[PATCH perf/core 01/10] [BUGFIX] perf-probe: Fix to show correct error message for $vars and $params

Masami Hiramatsu
2016-07-12T10:04:41Z

Fix to show correct error messages for $vars and $params because
those special variables requires debug information to find the
real variables or function parameters.

E.g. without this fix;
----
# perf probe -x /lib64/libc-2.23.so getaddrinfo \$params
Failed to write event: Invalid argument
Please upgrade your kernel to at least 3.14 to have access to feature $params
Error: Failed to add events.
----
Perf ends up with an error, but the message is not correct.
With this fix, perf shows correct error message as below.
----
# perf probe -x /lib64/libc-2.23.so getaddrinfo \$params
The /usr/lib64/libc-2.23.so file has no debug information.
Rebuild with -g, or install an appropriate debuginfo package.
Error: Failed to add events.
----

Reported-by: Arnaldo Carvalho de Melo <acme@kernel.org>
Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org>
---
tools/perf/util/probe-event.c | 4 +++-
1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/tools/perf/util/probe-event.c b/tools/perf/util/probe-event.c
index 0201f66..dff9a54 100644
--- a/tools/perf/util/probe-event.c
+++ b/tools/perf/util/probe-event.c
@@ -1547,7 +1547,9 @@ bool perf_probe_event_need_dwarf(struct perf_probe_event *pev)
return true;

for (i = 0; i < pev->nargs; i++)
- if (is_c_varname(pev->args[i].var))
+ if (is_c_varname(pev->args[i].var) ||
+ !strcmp(pev->args[i].var, "$params") ||
+ !strcmp(pev->args[i].var, "$vars"))
return true;

return false;