Re: [gentoo-dev] [PATCH] linux-mod.eclass: Support module compression

[Ionen Wolkens]

On Thu, Jun 09, 2022 at 06:11:00PM -0400, Mike Pagano wrote:
> The Linux kernel supports the compression of modules utilizing GZIP, XZ
> and ZSTD.  Add code into linux-mod.eclass to support this for out of
> tree modules utilizing the compression binary specified in the kernel
> config.
>
> Note that if the binary which provides the compression is not present on
> the system the kernel would have failed to build with an error
> indicating the missing binaries name.
>
> Signed-off-by: Mike Pagano <mpagano@g.o>
> ---
>   eclass/linux-mod.eclass | 17 ++++++++++++++++-
>   1 file changed, 16 insertions(+), 1 deletion(-)
>
> diff --git a/eclass/linux-mod.eclass b/eclass/linux-mod.eclass
> index 6a820371b..b7c13cbf7 100644
> --- a/eclass/linux-mod.eclass
> +++ b/eclass/linux-mod.eclass
> @@ -711,7 +711,22 @@ linux-mod_src_install() {
>   		einfo "Installing ${modulename} module"
>   		cd "${objdir}" || die "${objdir} does not exist"
>   		insinto "${INSTALL_MOD_PATH}"/lib/modules/${KV_FULL}/${libdir}
> -		doins ${modulename}.${KV_OBJ} || die "doins ${modulename}.${KV_OBJ} failed"
> +
> +		# check here for CONFIG_MODULE_COMPRESS_<compression option> (NONE, GZIP, XZ, ZSTD)
> +		# and similarily compress the module being built if != NONE.
> +
> +		if linux_chkconfig_present MODULE_COMPRESS_XZ; then
> +			xz ${modulename}.${KV_OBJ}
> +			doins ${modulename}.${KV_OBJ}.xz || die "doins ${modulename}.${KV_OBJ}.xz failed"
> +		elif linux_chkconfig_present MODULE_COMPRESS_GZIP; then
> +			gzip ${modulename}.${KV_OBJ}
> +			doins ${modulename}.${KV_OBJ}.gz || die "doins ${modulename}.${KV_OBJ}.gz failed"
> +		elif linux_chkconfig_present MODULE_COMPRESS_ZSTD; then
> +			zstd ${modulename}.${KV_OBJ}
> +			doins ${modulename}.${KV_OBJ}.zst || die "doins ${modulename}.${KV_OBJ}.zst failed"
> +		else
> +			doins ${modulename}.${KV_OBJ} || die "doins ${modulename}.${KV_OBJ} failed"
> +		fi

This is copied from what the ebuild used to do, but doins already dies
on its own and report what file failed. Be a good occasion to clean
that up rather than repeat it.

What does not die on its own is the compression commands though. doins
would fail right after, but feels kind of unclear/fragile.

That aside, I tend to wonder if the kernel build system could be used
to install (i.e. it'd do compression, signing, etc... at same time,
and even handle new methods without needing to add them to the eclass).
But it's not something I looked at for usability, so not picky about
how to handle this.

>   		cd "${OLDPWD}"
>
>   		generate_modulesd "${objdir}/${modulename}"
> --
> 2.35.1
>




-- 
ionen