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[2a01:cb08:8949:7e00:7657:27e3:4656:ae4a]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-3c4f77e969asm1175174f8f.20.2025.08.21.02.40.25 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 21 Aug 2025 02:40:25 -0700 (PDT) Date: Thu, 21 Aug 2025 11:40:23 +0200 From: Paul Chaignon To: Shung-Hsi Yu Cc: bpf@vger.kernel.org, Alexei Starovoitov , Daniel Borkmann , Andrii Nakryiko , Eduard Zingerman , Yonghong Song Subject: Re: [PATCH bpf-next 1/2] bpf: Use tnums for JEQ/JNE is_branch_taken logic Message-ID: References: Precedence: bulk X-Mailing-List: bpf@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: On Wed, Aug 20, 2025 at 01:09:22PM +0800, Shung-Hsi Yu wrote: > On Mon, Aug 18, 2025 at 07:44:05PM +0200, Paul Chaignon wrote: > > On Thu, Aug 14, 2025 at 08:55:22PM +0800, Shung-Hsi Yu wrote: > > > On Wed, Aug 13, 2025 at 05:34:08PM +0200, Paul Chaignon wrote: > [...] [...] > Acked-by: Shung-Hsi Yu > > Maybe add the check right after 'tnum_is_const(t1) && tnum_is_const(t2)' > check, and before 'umin/umax/smin/smax' check though? Bunching tnum > usage together for aesthetic. Done in the v2. Thanks again for the review! > > > ... That > > said, if others prefer the xor version, I don't mind much :) > > FWIW I'd ideally would like tnum_intersect to return 'false' if no > intersection can be found (similar to check_add_overflow), then we can > use it here. And forcing check to always be done should help avoid > running into some of the register bound violations. But such change felt > too intrusive for the purpose of this patchset, maybe for a future > refactor. > > __must_check bool tnum_intersect(struct tnum a, struct tnum b, struct tnum *out) I like the idea :) When checking the returned value in reg_bounds_sync and regs_refine_cond_op, we would probably want to throw a verifier bug, but that doesn't look too invasive.