On Thu, Dec 5, 2024 at 8:35 AM Charlie Jenkins <charlie@xxxxxxxxxxxx> wrote:
>
> On Sun, Nov 10, 2024 at 10:34:33AM +0900, Masahiro Yamada wrote:
> > Currently, Kbuild always operates in the output directory of the kernel,
> > even when building external modules. This increases the risk of external
> > module Makefiles attempting to write to the kernel directory.
> >
> > This commit switches the working directory to the external module
> > directory, allowing the removal of the $(KBUILD_EXTMOD)/ prefix from
> > some build artifacts.
> >
> > The command for building external modules maintains backward
> > compatibility, but Makefiles that rely on working in the kernel
> > directory may break. In such cases, $(objtree) and $(srctree) should
> > be used to refer to the output and source directories of the kernel.
> >
> > The appearance of the build log will change as follows:
> >
> > [Before]
> >
> > $ make -C /path/to/my/linux M=/path/to/my/externel/module
> > make: Entering directory '/path/to/my/linux'
> > CC [M] /path/to/my/externel/module/helloworld.o
> > MODPOST /path/to/my/externel/module/Module.symvers
> > CC [M] /path/to/my/externel/module/helloworld.mod.o
> > CC [M] /path/to/my/externel/module/.module-common.o
> > LD [M] /path/to/my/externel/module/helloworld.ko
> > make: Leaving directory '/path/to/my/linux'
> >
> > [After]
> >
> > $ make -C /path/to/my/linux M=/path/to/my/externel/module
> > make: Entering directory '/path/to/my/linux'
> > make[1]: Entering directory '/path/to/my/externel/module'
> > CC [M] helloworld.o
> > MODPOST Module.symvers
> > CC [M] helloworld.mod.o
> > CC [M] .module-common.o
> > LD [M] helloworld.ko
> > make[1]: Leaving directory '/path/to/my/externel/module'
> > make: Leaving directory '/path/to/my/linux'
> >
> > Printing "Entering directory" twice is cumbersome. This will be
> > addressed later.
>
> This change has caused O=<relative directory> to fail.
>
> For example:
>
> make O=build defconfig
> make -j$(nproc) V=1 O=build bindeb-pkg
>
> outputs:
>
> make ARCH=x86 KERNELRELEASE=6.13.0-rc1 KBUILD_BUILD_VERSION=3 run-command KBUILD_RUN_COMMAND='+$(srctree)/scripts/package/builddeb linux-libc-dev'
> dh_installchangelogs -plinux-image-6.13.0-rc1
> ../scripts/package/builddeb linux-headers-6.13.0-rc1
> dh_compress -plinux-image-6.13.0-rc1
> dh_fixperms -plinux-image-6.13.0-rc1
> dh_gencontrol -plinux-image-6.13.0-rc1 -- -fdebian/image.files
> Rebuilding host programs with x86_64-linux-gnu-gcc...
> make[6]: Entering directory '/scratch/kernels/linux/build'
> /scratch/kernels/linux/Makefile:190: *** specified kernel directory "build" does not exist. Stop.
>
> It is stepping into this directory and then trying to find the directory
> it just stepped into so $(realpath $(KBUILD_OUTPUT)) returns an empty
> string.
>
> Using an absolute directory resolves this problem, but I believe it
> shouldn't be necessary.
Agree.
I will apply the following fixup unless I have a better idea.
diff --git a/scripts/package/install-extmod-build
b/scripts/package/install-extmod-build
index 64d958ee45f3..85af1573db31 100755
--- a/scripts/package/install-extmod-build
+++ b/scripts/package/install-extmod-build
@@ -69,7 +69,7 @@ if [ "${CC}" != "${HOSTCC}" ]; then
#
# Use the single-target build to avoid the modpost invocation, which
# would overwrite Module.symvers.
- "${MAKE}" HOSTCC="${CC}" KBUILD_EXTMOD="${destdir}" scripts/
+ "${MAKE}" O=. HOSTCC="${CC}" KBUILD_EXTMOD="${destdir}" scripts/
cat <<-'EOF' > "${destdir}/scripts/Kbuild"
subdir-y := basic
@@ -78,7 +78,7 @@ if [ "${CC}" != "${HOSTCC}" ]; then
EOF
# Run once again to rebuild scripts/basic/ and scripts/mod/modpost.
- "${MAKE}" HOSTCC="${CC}" KBUILD_EXTMOD="${destdir}" scripts/
+ "${MAKE}" O=. HOSTCC="${CC}" KBUILD_EXTMOD="${destdir}" scripts/
rm -f "${destdir}/Kbuild" "${destdir}/scripts/Kbuild"
fi
--
Best Regards
Masahiro Yamada
