Date:	Tue, 3 Mar 2015 00:05:38 -0300
From:	Arnaldo Carvalho de Melo <acme@...nel.org>
To:	Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>
Cc:	Naohiro Aota <naota@...sp.net>,
	Peter Zijlstra <peterz@...radead.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	David Ahern <dsahern@...il.com>, namhyung@...nel.org,
	Jiri Olsa <jolsa@...hat.com>, Ingo Molnar <mingo@...nel.org>
Subject: Re: [PATCH perf/core 2/4] perf-probe: Fix to handle aliased symbols
 in glibc

Em Mon, Mar 02, 2015 at 11:45:12PM -0300, Arnaldo Carvalho de Melo escreveu:
> Em Tue, Mar 03, 2015 at 11:39:02AM +0900, Masami Hiramatsu escreveu:
> > (2015/03/03 0:46), Arnaldo Carvalho de Melo wrote:
> > > Em Mon, Mar 02, 2015 at 09:49:53PM +0900, Masami Hiramatsu escreveu:
> > >> With this patch;
> > >>   -----
> > >>   # ./perf probe -x /usr/lib64/libc-2.17.so -V malloc
> > >>   Available variables at malloc
> > >>           @<__libc_malloc+0>
> > >>                   size_t  bytes
> > >>   # ./perf probe -x /usr/lib64/libc-2.17.so -a "malloc bytes"
> > >>   Added new event:
> > >>     probe_libc:malloc    (on malloc in /usr/lib64/libc-2.17.so with bytes)
> > >>
> > >>   You can now use it in all perf tools, such as:
> > >>
> > >>           perf record -e probe_libc:malloc -aR sleep 1
> > > 
> > >> Reported-by: Arnaldo Carvalho de Melo <acme@...nel.org>
> > > 
> > > Humm, not working for me, after the patch:
> > > 
> > > [root@...andy ~]# perf probe -x /usr/lib64/libc-2.17.so -V malloc
> > > Available variables at malloc
> > >         @<__malloc_check_init+96>
> > >                 (No matched variables)
> > 
> 
> Will try after a 'make build-test' finishes for the current batch

[root@...andy ~]# perf probe -vvv -x /usr/lib64/libc-2.17.so -V malloc
probe-definition(0): malloc
symbol:malloc file:(null) line:0 offset:0 return:0 lazy:(null)
0 arguments
Open Debuginfo file: /usr/lib/debug/usr/lib64/libc-2.17.so.debug
Searching variables at malloc
Symbol malloc address found : 800c0
Get 2611 lines from this CU
Probe point found: __malloc_check_init+96
Available variables at malloc
        @<__malloc_check_init+96>
                (No matched variables)
[root@...andy ~]#

If I add one more 'v' I get the symtabs as read by symbol-elf.c and this is
what is there for the malloc routines:

[root@...andy ~]# grep malloc /tmp/4
probe-definition(0): malloc
symbol:malloc file:(null) line:0 offset:0 return:0 lazy:(null)
Searching variables at malloc
symbol__new: ptmalloc_lock_all 0x7b060-0x7b173
symbol__new: malloc_atfork 0x801c0-0x802dd
symbol__new: ptmalloc_unlock_all2 0x7b180-0x7b21e
symbol__new: ptmalloc_unlock_all 0x7ba90-0x7bb3e
symbol__new: malloc_printerr 0x7bb40-0x7bc28
symbol__new: malloc_consolidate 0x7c3d0-0x7c9be
symbol__new: _int_malloc 0x7dee0-0x7f32b
symbol__new: malloc_check 0x7f330-0x7f44a
symbol__new: ptmalloc_init.part.8 0x80fe0-0x813d7
symbol__new: ptmalloc_init 0x813e0-0x813f5
symbol__new: malloc_hook_ini 0x81400-0x8143c
symbol__new: mallochook 0x82fc0-0x831af
symbol__new: tr_mallochook 0x83fc0-0x8407d
symbol__new: __malloc_set_state 0x814f0-0x819f6
symbol__new: __malloc_usable_size 0x80d30-0x80e0e
symbol__new: __malloc_trim 0x81d50-0x81fac
symbol__new: __GI___libc_malloc 0x800c0-0x801b5
symbol__new: __malloc_get_state 0x802e0-0x804db
symbol__new: __malloc_stats 0x820c0-0x822aa
symbol__new: __malloc_check_init 0x80050-0x800bb
symbol__new: __malloc 0x800c0-0x801b5
symbol__new: malloc_set_state 0x814f0-0x819f6
symbol__new: malloc 0x800c0-0x801b5
symbol__new: malloc_info 0x82320-0x8240f
symbol__new: malloc_trim 0x81d50-0x81fac
symbol__new: malloc_usable_size 0x80d30-0x80e0e
symbol__new: malloc_get_state 0x802e0-0x804db
symbol__new: __libc_malloc 0x800c0-0x801b5
symbol__new: malloc_stats 0x820c0-0x822aa
symbol__new: malloc@plt 0x1f300-0x1f310
Symbol malloc address found : 800c0
Probe point found: __malloc_check_init+96
[root@...andy ~]#
 
> > > [root@...andy ~]#
> > > 
> > > And then the one asking for 'bytes' to be collectd fails.
> > > 
> > > After processing the other patches I'll try to debug this...
> > > 
> > > [root@...andy ~]# cat /etc/redhat-release 
> > > Red Hat Enterprise Linux Server release 7.0 (Maipo)
> > > [root@...andy ~]# rpm -q glibc glibc-debuginfo
> > > glibc-2.17-55.el7_0.3.x86_64
> > > glibc-debuginfo-2.17-55.el7_0.1.x86_64
> >                               ^^^ why is this different from the glibc version??
> > 
> > > [root@...andy ~]#
> > > [acme@...andy linux]$ readelf -Ws /usr/lib64/libc-2.17.so| grep malloc
> > [...]
> > >   4849: 0000000000080050   107 FUNC    LOCAL  DEFAULT   12 __malloc_check_init
> > 
> > __malloc_check_init+96(0x60) becomes 0x80050 + 0x60 = 0x800b0
> > 
> > >   5351: 00000000000800c0   245 FUNC    LOCAL  DEFAULT   12 __malloc
> > >   1170: 00000000000800c0   245 FUNC    GLOBAL DEFAULT   12 malloc@@GLIBC_2.2.5
> > 
> > that is not 0x800c0, so something goes wrong when translating the address
> > to probe point. Could you check the patch 1/4 was applied?
> > Actually there is a bug in the routine which gets the probe point from
> > address. 1/4 fixes it.
> 
> This one?
> 
> commit 0104fe69e0287cf3635657b4c6b26a18e0091697
> Author: Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>
> Date:   Mon Mar 2 21:49:46 2015 +0900
> 
>     perf probe: Remove bias offset to find probe point by address
>     
>     Remove bias offset to find probe point by address.
> 
> ----------------
> 
> Yes, it is applied.
> 
> - Arnaldo
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