Re: [PATCH v6 2/2] host/rootfs: Switch to systemd-udevd

[Demi Marie Obenour <demiobenour@gmail.com>]

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On 11/8/25 17:14, Alyssa Ross wrote:
> Alyssa Ross <hi@alyssa.is> writes:
> 
>> Demi Marie Obenour <demiobenour@gmail.com> writes:
>>
>>> On 11/8/25 14:49, Alyssa Ross wrote:
>>>> Demi Marie Obenour <demiobenour@gmail.com> writes:
>>>>
>>>>> @@ -113,14 +76,15 @@ let
>>>>>  
>>>>>    kernel = linux_latest;
>>>>>  
>>>>> -  appvm = callSpectrumPackage ../../img/app { inherit (foot) terminfo; };
>>>>> -  netvm = callSpectrumPackage ../../vm/sys/net { inherit (foot) terminfo; };
>>>>> +  appvm = callSpectrumPackage ../../img/app { inherit (no_pgo_foot) terminfo; };
>>>>> +  netvm = callSpectrumPackage ../../vm/sys/net { inherit (no_pgo_foot) terminfo; };
>>>>>  
>>>>>    # Packages that should be fully linked into /usr,
>>>>>    # (not just their bin/* files).
>>>>>    usrPackages = [
>>>>> -    appvm kernel.modules firmware netvm
>>>>> -  ] ++ (with pkgsGui; [ mesa dejavu_fonts westonLite ]);
>>>>> +    appvm kernel.modules firmware kmod kmod.lib
>>>>> +    netvm mesa dejavu_fonts westonLite
>>>>> +  ];
>>>>>  
>>>>>    appvms = {
>>>>>      appvm-firefox = callSpectrumPackage ../../vm/app/firefox.nix {};
>>>>
>>>> So based on what we'd discussed previously, I was ready to just apply
>>>> this and pare down the Nix changes myself since I don't have to worry
>>>> about rebuilds, etc., but in doing so I came across this.  Do you know
>>>> why kmod.lib is required?  Is something impurely dlopening it?  Seems
>>>> very strange, but I did verify that it's required for Weston to start.
>>>
>>> systemd uses dlopen heavily.  This allows dependencies to be optional
>>> at runtime.  I remember strace showing that systemd-udevd dlopen's
>>> kmod.lib.  In short, your diagnosis is correct.
>>
>> Okay, that's a packaging bug in Nixpkgs then.  (See e.g. [1].)  I'll see
>> what can be done.
>>
>> [1]: https://github.com/NixOS/nixpkgs/commit/2328731ad041735a2260698574ce6599591f33ad
> 
> I have looked into it a bit and am now even more confused.  From what I
> can see, loading libkmod should be done by libsystemd-shared.so, which
> has kmod.lib in its RUNPATH.

According to https://wiki.debian.org/RpathIssue, only the RUNPATH of
the executable is honored.  The RUNPATH of libraries is not honored.
For this to work, libsystemd-shared.so needs to have kmod.lib in its
RPATH, and udevadm *may* need to not have a RUNPATH.
-- 
Sincerely,
Demi Marie Obenour (she/her/hers)

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