Index: sys/cddl/dev/dtrace/aarch64/dtrace_subr.c
===================================================================
--- sys/cddl/dev/dtrace/aarch64/dtrace_subr.c
+++ sys/cddl/dev/dtrace/aarch64/dtrace_subr.c
@@ -49,6 +49,7 @@
 extern dtrace_id_t	dtrace_probeid_error;
 extern int (*dtrace_invop_jump_addr)(struct trapframe *);
 extern void dtrace_getnanotime(struct timespec *tsp);
+extern void dtrace_getnanouptime(struct timespec *tsp);
 
 int dtrace_invop(uintptr_t, struct trapframe *, uintptr_t);
 void dtrace_invop_init(void);
@@ -163,7 +164,7 @@
 {
 	struct timespec curtime;
 
-	nanouptime(&curtime);
+	dtrace_getnanouptime(&curtime);
 
 	return (curtime.tv_sec * 1000000000UL + curtime.tv_nsec);
 
Index: sys/cddl/dev/dtrace/arm/dtrace_subr.c
===================================================================
--- sys/cddl/dev/dtrace/arm/dtrace_subr.c
+++ sys/cddl/dev/dtrace/arm/dtrace_subr.c
@@ -54,6 +54,7 @@
 extern dtrace_id_t	dtrace_probeid_error;
 extern int (*dtrace_invop_jump_addr)(struct trapframe *);
 extern void dtrace_getnanotime(struct timespec *tsp);
+extern void dtrace_getnanouptime(struct timespec *tsp);
 
 int dtrace_invop(uintptr_t, struct trapframe *, uintptr_t);
 void dtrace_invop_init(void);
@@ -174,7 +175,7 @@
 {
 	struct	timespec curtime;
 
-	nanouptime(&curtime);
+	dtrace_getnanouptime(&curtime);
 
 	return (curtime.tv_sec * 1000000000UL + curtime.tv_nsec);
 
Index: sys/cddl/dev/dtrace/riscv/dtrace_subr.c
===================================================================
--- sys/cddl/dev/dtrace/riscv/dtrace_subr.c
+++ sys/cddl/dev/dtrace/riscv/dtrace_subr.c
@@ -52,6 +52,7 @@
 extern dtrace_id_t	dtrace_probeid_error;
 extern int (*dtrace_invop_jump_addr)(struct trapframe *);
 extern void dtrace_getnanotime(struct timespec *tsp);
+extern void dtrace_getnanouptime(struct timespec *tsp);
 
 int dtrace_invop(uintptr_t, struct trapframe *);
 void dtrace_invop_init(void);
@@ -165,7 +166,7 @@
 {
 	struct timespec curtime;
 
-	nanouptime(&curtime);
+	dtrace_getnanouptime(&curtime);
 
 	return (curtime.tv_sec * 1000000000UL + curtime.tv_nsec);
 
Index: sys/cddl/dev/fbt/fbt.c
===================================================================
--- sys/cddl/dev/fbt/fbt.c
+++ sys/cddl/dev/fbt/fbt.c
@@ -127,6 +127,13 @@
 		return (1);
 	}
 
+	/*
+	 * Omit instrumentation of functions that are probably in DDB.  It
+	 * makes it too hard to debug broken FBT.
+	 */
+	if (strncmp(name, "db_", 3) == 0)
+		return (1);
+
 	/*
 	 * Lock owner methods may be called from probe context.
 	 */
@@ -136,6 +143,15 @@
 	    strcmp(name, "owner_sx") == 0)
 		return (1);
 
+	/*
+	 * The compiler will sometimes replace memcpy()-like code with calls
+	 * to memcpy() (or similar), which can occur in the DTrace code
+	 * itself.  For now, rather than prevent that in the build, just don't
+	 * instrument at run time.
+	 */
+	if (strcmp(name, "memcpy") == 0)
+		return (1);
+
 	/*
 	 * Stack unwinders may be called from probe context on some
 	 * platforms.
@@ -145,6 +161,16 @@
 		return (1);
 #endif
 
+	/*
+	 * Some assembly-language exception handlers are not suitable for
+	 * instrumentation.
+	 */
+#if defined(__aarch64__)
+	 if (strcmp(name, "handle_el1h_sync") == 0 ||
+	    strcmp(name, "do_el1h_sync") == 0)
+		return (1);
+#endif
+
 	/*
 	 * When DTrace is built into the kernel we need to exclude
 	 * the FBT functions from instrumentation.
Index: sys/kern/kern_tc.c
===================================================================
--- sys/kern/kern_tc.c
+++ sys/kern/kern_tc.c
@@ -146,6 +146,7 @@
 static void cpu_tick_calibrate(int);
 
 void dtrace_getnanotime(struct timespec *tsp);
+void dtrace_getnanouptime(struct timespec *tsp);
 
 static int
 sysctl_kern_boottime(SYSCTL_HANDLER_ARGS)
@@ -997,6 +998,20 @@
 	GETTHMEMBER(tsp, th_nanotime);
 }
 
+/*
+ * This is a clone of getnanouptime used for time since boot.
+ * The dtrace_ prefix prevents fbt from creating probes for
+ * it so an uptime that can be safely used in all fbt probes.
+ */
+void
+dtrace_getnanouptime(struct timespec *tsp)
+{
+	struct bintime bt;
+
+	GETTHMEMBER(&bt, th_offset);
+	bintime2timespec(&bt, tsp);
+}
+
 /*
  * System clock currently providing time to the system. Modifiable via sysctl
  * when the FFCLOCK option is defined.