[$] Implicit arguments for BPF kfuncs

The kernel’s “kfunc” mechanism is a way of exporting kernel functions so
that they can be called directly from BPF programs. There are over 300
kfuncs in current kernels, ranging in functionality from string processing
(bpf_strnlen())
to custom schedulers (scx_bpf_kick_cpu())
and beyond. Sometimes these kfuncs need access to context information that
is not directly available to BPF programs, and which thus cannot be passed
in as arguments. The implicit
arguments patch set from Ihor Solodrai is the latest attempt to solve
this problem.