Index: share/man/man9/EVENTHANDLER.9
===================================================================
--- share/man/man9/EVENTHANDLER.9
+++ share/man/man9/EVENTHANDLER.9
@@ -318,6 +318,12 @@
 Callbacks invoked before a linker file is about to be unloaded.
 These callbacks may be used to return an error and prevent the unload from
 proceeding.
+.It Vt livedumper_start
+Callback invoked before beginning a minidump of the live system.
+.It Vt livedumper_dump
+Callback invoked for each dumped block of data during a live minidump.
+.It Vt livedumper_finish
+Callback invoked once a live minidump has completed.
 .It Vt lle_event
 Callback invoked when an link layer event has happened.
 .It Vt nmbclusters_change
Index: sys/kern/kern_vnodedumper.c
===================================================================
--- sys/kern/kern_vnodedumper.c
+++ sys/kern/kern_vnodedumper.c
@@ -31,6 +31,7 @@
 #include <sys/conf.h>
 #include <sys/caprights.h>
 #include <sys/disk.h>
+#include <sys/eventhandler.h>
 #include <sys/fcntl.h>
 #include <sys/file.h>
 #include <sys/kerneldump.h>
@@ -51,6 +52,14 @@
 static struct sx livedump_sx;
 SX_SYSINIT(livedump, &livedump_sx, "Livedump sx");
 
+typedef void (*livedump_fn)(void *arg, int *errorp);
+typedef void (*livedump_dump_fn)(void *arg, void *virtual, off_t offset,
+    size_t len, int *errorp);
+
+EVENTHANDLER_DECLARE(livedumper_start, livedump_fn);
+EVENTHANDLER_DECLARE(livedumper_dump, livedump_dump_fn);
+EVENTHANDLER_DECLARE(livedumper_finish, livedump_fn);
+
 /*
  * Invoke a live minidump on the system.
  */
@@ -94,9 +103,15 @@
 	/* Only allow one livedump to proceed at a time. */
 	sx_xlock(&livedump_sx);
 
+	EVENTHANDLER_INVOKE(livedumper_start, &error);
+	if (error != 0)
+		goto out;
+
 	dump_savectx();
 	error = minidumpsys(&di, true);
-
+	/* XXX: may clobber error. */
+	EVENTHANDLER_INVOKE(livedumper_finish, &error);
+out:
 	sx_xunlock(&livedump_sx);
 	vn_rangelock_unlock(vp, rl_cookie);
 	VOP_UNLOCK(vp);
@@ -149,6 +164,10 @@
 	MPASS(vp != NULL);
 	ASSERT_VOP_LOCKED(vp, __func__);
 
+	EVENTHANDLER_INVOKE(livedumper_dump, virtual, offset, length, &error);
+	if (error != 0)
+		return (error);
+
 	/* Done? */
 	if (virtual == NULL)
 		return (0);