From: Eduard Zingerman <eddyz87@gmail.com>
To: Andrii Nakryiko <andrii@kernel.org>,
bpf@vger.kernel.org, ast@kernel.org, daniel@iogearbox.net,
martin.lau@kernel.org
Cc: kernel-team@meta.com
Subject: Re: [PATCH v5 bpf-next 21/23] selftests/bpf: adjust OP_EQ/OP_NE handling to use subranges for branch taken
Date: Wed, 08 Nov 2023 20:22:04 +0200 [thread overview]
Message-ID: <a54dfe9cf85c41508acc7b31a399d7477e667a1d.camel@gmail.com> (raw)
In-Reply-To: <20231027181346.4019398-22-andrii@kernel.org>
On Fri, 2023-10-27 at 11:13 -0700, Andrii Nakryiko wrote:
> Similar to kernel-side BPF verifier logic enhancements, use 32-bit
> subrange knowledge for is_branch_taken() logic in reg_bounds selftests.
>
> Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
> ---
> .../selftests/bpf/prog_tests/reg_bounds.c | 19 +++++++++++++++----
> 1 file changed, 15 insertions(+), 4 deletions(-)
>
> diff --git a/tools/testing/selftests/bpf/prog_tests/reg_bounds.c b/tools/testing/selftests/bpf/prog_tests/reg_bounds.c
> index ac7354cfe139..330618cc12e7 100644
> --- a/tools/testing/selftests/bpf/prog_tests/reg_bounds.c
> +++ b/tools/testing/selftests/bpf/prog_tests/reg_bounds.c
> @@ -750,16 +750,27 @@ static int reg_state_branch_taken_op(enum num_t t, struct reg_state *x, struct r
> /* OP_EQ and OP_NE are sign-agnostic */
> enum num_t tu = t_unsigned(t);
> enum num_t ts = t_signed(t);
> - int br_u, br_s;
> + int br_u, br_s, br;
>
> br_u = range_branch_taken_op(tu, x->r[tu], y->r[tu], op);
> br_s = range_branch_taken_op(ts, x->r[ts], y->r[ts], op);
>
> if (br_u >= 0 && br_s >= 0 && br_u != br_s)
> ASSERT_FALSE(true, "branch taken inconsistency!\n");
> - if (br_u >= 0)
> - return br_u;
> - return br_s;
> +
> + /* if 64-bit ranges are indecisive, use 32-bit subranges to
> + * eliminate always/never taken branches, if possible
> + */
> + if (br_u == -1 && (t == U64 || t == S64)) {
> + br = range_branch_taken_op(U32, x->r[U32], y->r[U32], op);
> + if (br != -1)
> + return br;
> + br = range_branch_taken_op(S32, x->r[S32], y->r[S32], op);
> + if (br != -1)
> + return br;
I'm not sure that these two checks are consistent with kernel side.
In kernel:
- for BPF_JEQ we can derive "won't happen" from u32/s32 ranges;
- for BPF_JNE we can derive "will happen" from u32/s32 ranges.
But here we seem to accept "will happen" for OP_EQ, which does not
seem right. E.g. it is possible to have inconclusive upper 32 bits and
equal lower 32 bits. What am I missing?
next prev parent reply other threads:[~2023-11-08 18:22 UTC|newest]
Thread overview: 77+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-10-27 18:13 [PATCH v5 bpf-next 00/23] BPF register bounds logic and testing improvements Andrii Nakryiko
2023-10-27 18:13 ` [PATCH v5 bpf-next 01/23] selftests/bpf: fix RELEASE=1 build for tc_opts Andrii Nakryiko
2023-10-27 18:13 ` [PATCH v5 bpf-next 02/23] selftests/bpf: satisfy compiler by having explicit return in btf test Andrii Nakryiko
2023-10-27 18:13 ` [PATCH v5 bpf-next 03/23] bpf: derive smin/smax from umin/max bounds Andrii Nakryiko
2023-10-31 15:37 ` Eduard Zingerman
2023-10-31 17:30 ` Andrii Nakryiko
2023-10-27 18:13 ` [PATCH v5 bpf-next 04/23] bpf: derive smin32/smax32 from umin32/umax32 bounds Andrii Nakryiko
2023-10-31 15:37 ` Eduard Zingerman
2023-10-27 18:13 ` [PATCH v5 bpf-next 05/23] bpf: derive subreg bounds from full bounds when upper 32 bits are constant Andrii Nakryiko
2023-10-31 15:37 ` Eduard Zingerman
2023-10-27 18:13 ` [PATCH v5 bpf-next 06/23] bpf: add special smin32/smax32 derivation from 64-bit bounds Andrii Nakryiko
2023-10-31 15:37 ` Eduard Zingerman
2023-10-31 17:39 ` Andrii Nakryiko
2023-10-31 18:41 ` Alexei Starovoitov
2023-10-31 18:49 ` Andrii Nakryiko
2023-10-27 18:13 ` [PATCH v5 bpf-next 07/23] bpf: improve deduction of 64-bit bounds from 32-bit bounds Andrii Nakryiko
2023-10-31 15:37 ` Eduard Zingerman
2023-10-31 20:26 ` Alexei Starovoitov
