[PATCH v2] kbuild: check uniqueness of module names

[Masahiro Yamada <yamada.masahiro@socionext.com>]

In the recent build test of linux-next, Stephen saw a build error
caused by a broken .tmp_versions/*.mod file:

  https://lkml.org/lkml/2019/5/13/991

drivers/net/phy/asix.ko and drivers/net/usb/asix.ko have the same
basename, and there is a race in generating .tmp_versions/asix.mod

Kbuild has not checked this before, and it suddenly shows up with
obscure error message when this kind of race occurs.

Non-unique module names cause various sort of problems, but it is
not trivial to catch them by eyes.

Hence, this script.

It checks not only real modules, but also built-in modules (i.e.
controlled by tristate CONFIG option, but currently compiled with =y).
Non-unique names for built-in modules also cause problems because
/sys/modules/ would fall over.

I tested allmodconfig on the latest kernel, and it detected the
following:

warning: same basename if the following are built as modules:
  drivers/regulator/88pm800.ko
  drivers/mfd/88pm800.ko
warning: same basename if the following are built as modules:
  drivers/gpu/drm/bridge/adv7511/adv7511.ko
  drivers/media/i2c/adv7511.ko
warning: same basename if the following are built as modules:
  drivers/net/phy/asix.ko
  drivers/net/usb/asix.ko
warning: same basename if the following are built as modules:
  fs/coda/coda.ko
  drivers/media/platform/coda/coda.ko
warning: same basename if the following are built as modules:
  drivers/net/phy/realtek.ko
  drivers/net/dsa/realtek.ko

Reported-by: Stephen Rothwell <sfr@canb.auug.org.au>
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Reviewed-by: Kees Cook <keescook@chromium.org>
---

Changes in v2:
 - redirect messages to stderr
 - use '--' after 'basename -a'
 - use '-r' for xargs to cope with empty modules.order/modules.builtin

 Makefile                 |  1 +
 scripts/modules-check.sh | 20 ++++++++++++++++++++
 2 files changed, 21 insertions(+)
 create mode 100755 scripts/modules-check.sh

diff --git a/Makefile b/Makefile
index a61a95b6b38f..30792fec7a12 100644
--- a/Makefile
+++ b/Makefile
@@ -1290,6 +1290,7 @@ modules: $(vmlinux-dirs) $(if $(KBUILD_BUILTIN),vmlinux) modules.builtin
 	$(Q)$(AWK) '!x[$$0]++' $(vmlinux-dirs:%=$(objtree)/%/modules.order) > $(objtree)/modules.order
 	@$(kecho) '  Building modules, stage 2.';
 	$(Q)$(MAKE) -f $(srctree)/scripts/Makefile.modpost
+	$(Q)$(CONFIG_SHELL) $(srctree)/scripts/modules-check.sh
 
 modules.builtin: $(vmlinux-dirs:%=%/modules.builtin)
 	$(Q)$(AWK) '!x[$$0]++' $^ > $(objtree)/modules.builtin
diff --git a/scripts/modules-check.sh b/scripts/modules-check.sh
new file mode 100755
index 000000000000..c875f6eab01e
--- /dev/null
+++ b/scripts/modules-check.sh
@@ -0,0 +1,20 @@
+#!/bin/sh
+# SPDX-License-Identifier: GPL-2.0
+
+set -e
+
+# Check uniqueness of module names
+check_same_name_modules()
+{
+	same_name_modules=$(cat modules.order modules.builtin | \
+				xargs -r basename -a -- | sort | uniq -d)
+
+	for m in $same_name_modules
+	do
+		echo "warning: same basename if the following are built as modules:" >&2
+		grep -h -e "/$m" modules.order modules.builtin | \
+						sed 's:^kernel/:  :' >&2
+	done
+}
+
+check_same_name_modules
-- 
2.17.1