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Wed, 23 Sep 2026 15:55:46 -0700 (PDT) Content-Type: text/plain; charset=UTF-8 Date: Wed, 23 Sep 2026 22:55:46 +0000 Message-Id: Cc: "Andrii Nakryiko" , "Daniel Borkmann" , "Eduard Zingerman" , "Emil Tsalapatis" , "Tejun Heo" , , Subject: Re: [PATCH bpf-next v1 12/18] bpf: Size the per-frame verifier structures for a 2 KiB stack From: "Alexei Starovoitov" To: "Kumar Kartikeya Dwivedi" , In-Reply-To: <20260923191139.2816206-13-memxor@gmail.com> References: <20260923191139.2816206-1-memxor@gmail.com> <20260923191139.2816206-13-memxor@gmail.com> X-Mailer: mkdraft (claude review draft; edit before sending) Content-Transfer-Encoding: 8bit Precedence: bulk X-Mailing-List: bpf@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 On Wed, Sep 23, 2026 at 09:11 PM Kumar Kartikeya Dwivedi wrote: > -#define FRAME_HALF_SPIS (MAX_BPF_STACK / BPF_HALF_REG_SIZE) > +#define FRAME_HALF_SPIS (MAX_BPF_STACK_JIT / BPF_HALF_REG_SIZE) MAX_ARG_SPILL_SLOTS in liveness.c is still 64. fp_off_to_slot() returns -1 for anything below fp-512, so r6 = *(u64 *)(r10 - 520) makes r6 ARG_IMPRECISE in fill_from_stack() no matter what was spilled there. The next load or store through r6 goes to record_imprecise() and marks the whole stack of every frame as read. A prog that keeps spills below fp-512 gets no help from liveness and all of its frames carry 8 word masks. The numbers in the cover letter are for selftests that fit in 512. Pls share veristat numbers for progs that use more than that.