From nobody Fri Nov 29 19:35:47 2024 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 628DE1974FE; Tue, 17 Sep 2024 14:18:22 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1726582702; cv=none; b=rhe6V0Yp69d5cWeBcd4NlJ1QuW0vERgN3H3XSjciFnsbfyctVM7dtaVNxRgpxyl98VCg/BSPJ4CzfzQfldqnGKu/tnQNk4Ud3gZTwm6TzkN5rvSAV5Yt0nNDfyVgFBPzBfetqWPSBatKc97V2b+eYSuYcOAELjbpYM/Yo/3myxU= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1726582702; c=relaxed/simple; bh=pVqPlXHwRAmKMtMxmsQTphSqu9eVJ5zq5Yus+QdHq+Q=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=OFrJwUrqpPD6fKVonu1Kn2t2M1FXbI4bFHyjAWC4t2UlhYmn7b7P1xiRk28C02mxxNRLSFVYCBZg0WLuEBFn0GKwGTSF59xeqP8pesfp0F4ZMKfL7tBnBHivDTJqiceGcHfN5tNUGgpdhfutXNKnwaszgZRRzTaOP7K3AqshpeY= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=qFZRWt3b; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="qFZRWt3b" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 32AF8C4CEC5; Tue, 17 Sep 2024 14:18:20 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1726582702; bh=pVqPlXHwRAmKMtMxmsQTphSqu9eVJ5zq5Yus+QdHq+Q=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=qFZRWt3bLzlLXEazL48GBC+oGSAyKzF5TRwsK3RJi9kuKr7Wm+eTzqSILwkzH4l7t e7GF3zChXVOv/eL2+dq17FaFYgpGuKlqnTSgI3C77zxkQR6k6IC58Q6b199ewt+4iS 9xeqRkcEDLFM3aAt0l4AQhmXiAYQ2zGipdr3A2ovuX3yoIikkyf/mmTbttthFL9trF QxYX00wpSikIluRDyIqNdXjqKfXsLnn3FKCGw8vNIJwTbUhN3Xv0bv5c5Vfi1kcLjc cHDjtsj1NBLne3wa4+AI/4pXbIqjg4cGKByuzP3ssqKQil2NW8qSc79WJoWbv1qVz8 Zsvvwl0Jyw0Kw== From: Masahiro Yamada To: linux-kbuild@vger.kernel.org Cc: Miguel Ojeda , rust-for-linux@vger.kernel.org, linux-kernel@vger.kernel.org, Nathan Chancellor , Nicolas Schier , Masahiro Yamada Subject: [PATCH 23/23] kbuild: allow to start building external module in any directory Date: Tue, 17 Sep 2024 23:16:51 +0900 Message-ID: <20240917141725.466514-24-masahiroy@kernel.org> X-Mailer: git-send-email 2.43.0 In-Reply-To: <20240917141725.466514-1-masahiroy@kernel.org> References: <20240917141725.466514-1-masahiroy@kernel.org> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" Unless an explicit O=3D option is provided, external module builds must start from the kernel directory. This can be achieved by using the -C option: $ make -C /path/to/kernel M=3D/path/to/external/module This commit allows starting external module builds from any directory, so you can also do the following: $ make -f /path/to/kernel/Makefile M=3D/path/to/external/module The key difference is that the -C option changes the working directory and parses the Makefile located there, while the -f option only specifies the Makefile to use. As shown in the examples in Documentation/kbuild/modules.rst, external modules usually have a wrapper Makefile that allows you to build them without specifying any make arguments. The Makefile typically contains a rule as follows: KDIR ?=3D /path/to/kernel default: $(MAKE) -C $(KDIR) M=3D$(CURDIR) $(MAKECMDGOALS) The log will appear as follows: $ make make -C /path/to/kernel M=3D/path/to/external/module make[1]: Entering directory '/path/to/kernel' make[2]: Entering directory '/path/to/exernal/module' CC [M] helloworld.o MODPOST Module.symvers CC [M] helloworld.mod.o CC [M] .module-common.o LD [M] helloworld.ko make[2]: Leaving directory '/path/to/exernal/module' make[1]: Leaving directory '/path/to/kernel' This changes the working directory twice because the -C option first switches to the kernel directory, and then Kbuild internally recurses back to the external module directory. With this commit, the wrapper Makefile can directly include the kernel Makefile: KDIR ?=3D /path/to/kernel export KBUILD_EXTMOD =3D $(CURDIR) include $(KDIR)/Makefile This avoids unnecessary sub-make invocations: $ make CC [M] helloworld.o MODPOST Module.symvers CC [M] helloworld.mod.o CC [M] .module-common.o LD [M] helloworld.ko Signed-off-by: Masahiro Yamada Reviewed-by: Nicolas Schier --- Documentation/kbuild/modules.rst | 21 +++++++++++++++++++++ Makefile | 8 ++++++-- 2 files changed, 27 insertions(+), 2 deletions(-) diff --git a/Documentation/kbuild/modules.rst b/Documentation/kbuild/module= s.rst index 03347e13eeb5..5610cfa426bb 100644 --- a/Documentation/kbuild/modules.rst +++ b/Documentation/kbuild/modules.rst @@ -88,6 +88,12 @@ executed to make module versioning work. =20 $ make -C /lib/modules/`uname -r`/build M=3D$PWD modules_install =20 + Starting from Linux 6.13, you can use the -f option instead of -C. This + will avoid unnecessary change of the working directory. The external + module will be output to the directory where you invoke make. + + $ make -f /lib/modules/`uname -r`/build/Makefile M=3D$PWD + 2.2 Options =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D =20 @@ -246,6 +252,21 @@ module 8123.ko, which is built from the following file= s:: consisting of several hundred lines, and here it really pays off to separate the kbuild part from the rest. =20 + Linux 6.13 and later support another way. The external module Makefile + can include the kernel Makefile directly, rather than invoking sub Make. + + Example 3:: + + --> filename: Kbuild + obj-m :=3D 8123.o + 8123-y :=3D 8123_if.o 8123_pci.o + + --> filename: Makefile + KDIR ?=3D /lib/modules/`uname -r`/build + export KBUILD_EXTMOD =3D $(CURDIR) + include $(KDIR)/Makefile + + 3.4 Building Multiple Modules =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D=3D =20 diff --git a/Makefile b/Makefile index 81603a50c757..88c160ac7b3c 100644 --- a/Makefile +++ b/Makefile @@ -189,9 +189,13 @@ ifdef KBUILD_EXTMOD objtree :=3D $(realpath $(KBUILD_OUTPUT)) $(if $(objtree),,$(error specified kernel directory "$(KBUILD_OUTP= UT)" does not exist)) else - objtree :=3D $(CURDIR) + objtree :=3D $(abs_srctree) endif - output :=3D $(or $(KBUILD_EXTMOD_OUTPUT),$(KBUILD_EXTMOD)) + # If Make is invoked from the kernel directory (either kernel + # source directory or kernel build directory), external modules + # are built in $(KBUILD_EXTMOD) for backward compatibility, + # otherwise, built in the current directory. + output :=3D $(or $(KBUILD_EXTMOD_OUTPUT),$(if $(filter $(CURDIR),$(obj= tree) $(abs_srctree)),$(KBUILD_EXTMOD))) # KBUILD_EXTMOD might be a relative path. Remember its absolute path b= efore # Make changes the working directory. export abs_extmodtree :=3D $(realpath $(KBUILD_EXTMOD)) --=20 2.43.0