Re: [PATCH 04/23] kallsyms: output binary data to speed output and kallsyms assembly

[Linus Torvalds]

I'm finally going through this series, because I do care about build
speed, so I love the concept.

However, I haven't actually applied it and tried it, I'm just reading
the patches.

And this one triggered something:

On Tue, 8 Sept 2026 at 13:56, Lorenzo Stoakes (ARM) <ljs@xxxxxxxxxx> wrote:
>
> kallsyms generates an assembly file that consists mostly of .byte entries
> containing compressed names, token strings and name-sorted sequence
> numbers.
>
> For an x86-64 build with 158k symbols that is a 37 MiB .S file which takes
> 0.57s to assemble each of the two to three times it is built over a kernel
> build.

It strikes me that this is clearly a bit faster, but it still seems to
be not really fixing the underlying silliness of that code.

Wouldn't it be much better to actually create an object file directly?
Afaik, the *only* think we ever do with that kallsyms-generated file
is to immediately assemble it into an object file, because the actual
asm file is useless to anybody.

And we already require libelf as part of the build, and we already
kind of do things like that with gendwarfksyms.

Don't get my wrong: I think going through an asm file was very much
the right thing originally: not every architecture used ELF in the
first place, and when scripting things like this the current situation
makes 100% sense.

And no sane human wants to deal with this kind of grotty detail and
spend the effort on writing an ELF file writer.

But when there's a LLM that was used to find these things and help fix
them up, and it's something this mechanical and the result really
isn't ever human-readable and never has been, I feel like the obvious
step would be to just ask the little helper bot to switch the whole
kallsyms to using libelf-devel and writing an object file directly.

I don't think anybody has any deep emotional ties to the current
kallsyms code and that horrific step of the kernel build, do they?

               Linus