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([2620:10d:c090:600::1:468e]) by smtp.gmail.com with ESMTPSA id d9443c01a7336-215dc045a98sm15924795ad.32.2024.12.04.13.08.50 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 04 Dec 2024 13:08:51 -0800 (PST) Message-ID: Subject: Re: [PATCH bpf v1 2/2] selftests/bpf: Add raw_tp tests for PTR_MAYBE_NULL marking From: Eduard Zingerman To: Kumar Kartikeya Dwivedi , Alexei Starovoitov Cc: bpf , kkd@meta.com, Alexei Starovoitov , Andrii Nakryiko , Daniel Borkmann , Martin KaFai Lau , Manu Bretelle , Kernel Team Date: Wed, 04 Dec 2024 13:08:43 -0800 In-Reply-To: References: <20241204024154.21386-1-memxor@gmail.com> <20241204024154.21386-3-memxor@gmail.com> Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable User-Agent: Evolution 3.44.4-0ubuntu2 Precedence: bulk X-Mailing-List: bpf@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 On Wed, 2024-12-04 at 21:48 +0100, Kumar Kartikeya Dwivedi wrote: [...[ (A) ----. | v > > > What this will do in both cases:: > > > First, avoid walking states when off !=3D 0, and reset id. > > > If off =3D=3D 0, go inside mark_ptr_or_null_reg and walk all regs, an= d > > > remove marks for those with off !=3D 0. (B) ----. | v > > That's getting intrusive. > > How about we reset id=3D0 in adjust_ptr_min_max_vals() > > right after we suppressed "null-check it first" message for raw_tp-s. > >=20 > > That will address the issue as well, right? >=20 > Yes (minor detail, it needs to be reset to a new id, otherwise we have > warn on maybe_null set but !reg->id, but the idea is the same). > Let's see what Eduard thinks and then I can give it a go. Sorry for delay. I like what Kumar is proposing in (A) because it could be generalized: there is no real harm in doing 'r2 =3D r1; r2 +=3D 8; r1 !=3D 0; ...' and what Kumar suggests could be used to lift the "null-check it first ..." restriction. However, as far as I understand, the plan is to fix this by generating two entry tracepoint states: one with parameter as null, another with parameter not-null (all combinations for every parameter). If that is the plan, what Alexei suggests in (B) is simpler.