2023-10-31 20:33 ` Andrii Nakryiko
2023-10-27 18:13 ` [PATCH v5 bpf-next 08/23] bpf: try harder to deduce register bounds from different numeric domains Andrii Nakryiko
2023-10-27 18:13 ` [PATCH v5 bpf-next 09/23] bpf: drop knowledge-losing __reg_combine_{32,64}_into_{64,32} logic Andrii Nakryiko
2023-10-31 15:38 ` Eduard Zingerman
2023-10-27 18:13 ` [PATCH v5 bpf-next 10/23] selftests/bpf: BPF register range bounds tester Andrii Nakryiko
2023-11-08 22:08 ` Eduard Zingerman
2023-11-08 23:23 ` Andrii Nakryiko
2023-11-09 0:30 ` Eduard Zingerman
2023-10-27 18:13 ` [PATCH v5 bpf-next 11/23] bpf: rename is_branch_taken reg arguments to prepare for the second one Andrii Nakryiko
2023-10-30 19:39 ` Alexei Starovoitov
2023-10-31 5:19 ` Andrii Nakryiko
2023-10-27 18:13 ` [PATCH v5 bpf-next 12/23] bpf: generalize is_branch_taken() to work with two registers Andrii Nakryiko
2023-10-31 15:38 ` Eduard Zingerman
2023-10-31 17:41 ` Andrii Nakryiko
2023-10-27 18:13 ` [PATCH v5 bpf-next 13/23] bpf: move is_branch_taken() down Andrii Nakryiko
2023-10-27 18:13 ` [PATCH v5 bpf-next 14/23] bpf: generalize is_branch_taken to handle all conditional jumps in one place Andrii Nakryiko
2023-10-31 15:38 ` Eduard Zingerman
2023-10-27 18:13 ` [PATCH v5 bpf-next 15/23] bpf: unify 32-bit and 64-bit is_branch_taken logic Andrii Nakryiko
2023-10-30 19:52 ` Alexei Starovoitov
2023-10-31 5:28 ` Andrii Nakryiko
2023-10-31 17:35 ` Eduard Zingerman
2023-10-27 18:13 ` [PATCH v5 bpf-next 16/23] bpf: prepare reg_set_min_max for second set of registers Andrii Nakryiko
2023-10-27 18:13 ` [PATCH v5 bpf-next 17/23] bpf: generalize reg_set_min_max() to handle two sets of two registers Andrii Nakryiko
2023-10-31 2:02 ` Alexei Starovoitov
2023-10-31 6:03 ` Andrii Nakryiko
2023-10-31 16:23 ` Alexei Starovoitov
2023-10-31 17:50 ` Andrii Nakryiko
2023-10-31 17:56 ` Andrii Nakryiko
2023-10-31 18:04 ` Alexei Starovoitov
2023-10-31 18:06 ` Andrii Nakryiko
2023-10-31 18:14 ` Eduard Zingerman
2023-10-27 18:13 ` [PATCH v5 bpf-next 18/23] bpf: generalize reg_set_min_max() to handle non-const register comparisons Andrii Nakryiko
2023-10-31 23:25 ` Eduard Zingerman
2023-11-01 16:35 ` Andrii Nakryiko
2023-11-01 17:12 ` Eduard Zingerman
2023-10-27 18:13 ` [PATCH v5 bpf-next 19/23] bpf: generalize is_scalar_branch_taken() logic Andrii Nakryiko
2023-10-31 2:12 ` Alexei Starovoitov
2023-10-31 6:12 ` Andrii Nakryiko
2023-10-31 16:34 ` Alexei Starovoitov
2023-10-31 18:01 ` Andrii Nakryiko
2023-10-31 20:53 ` Andrii Nakryiko
2023-10-31 20:55 ` Andrii Nakryiko
2023-10-27 18:13 ` [PATCH v5 bpf-next 20/23] bpf: enhance BPF_JEQ/BPF_JNE is_branch_taken logic Andrii Nakryiko
2023-10-31 2:20 ` Alexei Starovoitov
2023-10-31 6:16 ` Andrii Nakryiko
2023-10-31 16:36 ` Alexei Starovoitov
2023-10-31 18:04 ` Andrii Nakryiko
2023-10-31 18:06 ` Alexei Starovoitov
2023-10-27 18:13 ` [PATCH v5 bpf-next 21/23] selftests/bpf: adjust OP_EQ/OP_NE handling to use subranges for branch taken Andrii Nakryiko
2023-11-08 18:22 ` Eduard Zingerman [this message]
2023-11-08 19:59 ` Andrii Nakryiko
2023-10-27 18:13 ` [PATCH v5 bpf-next 22/23] selftests/bpf: add range x range test to reg_bounds Andrii Nakryiko
2023-10-27 18:13 ` [PATCH v5 bpf-next 23/23] selftests/bpf: add iter test requiring range x range logic Andrii Nakryiko
2023-10-30 17:55 ` [PATCH v5 bpf-next 00/23] BPF register bounds logic and testing improvements Alexei Starovoitov
2023-10-31 5:19 ` Andrii Nakryiko
2023-11-01 12:37 ` Paul Chaignon
2023-11-01 17:13 ` Andrii Nakryiko
2023-11-07 6:37 ` Harishankar Vishwanathan
2023-11-07 16:38 ` Paul Chaignon
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=a54dfe9cf85c41508acc7b31a399d7477e667a1d.camel@gmail.com \
--to=eddyz87@gmail.com \
--cc=andrii@kernel.org \
--cc=ast@kernel.org \
--cc=bpf@vger.kernel.org \
--cc=daniel@iogearbox.net \
--cc=kernel-team@meta.com \
--cc=martin.lau@kernel.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox