perf: unwind: Fix symfs with libdw

Pass the full path including the symfs (if any) to libdw.  Without this
unwinding fails with errors like this when a symfs is used:

  unwind: failed with 'No such file or directory'"

Signed-off-by: Vincent Whitchurch <[email protected]>
Acked-by: Namhyung Kim <[email protected]>
Cc: Mark Rutland <[email protected]>
Cc: [email protected]
Cc: Ian Rogers <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Adrian Hunter <[email protected]>
Cc: Arnaldo Carvalho de Melo <[email protected]>
Cc: Jiri Olsa <[email protected]>
Cc: Alexander Shishkin <[email protected]>
Cc: Ingo Molnar <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Namhyung Kim <[email protected]>

Author: vwax

tools/perf/util/unwind-libdw.c

@@ -66,9 +66,13 @@ static int __report_module(struct addr_location *al, u64 ip,
 			mod = 0;
 	}
 
-	if (!mod)
-		mod = dwfl_report_elf(ui->dwfl, dso->short_name, dso->long_name, -1,
+	if (!mod) {
+		char filename[PATH_MAX];
+
+		__symbol__join_symfs(filename, sizeof(filename), dso->long_name);
+		mod = dwfl_report_elf(ui->dwfl, dso->short_name, filename, -1,
 				      map__start(al->map) - map__pgoff(al->map), false);
+	}
 	if (!mod) {
 		char filename[PATH_MAX];