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Date:   Mon, 17 Jul 2023 21:28:30 +0200 (CEST)
From:   Jan Engelhardt <jengelh@inai.de>
To:     Michal Suchanek <msuchanek@suse.de>
cc:     linux-modules@vger.kernel.org, Takashi Iwai <tiwai@suse.com>,
        Lucas De Marchi <lucas.de.marchi@gmail.com>,
        =?UTF-8?Q?Michal_Koutn=C3=BD?= <mkoutny@suse.com>,
        Jiri Slaby <jslaby@suse.com>,
        Masahiro Yamada <masahiroy@kernel.org>,
        Nathan Chancellor <nathan@kernel.org>,
        Nick Desaulniers <ndesaulniers@google.com>,
        Nicolas Schier <nicolas@fjasle.eu>,
        linux-kbuild@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH kmod v4 4/4] libkmod, depmod, modprobe: Make directory
 for kernel modules configurable
In-Reply-To: <cc04472084dc016679598fcffafc788bbb6d9c0f.1689589902.git.msuchanek@suse.de>
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References: <20230711153126.28876-1-msuchanek@suse.de> <cover.1689589902.git.msuchanek@suse.de> <cc04472084dc016679598fcffafc788bbb6d9c0f.1689589902.git.msuchanek@suse.de>
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On Monday 2023-07-17 12:39, Michal Suchanek wrote:

>modprobe.d is now searched under ${prefix}/lib, add ${module_directory} to
>specify the directory where to search for kernel modules.
>
>With this distributions that do not want to ship files in /lib can also
>move kernel modules to /usr while others can keep them in /lib.

This patch breaks kernel builds/installation.

 * assume $distro has given me a kmod that has your submission included,
   and such kmod was ./configure'd --with-module-directory=/usr/lib/modules

With such a kmod, the module installation of current and past kernels
is not possible, in other words, ** bisecting kernels ** is broken:


$ make modules_install INSTALL_MOD_PATH=$PWD/rt V=1
[...]
# INSTALL /tmp/linux/rt/lib/modules/6.4.3/kernel/virt/lib/irqbypass.ko
  mkdir -p /tmp/linux/rt/lib/modules/6.4.3/kernel/virt/lib/; cp virt/lib/irqbypass.ko /tmp/linux/rt/lib/modules/6.4.3/kernel/virt/lib/irqbypass.ko
[...]
# DEPMOD  /tmp/linux/rt/lib/modules/6.4.3
  sh ./scripts/depmod.sh depmod 6.4.3
depmod: ERROR: could not open directory /tmp/linux/rt/usr/lib/modules/99.98.6.4.3: No such file or directory
depmod: FATAL: could not search modules: No such file or directory
make: *** [Makefile:1956: modules_install] Error 1