linux-kernel - Re: [PATCH v2--to=linux-modules@...r.kernel.org] depmod: Handle installing modules under a prefix

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Message-ID: <20230712161515.GH9196@kitsune.suse.cz>
Date:   Wed, 12 Jul 2023 18:15:15 +0200
From:   Michal Suchánek <msuchanek@...e.de>
To:     Masahiro Yamada <masahiroy@...nel.org>
Cc:     Takashi Iwai <tiwai@...e.com>,
        Lucas De Marchi <lucas.de.marchi@...il.com>,
        Michal Koutný <mkoutny@...e.com>,
        Jiri Slaby <jslaby@...e.com>, Jan Engelhardt <jengelh@...i.de>,
        Nathan Chancellor <nathan@...nel.org>,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        Nicolas Schier <nicolas@...sle.eu>,
        linux-kbuild@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2--to=linux-modules@...r.kernel.org] depmod: Handle
 installing modules under a prefix

On Wed, Jul 12, 2023 at 11:14:33PM +0900, Masahiro Yamada wrote:
> On Wed, Jul 12, 2023 at 10:45 PM Michal Suchanek <msuchanek@...e.de> wrote:
> >
> > Some distributions aim at not shipping any files in / ustside of usr.
> >
> > The path under which kernel modules are instaleld is hardcoded to /lib
> > which conflicts with this goal.
> >
> > When kmod provides the config command use it to determine the correct
> > module installation prefix.
> >
> > On kmod that does not provide the command / is used as before.
> >
> > Signed-off-by: Michal Suchanek <msuchanek@...e.de>
> > ---
> > v2: Avoid error on systems with kmod that does not support config
> > command
> > ---
> >  Makefile          | 4 +++-
> >  scripts/depmod.sh | 8 ++++----
> >  2 files changed, 7 insertions(+), 5 deletions(-)
> >
> > diff --git a/Makefile b/Makefile
> > index 47690c28456a..b1fea135bdec 100644
> > --- a/Makefile
> > +++ b/Makefile
> > @@ -1165,7 +1165,9 @@ export INSTALL_DTBS_PATH ?= $(INSTALL_PATH)/dtbs/$(KERNELRELEASE)
> >  # makefile but the argument can be passed to make if needed.
> >  #
> >
> > -MODLIB = $(INSTALL_MOD_PATH)/lib/modules/$(KERNELRELEASE)
> > +export KERNEL_MODULE_PREFIX := $(shell kmod config &> /dev/null && kmod config | jq -r .module_prefix)
> > +
> > +MODLIB = $(INSTALL_MOD_PATH)$(KERNEL_MODULE_PREFIX)/lib/modules/$(KERNELRELEASE)
> 
> You can do "make modules_install INSTALL_MOD_PATH=/usr/what/ever/prefix"
> 
> This patch is unneeded.

It's very much needed.

INSTALL_MOD_PATH is temporary staging location, KERNEL_MODULE_PREFIX is
permanent prefix under which modules are searched.

Note that depmod.sh does not use INSTALL_MOD_PATH but uses
KERNEL_MODULE_PREFIX.

Support for this is added by the corresponding kmod patchset.

Thanks

Michal

> >  export MODLIB
> >
> >  PHONY += prepare0
> > diff --git a/scripts/depmod.sh b/scripts/depmod.sh
> > index 3643b4f896ed..88ac79056153 100755
> > --- a/scripts/depmod.sh
> > +++ b/scripts/depmod.sh
> > @@ -27,16 +27,16 @@ fi
> >  # numbers, so we cheat with a symlink here
> >  depmod_hack_needed=true
> >  tmp_dir=$(mktemp -d ${TMPDIR:-/tmp}/depmod.XXXXXX)
> > -mkdir -p "$tmp_dir/lib/modules/$KERNELRELEASE"
> > +mkdir -p "$tmp_dir$KERNEL_MODULE_PREFIX/lib/modules/$KERNELRELEASE"
> >  if "$DEPMOD" -b "$tmp_dir" $KERNELRELEASE 2>/dev/null; then
> > -       if test -e "$tmp_dir/lib/modules/$KERNELRELEASE/modules.dep" -o \
> > -               -e "$tmp_dir/lib/modules/$KERNELRELEASE/modules.dep.bin"; then
> > +       if test -e "$tmp_dir$KERNEL_MODULE_PREFIX/lib/modules/$KERNELRELEASE/modules.dep" -o \
> > +               -e "$tmp_dir$KERNEL_MODULE_PREFIX/lib/modules/$KERNELRELEASE/modules.dep.bin"; then
> >                 depmod_hack_needed=false
> >         fi
> >  fi
> >  rm -rf "$tmp_dir"
> >  if $depmod_hack_needed; then
> > -       symlink="$INSTALL_MOD_PATH/lib/modules/99.98.$KERNELRELEASE"
> > +       symlink="$INSTALL_MOD_PATH$KERNEL_MODULE_PREFIX/lib/modules/99.98.$KERNELRELEASE"
> >         ln -s "$KERNELRELEASE" "$symlink"
> >         KERNELRELEASE=99.98.$KERNELRELEASE
> >  fi
> > --
> > 2.41.0
> >
> 
> 
> -- 
> Best Regards
> Masahiro Yamada