bpf: Set MEM_RCU when generating kfunc argument types

The BTF ID argument of a kfunc has to be referenced or trusted unless
the kfunc is KF_RCU, in which case an RCU-protected pointer is accepted
too. check_kfunc_args() reads that off meta->kfunc_flags on every
verification of the call, which is the last thing keeping the argument
policy of ARG_PTR_TO_BTF_ID out of the generated prototype.

Set MEM_RCU in get_kfunc_arg_type() for ARG_PTR_TO_BTF_ID arguments of
KF_RCU kfuncs, the way it already sets OBJ_RELEASE for release
arguments, and test the generated flag instead. MEM_RCU represents the
KF_RCU relaxation applied by the ARG_PTR_TO_BTF_ID trust check; other
argument kinds have their own provenance requirements.

No functional change intended.

Signed-off-by: Amery Hung <ameryhung@gmail.com>
Link: https://lore.kernel.org/r/20260911220415.1396439-12-ameryhung@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

0 files changed, 0 insertions, 0 deletions