[PATCH bpf v4 09/11] selftests/bpf: test widening for iterating callbacks

[Eduard Zingerman <eddyz87@xxxxxxxxx>]

A test case to verify that imprecise scalars widening is applied to
callback entering state, when callback call is simulated repeatedly.

Signed-off-by: Eduard Zingerman <eddyz87@xxxxxxxxx>
---
 .../bpf/progs/verifier_iterating_callbacks.c  | 20 +++++++++++++++++++
 1 file changed, 20 insertions(+)

diff --git a/tools/testing/selftests/bpf/progs/verifier_iterating_callbacks.c b/tools/testing/selftests/bpf/progs/verifier_iterating_callbacks.c
index fa9429f77a81..598c1e984b26 100644
--- a/tools/testing/selftests/bpf/progs/verifier_iterating_callbacks.c
+++ b/tools/testing/selftests/bpf/progs/verifier_iterating_callbacks.c
@@ -25,6 +25,7 @@ struct buf_context {
 
 struct num_context {
 	__u64 i;
+	__u64 j;
 };
 
 __u8 choice_arr[2] = { 0, 1 };
@@ -69,6 +70,25 @@ int unsafe_on_zero_iter(void *unused)
 	return choice_arr[loop_ctx.i];
 }
 
+static int widening_cb(__u32 idx, struct num_context *ctx)
+{
+	++ctx->i;
+	return 0;
+}
+
+SEC("?raw_tp")
+__success
+int widening(void *unused)
+{
+	struct num_context loop_ctx = { .i = 0, .j = 1 };
+
+	bpf_loop(100, widening_cb, &loop_ctx, 0);
+	/* loop_ctx.j is not changed during callback iteration,
+	 * verifier should not apply widening to it.
+	 */
+	return choice_arr[loop_ctx.j];
+}
+
 static int loop_detection_cb(__u32 idx, struct num_context *ctx)
 {
 	for (;;) {}
-- 
2.42.1