[SOLVED] What does it meam a kernel module for wireless card ends with .ko.xz instead of .ko

Issue

I am on Fedora 38 and I cannot install the kernel module for a Broadcom BCM 43142 Network Controller. I eventually understood that it is because the module is not correctly signed and that I have to:

1. disable secure boot
2. self sign the module.

After disabling secure boot I could manage to have the module loaded and the wifi working.

But I came back re-enabling secure boot in order to try self sign the module.

I followed this tutorial Working with kerned modules but it didn't worked as I do not fully understand everything.

Particularly the module I have is /lib/modules/6.4.15-200.fc38.x86_64/extra/wl/wl.ko.xz

Question 1:

Is it normal that it ends with .ko.xz?

Question 2:

Will the signed module have the same name?

Solution

Is it normal that it ends with .ko.xz?

Yes.

.xz just means it's a compressed binary:

https://unix.stackexchange.com/questions/416397/centos7-latest-kernel-moved-from-kernel-ko-to-kernel-ko-xz

Modules can be compressed using either gzip or xz. Compression is enabled using the MODULE_COMPRESS kernel build option, with MODULE_COMPRESS_GZIP or MODULE_COMPRESS_XZ to select the compression tool.

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Will the signed module have the same name?

By default, No.

...though a thoroughly correct answer would depend on how, exactly, you intend to sign and recompress the module file, though:

1. You need to first unpack/decompress the module (i.e. from .ko.xz to just .ko).
2. Then sign the decompressed module.
3. Then either use the now-signed decompressed module .ko as-is, or you can recompress it again back with xz -f yourModule.ko
   • If you use just xz -f <output.ko> then the actual output filename will be output.ko.xz - this is because (by default) the xz program will append the compression algorithm's name to the file's name.

See also: https://unix.stackexchange.com/questions/438954/signing-a-compressed-kernel-module-for-use-with-secure-boot

Answered By - Dai

Answer Checked By - Clifford M. (WPSolving Volunteer)