Index: sys/kern/kern_prot.c
===================================================================
--- sys/kern/kern_prot.c
+++ sys/kern/kern_prot.c
@@ -158,24 +158,36 @@
 #endif
 int
 sys_getpgid(struct thread *td, struct getpgid_args *uap)
+{
+	pid_t pgid;
+	int error;
+
+	error = kern_getpgid(td, uap->pid, &pgid);
+	if (error == 0)
+		td->td_retval[0] = pgid;
+	return (error);
+}
+
+int
+kern_getpgid(struct thread *td, pid_t pid, pid_t *pgid)
 {
 	struct proc *p;
 	int error;
 
-	if (uap->pid == 0) {
+	if (pid == 0) {
 		p = td->td_proc;
 		PROC_LOCK(p);
 	} else {
-		p = pfind(uap->pid);
+		p = pfind(pid);
 		if (p == NULL)
 			return (ESRCH);
 		error = p_cansee(td, p);
-		if (error) {
+		if (error != 0) {
 			PROC_UNLOCK(p);
 			return (error);
 		}
 	}
-	td->td_retval[0] = p->p_pgrp->pg_id;
+	*pgid = p->p_pgrp->pg_id;
 	PROC_UNLOCK(p);
 	return (0);
 }
Index: sys/sys/syscallsubr.h
===================================================================
--- sys/sys/syscallsubr.h
+++ sys/sys/syscallsubr.h
@@ -158,6 +158,7 @@
 int	kern_getfsstat(struct thread *td, struct statfs **buf, size_t bufsize,
 	    size_t *countp, enum uio_seg bufseg, int mode);
 int	kern_getitimer(struct thread *, u_int, struct itimerval *);
+int	kern_getpgid(struct thread *, pid_t, pid_t *);
 int	kern_getppid(struct thread *);
 int	kern_getpeername(struct thread *td, int fd, struct sockaddr **sa,
 	    socklen_t *alen);