[PATCH] kbuild: modules-cpio-pkg: Respect INSTALL_MOD_PATH

[PATCH] kbuild: modules-cpio-pkg: Respect INSTALL_MOD_PATH

[Janne Grunau]

The modules-cpio-pkg target added in commit 2a9c8c0b59d3 ("kbuild: add
target to build a cpio containing modules") is incompatible with
initramfs with merged /lib and /usr/lib directories [1]. "/lib" cannot
be a link and directory at the same time.
Respect a non-empty INSTALL_MOD_PATH in the modules-cpio-pkg target so
that `make INSTALL_MOD_PATH=/usr modules-cpio-pkg` results in the same
module install location as `make INSTALL_MOD_PATH=/usr modules_install`.

Tested with Fedora distribution initramfs produced by dracut.

Link: https://systemd.io/THE_CASE_FOR_THE_USR_MERGE/ [1]
Signed-off-by: Janne Grunau <j@jannau.net>
---
Hej,

this patch allows to produce modules-cpio initramfs which are compatible
with initramfs with merged /lib and /usr/lib (/lib as symlink to
/usr/lib). I expect initramfs of distributions with merged /usr to have
a merged /usr as well. This is at least true for Fedora initramfs built
with dracut.

I'm not sure whether the trickery to avoid repeated '/' is justified. It
is necessary to add a slash between "$@" and a non empty
$(INSTALL_MOD_PATH) to avoid make failures due to non existing
.tmp_modules_cpio when INSTALL_MOD_PATH without leading slash is used.
modules-cpio-pkg`.

Better or shorter ways to document this not completely obvious behavior
would be appreciated.

Janne
---
 scripts/Makefile.package | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/scripts/Makefile.package b/scripts/Makefile.package
index 0ec946f9b905f74f8698d8d6967d22f5b76f64e0..ab18cf81622ae319380528c401f9aeb6d32070c6 100644
--- a/scripts/Makefile.package
+++ b/scripts/Makefile.package
@@ -195,7 +195,9 @@ tar%-pkg: linux-$(KERNELRELEASE)-$(ARCH).tar.% FORCE
 .tmp_modules_cpio: FORCE
 	$(Q)$(MAKE) -f $(srctree)/Makefile
 	$(Q)rm -rf $@
-	$(Q)$(MAKE) -f $(srctree)/Makefile INSTALL_MOD_PATH=$@ modules_install
+	$(Q)$(MAKE) -f $(srctree)/Makefile \
+		INSTALL_MOD_PATH=$@$(if $(INSTALL_MOD_PATH),/$(INSTALL_MOD_PATH:/%=%)) \
+		modules_install
 
 quiet_cmd_cpio = CPIO    $@
       cmd_cpio = $(CONFIG_SHELL) $(srctree)/usr/gen_initramfs.sh -o $@ $<
@@ -263,7 +265,7 @@ help:
 	@echo '  tarbz2-pkg          - Build the kernel as a bzip2 compressed tarball'
 	@echo '  tarxz-pkg           - Build the kernel as a xz compressed tarball'
 	@echo '  tarzst-pkg          - Build the kernel as a zstd compressed tarball'
-	@echo '  modules-cpio-pkg    - Build the kernel modules as cpio archive'
+	@echo '  modules-cpio-pkg    - Build the kernel modules as cpio archive (modules installed in INSTALL_MOD_PATH (default: /))'
 	@echo '  perf-tar-src-pkg    - Build the perf source tarball with no compression'
 	@echo '  perf-targz-src-pkg  - Build the perf source tarball with gzip compression'
 	@echo '  perf-tarbz2-src-pkg - Build the perf source tarball with bz2 compression'

---
base-commit: 6de23f81a5e08be8fbf5e8d7e9febc72a5b5f27f
change-id: 20260320-kbuild-modules-cpio-pkg-usr-merge-4266a460282c

Best regards,
-- 
Janne Grunau <j@jannau.net>

Re: [PATCH] kbuild: modules-cpio-pkg: Respect INSTALL_MOD_PATH

[Simon Glass]

