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[104.151.7.98]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-373082096bbsm11577786f8f.89.2024.08.26.15.01.46 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 26 Aug 2024 15:01:47 -0700 (PDT) From: Jiri Olsa X-Google-Original-From: Jiri Olsa Date: Tue, 27 Aug 2024 00:01:44 +0200 To: Oleg Nesterov Cc: Jiri Olsa , Tianyi Liu , andrii.nakryiko@gmail.com, mhiramat@kernel.org, ajor@meta.com, albancrequy@linux.microsoft.com, bpf@vger.kernel.org, flaniel@linux.microsoft.com, linux-trace-kernel@vger.kernel.org, linux@jordanrome.com, mathieu.desnoyers@efficios.com Subject: Re: [PATCH v2] tracing/uprobe: Add missing PID filter for uretprobe Message-ID: References: <20240825171417.GB3906@redhat.com> <20240825224018.GD3906@redhat.com> <20240826115752.GA21268@redhat.com> <20240826212552.GB30765@redhat.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: <20240826212552.GB30765@redhat.com> On Mon, Aug 26, 2024 at 11:25:53PM +0200, Oleg Nesterov wrote: > This is offtopic, sorry for the spam, but... > > On 08/26, Jiri Olsa wrote: > > > > On Mon, Aug 26, 2024 at 01:57:52PM +0200, Oleg Nesterov wrote: > > > > > > Does bpftrace use bpf_uprobe_multi_link_attach/etc ? I guess not... > > > Then which userspace tool uses this code? ;) > > > > yes, it will trigger if you attach to multiple uprobes, like with your > > test example with: > > > > # bpftrace -p xxx -e 'uprobe:./ex:func* { printf("%d\n", pid); }' > > Hmm. I reserved the testing machine with fedora 40 to play with bpftrace. > > dummy.c: > > #include > > void func1(void) {} > void func2(void) {} > > int main(void) { for (;;) pause(); } > > If I do > > # ./dummy & > # bpftrace -p $! -e 'uprobe:./dummy:func* { printf("%d\n", pid); }' > > and run > > # bpftrace -e 'kprobe:__uprobe_register { printf("%s\n", kstack); }' did you just bpftrace-ed bpftrace? ;-) on my setup I'm getting: [root@qemu ex]# ../bpftrace/build/src/bpftrace -e 'kprobe:uprobe_register { printf("%s\n", kstack); }' Attaching 1 probe... uprobe_register+1 bpf_uprobe_multi_link_attach+685 __sys_bpf+9395 __x64_sys_bpf+26 do_syscall_64+128 entry_SYSCALL_64_after_hwframe+118 I'm not sure what's bpftrace version in fedora 40, I'm using upstream build: [root@qemu ex]# ../bpftrace/build/src/bpftrace --info 2>&1 | grep uprobe_multi uprobe_multi: yes [root@qemu ex]# ../bpftrace/build/src/bpftrace --version bpftrace v0.20.0 jirka > > on another console I get > > Attaching 1 probe... > > __uprobe_register+1 > probe_event_enable+399 > perf_trace_event_init+440 > perf_uprobe_init+152 > perf_uprobe_event_init+74 > perf_try_init_event+71 > perf_event_alloc+1681 > __do_sys_perf_event_open+447 > do_syscall_64+130 > entry_SYSCALL_64_after_hwframe+118 > > __uprobe_register+1 > probe_event_enable+399 > perf_trace_event_init+440 > perf_uprobe_init+152 > perf_uprobe_event_init+74 > perf_try_init_event+71 > perf_event_alloc+1681 > __do_sys_perf_event_open+447 > do_syscall_64+130 > entry_SYSCALL_64_after_hwframe+118 > > so it seems that bpftrace doesn't use bpf_uprobe_multi_link_attach() > (called by sys_bpf(BPF_LINK_CREATE) ?) in this case. > > But again, this is offtopic, please forget. > > Oleg. >