perf record: Mark MAP_HUGETLB when synthesizing mmap events

When synthesizing mmap events, add MAP_HUGETLB map flag if the source of
mapping is file in hugetlbfs.

After this patch, perf can identify hugetlb mapping even if perf is
started after the mapping of huge pages (like with 'perf top').

Signed-off-by: Wang Nan <wangnan0@huawei.com>
Reviewed-by: Nilay Vaish <nilayvaish@gmail.com>
Cc: He Kuang <hekuang@huawei.com>
Cc: Hou Pengyang <houpengyang@huawei.com>
Cc: Zefan Li <lizefan@huawei.com>
Link: http://lkml.kernel.org/r/1473137909-142064-4-git-send-email-wangnan0@huawei.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

tools/perf/util/event.c

@@ -1,5 +1,6 @@
 #include <linux/types.h>
 #include <sys/mman.h>
+#include <api/fs/fs.h>
 #include "event.h"
 #include "debug.h"
 #include "hist.h"
@@ -248,6 +249,10 @@ int perf_event__synthesize_mmap_events(struct perf_tool *tool,
 	bool truncation = false;
 	unsigned long long timeout = proc_map_timeout * 1000000ULL;
 	int rc = 0;
+#ifdef MAP_HUGETLB
+	const char *hugetlbfs_mnt = hugetlbfs__mountpoint();
+	int hugetlbfs_mnt_len = hugetlbfs_mnt ? strlen(hugetlbfs_mnt) : 0;
+#endif
 
 	if (machine__is_default_guest(machine))
 		return 0;
@@ -342,6 +347,12 @@ out:
 
 		if (!strcmp(execname, ""))
 			strcpy(execname, anonstr);
+#ifdef MAP_HUGETLB
+		if (!strncmp(execname, hugetlbfs_mnt, hugetlbfs_mnt_len)) {
+			strcpy(execname, anonstr);
+			event->mmap2.flags |= MAP_HUGETLB;
+		}
+#endif
 
 		size = strlen(execname) + 1;
 		memcpy(event->mmap2.filename, execname, size);