Hi Janne,

On Fri, 20 Mar 2026 at 08:30, Janne Grunau <j@jannau.net> wrote:
>
> The modules-cpio-pkg target added in commit 2a9c8c0b59d3 ("kbuild: add
> target to build a cpio containing modules") is incompatible with
> initramfs with merged /lib and /usr/lib directories [1]. "/lib" cannot
> be a link and directory at the same time.
> Respect a non-empty INSTALL_MOD_PATH in the modules-cpio-pkg target so
> that `make INSTALL_MOD_PATH=/usr modules-cpio-pkg` results in the same
> module install location as `make INSTALL_MOD_PATH=/usr modules_install`.
>
> Tested with Fedora distribution initramfs produced by dracut.
>
> Link: https://systemd.io/THE_CASE_FOR_THE_USR_MERGE/ [1]
> Signed-off-by: Janne Grunau <j@jannau.net>
> ---
> Hej,
>
> this patch allows to produce modules-cpio initramfs which are compatible
> with initramfs with merged /lib and /usr/lib (/lib as symlink to
> /usr/lib). I expect initramfs of distributions with merged /usr to have
> a merged /usr as well. This is at least true for Fedora initramfs built
> with dracut.
>
> I'm not sure whether the trickery to avoid repeated '/' is justified. It
> is necessary to add a slash between "$@" and a non empty
> $(INSTALL_MOD_PATH) to avoid make failures due to non existing
> .tmp_modules_cpio when INSTALL_MOD_PATH without leading slash is used.
> modules-cpio-pkg`.
>
> Better or shorter ways to document this not completely obvious behavior
> would be appreciated.
>
> Janne
> ---
>  scripts/Makefile.package | 6 ++++--
>  1 file changed, 4 insertions(+), 2 deletions(-)
>
> diff --git a/scripts/Makefile.package b/scripts/Makefile.package
> index 0ec946f9b905f74f8698d8d6967d22f5b76f64e0..ab18cf81622ae319380528c401f9aeb6d32070c6 100644
> --- a/scripts/Makefile.package
> +++ b/scripts/Makefile.package
> @@ -195,7 +195,9 @@ tar%-pkg: linux-$(KERNELRELEASE)-$(ARCH).tar.% FORCE
>  .tmp_modules_cpio: FORCE
>         $(Q)$(MAKE) -f $(srctree)/Makefile
>         $(Q)rm -rf $@
> -       $(Q)$(MAKE) -f $(srctree)/Makefile INSTALL_MOD_PATH=$@ modules_install

How about a comment for this line, e.g.:

# Prepend INSTALL_MOD_PATH inside the staging dir, stripping leading /

> +       $(Q)$(MAKE) -f $(srctree)/Makefile \
> +               INSTALL_MOD_PATH=$@$(if $(INSTALL_MOD_PATH),/$(INSTALL_MOD_PATH:/%=%)) \
> +               modules_install
>
>  quiet_cmd_cpio = CPIO    $@
>        cmd_cpio = $(CONFIG_SHELL) $(srctree)/usr/gen_initramfs.sh -o $@ $<
> @@ -263,7 +265,7 @@ help:
>         @echo '  tarbz2-pkg          - Build the kernel as a bzip2 compressed tarball'
>         @echo '  tarxz-pkg           - Build the kernel as a xz compressed tarball'
>         @echo '  tarzst-pkg          - Build the kernel as a zstd compressed tarball'
> -       @echo '  modules-cpio-pkg    - Build the kernel modules as cpio archive'
> +       @echo '  modules-cpio-pkg    - Build the kernel modules as cpio archive (modules installed in INSTALL_MOD_PATH (default: /))'

Would this be clear enough? :

Build modules as cpio archive (respects INSTALL_MOD_PATH)

>         @echo '  perf-tar-src-pkg    - Build the perf source tarball with no compression'
>         @echo '  perf-targz-src-pkg  - Build the perf source tarball with gzip compression'
>         @echo '  perf-tarbz2-src-pkg - Build the perf source tarball with bz2 compression'
>
> ---
> base-commit: 6de23f81a5e08be8fbf5e8d7e9febc72a5b5f27f
> change-id: 20260320-kbuild-modules-cpio-pkg-usr-merge-4266a460282c

Reviewed-by: Simon Glass <sjg@chromium.org>

Regards,
Simon

Re: [PATCH] kbuild: modules-cpio-pkg: Respect INSTALL_MOD_PATH

[Nicolas Schier]

