[PATCH bpf-next 2/3] bpf: mark bpf_cast_to_kern_ctx and bpf_rdonly_cast as KF_NOCSR

[Eduard Zingerman <eddyz87@gmail.com>]

do_misc_fixups() relaces bpf_cast_to_kern_ctx() and bpf_rdonly_cast()
by a single instruction "r0 = r1". This clearly follows nocsr contract.
Mark these two functions as KF_NOCSR, in order to use them in
selftests checking KF_NOCSR behaviour for kfuncs.

Signed-off-by: Eduard Zingerman <eddyz87@gmail.com>
---
 kernel/bpf/helpers.c  | 4 ++--
 kernel/bpf/verifier.c | 3 ++-
 2 files changed, 4 insertions(+), 3 deletions(-)

diff --git a/kernel/bpf/helpers.c b/kernel/bpf/helpers.c
index d02ae323996b..cda3c326eeb1 100644
--- a/kernel/bpf/helpers.c
+++ b/kernel/bpf/helpers.c
@@ -2987,8 +2987,8 @@ BTF_ID(func, bpf_cgroup_release_dtor)
 #endif
 
 BTF_KFUNCS_START(common_btf_ids)
-BTF_ID_FLAGS(func, bpf_cast_to_kern_ctx)
-BTF_ID_FLAGS(func, bpf_rdonly_cast)
+BTF_ID_FLAGS(func, bpf_cast_to_kern_ctx, KF_NOCSR)
+BTF_ID_FLAGS(func, bpf_rdonly_cast, KF_NOCSR)
 BTF_ID_FLAGS(func, bpf_rcu_read_lock)
 BTF_ID_FLAGS(func, bpf_rcu_read_unlock)
 BTF_ID_FLAGS(func, bpf_dynptr_slice, KF_RET_NULL)
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index c579f74be3f9..88e583a37296 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -16159,7 +16159,8 @@ static u32 kfunc_nocsr_clobber_mask(struct bpf_kfunc_call_arg_meta *meta)
 /* Same as verifier_inlines_helper_call() but for kfuncs, see comment above */
 static bool verifier_inlines_kfunc_call(struct bpf_kfunc_call_arg_meta *meta)
 {
-	return false;
+	return meta->func_id == special_kfunc_list[KF_bpf_cast_to_kern_ctx] ||
+	       meta->func_id == special_kfunc_list[KF_bpf_rdonly_cast];
 }
 
 /* GCC and LLVM define a no_caller_saved_registers function attribute.
-- 
2.45.2