Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753272AbbFLT1Y (ORCPT ); Fri, 12 Jun 2015 15:27:24 -0400 Received: from mail.kernel.org ([198.145.29.136]:36372 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750698AbbFLT1V (ORCPT ); Fri, 12 Jun 2015 15:27:21 -0400 Date: Fri, 12 Jun 2015 16:27:16 -0300 From: Arnaldo Carvalho de Melo To: Masami Hiramatsu , Alexei Starovoitov Cc: David Ahern , Jiri Olsa , Namhyung Kim , Ingo Molnar , Linux Kernel Mailing List Subject: perf probe and structs Message-ID: <20150612192716.GE6850@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline X-Url: http://acmel.wordpress.com User-Agent: Mutt/1.5.23 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1539 Lines: 50 Hi Masami, I tried somethig with perf probe today, namely to ask for a variable that is a struct perf_event_attr to be collected after the perf_event_open syscall copies it from userspace, and got this message: [root@zoo ~]# perf probe SYSC_perf_event_open:23 args Failed to find 'args' in this function. Error: Failed to add events. [root@zoo ~]# Ok, I guess it should be instead: [root@zoo ~]# perf probe SYSC_perf_event_open:23 args The 'args' variable is a struct, this is not supported yet. Error: Failed to add events. [root@zoo ~]# :-) That said, can't we just go ahead and collect sizeof(args) into the buffer and let userspace cast the result to the right type, etc, i.e. kinda like what is done now for a string. Alexei, is this already possible with eBPF? This is all in the context of: [root@zoo ~]# perf trace -e perf_event_open & [1] 20775 [root@zoo ~]# perf stat -e cycles usleep 1 7304.425 ( 0.519 ms): perf/20776 perf_event_open(attr_uptr: 0x222b220, pid: 20777, cpu: -1, group_fd: -1, flags: FD_CLOEXEC) = 3 Performance counter stats for 'usleep 1': 2,024,026 cycles 0.005277428 seconds time elapsed [root@zoo ~]# I want to decode that attr_uptr thing :-) - Arnaldo -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/