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[2001:1ae9:1c2:4c00:726e:c10f:8833:ff22]) by smtp.gmail.com with ESMTPSA id gx25-20020a170906f1d900b0096b55be592asm5836447ejb.92.2023.05.29.05.06.40 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 29 May 2023 05:06:41 -0700 (PDT) From: Jiri Olsa X-Google-Original-From: Jiri Olsa Date: Mon, 29 May 2023 14:06:33 +0200 To: Yafang Shao Cc: ast@kernel.org, daniel@iogearbox.net, john.fastabend@gmail.com, andrii@kernel.org, martin.lau@linux.dev, song@kernel.org, yhs@fb.com, kpsingh@kernel.org, sdf@google.com, haoluo@google.com, quentin@isovalent.com, bpf@vger.kernel.org Subject: Re: [RFC PATCH bpf-next 1/8] bpf: Support ->show_fdinfo for kprobe_multi Message-ID: References: <20230528142027.5585-1-laoar.shao@gmail.com> <20230528142027.5585-2-laoar.shao@gmail.com> Precedence: bulk X-Mailing-List: bpf@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20230528142027.5585-2-laoar.shao@gmail.com> X-Spam-Status: No, score=-2.1 required=5.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,DKIM_VALID_EF,FREEMAIL_FROM, RCVD_IN_DNSWL_NONE,SPF_HELO_NONE,SPF_PASS,T_SCC_BODY_TEXT_LINE autolearn=ham autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on lindbergh.monkeyblade.net On Sun, May 28, 2023 at 02:20:20PM +0000, Yafang Shao wrote: > Currently, there is no way to check which functions are attached to a > kprobe_multi link, causing confusion for users. It is important that we > provide a means to expose these functions. The expected result is as follows, > > $ cat /proc/10936/fdinfo/9 > pos: 0 > flags: 02000000 > mnt_id: 15 > ino: 2094 > link_type: kprobe_multi > link_id: 2 > prog_tag: a04f5eef06a7f555 > prog_id: 11 > func_count: 4 > func_addrs: ffffffffaad475c0 > ffffffffaad47600 > ffffffffaad47640 > ffffffffaad47680 I like the idea of exposing this through the link_info syscall, but I'm bit concerned of potentially dumping thousands of addresses through fdinfo file, because I always thought of fdinfo as brief file info, but that might be just my problem ;-) jirka > > $ cat /proc/10936/fdinfo/9 | grep "func_addrs" -A 4 | \ > awk '{ if (NR ==1) {print $2} else {print $1}}' | \ > awk '{"grep " $1 " /proc/kallsyms"| getline f; print f}' > ffffffffaad475c0 T schedule_timeout_interruptible > ffffffffaad47600 T schedule_timeout_killable > ffffffffaad47640 T schedule_timeout_uninterruptible > ffffffffaad47680 T schedule_timeout_idle > > Signed-off-by: Yafang Shao > --- > kernel/trace/bpf_trace.c | 17 +++++++++++++++++ > 1 file changed, 17 insertions(+) > > diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c > index 2bc41e6..0d84a7a 100644 > --- a/kernel/trace/bpf_trace.c > +++ b/kernel/trace/bpf_trace.c > @@ -2548,9 +2548,26 @@ static void bpf_kprobe_multi_link_dealloc(struct bpf_link *link) > kfree(kmulti_link); > } > > +static void bpf_kprobe_multi_link_show_fdinfo(const struct bpf_link *link, > + struct seq_file *seq) > +{ > + struct bpf_kprobe_multi_link *kmulti_link; > + int i; > + > + kmulti_link = container_of(link, struct bpf_kprobe_multi_link, link); > + seq_printf(seq, "func_count:\t%d\n", kmulti_link->cnt); > + for (i = 0; i < kmulti_link->cnt; i++) { > + if (i == 0) > + seq_printf(seq, "func_addrs:\t%lx\n", kmulti_link->addrs[i]); > + else > + seq_printf(seq, " \t%lx\n", kmulti_link->addrs[i]); > + } > +} > + > static const struct bpf_link_ops bpf_kprobe_multi_link_lops = { > .release = bpf_kprobe_multi_link_release, > .dealloc = bpf_kprobe_multi_link_dealloc, > + .show_fdinfo = bpf_kprobe_multi_link_show_fdinfo, > }; > > static void bpf_kprobe_multi_cookie_swap(void *a, void *b, int size, const void *priv) > -- > 1.8.3.1 >