[RFC PATCH v1 03/14] selftests/bpf: Add test for throwing global subprog with acquired refs

[Kumar Kartikeya Dwivedi <memxor@gmail.com>]

Add a test case to exercise verifier logic where a global function that
may potentially throw an exception is invoked from the main subprog,
such that during exploration, the reference state is not visible when
the bpf_throw instruction is explored. Without the fixes in prior
commits, bpf_throw will not complain when unreleased resources are
lingering in the program when a possible exception may be thrown.

Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
---
 .../selftests/bpf/progs/exceptions_fail.c     | 21 +++++++++++++++++++
 1 file changed, 21 insertions(+)

diff --git a/tools/testing/selftests/bpf/progs/exceptions_fail.c b/tools/testing/selftests/bpf/progs/exceptions_fail.c
index 9cceb6521143..28602f905d7d 100644
--- a/tools/testing/selftests/bpf/progs/exceptions_fail.c
+++ b/tools/testing/selftests/bpf/progs/exceptions_fail.c
@@ -146,6 +146,13 @@ __noinline static int throwing_subprog(struct __sk_buff *ctx)
 	return 0;
 }
 
+__noinline int throwing_global_subprog(struct __sk_buff *ctx)
+{
+	if (ctx->len)
+		bpf_throw(0);
+	return 0;
+}
+
 SEC("?tc")
 __failure __msg("bpf_rcu_read_unlock is missing")
 int reject_subprog_with_rcu_read_lock(void *ctx)
@@ -346,4 +353,18 @@ int reject_exception_throw_cb_diff(struct __sk_buff *ctx)
 	return 0;
 }
 
+SEC("?tc")
+__failure __msg("exploring program path where exception is thrown")
+int reject_exception_throw_ref_call_throwing_global(struct __sk_buff *ctx)
+{
+	struct { long a; } *p = bpf_obj_new(typeof(*p));
+
+	if (!p)
+		return 0;
+	if (ctx->protocol)
+		throwing_global_subprog(ctx);
+	bpf_obj_drop(p);
+	return 0;
+}
+
 char _license[] SEC("license") = "GPL";
-- 
2.40.1