Re:

[Eduard Zingerman <eddyz87@gmail.com>]

On Wed, 2024-06-26 at 14:11 +0800, Totoro W wrote:
> Hi folks,
> 
> This is my first time to ask questions in this mailing list. I'm the
> author of https://github.com/tw4452852/zbpf which is a framework to
> write BPF programs with Zig toolchain.
> During the development, as the BTF is totally generated by the Zig
> toolchain, some naming conventions will make the BTF verifier refuse
> to load.
> Right now I have to patch the libbpf to do some fixup before loading
> into the kernel
> (https://github.com/tw4452852/libbpf_zig/blob/main/0001-temporary-WA-for-invalid-BTF-info-generated-by-Zig.patch).

> +		// https://github.com/tw4452852/zbpf/issues/3
> +		else if (btf_is_ptr(t)) {
> +			t->name_off = 0;

As far as I understand, you control BTF generation, why generate names
for pointers in a first place?

> Even though this just work-around the issue, I'm still curious about
> the current naming sanitation, I want to know some background about
> it.

Doing some git digging shows that name check was first introduced by
the following commit:

2667a2626f4d ("bpf: btf: Add BTF_KIND_FUNC and BTF_KIND_FUNC_PROTO")

And lived like that afterwards.

My guess is that kernel BTF is used to work with kernel functions and
data structures. All of which follow C naming convention.

> If possible, could we relax this to accept more languages (like Zig)
> to write BPF programs? Thanks in advance.

Could you please elaborate a bit?
Citation from [1]:

  Identifiers must start with an alphabetic character or underscore
  and may be followed by any number of alphanumeric characters or
  underscores. They must not overlap with any keywords.

  If a name that does not fit these requirements is needed, such as
  for linking with external libraries, the @"" syntax may be used.
  
Paragraph 1 matches C naming convention and should be accepted by
kernel/bpf/btf.c:btf_name_valid_identifier().
Paragraph 2 is basically any string.
Which one do you want?

[1] https://ziglang.org/documentation/master/#Identifiers