selftests/bpf: add iter test requiring range x range logic

Add a simple verifier test that requires deriving reg bounds for one
register from another register that's not a constant. This is
a realistic example of iterating elements of an array with fixed maximum
number of elements, but smaller actual number of elements.

This small example was an original motivation for doing this whole patch
set in the first place, yes.

Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/r/20231112010609.848406-14-andrii@kernel.org
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

diff --git a/tools/testing/selftests/bpf/progs/iters.c b/tools/testing/selftests/bpf/progs/iters.c
index c20c4e38b71c5b9a7db16b6519dfbdf3fea5b89b..b2181f850d3e55ed2194ae9c13366f0ae767fb7e 100644 (file)
--- a/tools/testing/selftests/bpf/progs/iters.c
+++ b/tools/testing/selftests/bpf/progs/iters.c
@@ -1411,4 +1411,26 @@ __naked int checkpoint_states_deletion(void)
        );
 }
 
+struct {
+       int data[32];
+       int n;
+} loop_data;
+
+SEC("raw_tp")
+__success
+int iter_arr_with_actual_elem_count(const void *ctx)
+{
+       int i, n = loop_data.n, sum = 0;
+
+       if (n > ARRAY_SIZE(loop_data.data))
+               return 0;
+
+       bpf_for(i, 0, n) {
+               /* no rechecking of i against ARRAY_SIZE(loop_data.n) */
+               sum += loop_data.data[i];
+       }
+
+       return sum;
+}
+
 char _license[] SEC("license") = "GPL";