RE: [PATCH 2/2] perf tools: Fix find_perf_probe_point_from_map() which incorrectly returns success

Date: Thu Nov 05 2015 - 09:08:56 EST

From: Wang Nan [mailto:wangnan0@xxxxxxxxxx]
>It is possible that find_perf_probe_point_from_map() fails to find
>symbol but still returns 0 because of an small error when coding:
>find_perf_probe_point_from_map() set 'ret' to error code at first,
>but also use it to hold return value of

OK, I didn't expect that there is a symbol which can be found by
kernel_get_symbol_address_by_name() but not by __find_kernel_function()...
Would you have any example of the error?

>This patch resets 'ret' to error even kernel_get_symbol_address_by_name()
>success, so if !sym, the whole function returns error correctly.

Hmm, that sounds tricky. I'd rather like to add *psym to kernel_get_symbol_address_by_name()
to save symbol and don't use __find_kernel_function() instead.

Thank you,

>Signed-off-by: Wang Nan <wangnan0@xxxxxxxxxx>
>Cc: Arnaldo Carvalho de Melo <acme@xxxxxxxxxx>
>Cc: Jiri Olsa <jolsa@xxxxxxxxxx>
>Cc: Masami Hiramatsu <>
>Cc: Namhyung Kim <namhyung@xxxxxxxxxx>
> tools/perf/util/probe-event.c | 3 +++
> 1 file changed, 3 insertions(+)
>diff --git a/tools/perf/util/probe-event.c b/tools/perf/util/probe-event.c
>index b51a8bf..e659c4f 100644
>--- a/tools/perf/util/probe-event.c
>+++ b/tools/perf/util/probe-event.c
>@@ -1905,6 +1905,9 @@ static int find_perf_probe_point_from_map(struct probe_trace_point *tp,
> sym = __find_kernel_function(addr, &map);
> }
> }
>+ /* ret may has be overwritten so reset it */
>+ ret = -ENOENT;
> if (!sym)
> goto out;