig_sym_check_excludes = undef;
> +$kconfig_sym_check_excludes = $ARGV[0] if (defined $ARGV[0]);
> +
> +my @files = `git ls-files '*Kconfig*'`;

What happens if you run this command on a release tarball? We should
probably use something like

  find $(srctree) -name '*Kconfig*'

here, which would avoid needing the 'cd $(srctree)' above (although
kconfig-sym-check.pl would need to be prefixed with $(srctree)/ to
ensure the path is valid).

Sashiko has some additional comments that may be relevant, if you have
not already seen them.

  https://sashiko.dev/#/patchset/19870

-- 
Cheers,
Nathan

Re: [PATCH] kconfig: add kconfig-sym-check static checker

[Andrew Jones]

On Thu, May 14, 2026 at 10:32:12PM +0900, Nathan Chancellor wrote:
> On Wed, 13 May 2026 16:03:29 -0500, Andrew Jones <andrew.jones@linux.dev> wrote:
> 
> Hi Andrew,
> 
> > [...]
> > 
> > This new static checker is the script used for [1] with a few
> > improvements to avoid some false positives.
> > 
> > Link: https://bugzilla.kernel.org/show_bug.cgi?id=216748 [1]
> > Signed-off-by: Andrew Jones <andrew.jones@linux.dev>
> 
> I think something like this is reasonable, as least until kconfirm
> is potentially ready for integration into the tree.
> 
>   https://lore.kernel.org/20260509203808.1142311-1-julianbraha@gmail.com/
> 
> That said, I don't know perl, so some superficial comments to follow.
> 
> >
> >
> > diff --git a/Makefile b/Makefile
> > index e27c91ea56fc..75487383805b 100644
> > --- a/Makefile
> > +++ b/Makefile
> > @@ -2240,6 +2242,9 @@ versioncheck:
> >  coccicheck:
> >  	$(Q)$(BASH) $(srctree)/scripts/$@
> >  
> > +kconfig-sym-check:
> > +	$(Q)cd $(srctree) && $(PERL) scripts/kconfig/kconfig-sym-check.pl $(KCONFIG_SYM_CHECK_EXCLUDES)
> 
> I would prefer to avoid the 'cd $(srctree)' here.
> 
> >
> > diff --git a/scripts/kconfig/kconfig-sym-check.pl b/scripts/kconfig/kconfig-sym-check.pl
> > new file mode 100755
> > index 000000000000..a6907e585962
> > --- /dev/null
> > +++ b/scripts/kconfig/kconfig-sym-check.pl
> > @@ -0,0 +1,93 @@
> > +#!/usr/bin/env perl
> > +# SPDX-License-Identifier: GPL-2.0
> > +
> > +use warnings;
> > +use strict;
> > +
> > +my $kconfig_sym_check_excludes = undef;
> > +$kconfig_sym_check_excludes = $ARGV[0] if (defined $ARGV[0]);
> > +
> > +my @files = `git ls-files '*Kconfig*'`;
> 
> What happens if you run this command on a release tarball? We should
> probably use something like
> 
>   find $(srctree) -name '*Kconfig*'
> 
> here, which would avoid needing the 'cd $(srctree)' above (although
> kconfig-sym-check.pl would need to be prefixed with $(srctree)/ to
> ensure the path is valid).
> 
> Sashiko has some additional comments that may be relevant, if you have
> not already seen them.
> 
>   https://sashiko.dev/#/patchset/19870

Thanks, Nathan. I'll make some improvements based on your and Sashiko's
comments and send a v2.

drew

Re: [PATCH] kconfig: add kconfig-sym-check static checker

[Julian Braha]

On 5/14/26 14:32, Nathan Chancellor wrote:
> On Wed, 13 May 2026 16:03:29 -0500, Andrew Jones <andrew.jones@linux.dev> wrote:
> 
> Hi Andrew,
> 
>> [...]
>>
>> This new static checker is the script used for [1] with a few
>> improvements to avoid some false positives.
>>
>> Link: https://bugzilla.kernel.org/show_bug.cgi?id=216748 [1]
>> Signed-off-by: Andrew Jones <andrew.jones@linux.dev>
> 
> I think something like this is reasonable, as least until kconfirm
> is potentially ready for integration into the tree.
> 
>   https://lore.kernel.org/20260509203808.1142311-1-julianbraha@gmail.com/
> 
Agreed, don't let kconfirm block this. While I do have future plans to
support these same alarms in that tool, there's currently no overlap
between these two, and no ETA on that support either ;)

Side note, this script was actually part of my inspiration to go
searching for more misusage of kconfig and build kconfirm. I also
previously cleaned up some dead code, thanks to this script:
https://lore.kernel.org/all/20260309122321.1528622-1-julianbraha@gmail.com/

- Julian Braha

Re: [PATCH] kconfig: add kconfig-sym-check static checker

[Nathan Chancellor]

On Thu, May 14, 2026 at 04:26:42PM +0100, Julian Braha wrote:
> On 5/14/26 14:32, Nathan Chancellor wrote:
> > On Wed, 13 May 2026 16:03:29 -0500, Andrew Jones <andrew.jones@linux.dev> wrote:
> > 
> > Hi Andrew,
> > 
> >> [...]
> >>
> >> This new static checker is the script used for [1] with a few
> >> improvements to avoid some false positives.
> >>
> >> Link: https://bugzilla.kernel.org/show_bug.cgi?id=216748 [1]
> >> Signed-off-by: Andrew Jones <andrew.jones@linux.dev>
> > 
> > I think something like this is reasonable, as least until kconfirm
> > is potentially ready for integration into the tree.
> > 
> >   https://lore.kernel.org/20260509203808.1142311-1-julianbraha@gmail.com/
> > 
> Agreed, don't let kconfirm block this. While I do have future plans to
> support these same alarms in that tool, there's currently no overlap
> between these two, and no ETA on that support either ;)
> 
> Side note, this script was actually part of my inspiration to go
> searching for more misusage of kconfig and build kconfirm. I also
> previously cleaned up some dead code, thanks to this script:
> https://lore.kernel.org/all/20260309122321.1528622-1-julianbraha@gmail.com/

Thanks a lot for that additional context, especially around the lack of
overlap between the two tools. This seems worth pursuing then.

-- 
Cheers,
Nathan