Re: [HELP] ubacktrace() problem

[Jinhua Luo <luajit dot io at gmail dot com>]

Hi,

2016-01-12 22:32 GMT+08:00 Frank Ch. Eigler <fche@redhat.com>:
>  % rpm -ql kernel-debuginfo | grep vdso
> /usr/lib/debug/lib/modules/4.2.6-200.fc22.x86_64/vdso
> /usr/lib/debug/lib/modules/4.2.6-200.fc22.x86_64/vdso/vdso32-int80.so.debug
> /usr/lib/debug/lib/modules/4.2.6-200.fc22.x86_64/vdso/vdso32-syscall.so.debug
> /usr/lib/debug/lib/modules/4.2.6-200.fc22.x86_64/vdso/vdso32-sysenter.so.debug
> /usr/lib/debug/lib/modules/4.2.6-200.fc22.x86_64/vdso/vdso64.so.debug
>
> These may be necessary to be able to unwind through the kernel-user
> transition (if a process is interrupted mid-syscall).  I seem to
> recall that, years ago, the Fedora kernel team had some struggles to
> ensure that these userspace libraries' debug data was generated &
> included properly.  Maybe the Debian/Ubuntu folks are about to have
> the same struggle.
>

Thanks for the information! The debian indeed lacks of vdso files in
the kernel package.


>
>> And, I am also get confused about the warnings:
>>
>> WARNING: Too many CFI instuctions
>> WARNING: DWARF expression stack underflow in CFI
>> WARNING: no or bad debug frame hdr
>> WARNING: No binary search table for eh frame, doing slow linear search
>> for stap_b9bfb422b7bd73acc448d7f775aaacd_37477
>
> These generally reflect imperfections in the gcc-generated unwind
> information.  These are not something a user can do anything about; we
> should probably stop warning about them (or give more information like
> the suspect module name).
>

I am still wondering if the warnings denotes that the collected
backtraces are not so accurate and complete.

Regards,
Jinhua Luo