21:16 <iskander> hi, i have one question about return probes for user process functions

21:17 <iskander> i'm getting this error when i use return probes and run stap as a non-root user: process return probes not available

21:17 <iskander> when i run stap as root then everything works

21:18 <iskander> non-return probes work when i run stap as a non-root user

21:18 <iskander> thanks in advance

21:19 <iskander> btw, my user is a member of stap* groups

21:20 <fche> iskander, wow that doesn't make sense!

21:21 <iskander> hmm, tell that my xubuntu machine

21:22 <fche> ah I think I know what's going on

21:22 <fche> stap's tapsets.cxx looks for the kernel function 'arch_uretprobe_hijack_return_addr' as a sign that a particular piece of functionality exists in the kernel

21:22 <fche> (it was added way in the 3.7ish timeframe)

21:23 <iskander> how does it work ? it looks in system.map ?

21:23 <fche> that function in turn uses a /System.map file in a couple of places

21:23 <fche> I bet on your distro that file is unreadable to mortal users

21:24 <iskander> yeah, let me test it

21:24 <fche> (an strace stap will probably show what it tries ... and actually stap may warn 'Kernel function symbol table missing [man warning::symbols]' also in that case

21:24 <fche> are you seeing that?

21:25 <iskander> correct, making system.map readable solves the problem, but i'm getting another warning

21:25 <iskander> something about disabling cache support

21:25 <fche> that's probably not important.

21:26 <iskander> thanks, works now, the error message about not supporing uretprobes is completely misleading, why not just say: yo dude, your system.map is unreadable

21:47 <fche> iskander, was the 'kernel function symbol table' warning printed at least?