On Fri, Mar 20, 2026 at 03:30:32PM +0100, Janne Grunau wrote:
> The modules-cpio-pkg target added in commit 2a9c8c0b59d3 ("kbuild: add
> target to build a cpio containing modules") is incompatible with
> initramfs with merged /lib and /usr/lib directories [1]. "/lib" cannot
> be a link and directory at the same time.
> Respect a non-empty INSTALL_MOD_PATH in the modules-cpio-pkg target so
> that `make INSTALL_MOD_PATH=/usr modules-cpio-pkg` results in the same
> module install location as `make INSTALL_MOD_PATH=/usr modules_install`.
> 
> Tested with Fedora distribution initramfs produced by dracut.
> 
> Link: https://systemd.io/THE_CASE_FOR_THE_USR_MERGE/ [1]
> Signed-off-by: Janne Grunau <j@jannau.net>
> ---
> Hej,
> 
> this patch allows to produce modules-cpio initramfs which are compatible
> with initramfs with merged /lib and /usr/lib (/lib as symlink to
> /usr/lib). I expect initramfs of distributions with merged /usr to have
> a merged /usr as well. This is at least true for Fedora initramfs built
> with dracut.
> 
> I'm not sure whether the trickery to avoid repeated '/' is justified. It
> is necessary to add a slash between "$@" and a non empty
> $(INSTALL_MOD_PATH) to avoid make failures due to non existing
> .tmp_modules_cpio when INSTALL_MOD_PATH without leading slash is used.
> modules-cpio-pkg`.
> 
> Better or shorter ways to document this not completely obvious behavior
> would be appreciated.
> 
> Janne
> ---
>  scripts/Makefile.package | 6 ++++--
>  1 file changed, 4 insertions(+), 2 deletions(-)
> 
> diff --git a/scripts/Makefile.package b/scripts/Makefile.package
> index 0ec946f9b905f74f8698d8d6967d22f5b76f64e0..ab18cf81622ae319380528c401f9aeb6d32070c6 100644
> --- a/scripts/Makefile.package
> +++ b/scripts/Makefile.package
> @@ -195,7 +195,9 @@ tar%-pkg: linux-$(KERNELRELEASE)-$(ARCH).tar.% FORCE
>  .tmp_modules_cpio: FORCE
>  	$(Q)$(MAKE) -f $(srctree)/Makefile
>  	$(Q)rm -rf $@
> -	$(Q)$(MAKE) -f $(srctree)/Makefile INSTALL_MOD_PATH=$@ modules_install
> +	$(Q)$(MAKE) -f $(srctree)/Makefile \
> +		INSTALL_MOD_PATH=$@$(if $(INSTALL_MOD_PATH),/$(INSTALL_MOD_PATH:/%=%)) \
> +		modules_install

Thanks for the patch along with its detailed description!

For completeness: I'd rather use $(addprefix):

    INSTALL_MOD_PATH=$@$(addprefix /,$(INSTALL_MOD_PATH:/%=%))

but as POSIX states:

| Multiple successive <slash> characters are considered to be the same
| as one <slash>, except it is implementation-defined whether the case
| of exactly two leading <slash> characters is treated specially.
https://pubs.opengroup.org/onlinepubs/9799919799.2024edition/
    
there is no need for handling possible repeated slashes here.  So, from
my point of view we can keep it as simple as:

    INSTALL_MOD_PATH=$@/$(INSTALL_MOD_PATH)

as a trailing slash in INSTALL_MOD_PATH should not be a problem here.



>  
>  quiet_cmd_cpio = CPIO    $@
>        cmd_cpio = $(CONFIG_SHELL) $(srctree)/usr/gen_initramfs.sh -o $@ $<
> @@ -263,7 +265,7 @@ help:
>  	@echo '  tarbz2-pkg          - Build the kernel as a bzip2 compressed tarball'
>  	@echo '  tarxz-pkg           - Build the kernel as a xz compressed tarball'
>  	@echo '  tarzst-pkg          - Build the kernel as a zstd compressed tarball'
> -	@echo '  modules-cpio-pkg    - Build the kernel modules as cpio archive'
> +	@echo '  modules-cpio-pkg    - Build the kernel modules as cpio archive (modules installed in INSTALL_MOD_PATH (default: /))'

Please break that line, e.g.:

	@echo '  modules-cpio-pkg    - Build the kernel modules as cpio archive'
	@echo '                        (modules installed in INSTALL_MOD_PATH (default: /))'


Fixes: 2a9c8c0b59d3 (\"kbuild: add target to build a cpio containing modules\")

Kind regards,
Nicolas

Re: [PATCH] kbuild: modules-cpio-pkg: Respect INSTALL_MOD_PATH

[Janne Grunau]

