linux-kernel - Re: [PATCH net-next v2 2/2] selftests/bpf: activate the OP_NE login in range

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Date:   Wed, 13 Dec 2023 01:37:55 +0200
From:   Eduard Zingerman <eddyz87@...il.com>
To:     Menglong Dong <menglong8.dong@...il.com>, andrii@...nel.org,
        yonghong.song@...ux.dev
Cc:     ast@...nel.org, daniel@...earbox.net, john.fastabend@...il.com,
        martin.lau@...ux.dev, song@...nel.org, kpsingh@...nel.org,
        sdf@...gle.com, haoluo@...gle.com, jolsa@...nel.org,
        bpf@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH net-next v2 2/2] selftests/bpf: activate the OP_NE login
 in range_cond()

On Tue, 2023-12-12 at 21:10 +0800, Menglong Dong wrote:
> The edge range checking for the registers is supported by the verifier
> now, so we can activate the extended login in
> tools/testing/selftests/bpf/prog_tests/reg_bounds.c/range_cond() to test
> such logic.
> 
> Signed-off-by: Menglong Dong <menglong8.dong@...il.com>
> ---
>  tools/testing/selftests/bpf/prog_tests/reg_bounds.c | 7 +------
>  1 file changed, 1 insertion(+), 6 deletions(-)
> 
> diff --git a/tools/testing/selftests/bpf/prog_tests/reg_bounds.c b/tools/testing/selftests/bpf/prog_tests/reg_bounds.c
> index 0c9abd279e18..49d8d4bafe99 100644
> --- a/tools/testing/selftests/bpf/prog_tests/reg_bounds.c
> +++ b/tools/testing/selftests/bpf/prog_tests/reg_bounds.c
> @@ -590,12 +590,7 @@ static void range_cond(enum num_t t, struct range x, struct range y,
>  		*newy = range(t, max_t(t, x.a, y.a), min_t(t, x.b, y.b));
>  		break;
>  	case OP_NE:
> -		/* generic case, can't derive more information */
> -		*newx = range(t, x.a, x.b);
> -		*newy = range(t, y.a, y.b);
> -		break;
> -
> -		/* below extended logic is not supported by verifier just yet */
> +		/* below logic is supported by the verifier now */
>  		if (x.a == x.b && x.a == y.a) {
>  			/* X is a constant matching left side of Y */
>  			*newx = range(t, x.a, x.b);

I think that some crafted tests have to be added.
Note that reg_bounds only runs a subset of tests during CI
(controlled by variable SLOW_TESTS).
By default only randomized and crafted tests are run.
It appears to me that probability of randomly generating specific
ranges explored by this series is quite low.