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Date:   Fri, 27 Mar 2020 18:03:19 +0430
From:   ahmadkhorrami <ahmadkhorrami@ut.ac.ir>
To:     Milian Wolff <milian.wolff@kdab.com>
Cc:     Jiri Olsa <jolsa@redhat.com>, Steven Rostedt <rostedt@goodmis.org>,
        Arnaldo Carvalho de Melo <acme@redhat.com>,
        Linux-trace Users <linux-trace-users@vger.kernel.org>,
        Peter Zijlstra <peterz@infradead.org>,
        linux-trace-users-owner@vger.kernel.org,
        Jin Yao <yao.jin@linux.intel.com>,
        Namhyung Kim <namhyung@kernel.org>,
        Changbin Du <changbin.du@intel.com>,
        Andi Kleen <ak@linux.intel.com>
Subject: Re: Wrong Perf Backtraces
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Sounds Good. Thanks for the help!

On 2020-03-27 17:55, Milian Wolff wrote:

> On Freitag, 27. März 2020 13:58:33 CET ahmadkhorrami wrote:
> 
>> Hi,
>> Thanks Milian. So if I am right, I should do the following:
>> 1) Run "perf buildid-list" and catch all the <file path, build-ids>
>> pairs.
>> 2) First check for the existence of the file path.
>> 3) If failed, concatenate "~/.debug", file path, "/" and buildid and 
>> use
>> it as the alternative.
> 
> you missed the trailing "/elf" but otherwise yes :)
> 
>> I thought that GDB is smart enough to detect these situations in the
>> same way that it detects debug info files.
>> Should I check any directory other than ~/.debug?
> 
> Hmm good point, GDB should indeed do that by default but maybe it 
> doesn't do
> it for the `file` command for some reason? I cannot answer this, sorry.
> 
> Cheers
> 
> On 2020-03-27 16:40, Milian Wolff wrote: On Freitag, 27. März 2020 
> 12:04:20 CET ahmadkhorrami wrote: I do the following:
> If this line is in the perf script backtrace:
> 7f21ffe256db g_main_context_iteration+0x2b
> (/usr/lib/x86_64-linux-gnu/libglib-2.0.so.0.5600.4)
> I run the following command:
> gdb -batch -ex 'file
> /usr/lib/x86_64-linux-gnu/libglib-2.0.so.0.5600.4'
> -ex 'disass g_main_context_iteration'.
> You can try to parse the output of `perf buildid-list` to get a mapping
> that
> can be used to run this on another person's machine. E.g.
> 
> ```
> $ perf buildid-list
> 5837b1e7495db791f9a3a56fb6ca29958da75b0c [kernel.kallsyms]
> 845f98f6a3019620c37a2f611b2f20c27de83d5b
> /home/milian/projects/kdab/rnd/
> hotspot/build/tests/test-clients/cpp-parallel/cpp-parallel
> f6ca5853dae87d9f0503a9ef230f6d1fa15a832d /usr/lib/ld-2.30.so
> 92883b06055e8e21ded8eb0cd5a61f5704531152 [vdso]
> 8b04d1825b63d9a600e3d57ac71058935e7ad757 /usr/lib/libpthread-2.30.so
> 09639b80a8fad179004f2484608764d2b336dd4a /usr/lib/libstdc++.so.6.0.27
> 33d1f350f13728651d74dd2a56bad1e4e4648f5e /usr/lib/libc-2.30.so
> $ file
> ~/.debug/usr/lib/ld-2.30.so/f6ca5853dae87d9f0503a9ef230f6d1fa15a832d/
> elf
> /home/milian/.debug/usr/lib/ld-2.30.so/
> f6ca5853dae87d9f0503a9ef230f6d1fa15a832d/elf: ELF 64-bit LSB shared
> object,
> x86-64, version 1 (SYSV), statically linked,
> BuildID[sha1]=f6ca5853dae87d9f0503a9ef230f6d1fa15a832d, not stripped
> ```
> 
> I'm afraid to say that I currently don't have the time required to be
> of more
> help in debugging this issue in general.
> 
> Good luck!