selftests/bpf: add more cases for __arg_trusted __arg_nullable args

Add extra layer of global functions to ensure that passing around
(trusted) PTR_TO_BTF_ID_OR_NULL registers works as expected. We also
extend trusted_task_arg_nullable subtest to check three possible valid
argumements: known NULL, known non-NULL, and maybe NULL cases.

Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/r/20240202190529.2374377-3-andrii@kernel.org
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

diff --git a/tools/testing/selftests/bpf/progs/verifier_global_ptr_args.c b/tools/testing/selftests/bpf/progs/verifier_global_ptr_args.c
index 484d6262363f4b2a8a7020dc5b0cdfadc5c7df08..4ab0ef18d7eb4d5bef467a58887b280b9bb438c9 100644 (file)
--- a/tools/testing/selftests/bpf/progs/verifier_global_ptr_args.c
+++ b/tools/testing/selftests/bpf/progs/verifier_global_ptr_args.c
@@ -19,15 +19,41 @@ __weak int subprog_trusted_task_nullable(struct task_struct *task __arg_trusted
        return task->pid + task->tgid;
 }
 
-SEC("?kprobe")
+__weak int subprog_trusted_task_nullable_extra_layer(struct task_struct *task __arg_trusted __arg_nullable)
+{
+       return subprog_trusted_task_nullable(task) + subprog_trusted_task_nullable(NULL);
+}
+
+SEC("?tp_btf/task_newtask")
 __success __log_level(2)
 __msg("Validating subprog_trusted_task_nullable() func#1...")
 __msg(": R1=trusted_ptr_or_null_task_struct(")
 int trusted_task_arg_nullable(void *ctx)
 {
-       struct task_struct *t = bpf_get_current_task_btf();
+       struct task_struct *t1 = bpf_get_current_task_btf();
+       struct task_struct *t2 = bpf_task_acquire(t1);
+       int res = 0;
 
-       return subprog_trusted_task_nullable(t) + subprog_trusted_task_nullable(NULL);
+       /* known NULL */
+       res += subprog_trusted_task_nullable(NULL);
+
+       /* known non-NULL */
+       res += subprog_trusted_task_nullable(t1);
+       res += subprog_trusted_task_nullable_extra_layer(t1);
+
+       /* unknown if NULL or not */
+       res += subprog_trusted_task_nullable(t2);
+       res += subprog_trusted_task_nullable_extra_layer(t2);
+
+       if (t2) {
+               /* known non-NULL after explicit NULL check, just in case */
+               res += subprog_trusted_task_nullable(t2);
+               res += subprog_trusted_task_nullable_extra_layer(t2);
+
+               bpf_task_release(t2);
+       }
+
+       return res;
 }
 
 __weak int subprog_trusted_task_nonnull(struct task_struct *task __arg_trusted)