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From: Jiri Olsa <jolsa@redhat.com>
To: Thomas Richter <tmricht@linux.ibm.com>
Cc: "linux-perf-use." <linux-perf-users@vger.kernel.org>,
	Arnaldo Carvalho de Melo <acme@kernel.org>,
	Sven Schnelle <svens@linux.ibm.com>,
	Heiko Carstens <hca@linux.ibm.com>,
	Namhyung Kim <namhyung@kernel.org>
Subject: Re: perf test case probe libc fails with latest Fedora34 glibc update
Date: Fri, 25 Jun 2021 12:34:14 +0200	[thread overview]
Message-ID: <YNWxJqxE5nOXBu3I@krava> (raw)
In-Reply-To: <cae863a4-bf83-f87b-6e71-b6a544678cae@linux.ibm.com>

On Wed, Jun 23, 2021 at 04:21:17PM +0200, Thomas Richter wrote:
> 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?

hi,
there's already glibc bug for that:
  https://bugzilla.redhat.com/show_bug.cgi?id=1975895

looks like they might restore the old behaviour

on the other hand, we could consider to read multiple
symbol tables and merge them together

I'm not sure there's some hidden issue in such approach,
otherwise we might be doing that already ;-)

jirka


  reply	other threads:[~2021-06-25 10:34 UTC|newest]

Thread overview: 11+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-06-23 14:21 Thomas Richter
2021-06-25 10:34 ` Jiri Olsa [this message]
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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