Has perf probe for userspace shared libraries been modified to use dwarf info?
The first commit to provide this useful functionality...
fb7345bbf7fad9 perf probe: Support basic dwarf-based operations on
uprobe events,
shows examples only with the executable perf, but not with a shared library.
With version 3.14 I'm able to set probes in application executable,
for example for the test application 'libunwind-test.out' I see the
usual args to main():
root@qemu0:~# perf probe -x ./libunwind-test.out --vars main
Available variables at main
@<main+0>
char** a
int c
But I can't access the variables in a library that has embedded (not
split out) dwarf debug info...
root@qemu0:~# perf probe -x /usr/lib64/libunwind.so --vars unw_backtrace
Failed to find symbol at 0x33c38039cd
Failed to find variables at unw_backtrace (-2)
Error: Failed to show vars. (-2)
I've used gdb to confirm that perf found the correct function address
for unw_backtrace(), and that gdb knows the symbolic names of the
arguments.
Is using dwarf debuginfo with shared libraries for perf uprobes on the
to-do list?
Or is this capability incomplete in version 3.14 and I need to pick up
other patches?
Thanks,
Dave
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