[PATCH bpf v1 4/8] selftests/bpf: Test btf lookup helper sleepability

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

Add an expected failure case which calls
bpf_btf_find_by_name_kind() from a BPF timer callback. Without the
helper prototype being marked sleepable, the verifier accepts the
program and the load unexpectedly succeeds.

Also add a positive control which calls the helper directly from a
syscall program. This verifies that marking the helper sleepable only
rejects it in non-sleepable regions.

Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
---
 .../bpf/progs/verifier_async_cb_context.c     | 34 +++++++++++++++++++
 1 file changed, 34 insertions(+)

diff --git a/tools/testing/selftests/bpf/progs/verifier_async_cb_context.c b/tools/testing/selftests/bpf/progs/verifier_async_cb_context.c
index a7c84d3fa4c7..e0926767bbd3 100644
--- a/tools/testing/selftests/bpf/progs/verifier_async_cb_context.c
+++ b/tools/testing/selftests/bpf/progs/verifier_async_cb_context.c
@@ -108,6 +108,30 @@ int timer_sys_close_prog(void *ctx)
 	return 0;
 }
 
+static int timer_btf_find_cb(void *map, int *key, struct bpf_timer *timer)
+{
+	char name[] = "task_struct";
+
+	bpf_btf_find_by_name_kind(name, sizeof(name), BTF_KIND_STRUCT, 0);
+	return 0;
+}
+
+SEC("syscall")
+__failure __msg("sleepable helper bpf_btf_find_by_name_kind#{{[0-9]+}} in non-sleepable prog")
+int timer_btf_find_prog(void *ctx)
+{
+	struct timer_elem *val;
+	int key = 0;
+
+	val = bpf_map_lookup_elem(&timer_map, &key);
+	if (!val)
+		return 0;
+
+	bpf_timer_init(&val->t, &timer_map, 0);
+	bpf_timer_set_callback(&val->t, timer_btf_find_cb);
+	return 0;
+}
+
 SEC("syscall")
 __success
 int syscall_sys_bpf_prog(void *ctx)
@@ -126,6 +150,16 @@ int syscall_sys_close_prog(void *ctx)
 	return 0;
 }
 
+SEC("syscall")
+__success
+int syscall_btf_find_prog(void *ctx)
+{
+	char name[] = "task_struct";
+
+	bpf_btf_find_by_name_kind(name, sizeof(name), BTF_KIND_STRUCT, 0);
+	return 0;
+}
+
 /* Workqueue tests */
 
 struct wq_elem {
-- 
2.53.0