linux-kernel - [PATCH 5.13 330/351] kbuild: remove trailing slashes from $(KBUILD

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Date:   Mon, 19 Jul 2021 16:54:36 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Johannes Berg <johannes@...solutions.net>,
        Masahiro Yamada <masahiroy@...nel.org>,
        Sasha Levin <sashal@...nel.org>
Subject: [PATCH 5.13 330/351] kbuild: remove trailing slashes from $(KBUILD_EXTMOD)

From: Masahiro Yamada <masahiroy@...nel.org>

[ Upstream commit 74ee585b7eecd98be3650e677625a0ee588d08e0 ]

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'.

The following commands correctly build and install 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 adds more slashes 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@sipsolutions.net/

Fixes: ccae4cfa7bfb ("kbuild: refactor scripts/Makefile.modinst")
Reported-by: Johannes Berg <johannes@...solutions.net>
Signed-off-by: Masahiro Yamada <masahiroy@...nel.org>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 Makefile | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/Makefile b/Makefile
index 83f4212e004f..4258a60f6119 100644
--- a/Makefile
+++ b/Makefile
@@ -129,6 +129,11 @@ endif
 $(if $(word 2, $(KBUILD_EXTMOD)), \
 	$(error building multiple external modules is not supported))

+# Remove trailing slashes
+ifneq ($(filter %/, $(KBUILD_EXTMOD)),)
+KBUILD_EXTMOD := $(shell dirname $(KBUILD_EXTMOD).)
+endif
+
 export KBUILD_EXTMOD

 # Kbuild will save output files in the current working directory.
-- 
2.30.2