(2014/09/11 23:51), Arnaldo Carvalho de Melo wrote: > Em Thu, Sep 04, 2014 at 03:11:31PM -0500, david lerner escreveu: >> 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? > > Have to check this, but perhaps Masami has this working already?
Hmm, I thought it should work. But no, it doesn't. I've checked it and have found it doesn't work as below. ---- $ ./perf probe -x /usr/lib64/libunwind.so -vvv -V access_reg probe-definition(0): access_reg symbol:access_reg file:(null) line:0 offset:0 return:0 lazy:(null) 0 arguments Open Debuginfo file: /usr/lib/debug/usr/lib64/libunwind.so.8.0.1.debug Searching variables at access_reg Failed to find symbol at 0x2f40 Failed to find the address of access_reg Error: Failed to show vars. Reason: No such file or directory (Code: -2) ---- I guess it might fail to verify the symbol address. Because it is a shared library, dwarf information will be a bit different. Anyway I'll try to fix that. Thank you for reporting! :) -- Masami HIRAMATSU Software Platform Research Dept. Linux Technology Research Center Hitachi, Ltd., Yokohama Research Laboratory E-mail: masami.hiramatsu...@hitachi.com -- To unsubscribe from this list: send the line "unsubscribe linux-perf-users" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
