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#1 2018-08-11 01:00:00

jernst
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From: Silicon Valley
Registered: 2014-03-04
Posts: 245
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[Fixed] Kernel module search path with modprobe

If I recall this correctly, modprobe would search for modules in the main module directory, and also in the extramodules directory. Somehow I can't get it to pay attention to the extramodules directory any more ... what am I doing wrong?

Kernel module: nuc_led (drives the LEDs on the Intel NUC), built like this: https://github.com/uboslinux/ubos-devic … d/PKGBUILD

It puts nuc_led.ko.gz into /usr/lib/modules/extramodules-ARCH/

where modprobe cannot find it:

modprobe: FATAL: Module nuc-led not found in directory /lib/modules/4.17.12-arch1-1-ARCH

The module itself loads fine if I use insmod rather than modprobe or move it into that directory.

Maybe two questions:

  • What exactly is /usr/lib/modules/extramodules-ARCH/ for?

  • Is /lib/modules/$(uname -r) the only place where modprobe looks?

Last edited by jernst (2018-08-12 23:18:19)

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#2 2018-08-11 01:02:07

jasonwryan
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From: .nz
Registered: 2009-05-09
Posts: 26,025
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Re: [Fixed] Kernel module search path with modprobe

Not an Installation issue, moving to Kernels...


Arch + dwm   •   Mercurial repos  •   Github

Registered Linux User #482438

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#3 2018-08-11 01:27:32

ooo
Member
Registered: 2013-04-10
Posts: 1,607

Re: [Fixed] Kernel module search path with modprobe

Are you sure you haven't updated to linux-4.17.13.arch1-1, and forgot to reboot after it?

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#4 2018-08-11 01:30:14

jernst
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From: Silicon Valley
Registered: 2014-03-04
Posts: 245
Website

Re: [Fixed] Kernel module search path with modprobe

# pacman -Qi linux
Name            : linux
Version         : 4.17.12.arch1-1

# uname -r
4.17.12-arch1-1-ARCH

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#5 2018-08-11 01:56:55

ooo
Member
Registered: 2013-04-10
Posts: 1,607

Re: [Fixed] Kernel module search path with modprobe

And the extramodules symlink is correct?

# readlink /lib/modules/4.17.12-arch1-1-ARCH/extramodules
../extramodules-ARCH

Other than that, I'm out of ideas. /lib/modules/extramodules-ARCH is correct for out of tree kernel modules, and /lib/modules/$(uname -r) should be the only module look up path for modprobe.

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#6 2018-08-11 02:04:53

jernst
Member
From: Silicon Valley
Registered: 2014-03-04
Posts: 245
Website

Re: [Fixed] Kernel module search path with modprobe

The symlink is there just as you have it. But here's a tidbit:

I decided to run "strace modprobe nuc-led". The output is surprisingly short, and it only touches these (of the relevant) files:

openat(AT_FDCWD, "/lib/modules/4.17.12-arch1-1-ARCH/modules.dep.bin", O_RDONLY|O_CLOEXEC) = 3
openat(AT_FDCWD, "/lib/modules/4.17.12-arch1-1-ARCH/modules.alias.bin", O_RDONLY|O_CLOEXEC) = 3
openat(AT_FDCWD, "/lib/modules/4.17.12-arch1-1-ARCH/modules.symbols.bin", O_RDONLY|O_CLOEXEC) = 3
openat(AT_FDCWD, "/lib/modules/4.17.12-arch1-1-ARCH/modules.builtin.bin", O_RDONLY|O_CLOEXEC) = 3

So I ran "depmod -a" and voila, it works.

Which poses the question: who is supposed to run depmod -a? Feels wrong that I have to do that myself ...

Addition: there is a pacman hook: 60-linux.hook, which runs

/usr/bin/depmod --quick 4.17.12-arch1-1-ARCH

It should have done the depmod for me, no?

Last edited by jernst (2018-08-11 02:09:09)

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#7 2018-08-11 02:54:59

ooo
Member
Registered: 2013-04-10
Posts: 1,607

Re: [Fixed] Kernel module search path with modprobe

I tried installing intel-nuc-led with the PKGBUILD, and the 60-linux.hook did run fine during post-transaction.

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#8 2018-08-11 20:35:29

jernst
Member
From: Silicon Valley
Registered: 2014-03-04
Posts: 245
Website

Re: [Fixed] Kernel module search path with modprobe

I confirm that the hook is running, but I think it's the "--quick" that is getting in my way.

If understand the man page correctly, this causes depmod to compare the date on the module with the date on the dependencies file. So if my kernel module was built before (but installed after) the depedencies file was last updated, we're out of luck, no?

Is there something special that a package containing a kernel module should do, e.g. in a post_install script? Like trigger depmod itself?

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#9 2018-08-11 20:45:58

loqs
Member
Registered: 2014-03-06
Posts: 6,128

Re: [Fixed] Kernel module search path with modprobe

You could override the hook in /etc/pacman.d/hooks/ with a version that does not use --quick as a test.
If that works as expected then somehow the modules mtime is older than that of the modules.dep.

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#10 2018-08-11 22:38:16

jernst
Member
From: Silicon Valley
Registered: 2014-03-04
Posts: 245
Website

Re: [Fixed] Kernel module search path with modprobe

It appears the --quick flag was introduced just a few days ago in this commit:

https://git.archlinux.org/svntogit/pack … 2fa00de6fe

which would explain why this used to work for me :-)

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#11 2018-08-11 23:45:51

loqs
Member
Registered: 2014-03-06
Posts: 6,128

Re: [Fixed] Kernel module search path with modprobe

File a bug report asking for the quick option to be dropped or CONFIG_MODVERSIONS to be disabled which would force strict version matching so the module would have to be built after the kernel.

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#12 2018-08-12 00:43:28

jernst
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From: Silicon Valley
Registered: 2014-03-04
Posts: 245
Website

Re: [Fixed] Kernel module search path with modprobe

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