[PATCH 3.16 062/148] perf probe: Skip if the function address is 0

Ben Hutchings
2020-02-08T18:31:22Z

From: Masami Hiramatsu <mhiramat@kernel.org>

commit 0ad45b33c58dca60dec7e1fb44766753bc4a7a38 upstream.

Skip probes if the entry address of the target function is 0. This can
happen when we're handling C++ debuginfo files.

E.g. without this fix, below case still fail.
----
$ ./perf probe -x /usr/lib64/libstdc++.so.6 -vD is_open
probe-definition(0): is_open
symbol:is_open file:(null) line:0 offset:0 return:0 lazy:(null)
0 arguments
symbol:catch file:(null) line:0 offset:0 return:0 lazy:(null)
symbol:throw file:(null) line:0 offset:0 return:0 lazy:(null)
symbol:rethrow file:(null) line:0 offset:0 return:0 lazy:(null)
Open Debuginfo file: /usr/lib/debug/usr/lib64/libstdc++.so.6.0.22.debug
Try to find probe point from debuginfo.
Matched function: is_open [295df]
found inline addr: 0x8ca80
Probe point found: is_open+0
found inline addr: 0x8ca70
Probe point found: is_open+0
found inline addr: 0x8ca60
Probe point found: is_open+0
Matched function: is_open [6527f]
Matched function: is_open [9fe8a]
Probe point found: is_open+0
Matched function: is_open [19710b]
found inline addr: 0xecca9
Probe point found: stdio_filebuf+57
found inline addr: 0x0
Probe point found: swap+0
Matched function: is_open [19fc9d]
Probe point found: is_open+0
Found 7 probe_trace_events.
p:probe_libstdc++/is_open /usr/lib64/libstdc++.so.6.0.22:0x8ca80
p:probe_libstdc++/is_open_1 /usr/lib64/libstdc++.so.6.0.22:0x8ca70
p:probe_libstdc++/is_open_2 /usr/lib64/libstdc++.so.6.0.22:0x8ca60
p:probe_libstdc++/is_open_3 /usr/lib64/libstdc++.so.6.0.22:0xb0ad0
p:probe_libstdc++/is_open_4 /usr/lib64/libstdc++.so.6.0.22:0xecca9
Failed to synthesize probe trace event.
Error: Failed to add events. Reason: Invalid argument (Code: -22)
----
This is because some instances have entry_pc == 0 (see 19710b and
19fc9d). With this fix, those are skipped.

----
$ ./perf probe -x /usr/lib64/libstdc++.so.6 -D is_open
p:probe_libstdc++/is_open /usr/lib64/libstdc++.so.6.0.22:0x8ca80
p:probe_libstdc++/is_open_1 /usr/lib64/libstdc++.so.6.0.22:0x8ca70
p:probe_libstdc++/is_open_2 /usr/lib64/libstdc++.so.6.0.22:0x8ca60
p:probe_libstdc++/is_open_3 /usr/lib64/libstdc++.so.6.0.22:0xb0ad0
p:probe_libstdc++/is_open_4 /usr/lib64/libstdc++.so.6.0.22:0xecca9
----

Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org>
Tested-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Tested-by: Jiri Olsa <jolsa@kernel.org>
Cc: David Ahern <dsahern@gmail.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/147464490707.29804.14277897643725143867.stgit@devbox
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
---
tools/perf/util/probe-finder.c | 12 +++++++++++-
1 file changed, 11 insertions(+), 1 deletion(-)

--- a/tools/perf/util/probe-finder.c
+++ b/tools/perf/util/probe-finder.c
@@ -871,6 +871,11 @@ static int probe_point_inline_cb(Dwarf_D
dwarf_diename(in_die));
return -ENOENT;
}
+ if (addr == 0) {
+ pr_debug("%s has no valid entry address. skipped.\n",
+ dwarf_diename(in_die));
+ return -ENOENT;
+ }
pf->addr = addr;
pf->addr += pp->offset;
pr_debug("found inline addr: 0x%jx\n",
@@ -912,8 +917,13 @@ static int probe_point_search_cb(Dwarf_D
} else if (die_is_func_instance(sp_die)) {
/* Instances always have the entry address */
dwarf_entrypc(sp_die, &pf->addr);
+ /* But in some case the entry address is 0 */
+ if (pf->addr == 0) {
+ pr_debug("%s has no entry PC. Skipped\n",
+ dwarf_diename(sp_die));
+ param->retval = 0;
/* Real function */
- if (pp->lazy_line)
+ } else if (pp->lazy_line)
param->retval = find_probe_point_lazy(sp_die, pf);
else {
pf->addr += pp->offset;