perf maps: Purge all maps from the 'names' tree

perf maps: Purge all maps from the 'names' tree

BugLink: https://bugs.launchpad.net/bugs/1830906
[ Upstream commit da3a53a7390a89391bd63bead0c2e9af4c5ef3d6 ]

Add function __maps__purge_names() to purge all maps from the names
tree.  We need to cleanup the names tree in maps__exit().

Detected with gcc's ASan.

Signed-off-by: Changbin Du <changbin.du@gmail.com>
Reviewed-by: Jiri Olsa <jolsa@kernel.org>
Cc: Alexei Starovoitov <ast@kernel.org>
Cc: Daniel Borkmann <daniel@iogearbox.net>
Cc: Eric Saint-Etienne <eric.saint.etienne@oracle.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Steven Rostedt (VMware) <rostedt@goodmis.org>
Fixes: 1e6285699b30 ("perf symbols: Fix slowness due to -ffunction-section")
Link: http://lkml.kernel.org/r/20190316080556.3075-12-changbin.du@gmail.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: Stefan Bader <stefan.bader@canonical.com>
Signed-off-by: Kleber Sacilotto de Souza <kleber.souza@canonical.com>