[PATCH] kbuild: check MODULE_* macros in non-modular code

[Masahiro Yamada]

Paul Gortmaker sent a lot of patches to remove orphan modular code.
You can see his contributions by:

  $ git log --grep='make.* explicitly non-modular'

To help this work, this commit adds simple shell-script to detect
MODULE_ tags used in non-modular code.

It displays suspicious use of MODULE_LICENSE, MODULE_AUTHOR,
MODULE_DESCRIPTION, etc.

I was not sure about module_param() or MODULE_PARM_DESC(). A lot of
non-modular code uses module_param() to prefix the kernel parameter
with the file name it resides in. If we changed module_param() to
core_param(), the interface would be broken. MODULE_PARM_DESC() in
non-modular code could be turned into comments or something, but I
am not sure. I did not check them.

I built x86_64_defconfig of v5.4-rc8, and this script detected
the following:

notice: asymmetric_keys: MODULE macros found in non-modular code
notice: binfmt_elf: MODULE macros found in non-modular code
notice: bsg: MODULE macros found in non-modular code
notice: compat_binfmt_elf: MODULE macros found in non-modular code
notice: component: MODULE macros found in non-modular code
notice: debugfs: MODULE macros found in non-modular code
notice: drm_mipi_dsi: MODULE macros found in non-modular code
notice: freq_table: MODULE macros found in non-modular code
notice: glob: MODULE macros found in non-modular code
notice: intel_pstate: MODULE macros found in non-modular code
notice: n_null: MODULE macros found in non-modular code
notice: nvmem_core: MODULE macros found in non-modular code
notice: power_supply: MODULE macros found in non-modular code
notice: thermal_sys: MODULE macros found in non-modular code
notice: tracefs: MODULE macros found in non-modular code
notice: vgacon: MODULE macros found in non-modular code
 To fix above, check MODULE_LICENSE(), MODULE_AUTHOR(), etc.
 Please check #include <linux/module.h>, THIS_MODULE, too.

I confirmed they are all valid.

Maybe the 'debugfs' is unclear because there are tons of debugfs
stuff in the source tree. It is talking about MODULE_ALIAS_FS()
in fs/debugfs/inode.c because fs/debugfs/debugfs.o never becomes
a module.

[How to fix the warnings]

Let's take 'asymmetric_keys' as an example.

(1) grep Makefiles to find the relevant code

$ git grep -A2 asymmetric_keys -- '*/Makefile' '*/Kbuild'
crypto/Makefile:obj-$(CONFIG_ASYMMETRIC_KEY_TYPE) += asymmetric_keys/
crypto/Makefile-obj-$(CONFIG_CRYPTO_HASH_INFO) += hash_info.o
crypto/Makefile-crypto_simd-y := simd.o
--
crypto/asymmetric_keys/Makefile:obj-$(CONFIG_ASYMMETRIC_KEY_TYPE) += asymmetric_keys.o
crypto/asymmetric_keys/Makefile-
crypto/asymmetric_keys/Makefile:asymmetric_keys-y := \
crypto/asymmetric_keys/Makefile-        asymmetric_type.o \
crypto/asymmetric_keys/Makefile-        restrict.o \

Then, you notice it is associated with CONFIG_ASYMMETRIC_KEY_TYPE
and is a composite object that consists of asymmetric_type.o,
restrict.o, ...

(2) Confirm the CONFIG is boolean

$ git grep -A2 'config ASYMMETRIC_KEY_TYPE' -- '*/Kconfig*'
crypto/asymmetric_keys/Kconfig:menuconfig ASYMMETRIC_KEY_TYPE
crypto/asymmetric_keys/Kconfig- bool "Asymmetric (public-key cryptographic) key type"
crypto/asymmetric_keys/Kconfig- depends on KEYS

Now you are sure it never get compiled as a module since
ASYMMETRIC_KEY_TYPE is a bool type option.

(3) Grep the source file(s)

$ grep '^MODULE' crypto/asymmetric_keys/asymmetric_type.c
MODULE_LICENSE("GPL");

Remove the orphan MODULE tags. You may also need to do some additional
works such as:

 - replace module_*_driver with builtin_*_driver
 - replace <linux/module.h> with <linux/init.h>
 - remove module_exit code
 - move credit in MODULE_AUTHOR() to the top of the file

Please see Paul's commits.

Signed-off-by: Masahiro Yamada <yamada.masahiro@xxxxxxxxxxxxx>
---

 scripts/modules-check.sh | 54 ++++++++++++++++++++++++++++++++++++++++
 1 file changed, 54 insertions(+)

diff --git a/scripts/modules-check.sh b/scripts/modules-check.sh
index f51f446707b8..5f1d98d4ee30 100755
--- a/scripts/modules-check.sh
+++ b/scripts/modules-check.sh
@@ -13,4 +13,58 @@ check_same_name_modules()
 	done
 }
 
+# Check MODULE_ macros in non-modular code
+check_orphan_module_macros()
+{
+	# modules.builtin.modinfo is created while linking vmlinux.
+	# It may not exist when you do 'make modules'.
+	if [ ! -r modules.builtin.modinfo ]; then
+		return
+	fi
+
+	# modules.builtin lists *real* built-in modules, i.e. controlled by
+	# tristate CONFIG options, but currently built with =y.
+	#
+	# modules.builtin.modinfo is the list of MODULE_ macros compiled
+	# into vmlinux.
+	#
+	# By diff'ing them, users of bogus MODULE_* macros will show up.
+
+	# Kbuild replaces ',' and '-' in file names with '_' for use in C.
+	real_builtin_modules=$(sed -e 's:.*/::' -e 's/\.ko$//' -e 's/,/_/g' \
+			       -e 's/-/_/g' modules.builtin | sort | uniq)
+
+	show_hint=
+
+	# Exclude '.paramtype=' and '.param=' to skip checking module_param()
+	# and MODULE_PARM_DESC().
+	module_macro_users=$(tr '\0' '\n' < modules.builtin.modinfo | \
+		sed -e '/\.parmtype=/d' -e '/\.parm=/d' | \
+		sed -n 's/\..*//p' | sort | uniq)
+
+	for m in $module_macro_users
+	do
+		warn=1
+
+		for n in $real_builtin_modules
+		do
+			if [ "$m" = "$n" ]; then
+				warn=
+				break
+			fi
+		done
+
+		if [ -n "$warn" ]; then
+			echo "notice: $m: MODULE macros found in non-modular code"
+			show_hint=1
+		fi
+	done
+
+	if [ -n "$show_hint" ]; then
+		echo " To fix above, check MODULE_LICENSE(), MODULE_AUTHOR(), etc."
+		echo " Please check #include <linux/module.h>, THIS_MODULE, too."
+	fi
+}
+
 check_same_name_modules
+check_orphan_module_macros
-- 
2.17.1