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[192.26.29.3]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-47fec232328sm3053933f8f.24.2026.08.04.13.28.00 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 04 Aug 2026 13:28:00 -0700 (PDT) Precedence: bulk X-Mailing-List: bpf@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset=UTF-8 Date: Tue, 04 Aug 2026 22:28:00 +0200 Message-Id: Cc: "Tejun Heo" , "Alexei Starovoitov" , "Andrii Nakryiko" , "Daniel Borkmann" , "Emil Tsalapatis" , , Subject: Re: [PATCH bpf-next v3 5/9] selftests/bpf: Add kfunc __arena and __arena_nullable argument tests From: "Kumar Kartikeya Dwivedi" To: "Eduard Zingerman" , X-Mailer: aerc 0.21.0 References: <20260803125115.2264733-1-memxor@gmail.com> <20260803125115.2264733-6-memxor@gmail.com> <7f0d996cbfb2703450b9974d18c9f60ac2a3a959.camel@gmail.com> <4d3b9137362fd9151ecdaf29d863a6cc0b0799d1.camel@gmail.com> <9552fc68c2d06c5dd88bb7494b4934e779bc45c6.camel@gmail.com> In-Reply-To: <9552fc68c2d06c5dd88bb7494b4934e779bc45c6.camel@gmail.com> On Tue Aug 4, 2026 at 10:26 PM CEST, Eduard Zingerman wrote: > On Tue, 2026-08-04 at 13:24 -0700, Eduard Zingerman wrote: >> On Tue, 2026-08-04 at 22:14 +0200, Kumar Kartikeya Dwivedi wrote: >> >> ... >> >> > > Which leads to several conclusions: >> > > - We should reach a consensus regarding KF_ARENA* usage, as these >> > > =C2=A0 kfuncs would clearly benefit from having __arena annotations = on >> > > =C2=A0 parameters (on the BPF side, on the host side these should be >> > > =C2=A0 declared as plain pointers). >> > >> > Yes, but even if we do, for the time begin, we won't have support for >> > automatically emitting it until resolve_btfids changes are done. That = said, I >> > can manually add the annotation for now. >> >> We can fast-track resolve_btfids. >> >> > > - In patch #1, it appears that there is no need to allow PTR_TO_AREN= A >> > > =C2=A0 for parameters passed to such a function. At-least I don't se= e a C >> > > =C2=A0 code not involving manual casts that would require such suppo= rt. >> > >> > This one I don't understand. Why wouldn't we get PTR_TO_ARENA typed pa= ramters as >> > arguments? >> >> `(u64 *)val` is translated as an address space cast instruction. >> This instruction yields PTR_TO_ARENA. Except for explicit casts, >> how else can you pass PTR_TO_ARENA to such a function? > > For example, `foo->ptr` yields a scalar from the verifier point of view. > Sure, but I don't think we should reject the case where someone does explic= it cast. See e.g. the global function __arena tag, which also accepts both cas= es. >> >> ...