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Wed, 24 Jun 2026 14:01:42 -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: Wed, 24 Jun 2026 14:01:41 -0700 Message-Id: Cc: , , , Subject: Re: [PATCH bpf-next v2 0/5] bpf: add bpf_memcmp and bpf_strpbrk kfuncs From: "Alexei Starovoitov" To: "Longjun Tang" , , X-Mailer: aerc References: <20260624093638.117062-1-lange_tang@163.com> In-Reply-To: <20260624093638.117062-1-lange_tang@163.com> On Wed Jun 24, 2026 at 2:36 AM PDT, Longjun Tang wrote: > From: Longjun Tang > > This series adds two new BPF kfuncs to kernel/bpf/helpers.c. > > =3D=3D=3D bpf_memcmp() =3D=3D=3D > > BPF programs frequently need to compare raw binary buffers, such as: > - MAC addresses (6 bytes) in XDP/TC for L2 filtering and forwarding; > - UUIDs (16 bytes) and hash digests for allowlist/denylist policies; > > Currently there is no safe way to do this =E2=80=94 bpf_strncmp (helper) = stops > at null bytes which corrupts binary data, and hand-rolled loops are > fragile with the verifier (as evidenced by the local_memcmp() workaround > in selftests/bpf/progs/dynptr_success.c). __builtin_memcmp may work in > some cases but is not verifier-safe for arbitrary kernel memory. Hand rolled loops were fragile in the past, but not any more. With bpf_for() and may_goto/can_loop the loops can be large. For MAC and UUIDs even old verifiers can deal just with with "bounded loop"= . Sorry, but I don't see a human driven motivation in this patch. Looks like AI flagged something and AI sloped a patch in response. pw-bot: cr