Arch Linux

harubyy

Member

Registered: 2017-03-09

Posts: 26

perf probe says vmlinux has no debug info, don't know how to add it

Hello,
I'm simply trying to watch the value of a varible using perf probe:
sudo perf probe ex:5 i

I received this output:
The /lib/modules/4.13.12-1-ARCH/build/vmlinux file has no debug information.
Rebuild with CONFIG_DEBUG_INFO=y, or install an appropriate debuginfo package.
  Error: Failed to add events.

I had a look at this: https://wiki.archlinux.org/index.php/De … ing_Traces
and this:
https://wiki.archlinux.org/index.php/ke … figuration

I'm scared to touch vmlinux and crash my system. I wonder if this is the only solution.
I hope somebody can give me some advice. 

P.S. I'm aware the system needs an upgrade. But I'm developing on this and need specific versions of some tools that I use until I'm done with my research.

Thanks!

loqs

Member

Registered: 2014-03-06

Posts: 19,113

Re: perf probe says vmlinux has no debug info, don't know how to add it

If you need to use that command then you would need a kernel built with CONFIG_DEBUG_INFO=y and rebuilding 4.13.12-1-ARCH will fail as the toolchain is not longer compatible with that source without patching.

harubyy

Member

Registered: 2017-03-09

Posts: 26

Re: perf probe says vmlinux has no debug info, don't know how to add it

hmm, so I'm stuck. Ok thanks for the reply

eschwartz

Fellow

Registered: 2014-08-08

Posts: 4,097

Re: perf probe says vmlinux has no debug info, don't know how to add it

Well, you could use https://wiki.archlinux.org/index.php/Arch_Linux_Archive to install all the packages from the date when you last updated, and use *that* toolchain to recompile the kernel.

---

Managing AUR repos The Right Way -- aurpublish (now a standalone tool)

loqs

Member

Registered: 2014-03-06

Posts: 19,113

Re: perf probe says vmlinux has no debug info, don't know how to add it

There may also be other ways to monitor the variable.

harubyy

Member

Registered: 2017-03-09

Posts: 26

Re: perf probe says vmlinux has no debug info, don't know how to add it

@Eschwartz: I'm not super confidant to try it tbh ^^
@loqs: I'm actually trying to estimate loop trip counts. I'm not very knowledgeable about perf. I was poking around since I saw some "iterations" in the output of perf record where I sample branches taken. I couldn't go further than that