[arch-projects] [initscripts][udev][RFC] first step towards removing load-modules.sh

Tue May 10 09:02:37 EDT 2011

On Tue, May 10, 2011 at 10:02:07AM +0200, Tom Gundersen wrote:
> Hi guys,
> 
> This is in regards to FS#18421.
> 
> I am looking at ways to move our udev package closer to upstream. The
> biggest difference is currently our load-modules.sh script which
> filters out what modules to load. This adds significant overhead to
> boot, so I think it is the first thing that should go.
> 
> The below patch generate a blacklist file at boot from rc.conf, which
> should be linked to by a softlink in /etc/modprobe.d/. This allows
> udev to figure out blacklisting by itself.
> 
> Once this is in initscripts and a similar patch is in mkinitcpio, then
> we can ditch load-modules.sh.
> 
> One thing to note: the attached patch does "blacklist <module>" (which
> allows modules to be pulled in as dependencies). We could also do
> "install <module> /bin/false" (which has the same effect as deleting
> the module altogether), if that is necessary. I chose to use blacklist
> as it looks to be the recommended way.
> 
> Thoughts?
> 
> Cheers,
> 
> Tom

I'm going to argue that we should be going the install /bin/false route,
as it more accurately mimics what we currently do with load-modules.sh.
This does have the drawback that if a user really does in fact want to
install a given module, they need to run modprobe with -i. I don't
recall if load-modules.sh allows explicit installation of a "blacklisted"
module.

Important: for your patchwork to be effective, we need to alter the udev
rules that reference load-modules.sh. If this isn't done for the
initcpio, you will almost assuredly be dumped to a rescue shell.

Other than alteration of the rules, this should be an easy win in the
initcpio, as we have a writeable filesystem from the start. And (correct
me if im wrong), the only reason we ever need to write a blacklist file
is if disablemodules= is specified on the kernel cmdline. /etc/rc.conf is
verboten in early userspace because it uses arrays.

As I mentioned to you on your GH pull request, I'm still a bit weary of
starting up a symlink farming business in /run. I would love to see
module-init-tools support for reading from /run/modprobe.d, but perhaps
that's a bit of an exotic request. With the FHS revived and gearing up
for a release, it seems likely that /run will be standardized, but I'm
not sure if that has any clout here.

semi-random aside: does anyone other than systemd support
/etc/modules-load.d?

d

(uggh, way longer than i wanted this to be)

> 
> From 56e6e5684d40b66d810a3d7d424b5aabec6d660e Mon Sep 17 00:00:00 2001
> From: Tom Gundersen <teg at jklm.no>
> Date: Mon, 9 May 2011 22:15:43 +0200
> Subject: [PATCH] udev: generate blacklist on boot
> 
> udev will read /etc/modprobe.d/*.conf and blacklist all modules that
> are listed as
> 
> blacklist <module>
> 
> We parse rc.conf at boot and generate such a .conf file. It cannot be
> written to /etc this early, so we save it to /run. A symlink exists in
> /etc to get the desired functionality.
> 
> While we are at it we also write the list of autoloaded. This is
> useful in case we ever want to move to using
> /etc/modules-load.d/*.conf for loading modules.
> 
> With this patch load-modules.sh can be removed from the udev package
> without loss of functionality.
> 
> Original-idea-by: Benjamen Richer <br at waldteufel-online.net>
> Based-on-patch-by: David Reisner <d at falconindy.com>
> Signed-off-by: Tom Gundersen <teg at jklm.no>
> ---
>  Makefile            |    4 +++-
>  rc.gen-module-lists |   32 ++++++++++++++++++++++++++++++++
>  rc.sysinit          |    3 +++
>  3 files changed, 38 insertions(+), 1 deletions(-)
>  create mode 100755 rc.gen-module-lists
> 
> diff --git a/Makefile b/Makefile
> index d3a1824..dfb2ff0 100644
> --- a/Makefile
> +++ b/Makefile
> @@ -1,5 +1,5 @@
>  VER  := $(shell git describe)
> -DIRS := /etc/rc.d /etc/conf.d /etc/rc.d/functions.d /etc/cron.hourly /sbin
> +DIRS := /etc/rc.d /etc/conf.d /etc/rc.d/functions.d /etc/cron.hourly
> /sbin /etc/modprobe.d /etc/module-load.d
> 
>  minilogd: minilogd.o
> 
> @@ -13,6 +13,8 @@ install: minilogd installdirs
>  	install -m755 -t $(DESTDIR)/etc/cron.hourly adjtime
>  	install -m755 -t $(DESTDIR)/etc/rc.d functions hwclock network netfs
>  	install -m755 -t $(DESTDIR)/sbin minilogd rc
> +	ln -s /run/initscripts/modules-blacklist.conf
> $(DESTDIR)/etc/modprobe.d/arch-blacklist.conf
> +	ln -s /run/initscripts/modules-load.conf
> $(DESTDIR)/etc/modules-load.d/arch-modules.conf
> 
>  clean:
>  	rm -f minilogd minilogd.o
> diff --git a/rc.gen-module-lists b/rc.gen-module-lists
> new file mode 100755
> index 0000000..14f9619
> --- /dev/null
> +++ b/rc.gen-module-lists
> @@ -0,0 +1,32 @@
> +#!/bin/bash
> +#
> +# /etc/rc.gen-modules-list
> +#
> +
> +. /etc/rc.conf
> +
> +declare -a modules blacklist
> +for mod in "${MODULES[@]}"; do
> +	case $mod in
> +		!*) blacklist+=("${mod:1}") ;;
> +		*) modules+=("$mod") ;;
> +	esac
> +done
> +
> +# create new module blacklist in /run/initscripts, there should be a
> symlink in /etc/modprobe.d/ pointing here
> +if [[ $blacklist ]]; then
> +	/bin/mkdir -p /run/initscripts
> +	echo "# Autogenerated from rc.conf at boot, do not edit" >
> /run/initscripts/modules-blacklist.conf
> +	(( ${#blacklist[@]} )) && printf 'blacklist %s\n' "${blacklist[@]}"
> >> /run/initscripts/modules-blacklist.conf
> +fi
> +
> +# create new module list in /run/initscripts, there should be a
> symlink in /etc/modules-load.d/ pointing here
> +if [[ $modules ]]; then
> +	/bin/mkdir -p /run/initscripts
> +	echo "# Autogenerated from rc.conf at boot, do not edit" >
> /run/initscripts/modules-load.conf
> +	printf '%s\n' "${modules[@]}" >> /run/initscripts/modules-load.conf
> +fi
> +
> +unset blacklist modules
> +
> +# vim: set noet ts=2 sw=2:
> diff --git a/rc.sysinit b/rc.sysinit
> index 1521299..4e45d7c 100755
> --- a/rc.sysinit
> +++ b/rc.sysinit
> @@ -83,6 +83,9 @@ if [[ $HWCLOCK_PARAMS ]]; then
>  	fi
>  fi
> 
> +# parse rc.conf and create the blacklist file for use by udev
> +status "Creating UDev blacklist" /etc/rc.gen-module-lists
> +
>  status "Starting UDev Daemon" /sbin/udevd --daemon
> 
>  run_hook sysinit_udevlaunched
> -- 
> 1.7.5.1