From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mx0a-001b2d01.pphosted.com (mx0b-001b2d01.pphosted.com [148.163.158.5]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by lists.ozlabs.org (Postfix) with ESMTPS id 3vcQ4p63JtzDq5x for ; Tue, 7 Mar 2017 03:20:42 +1100 (AEDT) Received: from pps.filterd (m0098413.ppops.net [127.0.0.1]) by mx0b-001b2d01.pphosted.com (8.16.0.20/8.16.0.20) with SMTP id v26GDmTx047014 for ; Mon, 6 Mar 2017 11:20:39 -0500 Received: from e28smtp05.in.ibm.com (e28smtp05.in.ibm.com [125.16.236.5]) by mx0b-001b2d01.pphosted.com with ESMTP id 2917d3kn3c-1 (version=TLSv1.2 cipher=AES256-SHA bits=256 verify=NOT) for ; Mon, 06 Mar 2017 11:20:39 -0500 Received: from localhost by e28smtp05.in.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Mon, 6 Mar 2017 21:50:34 +0530 Received: from d28relay05.in.ibm.com (d28relay05.in.ibm.com [9.184.220.62]) by d28dlp03.in.ibm.com (Postfix) with ESMTP id 71AE7125804F for ; Mon, 6 Mar 2017 21:50:46 +0530 (IST) Received: from d28av04.in.ibm.com (d28av04.in.ibm.com [9.184.220.66]) by d28relay05.in.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id v26GKRDT15728796 for ; Mon, 6 Mar 2017 21:50:27 +0530 Received: from d28av04.in.ibm.com (localhost [127.0.0.1]) by d28av04.in.ibm.com (8.14.4/8.14.4/NCO v10.0 AVout) with ESMTP id v26GKU6r002412 for ; Mon, 6 Mar 2017 21:50:30 +0530 Date: Mon, 6 Mar 2017 21:50:29 +0530 From: "Naveen N. Rao" To: Masami Hiramatsu Cc: linux-kernel@vger.kernel.org, Steven Rostedt , Ingo Molnar , Arnaldo Carvalho de Melo , linuxppc-dev@lists.ozlabs.org Subject: Re: [PATCH v4 2/3] perf: kretprobes: offset from reloc_sym if kernel supports it References: <20170304094911.5f96a10a9f075b6f16fe90d3@kernel.org> <20170304113551.6a008b969a3ed713729cbd57@kernel.org> <20170304133405.176da43d40cec7cb00e757e1@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii In-Reply-To: <20170304133405.176da43d40cec7cb00e757e1@kernel.org> Message-Id: <20170306162029.GB7467@naverao1-tp.localdomain> List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , On 2017/03/04 01:34PM, Masami Hiramatsu wrote: > On Sat, 4 Mar 2017 11:35:51 +0900 > Masami Hiramatsu wrote: > > > On Sat, 4 Mar 2017 09:49:11 +0900 > > Masami Hiramatsu wrote: > > > > > On Thu, 2 Mar 2017 23:25:06 +0530 > > > "Naveen N. Rao" wrote: > > > > > > > We indicate support for accepting sym+offset with kretprobes through a > > > > line in ftrace README. Parse the same to identify support and choose the > > > > appropriate format for kprobe_events. > > > > > > Could you give us an example of this change here? :) > > > for example, comment of commit 613f050d68a8 . > > > > > > I think the code is OK, but we need actual example of result. > > > > Hi Naveen, > > > > I've tried following commands > > > > $ grep "[Tt] user_read$" /proc/kallsyms > > 0000000000000000 T user_read > > 0000000000000000 t user_read > > $ sudo ./perf probe -D user_read%return > > r:probe/user_read _text+3539616 > > r:probe/user_read_1 _text+3653408 > > > > OK, looks good. However, when I set the retprobes, I got an error. > > > > $ sudo ./perf probe -a user_read%return > > Failed to write event: Invalid argument > > Error: Failed to add events. > > > > And kernel rejected that. > > > > $ dmesg -k | tail -n 1 > > [ 850.315068] Given offset is not valid for return probe. > > > > Hmm, curious.. > > Ah, I see. > > static int create_trace_kprobe(int argc, char **argv) > ... > } else { > /* a symbol specified */ > symbol = argv[1]; > /* TODO: support .init module functions */ > ret = traceprobe_split_symbol_offset(symbol, &offset); > if (ret) { > pr_info("Failed to parse symbol.\n"); > return ret; > } > if (offset && is_return && > !arch_function_offset_within_entry(offset)) { > pr_info("Given offset is not valid for return probe.\n"); > return -EINVAL; > } > } > > So, actually, traceprobe_split_symbol_offset() just split out symbol > and offset from symbol string (e.g. "_text+3539616"). > So, you should use kallsyms_lookup_size_offset() here again to check > offset. Ah, nice catch! I should have tested Steven's patch... > > Please try attached patch (I've already tested on x86-64). > > $ sudo ./perf probe -a user_read%return > Added new events: > probe:user_read (on user_read%return) > probe:user_read_1 (on user_read%return) > > You can now use it in all perf tools, such as: > > perf record -e probe:user_read_1 -aR sleep 1 > > $ sudo ./perf probe -l > probe:user_read (on user_read%return@security/keys/user_defined.c) > probe:user_read_1 (on user_read%return@selinux/ss/policydb.c) > $ sudo cat /sys/kernel/debug/kprobes/list > ffffffff9637bf70 r user_read+0x0 [DISABLED][FTRACE] > ffffffff963602f0 r user_read+0x0 [DISABLED][FTRACE] Thanks, I will test this. - Naveen