selftests/bpf: Cover writable BTF field global subprog args

Add a verifier test for passing a BTF-backed task_struct field pointer to a
global subprogram argument typed as writable memory.

The direct field store is already rejected.
The global subprogram path should be rejected too.
The callee must not lose the BTF pointer's read-only provenance.
It must not validate the argument as ordinary writable memory.

Signed-off-by: Nuoqi Gui <gnq25@mails.tsinghua.edu.cn>
Link: https://lore.kernel.org/bpf/20260609-f01-04-btf-writable-arg-v1-2-f449cd970669@mails.tsinghua.edu.cn
Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>

0 files changed, 0 insertions, 0 deletions