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Fri, 30 Oct 2026 03:50:31 -0700 (PDT) From: Jiri Olsa X-Google-Original-From: Jiri Olsa Date: Fri, 30 Oct 2026 11:50:29 +0100 To: Andrii Nakryiko Cc: Alexei Starovoitov , Daniel Borkmann , bpf@vger.kernel.org, linux-mm@kvack.org, Andrii Nakryiko , Eduard Zingerman , Kumar Kartikeya Dwivedi , Lorenzo Stoakes , John Fastabend , Federico Di Pierro Subject: Re: [PATCH bpf-next 1/8] bpf: Add __srcptr kfunc argument suffix Message-ID: References: <20261029212551.56964-1-jolsa@kernel.org> <20261029212551.56964-2-jolsa@kernel.org> X-Archived-By: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: X-Rspamd-Server: rspam12 X-Rspamd-Queue-Id: D09DFA0007 X-Stat-Signature: p8ngsrg897hftnzffuxniumbwojc6sit X-Spam-Status: No, score=-12.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_PASS,SPF_PASS autolearn=ham autolearn_force=no version=4.0.1 X-Rspam-User: X-HE-Tag: 1793357433-479414 X-HE-Meta: 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 5nmkTa1f 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 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: X-Spam-Checker-Version: SpamAssassin 4.0.1 (2024-03-26) on aws-us-west-2-korg-listserv-alma10-1 On Thu, Oct 29, 2026 at 02:49:22PM -0700, Andrii Nakryiko wrote: > On Thu, Oct 29, 2026 at 2:26 PM Jiri Olsa wrote: > > > > Generic sized pointer arguments are treated as writable memory. This > > prevents kfuncs that only read from a source buffer from accepting > > read-only BPF memory, such as const data. > > > > Adding __srcptr to mark pointers the kfunc only reads. > > why can't we infer read-only from constness of a pointer? what's the > advantage of __srcptr (which, honestly, says absolutely nothing, > "__readonly" or "__ro" would probably make more sense if we have to go > with suffix) the reason was that current pointer arguments are marked as MEM_WRITE, so passing readonly pointer to bpf_copy_to_user caused verifier error but I think we can use const, did not think of that.. will change thanks, jirka > > > > > The get_kfunc_arg_type change sets the initial memory access mode > > and the resolve_func_arg_type preserves the suffix’s access mode > > when it converts a BTF pointer classification into a memory argument. > > > > Assisted-by: Codex:GPT-6 > > Signed-off-by: Jiri Olsa > > --- > > Documentation/bpf/kfuncs.rst | 24 ++++++++++++++++++++++++ > > kernel/bpf/verifier.c | 20 +++++++++++++++++--- > > 2 files changed, 41 insertions(+), 3 deletions(-) > > > > [...]