libperf: Introduce perf_evlist__for_each_mmap()

Add the perf_evlist__for_each_mmap() function and export it in the
perf/evlist.h header, so that the user can iterate through 'struct
perf_mmap' objects.

Add a internal perf_mmap__link() function to do the actual linking.

Signed-off-by: Jiri Olsa <jolsa@kernel.org>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Alexey Budankov <alexey.budankov@linux.intel.com>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Jin Yao <yao.jin@linux.intel.com>
Cc: Michael Petlan <mpetlan@redhat.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephane Eranian <eranian@google.com>
Link: http://lore.kernel.org/lkml/20191017105918.20873-2-jolsa@kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
diff --git a/tools/perf/lib/include/internal/mmap.h b/tools/perf/lib/include/internal/mmap.h
index ee536c4..be7556e 100644
--- a/tools/perf/lib/include/internal/mmap.h
+++ b/tools/perf/lib/include/internal/mmap.h
@@ -32,6 +32,7 @@ struct perf_mmap {
 	u64			 flush;
 	libperf_unmap_cb_t	 unmap_cb;
 	char			 event_copy[PERF_SAMPLE_MAX_SIZE] __aligned(8);
+	struct perf_mmap	*next;
 };
 
 struct perf_mmap_param {
@@ -41,8 +42,8 @@ struct perf_mmap_param {
 
 size_t perf_mmap__mmap_len(struct perf_mmap *map);
 
-void perf_mmap__init(struct perf_mmap *map, bool overwrite,
-		     libperf_unmap_cb_t unmap_cb);
+void perf_mmap__init(struct perf_mmap *map, struct perf_mmap *prev,
+		     bool overwrite, libperf_unmap_cb_t unmap_cb);
 int perf_mmap__mmap(struct perf_mmap *map, struct perf_mmap_param *mp,
 		    int fd, int cpu);
 void perf_mmap__munmap(struct perf_mmap *map);