perf probe: Return a better scope DIE if there is no best scope

[ Upstream commit c701636aeec4c173208697d68da6e4271125564b ]

Make find_best_scope() returns innermost DIE at given address if there
is no best matched scope DIE. Since Gcc sometimes generates intuitively
strange line info which is out of inlined function address range, we
need this fixup.

Without this, sometimes perf probe failed to probe on a line inside an
inlined function:

  # perf probe -D ksys_open:3
  Failed to find scope of probe point.
    Error: Failed to add events.

With this fix, 'perf probe' can probe it:

  # perf probe -D ksys_open:3
  p:probe/ksys_open _text+25707308
  p:probe/ksys_open_1 _text+25710596
  p:probe/ksys_open_2 _text+25711114
  p:probe/ksys_open_3 _text+25711343
  p:probe/ksys_open_4 _text+25714058
  p:probe/ksys_open_5 _text+2819653
  p:probe/ksys_open_6 _text+2819701

Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org>
Tested-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Ravi Bangoria <ravi.bangoria@linux.ibm.com>
Cc: Steven Rostedt (VMware) <rostedt@goodmis.org>
Cc: Tom Zanussi <tom.zanussi@linux.intel.com>
Link: http://lore.kernel.org/lkml/157291300887.19771.14936015360963292236.stgit@devnote2
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>

diff --git a/tools/perf/util/probe-finder.c b/tools/perf/util/probe-finder.c
index 440f0a92ade6571bb6af3825b66c05a8b6d214c3..6ca804a01cf9f7b73446a90a23902d01965c02ee 100644 (file)
--- a/tools/perf/util/probe-finder.c
+++ b/tools/perf/util/probe-finder.c
@@ -764,6 +764,16 @@ static int find_best_scope_cb(Dwarf_Die *fn_die, void *data)
        return 0;
 }
 
+/* Return innermost DIE */
+static int find_inner_scope_cb(Dwarf_Die *fn_die, void *data)
+{
+       struct find_scope_param *fsp = data;
+
+       memcpy(fsp->die_mem, fn_die, sizeof(Dwarf_Die));
+       fsp->found = true;
+       return 1;
+}
+
 /* Find an appropriate scope fits to given conditions */
 static Dwarf_Die *find_best_scope(struct probe_finder *pf, Dwarf_Die *die_mem)
 {
@@ -775,8 +785,13 @@ static Dwarf_Die *find_best_scope(struct probe_finder *pf, Dwarf_Die *die_mem)
                .die_mem = die_mem,
                .found = false,
        };
+       int ret;
 
-       cu_walk_functions_at(&pf->cu_die, pf->addr, find_best_scope_cb, &fsp);
+       ret = cu_walk_functions_at(&pf->cu_die, pf->addr, find_best_scope_cb,
+                                  &fsp);
+       if (!ret && !fsp.found)
+               cu_walk_functions_at(&pf->cu_die, pf->addr,
+                                    find_inner_scope_cb, &fsp);
 
        return fsp.found ? die_mem : NULL;
 }