M= (or KBUILD_EXTMOD) generally expects a directory path without any
trailing slashes, like M=a/b/c.
If you add a trailing slash, like M=a/b/c/, you will get ugly build
logs (two slashes in a series), but it still works fine as long as it
is consistent between 'make modules' and 'make modules_install'.
So, the following code correctly builds and installs the modules.
$ make M=a/b/c/ modules
$ sudo make M=a/b/c/ modules_install
Since commit ccae4cfa7bfb ("kbuild: refactor scripts/Makefile.modinst"),
a problem happens if you add a trailing slash only for modules_install.
$ make M=a/b/c modules
$ sudo make M=a/b/c/ modules_install
No module is installed in this case, Johannes Berg reported. [1]
Trim any trailing slashes from $(KBUILD_EXTMOD).
I used the 'dirname' command to remove all the trailing slashes in
case someone plays with a crazy directory path like M=a/b/c/////.
The Make's built-in function, $(dir ...) cannot take care of such
a case.
[1]: https://lore.kernel.org/lkml/10cc8522b27a051e6a9c3e158a4c4b6414fd04a0.camel@xxxxxxxxxxxxxxxx/
Fixes: ccae4cfa7bfb ("kbuild: refactor scripts/Makefile.modinst")
Reported-by: Johannes Berg <johannes@xxxxxxxxxxxxxxxx>
Signed-off-by: Masahiro Yamada <masahiroy@xxxxxxxxxx>
---
Makefile | 5 +++++
1 file changed, 5 insertions(+)
diff --git a/Makefile b/Makefile
index b79e0e8acbe3..6dabf3a1f635 100644
--- a/Makefile
+++ b/Makefile
@@ -129,6 +129,11 @@ endif
$(if $(word 2, $(KBUILD_EXTMOD)), \
$(error building multiple external modules is not supported))
+ifneq ($(KBUILD_EXTMOD),)
+# remove trailing slashes
+KBUILD_EXTMOD := $(shell dirname $(KBUILD_EXTMOD)/.)
+endif
+
export KBUILD_EXTMOD
# Kbuild will save output files in the current working directory.
--
2.27.0
