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From: Thomas Richter <tmricht@linux.ibm.com>
To: "linux-perf-use." <linux-perf-users@vger.kernel.org>,
	Arnaldo Carvalho de Melo <acme@kernel.org>
Cc: Sven Schnelle <svens@linux.ibm.com>, Heiko Carstens <hca@linux.ibm.com>
Subject: perf test case probe libc fails with latest Fedora34 glibc update
Date: Wed, 23 Jun 2021 16:21:17 +0200	[thread overview]
Message-ID: <cae863a4-bf83-f87b-6e71-b6a544678cae@linux.ibm.com> (raw)

I just updated Fedora34 to the latest level and discovered that perf test 78 fails:
[root@m46lp22 perf]# ./perf test 78
78: probe libc's inet_pton & backtrace it with ping                 : FAILED!
[root@m46lp22 perf]#

It boils down to this command and happens after glibc is update to level 2.33-18.

[root@f34 ~]# perf probe -f -x /usr/lib64/libc-2.33.so -a inet_pton
Probe point 'inet_pton' not found.
  Error: Failed to add events.
[root@f34 ~]# rpm -qa | fgrep glibc
glibc-all-langpacks-2.33-18.fc34.x86_64
glibc-common-2.33-18.fc34.x86_64
glibc-langpack-en-2.33-18.fc34.x86_64
glibc-2.33-18.fc34.x86_64
glibc-doc-2.33-18.fc34.noarch
glibc-headers-x86-2.33-18.fc34.noarch
glibc-devel-2.33-18.fc34.x86_64
glibc-debugsource-2.33-18.fc34.x86_64
glibc-debuginfo-2.33-18.fc34.x86_64
[root@f34 ~]# 

The symbol inet_pton is now in the .dynsym section of glibc:
[root@f34 ~]# readelf -sW /usr/lib64/libc-2.33.so | egrep '(dynsym|symtab|inet_pton)'
Symbol table '.dynsym' contains 2419 entries:
   628: 000000000011ea00   108 FUNC    WEAK   DEFAULT   15 inet_pton@@GLIBC_2.2.5
  2251: 000000000011e9b0    76 FUNC    GLOBAL DEFAULT   15 __inet_pton_length@@GLIBC_PRIVATE
Symbol table '.symtab' contains 104 entries:
[root@f34 ~]#

The .symtab section does not contain symbol inet_pton. It contains very few symbols
compared to previous versions.

Now perf does not find it. In the older version of the library the
symbol inet_pton was listed in the .symtab section. Here is the output from version 2.32-4:


[root@m35lp76 ~]# rpm -qa | fgrep glibc
glibc-common-2.32-4.fc33.s390x
glibc-langpack-en-2.32-4.fc33.s390x
glibc-2.32-4.fc33.s390x
glibc-headers-s390-2.32-4.fc33.noarch
glibc-devel-2.32-4.fc33.s390x
glibc-debuginfo-common-2.32-4.fc33.s390x
glibc-debuginfo-2.32-4.fc33.s390x
[root@m35lp76 ~]# 