On Sat, Mar 21, 2026 at 04:18:46PM +0100, Nicolas Schier wrote:
> On Fri, Mar 20, 2026 at 03:30:32PM +0100, Janne Grunau wrote:
> > The modules-cpio-pkg target added in commit 2a9c8c0b59d3 ("kbuild: add
> > target to build a cpio containing modules") is incompatible with
> > initramfs with merged /lib and /usr/lib directories [1]. "/lib" cannot
> > be a link and directory at the same time.
> > Respect a non-empty INSTALL_MOD_PATH in the modules-cpio-pkg target so
> > that `make INSTALL_MOD_PATH=/usr modules-cpio-pkg` results in the same
> > module install location as `make INSTALL_MOD_PATH=/usr modules_install`.
> > 
> > Tested with Fedora distribution initramfs produced by dracut.
> > 
> > Link: https://systemd.io/THE_CASE_FOR_THE_USR_MERGE/ [1]
> > Signed-off-by: Janne Grunau <j@jannau.net>
> > ---
> > Hej,
> > 
> > this patch allows to produce modules-cpio initramfs which are compatible
> > with initramfs with merged /lib and /usr/lib (/lib as symlink to
> > /usr/lib). I expect initramfs of distributions with merged /usr to have
> > a merged /usr as well. This is at least true for Fedora initramfs built
> > with dracut.
> > 
> > I'm not sure whether the trickery to avoid repeated '/' is justified. It
> > is necessary to add a slash between "$@" and a non empty
> > $(INSTALL_MOD_PATH) to avoid make failures due to non existing
> > .tmp_modules_cpio when INSTALL_MOD_PATH without leading slash is used.
> > modules-cpio-pkg`.
> > 
> > Better or shorter ways to document this not completely obvious behavior
> > would be appreciated.
> > 
> > Janne
> > ---
> >  scripts/Makefile.package | 6 ++++--
> >  1 file changed, 4 insertions(+), 2 deletions(-)
> > 
> > diff --git a/scripts/Makefile.package b/scripts/Makefile.package
> > index 0ec946f9b905f74f8698d8d6967d22f5b76f64e0..ab18cf81622ae319380528c401f9aeb6d32070c6 100644
> > --- a/scripts/Makefile.package
> > +++ b/scripts/Makefile.package
> > @@ -195,7 +195,9 @@ tar%-pkg: linux-$(KERNELRELEASE)-$(ARCH).tar.% FORCE
> >  .tmp_modules_cpio: FORCE
> >  	$(Q)$(MAKE) -f $(srctree)/Makefile
> >  	$(Q)rm -rf $@
> > -	$(Q)$(MAKE) -f $(srctree)/Makefile INSTALL_MOD_PATH=$@ modules_install
> > +	$(Q)$(MAKE) -f $(srctree)/Makefile \
> > +		INSTALL_MOD_PATH=$@$(if $(INSTALL_MOD_PATH),/$(INSTALL_MOD_PATH:/%=%)) \
> > +		modules_install
> 
> Thanks for the patch along with its detailed description!
> 
> For completeness: I'd rather use $(addprefix):
> 
>     INSTALL_MOD_PATH=$@$(addprefix /,$(INSTALL_MOD_PATH:/%=%))
> 
> but as POSIX states:
> 
> | Multiple successive <slash> characters are considered to be the same
> | as one <slash>, except it is implementation-defined whether the case
> | of exactly two leading <slash> characters is treated specially.
> https://pubs.opengroup.org/onlinepubs/9799919799.2024edition/

argh, I did read this but confused myself by the second part to think it
was only for leading slashes.

> there is no need for handling possible repeated slashes here.  So, from
> my point of view we can keep it as simple as:
> 
>     INSTALL_MOD_PATH=$@/$(INSTALL_MOD_PATH)
> 
> as a trailing slash in INSTALL_MOD_PATH should not be a problem here.

ack, I'll just do that and I would have sent it if I did not confuse
myself with the POSIX wording.

> 
> >  
> >  quiet_cmd_cpio = CPIO    $@
> >        cmd_cpio = $(CONFIG_SHELL) $(srctree)/usr/gen_initramfs.sh -o $@ $<
> > @@ -263,7 +265,7 @@ help:
> >  	@echo '  tarbz2-pkg          - Build the kernel as a bzip2 compressed tarball'
> >  	@echo '  tarxz-pkg           - Build the kernel as a xz compressed tarball'
> >  	@echo '  tarzst-pkg          - Build the kernel as a zstd compressed tarball'
> > -	@echo '  modules-cpio-pkg    - Build the kernel modules as cpio archive'
> > +	@echo '  modules-cpio-pkg    - Build the kernel modules as cpio archive (modules installed in INSTALL_MOD_PATH (default: /))'
> 
> Please break that line, e.g.:
> 
> 	@echo '  modules-cpio-pkg    - Build the kernel modules as cpio archive'
> 	@echo '                        (modules installed in INSTALL_MOD_PATH (default: /))'
> 
> 
> Fixes: 2a9c8c0b59d3 (\"kbuild: add target to build a cpio containing modules\")

