3 files changed, 92 insertions, 0 deletions

diff --git a/tools/lib/api/Makefile b/tools/lib/api/Makefile
index 22b2f15d7255..212aa4fd65a0 100644
--- a/tools/lib/api/Makefile
+++ b/tools/lib/api/Makefile
@@ -9,12 +9,14 @@ LIB_H=
 LIB_OBJS=
 
 LIB_H += fs/debugfs.h
+LIB_H += fs/tracefs.h
 LIB_H += fs/findfs.h
 LIB_H += fs/fs.h
 # See comment below about piggybacking...
 LIB_H += fd/array.h
 
 LIB_OBJS += $(OUTPUT)fs/debugfs.o
+LIB_OBJS += $(OUTPUT)fs/tracefs.o
 LIB_OBJS += $(OUTPUT)fs/findfs.o
 LIB_OBJS += $(OUTPUT)fs/fs.o
 # XXX piggybacking here, need to introduce libapikfd, or rename this
diff --git a/tools/lib/api/fs/tracefs.c b/tools/lib/api/fs/tracefs.c
new file mode 100644
index 000000000000..ef40d15821e9
--- /dev/null
+++ b/tools/lib/api/fs/tracefs.c
@@ -0,0 +1,70 @@
+#include <errno.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <stdbool.h>
+#include <sys/vfs.h>
+#include <sys/mount.h>
+#include <linux/kernel.h>
+
+#include "tracefs.h"
+
+#ifndef TRACEFS_DEFAULT_PATH
+#define TRACEFS_DEFAULT_PATH            "/sys/kernel/tracing"
+#endif
+
+char tracefs_mountpoint[PATH_MAX + 1] = TRACEFS_DEFAULT_PATH;
+
+static const char * const tracefs_known_mountpoints[] = {
+        TRACEFS_DEFAULT_PATH,
+        "/sys/kernel/debug/tracing",
+        "/tracing",
+        "/trace",
+        0,
+};
+
+static bool tracefs_found;
+
+/* find the path to the mounted tracefs */
+const char *tracefs_find_mountpoint(void)
+{
+        const char *ret;
+
+        if (tracefs_found)
+                return (const char *)tracefs_mountpoint;
+
+        ret = find_mountpoint("tracefs", (long) TRACEFS_MAGIC,
+                              tracefs_mountpoint, PATH_MAX + 1,
+                              tracefs_known_mountpoints);
+
+        if (ret)
+                tracefs_found = true;
+
+        return ret;
+}
+
+/* mount the tracefs somewhere if it's not mounted */
+char *tracefs_mount(const char *mountpoint)
+{
+        /* see if it's already mounted */
+        if (tracefs_find_mountpoint())
+                goto out;
+
+        /* if not mounted and no argument */
+        if (mountpoint == NULL) {
+                /* see if environment variable set */
+                mountpoint = getenv(PERF_TRACEFS_ENVIRONMENT);
+                /* if no environment variable, use default */
+                if (mountpoint == NULL)
+                        mountpoint = TRACEFS_DEFAULT_PATH;
+        }
+
+        if (mount(NULL, mountpoint, "tracefs", 0, NULL) < 0)
+                return NULL;
+
+        /* save the mountpoint */
+        tracefs_found = true;
+        strncpy(tracefs_mountpoint, mountpoint, sizeof(tracefs_mountpoint));
+out:
+        return tracefs_mountpoint;
+}
diff --git a/tools/lib/api/fs/tracefs.h b/tools/lib/api/fs/tracefs.h
new file mode 100644
index 000000000000..e6f7f5183c87
--- /dev/null
+++ b/tools/lib/api/fs/tracefs.h
@@ -0,0 +1,20 @@
+#ifndef __API_TRACEFS_H__
+#define __API_TRACEFS_H__
+
+#include "findfs.h"
+
+#ifndef TRACEFS_MAGIC
+#define TRACEFS_MAGIC          0x74726163
+#endif
+
+#ifndef PERF_TRACEFS_ENVIRONMENT
+#define PERF_TRACEFS_ENVIRONMENT "PERF_TRACEFS_DIR"
+#endif
+
+const char *tracefs_find_mountpoint(void);
+int tracefs_valid_mountpoint(const char *debugfs);
+char *tracefs_mount(const char *mountpoint);
+
+extern char tracefs_mountpoint[];
+
+#endif /* __API_DEBUGFS_H__ */