1 files changed, 101 insertions, 0 deletions

diff --git a/tools/lib/lk/debugfs.c b/tools/lib/lk/debugfs.c
new file mode 100644
index 000000000000..099e7cd022e4
--- /dev/null
+++ b/tools/lib/lk/debugfs.c
@@ -0,0 +1,101 @@
+#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/magic.h>
+#include <linux/kernel.h>
+
+#include "debugfs.h"
+
+char debugfs_mountpoint[PATH_MAX + 1] = "/sys/kernel/debug";
+
+static const char * const debugfs_known_mountpoints[] = {
+        "/sys/kernel/debug/",
+        "/debug/",
+        0,
+};
+
+static bool debugfs_found;
+
+/* find the path to the mounted debugfs */
+const char *debugfs_find_mountpoint(void)
+{
+        const char * const *ptr;
+        char type[100];
+        FILE *fp;
+
+        if (debugfs_found)
+                return (const char *)debugfs_mountpoint;
+
+        ptr = debugfs_known_mountpoints;
+        while (*ptr) {
+                if (debugfs_valid_mountpoint(*ptr) == 0) {
+                        debugfs_found = true;
+                        strcpy(debugfs_mountpoint, *ptr);
+                        return debugfs_mountpoint;
+                }
+                ptr++;
+        }
+
+        /* give up and parse /proc/mounts */
+        fp = fopen("/proc/mounts", "r");
+        if (fp == NULL)
+                return NULL;
+
+        while (fscanf(fp, "%*s %" STR(PATH_MAX) "s %99s %*s %*d %*d\n",
+                      debugfs_mountpoint, type) == 2) {
+                if (strcmp(type, "debugfs") == 0)
+                        break;
+        }
+        fclose(fp);
+
+        if (strcmp(type, "debugfs") != 0)
+                return NULL;
+
+        debugfs_found = true;
+
+        return debugfs_mountpoint;
+}
+
+/* verify that a mountpoint is actually a debugfs instance */
+
+int debugfs_valid_mountpoint(const char *debugfs)
+{
+        struct statfs st_fs;
+
+        if (statfs(debugfs, &st_fs) < 0)
+                return -ENOENT;
+        else if (st_fs.f_type != (long) DEBUGFS_MAGIC)
+                return -ENOENT;
+
+        return 0;
+}
+
+/* mount the debugfs somewhere if it's not mounted */
+char *debugfs_mount(const char *mountpoint)
+{
+        /* see if it's already mounted */
+        if (debugfs_find_mountpoint())
+                goto out;
+
+        /* if not mounted and no argument */
+        if (mountpoint == NULL) {
+                /* see if environment variable set */
+                mountpoint = getenv(PERF_DEBUGFS_ENVIRONMENT);
+                /* if no environment variable, use default */
+                if (mountpoint == NULL)
+                        mountpoint = "/sys/kernel/debug";
+        }
+
+        if (mount(NULL, mountpoint, "debugfs", 0, NULL) < 0)
+                return NULL;
+
+        /* save the mountpoint */
+        debugfs_found = true;
+        strncpy(debugfs_mountpoint, mountpoint, sizeof(debugfs_mountpoint));
+out:
+        return debugfs_mountpoint;
+}