path: root/tools/perf/builtin-mem.c
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authorNamhyung Kim <>2015-01-14 20:18:08 +0900
committerArnaldo Carvalho de Melo <>2015-01-21 10:06:24 -0300
commit25dd9171f51c482eb7c4dc8618766ae733756e2d (patch)
tree3432a7816c5404a8f7a7115ef8285a5f4fb494ad /tools/perf/builtin-mem.c
parent0a3873a8e2709ebc759361e2d872d9f71541806c (diff)
perf probe: Fix probing kretprobes
The commit dfef99cd0b2c ("perf probe: Use ref_reloc_sym based address instead of the symbol name") converts kprobes to use ref_reloc_sym (i.e. _stext) and offset instead of using symbol's name directly. So on my system, adding do_fork ends up with like below: $ sudo perf probe -v --add do_fork%return probe-definition(0): do_fork%return symbol:do_fork file:(null) line:0 offset:0 return:1 lazy:(null) 0 arguments Looking at the vmlinux_path (7 entries long) Using /lib/modules/3.17.6-1-ARCH/build/vmlinux for symbols Could not open debuginfo. Try to use symbols. Opening /sys/kernel/debug/tracing/kprobe_events write=1 Added new event: Writing event: r:probe/do_fork _stext+456136 Failed to write event: Invalid argument Error: Failed to add events. Reason: Operation not permitted (Code: -1) As you can see, the do_fork was translated to _stext+456136. This was because to support (local) symbols that have same name. But the problem is that kretprobe requires to be inserted at function start point so it simply checks whether it's called with offset 0. And if not, it'll return with -EINVAL. You can see it with dmesg. $ dmesg | tail -1 [125621.764103] Return probe must be used without offset. So we need to use the symbol name instead of ref_reloc_sym in case of return probes. Reported-by: Jiri Olsa <> Signed-off-by: Namhyung Kim <> Tested-by: Jiri Olsa <> Acked-by: Masami Hiramatsu <> Cc: David Ahern <> Link: Signed-off-by: Arnaldo Carvalho de Melo <>
Diffstat (limited to 'tools/perf/builtin-mem.c')
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