Merge branch 'unify-helper-and-kfunc-argument-checks'

Amery Hung says:

====================
Unify helper and kfunc argument checks

Hi,

This is the third and final patchset unifying helper and kfunc checks.

Helper and kfunc calls currently validate arguments through separate
loops despite enforcing many of the same contracts. This duplicates
type admission, nullability, memory, BTF, packet-access, and resource
ownership handling.

This series completes the generation of helper-style argument metadata
for kfuncs and then routes both call kinds through check_func_args().
Call-specific behavior remains selected through call metadata where the
helper and kfunc contracts intentionally differ.

The series is organized as follows:

- Patches 1-8 prepare shared call metadata, argument indexing, and
  argument kinds.

- Patches 9-13 populate kfunc argument flags, BTF IDs, and fixed sizes
  while generating the kfunc prototype.

- Patches 14-18 consolidate runtime type resolution, nullability, BTF
  matching, and register admission.

- Patches 19-22 consolidate packet-access and release validation, with
  coverage for kfunc packet writes and nullable per-CPU kptr identity.

- Patch 23 replaces the duplicate helper and kfunc loops with the
  common check_func_args() path.

[1/3] https://lore.kernel.org/bpf/20260715064047.1793790-1-ameryhung@gmail.com/
[2/3] https://lore.kernel.org/bpf/20260801074633.1595644-1-ameryhung@gmail.com/

Changelog:

v1 -> v2
  - Rebased onto the latest bpf-next
  - Reordered and folded patches for bisectability
  - Fixed kfunc memory admission and nullable per-CPU kptr identity
  - Tweaked style to reduce indent (Alexei)
  - Fixed minor wording error in comments and commit msgs (AI)
  Link: https://lore.kernel.org/bpf/20260905220117.922028-1-ameryhung@gmail.com/
====================

Link: https://patch.msgid.link/20260911220415.1396439-1-ameryhung@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>