From: Eduard Zingerman <eddyz87@gmail.com>
To: Alexei Starovoitov <alexei.starovoitov@gmail.com>
Cc: Andrii Nakryiko <andrii.nakryiko@gmail.com>,
Hao Sun <sunhao.th@gmail.com>,
Alexei Starovoitov <ast@kernel.org>,
Andrii Nakryiko <andrii@kernel.org>,
Daniel Borkmann <daniel@iogearbox.net>, bpf <bpf@vger.kernel.org>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
Subject: Re: [Bug Report] bpf: incorrectly pruning runtime execution path
Date: Fri, 15 Dec 2023 04:28:20 +0200 [thread overview]
Message-ID: <66b2a6c45045c207d8452ad3b5786a9dc0082d79.camel@gmail.com> (raw)
In-Reply-To: <CAADnVQ+RVT1pO1hTzMawdkfc9B0xAxas2XmSk6+_EiqX9Xy9Ug@mail.gmail.com>
On Thu, 2023-12-14 at 18:16 -0800, Alexei Starovoitov wrote:
[...]
> > E.g. for the test-case at hand:
> >
> > 0: (85) call bpf_get_prandom_u32#7 ; R0=scalar()
> > 1: (bf) r7 = r0 ; R0=scalar(id=1) R7_w=scalar(id=1)
> > 2: (bf) r8 = r0 ; R0=scalar(id=1) R8_w=scalar(id=1)
> > 3: (85) call bpf_get_prandom_u32#7 ; R0=scalar()
> > --- checkpoint #1 r7.id = 1, r8.id = 1 ---
> > 4: (25) if r0 > 0x1 goto pc+0 ; R0=scalar(smin=smin32=0,smax=umax=smax32=umax32=1,...)
> > --- checkpoint #2 r7.id = 1, r8.id = 1 ---
> > 5: (3d) if r8 >= r0 goto pc+3 ; R0=1 R8=0 | record r8.id=1 in jump history
> > 6: (0f) r8 += r8 ; R8=0
>
> can we detect that any register link is broken and force checkpoint here?
Should be possible. I'll try this in the morning and check veristat results.
By the way, I added some stats collection for find_equal_scalars() and see
the following results when run on ./test_progs:
- maximal number of registers with same id per call: 3
- average number of registers with same id per call: 1.4
next prev parent reply other threads:[~2023-12-15 2:28 UTC|newest]
Thread overview: 24+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-12-11 15:31 [Bug Report] bpf: incorrectly pruning runtime execution path Hao Sun
2023-12-13 0:51 ` Andrii Nakryiko
2023-12-13 10:25 ` Hao Sun
2023-12-13 23:30 ` Andrii Nakryiko
2023-12-14 0:08 ` Eduard Zingerman
2023-12-14 0:36 ` Andrii Nakryiko
2023-12-13 23:35 ` Eduard Zingerman
2023-12-13 23:40 ` Andrii Nakryiko
2023-12-13 23:47 ` Eduard Zingerman
2023-12-13 23:50 ` Andrii Nakryiko
2023-12-14 9:38 ` Hao Sun
2023-12-14 15:10 ` Eduard Zingerman
2023-12-14 16:26 ` Eduard Zingerman
2023-12-15 0:06 ` Andrii Nakryiko
2023-12-15 0:16 ` Eduard Zingerman
2023-12-15 0:49 ` Eduard Zingerman
2023-12-15 1:24 ` Eduard Zingerman
2023-12-15 1:43 ` Eduard Zingerman
2023-12-15 2:16 ` Alexei Starovoitov
2023-12-15 2:28 ` Eduard Zingerman [this message]
2023-12-15 5:20 ` Andrii Nakryiko
2023-12-15 16:22 ` Eduard Zingerman
2023-12-15 17:01 ` Andrii Nakryiko
2023-12-15 20:55 ` Eduard Zingerman
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