From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-1.1 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 2BD00C432C3 for ; Thu, 14 Nov 2019 04:14:46 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 07C35206E4 for ; Thu, 14 Nov 2019 04:14:45 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1573704886; bh=OhClmUW9q2p5vazL+PPl6LPUsbvP6Yq/wBursDlyo9Q=; h=Date:From:To:Cc:Subject:In-Reply-To:References:List-ID:From; b=IhwPKwiCEmaX7Dacuj2U7S9nZmc+P5AP/ny33YWXgQuk59HAvHadzD9rp3kTVN2Ic CbQCZ+Ry7ABQdJEnOaq5HUNnxRpVPNYmsM0hnZbZazDpVxxjDEzGLrjKwSQm3wVJNi 4Ooi+aemQ8LJTMi+LZojHdp82UmxUrDq8Wc2rEx0= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726613AbfKNEOo (ORCPT ); Wed, 13 Nov 2019 23:14:44 -0500 Received: from mail.kernel.org ([198.145.29.99]:45040 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726489AbfKNEOo (ORCPT ); Wed, 13 Nov 2019 23:14:44 -0500 Received: from devnote2 (unknown [147.50.43.59]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id B0E70206D7; Thu, 14 Nov 2019 04:14:40 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1573704883; bh=OhClmUW9q2p5vazL+PPl6LPUsbvP6Yq/wBursDlyo9Q=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=MD3fYvTKkiyX2oQcdao84RyGV0x8kzuETF0IE9VafIkFjekyxl/OPpBh8TZ8B4FLE JN2WwZsm+1Xt76Po5qwadp88F02tlYuRlUlFErSRE4jwdZCrI3JV29GG3rzIEIoAnc oytuVrK/TVePlA8kO2MFLnbQ5xH8bz17wt2SLEsU= Date: Thu, 14 Nov 2019 11:14:36 +0700 From: Masami Hiramatsu To: Arnaldo Carvalho de Melo Cc: Ingo Molnar , Steven Rostedt , linux-kernel@vger.kernel.org, Tom Zanussi , Ravi Bangoria , Namhyung Kim Subject: Re: [PATCH v2 1/4] perf probe: Generate event name with line number Message-Id: <20191114111436.c02d60d9b9e42e8f86df7696@kernel.org> In-Reply-To: <20191113120927.GA14646@kernel.org> References: <157314406866.4063.16995747442215702109.stgit@devnote2> <157314407850.4063.2307803945694526578.stgit@devnote2> <20191111140450.GB9365@kernel.org> <20191111140625.GC9365@kernel.org> <20191111140733.GD9365@kernel.org> <20191112173131.e484666a4ae1bbd7708ccf15@kernel.org> <20191113080157.9d6316e9826dd5aed874537e@kernel.org> <20191113120927.GA14646@kernel.org> X-Mailer: Sylpheed 3.5.1 (GTK+ 2.24.32; x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, 13 Nov 2019 09:09:27 -0300 Arnaldo Carvalho de Melo wrote: > Em Wed, Nov 13, 2019 at 08:01:57AM +0700, Masami Hiramatsu escreveu: > > Hi Arnaldo, > > > > On Tue, 12 Nov 2019 17:31:31 +0700 > > Masami Hiramatsu wrote: > > > > > > # perf probe --list > > > > > > probe:kernel_read_l1 (on kernel_read@fs/read_write.c) > > > > > > probe:kernel_read_l2 (on kernel_read:1@fs/read_write.c) > > > > > > > > > > > > > > > Also look above at the listing, I would expect this instead: > > > > > > > > > > # perf probe --list > > > > > probe:kernel_read_l1 (on kernel_read:1@fs/read_write.c) > > > > > probe:kernel_read_l2 (on kernel_read:2@fs/read_write.c) > > > > > > > > > > Right? > > > > > > Yes, it should be so. > > > > Hmm, this looks the limiation of debuginfo generated by gcc. > > Let me explain what happens. So, here is the decoded Line info in > > debuginfo for kernel_read (is defined in fs/read_write.c:423) > > > > --- > > $ readelf -wL /usr/lib/debug/boot/vmlinux-5.0.0-32-generic > > ... > > read_write.c 444 0xffffffff812b435d > ^^^ > 424, right? No, the line info is sorted by address. This seems strange, but happens sometimes :) > > read_write.c 424 0xffffffff812b4370 x > > read_write.c 425 0xffffffff812b4375 x > > read_write.c 426 0xffffffff812b4375 1 x > > read_write.c 428 0xffffffff812b4375 2 x > > > > --- > > This shows the line number info points the kernel_read entry address is > > on #424, this means we can not distinguish kernel_read:0 and kernel_read:1 > > from only the address information.cw > > If both 0xffffffff812b435d and 0xffffffff812b4370 are associated with > line 424, then we should present on 'perf probe -L' just the first one > and do the same when converting from address to name when presenting > with 'perf probe -l'? OK, so we can pick only one of them (the first "statement" line among several lines which shares same address), and show only that line can be probed by perf probe -L. > > > (maybe huristically we can distinguish it by the "_L1" suffix. But if > > user gives another event name, it doesn't work.) > > > --- > > > > /build/linux-pvZVvI/linux-5.0.0/arch/x86/include/asm/current.h: > > current.h 13 0xffffffff812b4375 3 x > > current.h 15 0xffffffff812b4375 4 x > > current.h 15 0xffffffff812b4375 5 x > > current.h 15 0xffffffff812b4375 6 x > > current.h 15 0xffffffff812b4375 7 x > > > > /build/linux-pvZVvI/linux-5.0.0/fs/read_write.c: > > read_write.c 424 0xffffffff812b4375 8 > > > > --- > > And it seems that the dwarf_getsrc_die() returns the last line info > > correspoinding to given address (0xffffffff812b4375) even if it is > > not a stetement line. This is why probe:kernel_read_l2 is > > on kernel_read:1. I will fix that. > > by going backwards from what dwarf_getsrc_die() returns till it finds a > statement line? Moreover, going backward and forward until it finds the smallest line number which is a statement. Because it uses a binary search, it can find non-statement lines. > > > However, again, as long as the different lines are encoded in same > > It is possible as well to have different addresses associated with the > same source code line. That is OK, since we now support multiprobes. We can put probes on different addresses on same line (but different column). Thank you, -- Masami Hiramatsu