Index: sys/amd64/amd64/trap.c
===================================================================
--- sys/amd64/amd64/trap.c
+++ sys/amd64/amd64/trap.c
@@ -761,6 +761,9 @@
 	u_int type;
 	struct soft_segment_descriptor softseg;
 	char *msg;
+#ifdef KDB
+	bool handled, reenter;
+#endif
 
 	code = frame->tf_err;
 	type = frame->tf_trapno;
@@ -811,9 +814,16 @@
 	    curproc->p_pid, curthread->td_name);
 
 #ifdef KDB
-	if (debugger_on_panic || kdb_active)
-		if (kdb_trap(type, 0, frame))
+	if (debugger_on_panic || kdb_active) {
+		reenter = kdb_active;
+		if (!reenter)
+			kdb_why = KDB_WHY_TRAP;
+		handled = kdb_trap(type, 0, frame);
+		if (!reenter)
+			kdb_why = KDB_WHY_UNSET;
+		if (handled)
 			return;
+	}
 #endif
 	printf("trap number		= %d\n", type);
 	if (type <= MAX_TRAP_MSG)
Index: sys/i386/i386/trap.c
===================================================================
--- sys/i386/i386/trap.c
+++ sys/i386/i386/trap.c
@@ -879,6 +879,9 @@
 	int code, ss, esp;
 	u_int type;
 	struct soft_segment_descriptor softseg;
+#ifdef KDB
+	bool handled, reenter;
+#endif
 
 	code = frame->tf_err;
 	type = frame->tf_trapno;
@@ -938,12 +941,16 @@
 
 #ifdef KDB
 	if (debugger_on_panic || kdb_active) {
+		reenter = kdb_active;
+		if (!reenter)
+			kdb_why = KDB_WHY_TRAP;
 		frame->tf_err = eva;	/* smuggle fault address to ddb */
-		if (kdb_trap(type, 0, frame)) {
-			frame->tf_err = code;	/* restore error code */
+		handled = kdb_trap(type, 0, frame);
+		frame->tf_err = code;	/* restore error code */
+		if (!reenter)
+			kdb_why = KDB_WHY_UNSET;
+		if (handled)
 			return;
-		}
-		frame->tf_err = code;		/* restore error code */
 	}
 #endif
 	printf("trap number		= %d\n", type);
Index: sys/powerpc/powerpc/trap.c
===================================================================
--- sys/powerpc/powerpc/trap.c
+++ sys/powerpc/powerpc/trap.c
@@ -449,12 +449,22 @@
 static void
 trap_fatal(struct trapframe *frame)
 {
+#ifdef KDB
+	bool handled, reenter;
+#endif
 
 	printtrap(frame->exc, frame, 1, (frame->srr1 & PSL_PR));
 #ifdef KDB
-	if ((debugger_on_panic || kdb_active) &&
-	    kdb_trap(frame->exc, 0, frame))
-		return;
+	if (debugger_on_panic || kdb_active) {
+		reenter = kdb_active;
+		if (!reenter)
+			kdb_why = KDB_WHY_TRAP;
+		handled = kdb_trap(frame->exc, 0, frame);
+		if (!reenter)
+			kdb_why = KDB_WHY_UNSET;
+		if (handled)
+			return;
+	}
 #endif
 	panic("%s trap", trapname(frame->exc));
 }
Index: sys/sys/kdb.h
===================================================================
--- sys/sys/kdb.h
+++ sys/sys/kdb.h
@@ -101,6 +101,7 @@
 #define	KDB_WHY_UNSET		NULL		/* No reason set. */
 #define	KDB_WHY_PANIC		"panic"		/* panic() was called. */
 #define	KDB_WHY_KASSERT		"kassert"	/* kassert failed. */
+#define	KDB_WHY_TRAP		"trap"		/* Fatal trap. */
 #define	KDB_WHY_SYSCTL		"sysctl"	/* Sysctl entered debugger. */
 #define	KDB_WHY_BOOTFLAGS	"bootflags"	/* Boot flags were set. */
 #define	KDB_WHY_WITNESS		"witness"	/* Witness entered debugger. */