libperf: Adopt perf_mmap__read_event() from tools/perf

Move perf_mmap__read_event() from tools/perf to libperf and export it in
the perf/mmap.h header.

Signed-off-by: Jiri Olsa <jolsa@kernel.org>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Michael Petlan <mpetlan@redhat.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: http://lore.kernel.org/lkml/20191007125344.14268-13-jolsa@kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

3 files changed, 82 insertions, 0 deletions

diff --git a/tools/perf/lib/include/perf/mmap.h b/tools/perf/lib/include/perf/mmap.h
index 4f946e7f724b..9508ad90d8b9 100644
--- a/tools/perf/lib/include/perf/mmap.h
+++ b/tools/perf/lib/include/perf/mmap.h
@@ -5,9 +5,11 @@
 #include <perf/core.h>
 
 struct perf_mmap;
+union perf_event;
 
 LIBPERF_API void perf_mmap__consume(struct perf_mmap *map);
 LIBPERF_API int perf_mmap__read_init(struct perf_mmap *map);
 LIBPERF_API void perf_mmap__read_done(struct perf_mmap *map);
+LIBPERF_API union perf_event *perf_mmap__read_event(struct perf_mmap *map);
 
 #endif /* __LIBPERF_MMAP_H */
diff --git a/tools/perf/lib/libperf.map b/tools/perf/lib/libperf.map
index 7e3ea2e9c917..8bb0d73e0c6c 100644
--- a/tools/perf/lib/libperf.map
+++ b/tools/perf/lib/libperf.map
@@ -43,6 +43,7 @@ LIBPERF_0.0.1 {
 		perf_mmap__consume;
 		perf_mmap__read_init;
 		perf_mmap__read_done;
+		perf_mmap__read_event;
 	local:
 		*;
 };
diff --git a/tools/perf/lib/mmap.c b/tools/perf/lib/mmap.c
index 97297cba44e3..0752c193b0fb 100644
--- a/tools/perf/lib/mmap.c
+++ b/tools/perf/lib/mmap.c
@@ -3,9 +3,11 @@
 #include <inttypes.h>
 #include <asm/bug.h>
 #include <errno.h>
+#include <string.h>
 #include <linux/ring_buffer.h>
 #include <linux/perf_event.h>
 #include <perf/mmap.h>
+#include <perf/event.h>
 #include <internal/mmap.h>
 #include <internal/lib.h>
 #include <linux/kernel.h>
@@ -192,3 +194,80 @@ void perf_mmap__read_done(struct perf_mmap *map)
 
 	map->prev = perf_mmap__read_head(map);
 }
+
+/* When check_messup is true, 'end' must points to a good entry */
+static union perf_event *perf_mmap__read(struct perf_mmap *map,
+					 u64 *startp, u64 end)
+{
+	unsigned char *data = map->base + page_size;
+	union perf_event *event = NULL;
+	int diff = end - *startp;
+
+	if (diff >= (int)sizeof(event->header)) {
+		size_t size;
+
+		event = (union perf_event *)&data[*startp & map->mask];
+		size = event->header.size;
+
+		if (size < sizeof(event->header) || diff < (int)size)
+			return NULL;
+
+		/*
+		 * Event straddles the mmap boundary -- header should always
+		 * be inside due to u64 alignment of output.
+		 */
+		if ((*startp & map->mask) + size != ((*startp + size) & map->mask)) {
+			unsigned int offset = *startp;
+			unsigned int len = min(sizeof(*event), size), cpy;
+			void *dst = map->event_copy;
+
+			do {
+				cpy = min(map->mask + 1 - (offset & map->mask), len);
+				memcpy(dst, &data[offset & map->mask], cpy);
+				offset += cpy;
+				dst += cpy;
+				len -= cpy;
+			} while (len);
+
+			event = (union perf_event *)map->event_copy;
+		}
+
+		*startp += size;
+	}
+
+	return event;
+}
+
+/*
+ * Read event from ring buffer one by one.
+ * Return one event for each call.
+ *
+ * Usage:
+ * perf_mmap__read_init()
+ * while(event = perf_mmap__read_event()) {
+ *	//process the event
+ *	perf_mmap__consume()
+ * }
+ * perf_mmap__read_done()
+ */
+union perf_event *perf_mmap__read_event(struct perf_mmap *map)
+{
+	union perf_event *event;
+
+	/*
+	 * Check if event was unmapped due to a POLLHUP/POLLERR.
+	 */
+	if (!refcount_read(&map->refcnt))
+		return NULL;
+
+	/* non-overwirte doesn't pause the ringbuffer */
+	if (!map->overwrite)
+		map->end = perf_mmap__read_head(map);
+
+	event = perf_mmap__read(map, &map->start, map->end);
+
+	if (!map->overwrite)
+		map->prev = map->start;
+
+	return event;
+}