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 17:37, Alyssa Ross wrote:
> Demi Marie Obenour <demiobenour@gmail.com> writes:
> 
>> 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.
> 
> Right, so we might need to add --force-rpath to the patchelf invocation.
> 
> I wonder why this doesn't affect every NixOS system, though.  They
> certainly don't have /usr/lib/libkmod.so.2.

Difference between musl and glibc is the first thing that comes to mind.
-- 
Sincerely,
Demi Marie Obenour (she/her/hers)

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