Re: [PATCH] selftests/bpf: skip verif_scale_pyperf600 on -E2BIG jump complexity limit

[Paul Chaignon <paul.chaignon@gmail.com>]

On Mon, Mar 02, 2026 at 03:14:34PM +0800, Sun Jian wrote:
> verif_scale_pyperf600 loads pyperf600.bpf.o, a large scale case produced
> by partial LLVM unrolling.
> 
> On some kernel/toolchain combinations, the verifier rejects it with -E2BIG:
> 
>   The sequence of 8193 jumps is too complex.
> 
> This hits the verifier jump sequence complexity limit (8192).
> 
> Treat -E2BIG for this test as SKIP rather than FAIL. Other pyperf600
> variants are unaffected.

This is a known issue with LLVM 19+ [1] and this test is already
skipped in CI [2, 3]. I don't think ignoring the error is the proper
fix here.

1 - https://lore.kernel.org/all/c8c590b2-40b2-4cc0-9eb7-410dbd080a49@linux.dev/
2 - https://github.com/kernel-patches/vmtest/commit/da142df34750386cac2ba10283d15216d5c8d033
3 - https://github.com/libbpf/libbpf/commit/02b3ec9ffc1b7000afa2a9ccc3dfd37de3bad8cb

Paul

> 
> Signed-off-by: Sun Jian <sun.jian.kdev@gmail.com>
> ---
>  .../bpf/prog_tests/bpf_verif_scale.c          | 22 ++++++++++++++++++-
>  1 file changed, 21 insertions(+), 1 deletion(-)
> 
> diff --git a/tools/testing/selftests/bpf/prog_tests/bpf_verif_scale.c b/tools/testing/selftests/bpf/prog_tests/bpf_verif_scale.c
> index 73f669014b69..181acdddea1c 100644
> --- a/tools/testing/selftests/bpf/prog_tests/bpf_verif_scale.c
> +++ b/tools/testing/selftests/bpf/prog_tests/bpf_verif_scale.c
> @@ -112,13 +112,33 @@ void test_verif_scale_pyperf180()
>  
>  void test_verif_scale_pyperf600()
>  {
> +	libbpf_print_fn_t old_print_fn = NULL;
> +	int err;
> +
>  	/* partial unroll. llvm will unroll loop ~150 times.
>  	 * C loop count -> 600.
>  	 * Asm loop count -> 4.
>  	 * 16k insns in loop body.
>  	 * Total of 5 such loops. Total program size ~82k insns.
>  	 */
> -	scale_test("pyperf600.bpf.o", BPF_PROG_TYPE_RAW_TRACEPOINT, false);
> +
> +	if (env.verifier_stats) {
> +		test__force_log();
> +		old_print_fn = libbpf_set_print(libbpf_debug_print);
> +	}
> +
> +	err = check_load("pyperf600.bpf.o", BPF_PROG_TYPE_RAW_TRACEPOINT);
> +
> +	if (env.verifier_stats)
> +		libbpf_set_print(old_print_fn);
> +
> +	if (err == -E2BIG) {
> +		test__skip();
> +		return;
> +	}
> +
> +	ASSERT_OK(err, "expect_success");
> +
>  }
>  
>  void test_verif_scale_pyperf600_bpf_loop(void)
> 
> base-commit: 11439c4635edd669ae435eec308f4ab8a0804808
> -- 
> 2.43.0
> 
>