I saw it more as an additional thing but without the complications of
suppressing repeated slashes the change is easy enough

thanks,
Janne

Re: [PATCH] kbuild: modules-cpio-pkg: Respect INSTALL_MOD_PATH

[Nicolas Schier]

On Wed, Mar 25, 2026 at 03:48:26PM +0100, Janne Grunau wrote:
> On Sat, Mar 21, 2026 at 04:18:46PM +0100, Nicolas Schier wrote:
> > On Fri, Mar 20, 2026 at 03:30:32PM +0100, Janne Grunau wrote:
> > > The modules-cpio-pkg target added in commit 2a9c8c0b59d3 ("kbuild: add
> > > target to build a cpio containing modules") is incompatible with
> > > initramfs with merged /lib and /usr/lib directories [1]. "/lib" cannot
> > > be a link and directory at the same time.
> > > Respect a non-empty INSTALL_MOD_PATH in the modules-cpio-pkg target so
> > > that `make INSTALL_MOD_PATH=/usr modules-cpio-pkg` results in the same
> > > module install location as `make INSTALL_MOD_PATH=/usr modules_install`.
> > > 
> > > Tested with Fedora distribution initramfs produced by dracut.
> > > 
> > > Link: https://systemd.io/THE_CASE_FOR_THE_USR_MERGE/ [1]
> > > Signed-off-by: Janne Grunau <j@jannau.net>
> > > ---
> > > Hej,
> > > 
> > > this patch allows to produce modules-cpio initramfs which are compatible
> > > with initramfs with merged /lib and /usr/lib (/lib as symlink to
> > > /usr/lib). I expect initramfs of distributions with merged /usr to have
> > > a merged /usr as well. This is at least true for Fedora initramfs built
> > > with dracut.
> > > 
> > > I'm not sure whether the trickery to avoid repeated '/' is justified. It
> > > is necessary to add a slash between "$@" and a non empty
> > > $(INSTALL_MOD_PATH) to avoid make failures due to non existing
> > > .tmp_modules_cpio when INSTALL_MOD_PATH without leading slash is used.
> > > modules-cpio-pkg`.
> > > 
> > > Better or shorter ways to document this not completely obvious behavior
> > > would be appreciated.
> > > 
> > > Janne
> > > ---
> > >  scripts/Makefile.package | 6 ++++--
> > >  1 file changed, 4 insertions(+), 2 deletions(-)
> > > 
> > > diff --git a/scripts/Makefile.package b/scripts/Makefile.package
> > > index 0ec946f9b905f74f8698d8d6967d22f5b76f64e0..ab18cf81622ae319380528c401f9aeb6d32070c6 100644
> > > --- a/scripts/Makefile.package
> > > +++ b/scripts/Makefile.package
> > > @@ -195,7 +195,9 @@ tar%-pkg: linux-$(KERNELRELEASE)-$(ARCH).tar.% FORCE
> > >  .tmp_modules_cpio: FORCE
> > >  	$(Q)$(MAKE) -f $(srctree)/Makefile
> > >  	$(Q)rm -rf $@
> > > -	$(Q)$(MAKE) -f $(srctree)/Makefile INSTALL_MOD_PATH=$@ modules_install
> > > +	$(Q)$(MAKE) -f $(srctree)/Makefile \
> > > +		INSTALL_MOD_PATH=$@$(if $(INSTALL_MOD_PATH),/$(INSTALL_MOD_PATH:/%=%)) \
> > > +		modules_install
> > 
> > Thanks for the patch along with its detailed description!
> > 
> > For completeness: I'd rather use $(addprefix):
> > 
> >     INSTALL_MOD_PATH=$@$(addprefix /,$(INSTALL_MOD_PATH:/%=%))
> > 
> > but as POSIX states:
> > 
> > | Multiple successive <slash> characters are considered to be the same
> > | as one <slash>, except it is implementation-defined whether the case
> > | of exactly two leading <slash> characters is treated specially.
> > https://pubs.opengroup.org/onlinepubs/9799919799.2024edition/
> 
> argh, I did read this but confused myself by the second part to think it
> was only for leading slashes.

:)  you are by far not the only one who gets confused by that.


-- 
Nicolas