Index: share/man/man5/core.5
===================================================================
--- share/man/man5/core.5
+++ share/man/man5/core.5
@@ -82,6 +82,8 @@
 process name.
 .It Em \&%P
 processes PID.
+.It Em \&%S
+signal during core.
 .It Em \&%U
 process UID.
 .El
Index: sys/kern/kern_sig.c
===================================================================
--- sys/kern/kern_sig.c
+++ sys/kern/kern_sig.c
@@ -3433,7 +3433,7 @@
  */
 static int
 corefile_open(const char *comm, uid_t uid, pid_t pid, struct thread *td,
-    int compress, struct vnode **vpp, char **namep)
+    int compress, int signum, struct vnode **vpp, char **namep)
 {
 	struct sbuf sb;
 	struct nameidata nd;
@@ -3482,6 +3482,9 @@
 			case 'P':	/* process id */
 				sbuf_printf(&sb, "%u", pid);
 				break;
+			case 'S':	/* signal number */
+				sbuf_printf(&sb, "%i", signum);
+				break;
 			case 'U':	/* user id */
 				sbuf_printf(&sb, "%u", uid);
 				break;
@@ -3599,7 +3602,7 @@
 	PROC_UNLOCK(p);
 
 	error = corefile_open(p->p_comm, cred->cr_uid, p->p_pid, td,
-	    compress_user_cores, &vp, &name);
+	    compress_user_cores, p->p_sig, &vp, &name);
 	if (error != 0)
 		return (error);