perf symbols: Support to read compressed module from build-id cache

The commit c00c48fc ("perf symbols: Preparation for compressed
kernel module support") added support for compressed kernel modules but
it only supports system path DSOs.  When a dso is read from build-id
cache, its filename doesn't end with ".gz" but has build-id.  In this
case, we should fallback to the original dso->name.
Signed-off-by: Namhyung Kim <namhyung@kernel.org>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Andi Kleen <andi@firstfloor.org>
Cc: David Ahern <dsahern@gmail.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Stephane Eranian <eranian@google.com>
Link: http://lkml.kernel.org/r/1422518843-25818-2-git-send-email-namhyung@kernel.orgSigned-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

tools/perf/util/symbol-elf.c

@@ -574,13 +574,16 @@ static int decompress_kmodule(struct dso *dso, const char *name,
 	const char *ext = strrchr(name, '.');
 	char tmpbuf[] = "/tmp/perf-kmod-XXXXXX";
 
-	if ((type != DSO_BINARY_TYPE__SYSTEM_PATH_KMODULE_COMP &&
-	     type != DSO_BINARY_TYPE__GUEST_KMODULE_COMP) ||
-	    type != dso->symtab_type)
+	if (type != DSO_BINARY_TYPE__SYSTEM_PATH_KMODULE_COMP &&
+	    type != DSO_BINARY_TYPE__GUEST_KMODULE_COMP &&
+	    type != DSO_BINARY_TYPE__BUILD_ID_CACHE)
 		return -1;
 
+	if (!ext || !is_supported_compression(ext + 1)) {
+		ext = strrchr(dso->name, '.');
 		if (!ext || !is_supported_compression(ext + 1))
 			return -1;
+	}
 
 	fd = mkstemp(tmpbuf);
 	if (fd < 0)