linux-kernel - Re: [PATCH v5 6/8] kbuild: Allow adding modules into the FIT ramdisk

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Message-ID: <aReIA8YuOM7JIXIe@derry.ads.avm.de>
Date: Fri, 14 Nov 2025 20:50:27 +0100
From: Nicolas Schier <nsc@...nel.org>
To: Thomas Weißschuh <thomas.weissschuh@...utronix.de>
Cc: Simon Glass <sjg@...omium.org>, linux-arm-kernel@...ts.infradead.org,
	Masahiro Yamada <masahiroy@...nel.org>,
	Chen-Yu Tsai <wenst@...omium.org>, Tom Rini <trini@...sulko.com>,
	Ahmad Fatoum <a.fatoum@...gutronix.de>,
	J . Neuschäfer <j.ne@...teo.net>,
	Nathan Chancellor <nathan@...nel.org>,
	Ard Biesheuvel <ardb@...nel.org>,
	Catalin Marinas <catalin.marinas@....com>,
	Josh Poimboeuf <jpoimboe@...nel.org>, Kees Cook <kees@...nel.org>,
	Miguel Ojeda <ojeda@...nel.org>,
	Parth Pancholi <parth.pancholi@...adex.com>,
	Rong Xu <xur@...gle.com>, Tamir Duberstein <tamird@...il.com>,
	Will Deacon <will@...nel.org>, linux-kbuild@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v5 6/8] kbuild: Allow adding modules into the FIT ramdisk

On Fri, Nov 14, 2025 at 04:29:33PM +0100, Thomas Weißschuh wrote:
> On Fri, Nov 14, 2025 at 07:27:32AM -0700, Simon Glass wrote:
> > Support 'make image.fit FIT_MODULES=1' to put all the modules into a
> > ramdisk image within the FIT.
> > 
> > Add image.fit as a target which requires modules, so that modules will
> > built automatically when using FIT_MODULES=1
> > 
> > Signed-off-by: Simon Glass <sjg@...omium.org>
> > Suggested-by: Ahmad Fatoum <a.fatoum@...gutronix.de>
> > Suggested-by: Reviewed-by: Nicolas Schier <nsc@...nel.org>
> > Acked-by: Nathan Chancellor <nathan@...nel.org>
> > ---
> > 
> > Changes in v5:
> > - Build modules automatically if needed (fix from Nicolas Schier)
> > 
> > Changes in v4:
> > - Rename the Makefile variable from 'EXTRA' to 'MAKE_FIT_FLAGS'
> > - Use an empty FIT_MODULES to disable the feature, instead of '0'
> > - Make use of the 'modules' dependency to ensure modules are built
> > - Pass the list of modules to the script
> > 
> >  Makefile             |  1 +
> >  arch/arm64/Makefile  |  1 +
> >  scripts/Makefile.lib | 10 ++++++++--
> >  3 files changed, 10 insertions(+), 2 deletions(-)
> > 
> > diff --git a/Makefile b/Makefile
> > index 8cd46222fc48..4eccaef95826 100644
> > --- a/Makefile
> > +++ b/Makefile
> > @@ -773,6 +773,7 @@ endif
> >  # Just "make" or "make all" shall build modules as well
> >  
> >  modules-targets := all
> > +modules-targets += $(if $(FIT_MODULES),image.fit)
> >  modules-targets += modules
> >  modules-targets += nsdeps
> >  modules-targets += compile_commands.json
> > diff --git a/arch/arm64/Makefile b/arch/arm64/Makefile
> > index 73a10f65ce8b..7036f251ab40 100644
> > --- a/arch/arm64/Makefile
> > +++ b/arch/arm64/Makefile
> > @@ -174,6 +174,7 @@ endif
> >  all:	$(notdir $(KBUILD_IMAGE))
> >  
> >  image.fit: dtbs
> > +image.fit: $(if $(FIT_MODULES),modules)
> >  
> >  vmlinuz.efi image.fit: Image
> >  $(BOOT_TARGETS): vmlinux
> > diff --git a/scripts/Makefile.lib b/scripts/Makefile.lib
> > index 1d581ba5df66..c6a3aa653035 100644
> > --- a/scripts/Makefile.lib
> > +++ b/scripts/Makefile.lib
> > @@ -398,11 +398,17 @@ MAKE_FIT := $(srctree)/scripts/make_fit.py
> >  # Use this to override the compression algorithm
> >  FIT_COMPRESSION ?= gzip
> >  
> > +# Set this to 1 to include an initrd with all the kernel modules
> > +FIT_MODULES ?=
> 
> '0' will also trigger that behavior.
> 
> > +
> >  quiet_cmd_fit = FIT     $@
> > -      cmd_fit = $(MAKE_FIT) -o $@ --arch $(UIMAGE_ARCH) --os linux \
> > -		--name '$(UIMAGE_NAME)' \
> > +      cmd_fit = $(if $(FIT_MODULES), \
> > +		find $(objtree) -name '*.ko' > $(objtree)/.modules-list 2>/dev/null &&) \
> 
> This will include stale module files. You can get an up-to-date list from
> $(objtree)/modules.order with a bit post-processing.
> Maybe kbuild can be extended to also create a list of the .ko files.
> (I would be interested in that for my own usecases, too)

oh yes, thanks for the pointer.  This is indeed quite simple and much
better than calling find.  For in-tree kmods:

    compiled-modules = $(patsubst %.o,%.ko,$(call read-file, $(objtree)/modules.order))

But as we need the list of modules in a file, we can also add a
$(call write-file,FILE,TEXT) macro (cp. read-file in
scripts/Kbuild.include).

Thomas, is this sufficient for your use case?  Or do you also need a
make target outputting the list of kmods?


Kind regards,
Nicolas