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SubjectPerf tool regression from 07d369857808
Hi Masami,

The commit 07d369857808 ("perf probe: Fix wrong address verification)
found its way in kernel 4.19.98 (and debian 10) and I observed some
regressions when I try to add probes in shared libraries.
The symptoms are:

$ perf probe -f --exec=/home/aghiti/lib/ --add
'log_rank_path=log_rank_path rank path:string'
Failed to find symbol at 0x3bf0
Error: Failed to add events.

Whereas when I revert this patch, on the same shared library:

$ perf probe -f --exec=/home/aghiti/lib/ --add
'log_rank_path=log_rank_path rank path:string'
Added new event:
probe_libdpuhw:log_rank_path_4 (on log_rank_path in
/home/aghiti/lib/ with rank path:string)

You can now use it in all perf tools, such as:

perf record -e probe_libdpuhw:log_rank_path_4 -aR sleep 1

Actually, I noted that this patch reverts a previous patch that stated
that dwfl_module_addrsym could fail on shared libraries 664fee3dc379
("perf probe: Do not use dwfl_module_addrsym if dwarf_diename finds
symbol name").

Let me know if I can be of any help,


Alexandre Ghiti

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