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Date:   Mon, 23 Apr 2018 11:12:04 -0300
From:   Arnaldo Carvalho de Melo <acme@kernel.org>
To:     Thomas Richter <tmricht@linux.ibm.com>
Cc:     linux-kernel@vger.kernel.org, linux-perf-users@vger.kernel.org,
        brueckner@linux.vnet.ibm.com, schwidefsky@de.ibm.com,
        heiko.carstens@de.ibm.com
Subject: Re: [PATCH v2] perf test: Adapt test case
 record+probe_libc_inet_pton.sh for s390
Message-ID: <20180423141204.GA30324@kernel.org>
References: <20180423082428.7930-1-tmricht@linux.ibm.com>
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Em Mon, Apr 23, 2018 at 10:24:28AM +0200, Thomas Richter escreveu:
> perf test case 58 (record+probe_libc_inet_pton.sh)
> executed on s390x using kernel 4.16.0rc3
> displays this result:
>  # ./perf trace --no-syscalls
>            -e probe_libc:inet_pton/call-graph=dwarf/ ping -6 -c 1 ::1
>      probe_libc:inet_pton: (3ffa0240448)
> 	      __GI___inet_pton (/usr/lib64/libc-2.26.so)
> 	      gaih_inet (inlined)
> 	      __GI_getaddrinfo (inlined)
> 	      main (/usr/bin/ping)
> 	      __libc_start_main (/usr/lib64/libc-2.26.so)
> 	     _start (/usr/bin/ping)
> 
> After I installed kernel 4.16.0 the same tests uses
> commands
>  # perf record -e probe_libc:inet_pton/call-graph=dwarf/
>       -o /tmp/perf.data.abc ping -6 -c 1 ::1
>  # perf script -i /tmp/perf.data.abc
> and displays:
>  ping 39048 [006] 84230.381198: probe_libc:inet_pton: (3ffa0240448)
> 	       140448 __GI___inet_pton (/usr/lib64/libc-2.26.so)
> 	       fbde1 gaih_inet (inlined)
> 	       fe2b9 __GI_getaddrinfo (inlined)
> 	        398d main (/usr/bin/ping)
> 
> Nothing else changed including glibc elfutils and other libraries
> picked up by the build.
> The entries for __libc_start_main and _start are missing.
> 
> I bisected missing __libc_start_main and _start to commit
> 3d20c6246690219881786de10d2dda93f616d0ac
> ("perf unwind: Unwind with libdw doesn't take symfs into account")
> 
> When I undo this commit I get this call stack on s390:
>  [root@s35lp76 perf]# ./perf script  -i /tmp/perf.data.abc
>  ping 39048 [006] 84230.381198: probe_libc:inet_pton: (3ffa0240448)
> 	140448 __GI___inet_pton (/usr/lib64/libc-2.26.so)
> 	 fbde1 gaih_inet (inlined)
> 	 fe2b9 __GI_getaddrinfo (inlined)
> 	  398d main (/usr/bin/ping)
> 	 22fbd __libc_start_main (/usr/lib64/libc-2.26.so)
> 	  457b _start (/usr/bin/ping)
> 
> Looks like dwarf functions dwfl_xxx  create different call back
> stack trace when using file
> /usr/lib/debug/usr/bin/ping-20161105-7.fc27.s390x.debug instead of
> file /usr/bin/ping.
> 
> Fix this test case on s390 and do not expect any call back stack
> entry after the main() function. Also be more robust and accept a
> leading __GI_ prefix in front of getaddrinfo.
> 
> On x86 this test case shows the same call stack using
> both kernel versions 4.16.0rc3 and 4.16.0 and also
> stops at main:

Thanks, applied.