Index: sys/amd64/amd64/db_trace.c
===================================================================
--- sys/amd64/amd64/db_trace.c
+++ sys/amd64/amd64/db_trace.c
@@ -202,7 +202,7 @@
     db_addr_t callpc, void *frame)
 {
 
-	db_printf("%s() at ", name);
+	db_printf("%s() at ", name != NULL ? name : "??");
 	db_printsym(callpc, DB_STGY_PROC);
 	if (frame != NULL)
 		db_printf("/frame 0x%lx", (register_t)frame);
@@ -334,7 +334,7 @@
 
 static int
 db_backtrace(struct thread *td, struct amd64_frame *frame, db_addr_t pc,
-    int count)
+    register_t rsp, int count)
 {
 	struct amd64_frame *actframe;
 #define MAXNARG	16
@@ -356,7 +356,20 @@
 
 		actframe = frame;
 		if (first) {
-			if (strcmp(name, "fork_trampoline") == 0) {
+			first = FALSE;
+			if (sym == C_DB_SYM_NULL && rsp != 0) {
+				/*
+				 * If a symbol couldn't be found, we've probably
+				 * jumped to a bogus location, so try and use
+				 * the return address to find our caller.
+				 */
+				db_print_stack_entry(name, 0, 0, 0, pc, NULL);
+				pc = db_get_value(rsp, 8, FALSE);
+				if (db_search_symbol(pc, DB_STGY_PROC,
+				    &offset) == C_DB_SYM_NULL)
+					break;
+				continue;
+			} else if (strcmp(name, "fork_trampoline") == 0) {
 				/*
 				 * Don't try to walk back on a stack for a
 				 * process that hasn't actually been run yet.
@@ -365,7 +378,6 @@
 				    actframe);
 				break;
 			}
-			first = FALSE;
 		}
 
 		argp = &actframe->f_arg0;
@@ -412,7 +424,7 @@
 	frame = (struct amd64_frame *)rbp;
 	callpc = (db_addr_t)db_get_value((long)&frame->f_retaddr, 8, FALSE);
 	frame = frame->f_frame;
-	db_backtrace(curthread, frame, callpc, -1);
+	db_backtrace(curthread, frame, callpc, 0, -1);
 }
 
 int
@@ -422,7 +434,7 @@
 
 	ctx = kdb_thr_ctx(thr);
 	return (db_backtrace(thr, (struct amd64_frame *)ctx->pcb_rbp,
-	    ctx->pcb_rip, count));
+	    ctx->pcb_rip, ctx->pcb_rsp, count));
 }
 
 int