perf DWARF unwind failed

[Zeno]

Ubuntu 17.10. To reproduce:

$ perf test
[...]
57: DWARF unwind : FAILED!
[...]

It seems perf is somehow mis-configured.

[Ubuntu Foundations Team Bug Bot (crichton)]

Thank you for taking the time to report this bug and helping to make Ubuntu better. It seems that your bug report is not filed about a specific source package though, rather it is just filed against Ubuntu in general. It is important that bug reports be filed about source packages so that people interested in the package can find the bugs about it. You can find some hints about determining what package your bug might be about at https://wiki.ubuntu.com/Bugs/FindRightPackage. You might also ask for help in the #ubuntu-bugs irc channel on Freenode.

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[Ubuntu Kernel Bot (ubuntu-kernel-bot)]

This bug is missing log files that will aid in diagnosing the problem. While running an Ubuntu kernel (not a mainline or third-party kernel) please enter the following command in a terminal window:

apport-collect 1762652

and then change the status of the bug to 'Confirmed'.

If, due to the nature of the issue you have encountered, you are unable to run this command, please add a comment stating that fact and change the bug status to 'Confirmed'.

This change has been made by an automated script, maintained by the Ubuntu Kernel Team.

[Zeno (zeno-endemann)]

apport-collect crashes here, sorry. I'm using a German locale and KDE. Error:

  File "/usr/share/apport/apport-kde", line 359, in ui_update_view
    QTreeWidgetItem(keyitem, [str(line)])
UnicodeEncodeError: 'ascii' codec can't encode character u'\xfc' in position 87: ordinal not in range(128)

[Joseph Salisbury (jsalisbury)]

Did this issue start happening after an update/upgrade? Was there a prior kernel version where you were not having this particular problem?

Would it be possible for you to test the latest upstream kernel? Refer to https://wiki.ubuntu.com/KernelMainlineBuilds . Please test the latest v4.16 kernel[0].

If this bug is fixed in the mainline kernel, please add the following tag 'kernel-fixed-upstream'.

If the mainline kernel does not fix this bug, please add the tag: 'kernel-bug-exists-upstream'.

Once testing of the upstream kernel is complete, please mark this bug as "Confirmed".

Thanks in advance.

[0] http://kernel.ubuntu.com/~kernel-ppa/mainline/v4.16

[Zeno (zeno-endemann)]

Well this is more about the user space tool perf, not really the kernel itself. And I can't really imagine why DWARF unwinding would have anything to do with the kernel used. I'm on stock ubuntu 4.13.0-38-generic btw.

When I compile perf from the kernel source (commit 2bf1ab321a06a7faeb95c56d02139140fb56199a) it seems that it fails when only having libdw-dwarf-unwind as system feature. When having both libdw-dwarf-unwind and libunwind available the compiled perf does not fail the test. I think that for DWARF unwinding either one of those two libraries should be enough, so maybe this is a bug in libdwarf or how perf uses libdwarf, and when libunwind is available it uses it instead. But just a wild guess, I don't really know what's going on.

In any case, a quick "fix" seems to be building perf with libunwind - even if that just masks the actual bug here.