readelf -sW /usr/lib64/libc-2.32.so | egrep '(dynsym|symtab|inet_pton)'
Symbol table '.dynsym' contains 2604 entries:
   668: 00000000001444b0   788 FUNC    WEAK   DEFAULT   13 inet_pton@@GLIBC_2.2
  2418: 00000000001441b0   764 FUNC    GLOBAL DEFAULT   13 __inet_pton_length@@GLIBC_PRIVATE
Symbol table '.symtab' contains 28858 entries:
 20655: 0000000000000000     0 FILE    LOCAL  DEFAULT  ABS inet_pton.c
 20656: 00000000001440b0     0 NOTYPE  LOCAL  HIDDEN    13 .annobin_inet_pton.c
 20657: 00000000001447c4     0 NOTYPE  LOCAL  HIDDEN    13 .annobin_inet_pton.c_end
 20658: 000000000002ba70     0 NOTYPE  LOCAL  HIDDEN    13 .annobin_inet_pton.c.hot
 20659: 000000000002ba70     0 NOTYPE  LOCAL  HIDDEN    13 .annobin_inet_pton.c_end.hot
 20660: 000000000002b938     0 NOTYPE  LOCAL  HIDDEN    13 .annobin_inet_pton.c.unlikely
 20661: 000000000002b938     0 NOTYPE  LOCAL  HIDDEN    13 .annobin_inet_pton.c_end.unlikely
 20662: 000000000002ba70     0 NOTYPE  LOCAL  HIDDEN    13 .annobin_inet_pton.c.startup
 20663: 000000000002ba70     0 NOTYPE  LOCAL  HIDDEN    13 .annobin_inet_pton.c_end.startup
 20664: 000000000002b968     0 NOTYPE  LOCAL  HIDDEN    13 .annobin_inet_pton.c.exit
 20665: 000000000002b968     0 NOTYPE  LOCAL  HIDDEN    13 .annobin_inet_pton.c_end.exit
 20666: 00000000001440b0     0 NOTYPE  LOCAL  HIDDEN    13 .annobin_inet_pton4.start
 20667: 00000000001441aa     0 NOTYPE  LOCAL  HIDDEN    13 .annobin_inet_pton4.end
 20668: 00000000001440b0   250 FUNC    LOCAL  DEFAULT   13 inet_pton4
 20669: 00000000001441aa     0 NOTYPE  LOCAL  HIDDEN    13 .annobin___GI___inet_pton_length.start
 20670: 00000000001444ac     0 NOTYPE  LOCAL  HIDDEN    13 .annobin___GI___inet_pton_length.end
 20671: 00000000001444ac     0 NOTYPE  LOCAL  HIDDEN    13 .annobin___GI___inet_pton.start
 20672: 00000000001447c4     0 NOTYPE  LOCAL  HIDDEN    13 .annobin___GI___inet_pton.end
 23591: 00000000001441b0   764 FUNC    LOCAL  DEFAULT   13 __GI___inet_pton_length
 23871: 00000000001444b0   788 FUNC    LOCAL  DEFAULT   13 __inet_pton
 24506: 00000000001444b0   788 FUNC    LOCAL  DEFAULT   13 __GI___inet_pton
 25831: 00000000001444b0   788 FUNC    LOCAL  DEFAULT   13 __GI_inet_pton
 26410: 00000000001441b0   764 FUNC    GLOBAL DEFAULT   13 __inet_pton_length
 27288: 00000000001444b0   788 FUNC    WEAK   DEFAULT   13 inet_pton
[root@m35lp76 ~]#

And perf could find the symbol, extract its address and install a probe
on that address.
So is this a bug related to the perf tool because it can not handle .dynsym section?
Or is it releated to glibc's rework?

Thanks for your help.
-- 
Thomas Richter, Dept 3303, IBM s390 Linux Development, Boeblingen, Germany
--
Vorsitzender des Aufsichtsrats: Gregor Pillen
Geschäftsführung: Dirk Wittkopp
Sitz der Gesellschaft: Böblingen / Registergericht: Amtsgericht Stuttgart, HRB 243294

             reply	other threads:[~2021-06-23 14:21 UTC|newest]

Thread overview: 11+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-06-23 14:21 Thomas Richter [this message]
2021-06-25 10:34 ` Jiri Olsa
2021-06-25 10:57   ` Thomas Richter
2021-06-25 10:43 ` Part 2: " Thomas Richter
2021-06-29  5:02   ` Masami Hiramatsu
2021-06-29  6:42     ` Thomas Richter
2021-06-29 14:06       ` Masami Hiramatsu
2021-06-30 16:02       ` Masami Hiramatsu
2021-07-02  0:41         ` Masami Hiramatsu
2021-06-29  7:21     ` perf test case probe libc fails with latest Fedora34 glibc update, more info Thomas Richter
2021-06-29 14:01       ` Masami Hiramatsu

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