[HELP] ubacktrace() problem

[Jinhua Luo]

Hi,

I reported the issue to debian-kernel mailing list:

https://lists.debian.org/debian-kernel/2016/01/msg00266.html

I recompile the kernel, include the vdso files, now I could see the
backtrace, but it's not complete.
It lacks of main, __libc_start_main, _start.
And some functions should not be the first entry in the backtrace.

The correct graph on Ubuntu 14.04:
http://luajit.io/systemtap/pgsql/postgres_1.svg

The wrong graph on Debian8:
http://luajit.io//systemtap/pgsql/postgres_wrong.svg

Maybe the glibc and its debuginfo on Debian8 is bad?

Regards,
Jinhua Luo


2016-01-13 23:23 GMT+08:00 Frank Ch. Eigler <fche@redhat.com>:
> Hi -
>
>> >  % rpm -ql kernel-debuginfo | grep vdso
>> > /usr/lib/debug/lib/modules/4.2.6-200.fc22.x86_64/vdso
>> > [...]
>> > These may be necessary to be able to unwind through the kernel-user
>> > transition [...]
>>
>> Thanks for the information! The debian indeed lacks of vdso files in
>> the kernel package.
>
> Please let us know when/if a debian bug is opened, so we can track it.
>
>
>> [...]  I am still wondering if the warnings denotes that the
>> collected backtraces are not so accurate and complete.
>
> Well, they will be as accurate and complete as systemtap can make it,
> with the imperfect data it is given.  Use the warnings to help (us)
> diagnose known problem cases, otherwise please don't worry about them.
>
>
> - FChE