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([2620:10d:c090:500::3:4473]) by smtp.gmail.com with ESMTPSA id a92af1059eb24-127899df36asm17666099c88.4.2026.03.03.17.15.50 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 03 Mar 2026 17:15:52 -0800 (PST) Message-ID: Subject: Re: [PATCH bpf-next v3 2/2] bpf: Add deep call stack selftests From: Eduard Zingerman To: Emil Tsalapatis , bpf@vger.kernel.org Cc: andrii@kernel.org, ast@kernel.org, daniel@iogearbox.net, martin.lau@kernel.org, memxor@gmail.com, song@kernel.org, yonghong.song@linux.dev Date: Tue, 03 Mar 2026 17:15:49 -0800 In-Reply-To: <20260303043106.406099-3-emil@etsalapatis.com> References: <20260303043106.406099-1-emil@etsalapatis.com> <20260303043106.406099-3-emil@etsalapatis.com> Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable User-Agent: Evolution 3.58.2 (3.58.2-1.fc43) Precedence: bulk X-Mailing-List: bpf@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 On Mon, 2026-03-02 at 23:31 -0500, Emil Tsalapatis wrote: > Add tests that demonstrate the verifier support for deep call stacks > while still enforcing maximum stack size limits. >=20 > Signed-off-by: Emil Tsalapatis > --- Acked-by: Eduard Zingerman [...] > +/* Check we actually honor stack limits (33 * 16 =3D 528 > 512 =3D MAX_S= TACK_DEPTH). */ Nit: I was wondering why stack usage per func is 16, as each one only consumes one slot. Turns out round_up_stack_depth() rounds things up to 16. Could you please either add a comment here, or just add a second long in each function? > +SEC("syscall") > +__failure __msg("combined stack size of 34 calls") > +int global_func_deep_stack_fail(struct __sk_buff *skb) > +{ > + return f32(123); > +}