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Fri, 17 Apr 2026 17:45:51 -0700 (PDT) Received: from [192.168.0.226] ([38.34.87.7]) by smtp.gmail.com with ESMTPSA id d9443c01a7336-2b5faa17632sm32598535ad.24.2026.04.17.17.45.50 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 17 Apr 2026 17:45:51 -0700 (PDT) Message-ID: Subject: Re: [PATCH bpf-next 1/2] bpf/verifier: Use intersection checks when simulating to detect dead branches From: Eduard Zingerman To: Harishankar Vishwanathan Cc: bpf@vger.kernel.org, Alexei Starovoitov , Daniel Borkmann , Andrii Nakryiko , Paul Chaignon , Shung-Hsi Yu , Srinivas Narayana , Santosh Nagarakatte Date: Fri, 17 Apr 2026 17:45:48 -0700 In-Reply-To: References: <20260415160728.657270-1-harishankar.vishwanathan@gmail.com> <20260415160728.657270-2-harishankar.vishwanathan@gmail.com> <2ec3db2d2960d9c13577d630306f16873ebb53e5.camel@gmail.com> Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable User-Agent: Evolution 3.58.3 (3.58.3-1.fc43) Precedence: bulk X-Mailing-List: bpf@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 On Fri, 2026-04-17 at 20:38 -0400, Harishankar Vishwanathan wrote: > On Fri, Apr 17, 2026 at 7:19=E2=80=AFPM Eduard Zingerman wrote: > >=20 > > On Fri, 2026-04-17 at 14:17 -0700, Eduard Zingerman wrote: > > > On Fri, 2026-04-17 at 01:34 -0400, Harishankar Vishwanathan wrote: > > >=20 > [...] > >=20 > > Pushed complete find_witness() implementation in [1]. > > cbmc verification passes. >=20 > Just saw this. I shared my complete implementation in another email reply > as well. >=20 > > In any case, please let me know what you think. >=20 > I think the ideas are essentially similar. We can decide which one to > proceed with. Thank you for sharing the code. Indeed very similar logic. I was under impression that you don't like the witness idea hence proceeded on my own. Would have deferred to you if not for that. Tbh, my version looks a bit shorter/simpler. > Alternatively, might we also consider continuing with the pairwise > intersection? Since we have the complete intersection logic now and it is about the same size as pairwise, I think we should use the complete intersection version.