linux-kernel - Re: [PATCH] kbuild: add target to build a cpio containing modules

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Message-ID: <e358027d-a996-404f-b043-62b9c1b4d06c@pengutronix.de>
Date: Tue, 25 Nov 2025 13:07:20 +0100
From: Ahmad Fatoum <a.fatoum@...gutronix.de>
To: Thomas Weißschuh <thomas.weissschuh@...utronix.de>
Cc: Nathan Chancellor <nathan@...nel.org>,
 Nicolas Schier <nicolas.schier@...ux.dev>, Simon Glass <sjg@...omium.org>,
 kernel@...gutronix.de, linux-kernel@...r.kernel.org,
 linux-kbuild@...r.kernel.org, Sascha Hauer <s.hauer@...gutronix.de>
Subject: Re: [PATCH] kbuild: add target to build a cpio containing modules

Hello Thomas,

On 11/20/25 8:32 AM, Thomas Weißschuh wrote:
>> diff --git a/scripts/Makefile.package b/scripts/Makefile.package
>> index 74bcb9e7f7a4516473481468a0fcf700c3bead33..20eec9e2dec4dda3fa0ef64a15b80dccdcb55f90 100644
>> --- a/scripts/Makefile.package
>> +++ b/scripts/Makefile.package
>> @@ -189,6 +189,22 @@ tar-pkg: linux-$(KERNELRELEASE)-$(ARCH).tar
>>  tar%-pkg: linux-$(KERNELRELEASE)-$(ARCH).tar.% FORCE
>>  	@:
> 
> The other package targets have a separator and documentation comment.

Ack.

>> +modules-install: FORCE
>> +	$(Q)$(MAKE) -f $(srctree)/Makefile
>> +	$(Q)rm -rf $@
> 
> We have the filename prefix ".tmp_" for temporary files and directories.
> These will be automatically ignored by git and cleaned up by "make clean".

The commit originally followed what the tar target did, but it seems
doing it like perf is the better template. Will adapt.

>> +quiet_cmd_cpio = CPIO    $@
>> +      cmd_cpio = $(srctree)/usr/gen_initramfs.sh $< > $@
> 
> Use $(CONFIG_SHELL).

Can do. Is this to allow users to override CONFIG_SHELL from outside?
If so, why not go one step further and remove shebangs from scripts
altogether to enforce that they are called with a $(VARIABLE) that can
be overridden?

> Using '-o' instead of redirecting stdout to the output file should enable the
> usage of the recent copy_file_range() optimizations in gen_init_cpio.

Will give it a try, thanks.

>> +modules-$(KERNELRELEASE)-$(ARCH).cpio: modules-install
>> +	$(Q)$(MAKE) -f $(srctree)/Makefile $(build)=usr cpio-data= usr/gen_init_cpio
> 
> Drop the explicit '-f'; $(build) overwrites it.

Indeed, will drop.

> Is the cpio-data= intended to make sure the line 'hostprogs := gen_init_cpio'
> is executed? I don't think this works as usr/Makefile will overwrite 'cpio-data'
> in any case. But it should be fine to make hostprogs definition unconditional.

Will add a commit making hostprogs := gen_init_cpio unconditional.
The current approach worked though, because specifying the variable on
the command line overrides cpio-data := assignments even if there are
multiple.

Thanks,
Ahmad

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