From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751200AbeDQG7e (ORCPT ); Tue, 17 Apr 2018 02:59:34 -0400 Received: from mx0b-001b2d01.pphosted.com ([148.163.158.5]:33326 "EHLO mx0a-001b2d01.pphosted.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1750821AbeDQG7d (ORCPT ); Tue, 17 Apr 2018 02:59:33 -0400 Subject: Re: [PATCH 1/2] perf tools powerpc: Fix callchain ip filtering To: Sandipan Das Cc: acme@kernel.org, jolsa@redhat.com, linux-kernel@vger.kernel.org, naveen.n.rao@linux.vnet.ibm.com, ravi.bangoria@linux.vnet.ibm.com, sukadev@linux.vnet.ibm.com, maynard@us.ibm.com References: <20180412171129.4422-1-sandipan@linux.vnet.ibm.com> <20180412171129.4422-2-sandipan@linux.vnet.ibm.com> From: Ravi Bangoria Date: Tue, 17 Apr 2018 12:29:25 +0530 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.7.0 MIME-Version: 1.0 In-Reply-To: <20180412171129.4422-2-sandipan@linux.vnet.ibm.com> Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 8bit Content-Language: en-US X-TM-AS-GCONF: 00 x-cbid: 18041706-0008-0000-0000-000004EC23F2 X-IBM-AV-DETECTION: SAVI=unused REMOTE=unused XFE=unused x-cbparentid: 18041706-0009-0000-0000-00001E80260D Message-Id: <3471e3e0-80ad-7a7f-96b8-60d24a4931a2@linux.ibm.com> X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:,, definitions=2018-04-17_03:,, signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 priorityscore=1501 malwarescore=0 suspectscore=0 phishscore=0 bulkscore=0 spamscore=0 clxscore=1011 lowpriorityscore=0 impostorscore=0 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1709140000 definitions=main-1804170063 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 04/12/2018 10:41 PM, Sandipan Das wrote: > For powerpc64, if a probe is added for a function without specifying > a line number, the corresponding trap instruction is placed at offset > 0 (for big endian) or 8 (for little endian) from the start address of > the function. This address is in the function prologue and the trap > instruction preceeds the instructions to set up the stack frame. > > Therefore, at this point during execution, the return address for the > function is yet to be written to its caller's stack frame. So, the LR > value at index 2 of the callchain ips provided by the kernel is still > valid and must not be skipped. > > This can be observed on a powerpc64le system running Fedora 27 as > shown below. > > # perf probe -x /usr/lib64/libc-2.26.so -a inet_pton > # perf record -e probe_libc:inet_pton/max-stack=3/ ping -6 -c 1 ::1 > # perf script > > Without this patch, the output is: > > ping 27909 [007] 532219.943481: probe_libc:inet_pton: (7fff99b0af28) > 15af28 __GI___inet_pton (/usr/lib64/libc-2.26.so) > 1105b4 getaddrinfo (/usr/lib64/libc-2.26.so) > > With this patch applied, the output is: > > ping 27909 [007] 532219.943481: probe_libc:inet_pton: (7fff99b0af28) > 15af28 __GI___inet_pton (/usr/lib64/libc-2.26.so) > 10fa54 gaih_inet.constprop.7 (/usr/lib64/libc-2.26.so) > 1105b4 getaddrinfo (/usr/lib64/libc-2.26.so) > > Fixes: a60335ba3298 ("perf tools powerpc: Adjust callchain based on DWARF debug info") > Signed-off-by: Sandipan Das > --- This change looks good to me but seems it fixed the issue partially.Ex,     # readelf --debug-dump=frames-interp /lib64/libc-2.26.so | less     ...     00005778 0000000000000024 0000577c FDE cie=00000000 pc=0000000000048b30..0000000000048c64        LOC           CFA      r31   ra        0000000000048b30 r1+0     u     u         0000000000048b40 r1+0     c-8   r0        0000000000048b58 r1+64    c-8   c+16      0000000000048bd8 r1+0     c-8   c+16      0000000000048be4 r1+0     u         0000000000048bf0 r1+64    c-8   c+16  0000000000048b30..0000000000048c64 is arandom() function from libc:     0000000000048b30 :        48b30:       1c 00 4c 3c     addis   r2,r12,28        48b34:       d0 e5 42 38     addi    r2,r2,-6704        48b38:       a6 02 08 7c     mflr    r0        48b3c:       f8 ff e1 fb     std     r31,-8(r1)        48b40:       00 00 00 60     nop        48b44:       00 00 20 39     li      r9,0        48b48:       80 b5 e2 3b     addi    r31,r2,-19072        48b4c:       01 00 00 39     li      r8,1        48b50:       10 00 01 f8     std     r0,16(r1)        48b54:       c1 ff 21 f8     stdu    r1,-64(r1)        48b58:       f0 8f 4d e9     ld      r10,-28688(r13)        ... Your change fixed the issue for 48b30..48b40. But not for 48b40..48b58. I probed at 0x48b40.     # ./perf record -g -e probe_libc:abs_48b40 ~/rand perf report without Suka's and your change:     # Children      Self  Trace output      # ........  ........  ..............     #        100.00%   100.00%  (7fffb7d28b40)                 |                 ---0                    __libc_start_main                    generic_start_main.isra.0                    main                    rand                    __random perf report with only Suka's change:     # Children      Self  Trace output      # ........  ........  ..............     #        100.00%   100.00%  (7fffb7d28b40)                 |                 ---0                    __libc_start_main                    generic_start_main.isra.0                    main                    __random perf report with Suka's and your change:     # Children      Self  Trace output      # ........  ........  ..............     #        100.00%   100.00%  (7fffb7d28b40)                 |                 ---0                    __libc_start_main                    generic_start_main.isra.0                    main                    __random I think rand() is a valid entry which is missing in last two cases.