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Message-ID: References: <20260330110019.549079-1-varunrmallya@gmail.com> <20260330110019.549079-3-varunrmallya@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: On Mon, Mar 30, 2026 at 04:52:46PM +0200, Jiri Olsa wrote: > > + > > + /* attaching to a valid symbol should succeed */ > > + link_opts.kprobe_multi.syms = &sym; > > + link_opts.kprobe_multi.cnt = 1; > > maybe we could set cnt > MAX_KPROBE_MULTI_CNT and check if the fail > is E2BIG ? this could save some cycles, but haven't tried that > > jirka > Thanks for the suggestion! I tested this out on an older kernel (<5.8) to see if it fails with a different error code and it did. On newer kernels it always fails with -E2BIG. Implemented this in my latest version (which I will send out in a while). > > + link_fd = bpf_link_create(prog_fd, -1, BPF_TRACE_KPROBE_MULTI, &link_opts); > > + err = -errno; > > + if (link_fd >= 0) > > + close(link_fd); > > + close(prog_fd); > > + /* if kprobe_multi is supported, link creation either succeeds or > > + * fails with something other than -EINVAL due to permissions, > > + */ > > + return link_fd >= 0 || (err != -EINVAL); > > +} > > + > > SNIP