Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755640AbaLJKmG (ORCPT ); Wed, 10 Dec 2014 05:42:06 -0500 Received: from e28smtp02.in.ibm.com ([122.248.162.2]:33027 "EHLO e28smtp02.in.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751607AbaLJKmE (ORCPT ); Wed, 10 Dec 2014 05:42:04 -0500 Date: Wed, 10 Dec 2014 16:11:24 +0530 From: "Naveen N. Rao" To: Michael Ellerman Cc: linuxppc-dev@lists.ozlabs.org, linux-kernel@vger.kernel.org, acme@kernel.org, ananth@in.ibm.com Subject: Re: [RFC PATCH 2/8] perf probe powerpc: Fix symbol fixup issues due to ELF type Message-ID: <20141210104124.GB16045@naverao1-tp.in.ibm.com> References: <0412a00009a22762f92c208964df6f842796464e.1418146300.git.naveen.n.rao@linux.vnet.ibm.com> <1418205050.9279.5.camel@ellerman.id.au> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1418205050.9279.5.camel@ellerman.id.au> User-Agent: Mutt/1.5.23 (2014-03-12) X-TM-AS-MML: disable X-Content-Scanned: Fidelis XPS MAILER x-cbid: 14121010-0005-0000-0000-000002B94E99 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2014/12/10 08:50PM, Michael Ellerman wrote: > On Tue, 2014-12-09 at 23:04 +0530, Naveen N. Rao wrote: > > If using the symbol table, symbol addresses are not being fixed up > > properly, resulting in probes being placed at wrong addresses: > > > > # perf probe do_fork > > Added new event: > > probe:do_fork (on do_fork) > > > > You can now use it in all perf tools, such as: > > > > perf record -e probe:do_fork -aR sleep 1 > > > > # cat /sys/kernel/debug/tracing/kprobe_events > > p:probe/do_fork _text+635952 > > # printf "%x" 635952 > > 9b430 > > # grep do_fork /boot/System.map > > c0000000000ab430 T .do_fork > > OK, but why is that happening? And why does checking for ET_DYN fix it? The section header indicates 0x10000 as the offset: Section Headers: [Nr] Name Type Address Offset Size EntSize Flags Link Info Align [ 0] NULL 0000000000000000 00000000 0000000000000000 0000000000000000 0 0 0 [ 1] .text PROGBITS c000000000000000 00010000 0000000000806678 0000000000000000 AX 0 0 256 This is used during fixup and perf only expects this to be needed for ET_EXEC, though we use ET_DYN on ppc64. > > Fix by checking for ELF type ET_DYN used by ppc64 kernels. > > We sometimes produce ET_DYN kernels, but only if CONFIG_RELOCATABLE=y. Ok. - Naveen -- 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/