perf machine: Add a kallsyms loading constructor

To reduce the boilerplate for searching for functions in the running
kernel and modules.

Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: David Ahern <dsahern@gmail.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Wang Nan <wangnan0@huawei.com>
Link: http://lkml.kernel.org/n/tip-93iqzayafpaxaguoiwjqezgz@git.kernel.orgSigned-off-by: NArnaldo Carvalho de Melo <acme@redhat.com>

tools/perf/util/machine.c

@@ -87,6 +87,25 @@ struct machine *machine__new_host(void)
 	return NULL;
 }
 
+struct machine *machine__new_kallsyms(void)
+{
+	struct machine *machine = machine__new_host();
+	/*
+	 * FIXME:
+	 * 1) MAP__FUNCTION will go away when we stop loading separate maps for
+	 *    functions and data objects.
+	 * 2) We should switch to machine__load_kallsyms(), i.e. not explicitely
+	 *    ask for not using the kcore parsing code, once this one is fixed
+	 *    to create a map per module.
+	 */
+	if (machine && __machine__load_kallsyms(machine, "/proc/kallsyms", MAP__FUNCTION, true) <= 0) {
+		machine__delete(machine);
+		machine = NULL;
+	}
+
+	return machine;
+}
+
 static void dsos__purge(struct dsos *dsos)
 {
 	struct dso *pos, *n;

tools/perf/util/machine.h

@@ -129,6 +129,7 @@ char *machine__mmap_name(struct machine *machine, char *bf, size_t size);
 void machines__set_comm_exec(struct machines *machines, bool comm_exec);
 
 struct machine *machine__new_host(void);
+struct machine *machine__new_kallsyms(void);
 int machine__init(struct machine *machine, const char *root_dir, pid_t pid);
 void machine__exit(struct machine *machine);
 void machine__delete_threads(struct machine *machine);