overrideAttrs on kernel derivation loses passthru values

[samueldr]

Describe the bug

There is an oddity with how the kernel derivations react when overrideAttrs is used with them. Some passthru values are lost, namely features and commonStructuredConfig.

In turn, this makes customizing them harder than expected. These values are used in the NixOS modules.

To Reproduce

Using overrideAttrs, the passthru value given to the function does not hold all values found on the derivation's own passthru.

Details:

• https://gist.github.com/samueldr/5cb327043a2f451edb5b38175eb07c73

let
  kernel = pkgs.linux_latest;
  overriddenKernel = kernel.overrideAttrs({ passthru ? {}, ... }: {
    passthru = passthru // {
      world = "y'all";
    };
  });
in
  /* ok   */ assert kernel ? features;
  /* ok   */ assert kernel ? commonStructuredConfig;
  /* fail */ assert overriddenKernel ? features;
  /* fail */ assert overriddenKernel ? commonStructuredConfig;

Expected behavior

Values in passthru on the derivation should all be present in the overrideAttrs call.

Workaround

let
  kernel = pkgs.linux_latest;
  overriddenKernel = kernel.overrideAttrs({ passthru ? {}, ... }: {
    passthru = kernel.passthru // { # <- use the derivation rather than the param
      world = "y'all";
    };
  });
in

Additional context

• https://gist.github.com/samueldr/5cb327043a2f451edb5b38175eb07c73

And where I suspect this is coming from:

• nixpkgs/pkgs/os-specific/linux/kernel/generic.nix

  Lines 179 to 187 in 21a2aeb

  	passthru = {
  	features = kernelFeatures;
  	inherit commonStructuredConfig isXen isZen isHardened isLibre;
  	kernelOlder = lib.versionOlder version;
  	kernelAtLeast = lib.versionAtLeast version;
  	passthru = kernel.passthru // (removeAttrs passthru [ "passthru" ]);
  	};
  	in lib.extendDerivation true passthru kernel

This is can be observed against 891f607, and is an evaluation issue. No builds happened.

The linked gist contains a full reproduction.

Maintainer information:

# a list of nixpkgs attributes affected by the problem
attribute:
# a list of nixos modules affected by the problem
module:

[infinisil]

Haven't tested this properly, but

diff --git a/pkgs/os-specific/linux/kernel/generic.nix b/pkgs/os-specific/linux/kernel/generic.nix
index dd3050a93ee..a90245b8a91 100644
--- a/pkgs/os-specific/linux/kernel/generic.nix
+++ b/pkgs/os-specific/linux/kernel/generic.nix
@@ -186,4 +186,6 @@ let
     passthru = kernel.passthru // (removeAttrs passthru [ "passthru" ]);
   };
 
-in lib.extendDerivation true passthru kernel
+in kernel.overrideAttrs (old: {
+  passthru = old.passthru // passthru;
+})

works

We wouldn't have these kinds of problems if some generic override interface like NixOS/rfcs#67 (comment) existed

[infinisil]

Short explanation: extendDerivation updates the derivation without updating all the override functions. So .overrideAttrs still points to the one from kernel. So once you call that, all the changes from extendDerivation are undone.

[kira-bruneau]

Wow what a coincidence. I ran into this same problem today trying to adapt @thefloweringash's port of lg-hammerhead to work on Mobile NixOS's master 😄 (specifically with the kernelWithDTB wrapper).

[stale]

I marked this as stale due to inactivity. → More info

[ShamrockLee]

I made a new PR (#288154) to tackle this issue. Please take a look.