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[2001:1ae9:1c2:4c00:726e:c10f:8833:ff22]) by smtp.gmail.com with ESMTPSA id u7-20020a509507000000b005722d871e4csm1079624eda.90.2024.04.24.04.45.04 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 24 Apr 2024 04:45:04 -0700 (PDT) From: Jiri Olsa X-Google-Original-From: Jiri Olsa Date: Wed, 24 Apr 2024 13:45:02 +0200 To: Andrii Nakryiko Cc: Alexei Starovoitov , Daniel Borkmann , Andrii Nakryiko , bpf@vger.kernel.org, Martin KaFai Lau , Song Liu , Yonghong Song , John Fastabend , KP Singh , Stanislav Fomichev , Hao Luo , Viktor Malik , "Masami Hiramatsu (Google)" Subject: Re: [PATCH bpf-next 3/7] bpf: Add support for kprobe multi session cookie Message-ID: References: <20240422121241.1307168-1-jolsa@kernel.org> <20240422121241.1307168-4-jolsa@kernel.org> Precedence: bulk X-Mailing-List: bpf@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: On Tue, Apr 23, 2024 at 05:26:51PM -0700, Andrii Nakryiko wrote: > On Mon, Apr 22, 2024 at 5:13 AM Jiri Olsa wrote: > > > > Adding support for cookie within the session of kprobe multi > > entry and return program. > > > > The session cookie is u64 value and can be retrieved be new > > kfunc bpf_session_cookie, which returns pointer to the cookie > > value. The bpf program can use the pointer to store (on entry) > > and load (on return) the value. > > > > The cookie value is implemented via fprobe feature that allows > > to share values between entry and return ftrace fprobe callbacks. > > > > Signed-off-by: Jiri Olsa > > --- > > kernel/bpf/verifier.c | 7 +++++++ > > kernel/trace/bpf_trace.c | 19 ++++++++++++++++--- > > 2 files changed, 23 insertions(+), 3 deletions(-) > > > > Had the same question as Alexei, but this read-write semantics quirk > makes sense. But it's probably a bit more reliable and cleaner to > handle it by special casing this kfunc a bit earlier (see > KF_bpf_rbtree_add_impl) and setting r0_size = 8, r0_rdonly = false. > And then let generic PTR -> INT logic kick in. You'll be futzing with > register state much less. ok, will try it this way thanks, jirka > > Other than that looks good: > > Acked-by: Andrii Nakryiko > > > diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c > > index 68cfd6fc6ad4..baaca451aebc 100644 > > --- a/kernel/bpf/verifier.c > > +++ b/kernel/bpf/verifier.c > > @@ -10987,6 +10987,7 @@ enum special_kfunc_type { > > KF_bpf_percpu_obj_drop_impl, > > KF_bpf_throw, > > KF_bpf_iter_css_task_new, > > + KF_bpf_session_cookie, > > }; > > [...]