Apply by doing:
       cd /usr/src
       patch -p0 < 006_locore.patch

And then rebuild your kernel.

Index: sys/arch/alpha/alpha/locore.s
===================================================================
RCS file: /cvs/src/sys/arch/alpha/alpha/locore.s,v
retrieving revision 1.10
retrieving revision 1.11
diff -u -r1.10 -r1.11
--- sys/arch/alpha/alpha/locore.s       1999/09/26 11:07:32     1.10
+++ sys/arch/alpha/alpha/locore.s       1999/11/13 21:33:44     1.11
@@ -1,4 +1,4 @@
-/*     $OpenBSD: locore.s,v 1.10 1999/09/26 11:07:32 kstailey Exp $    */
+/*     $OpenBSD: locore.s,v 1.11 1999/11/13 21:33:44 deraadt Exp $     */
/*     $NetBSD: locore.s,v 1.27 1996/12/03 19:54:16 cgd Exp $  */

/*
@@ -858,7 +858,9 @@
       LDGP(pv)

       mov     a2, t0                  /* t0 = i = len */
-       beq     a2, Lcopystr2           /* if (len == 0), bail out */
+       bne     a2, Lcopystr1           /* if (len != 0), proceed */
+       ldiq    t1, 1                   /* else bail */
+       br      zero, Lcopystr2

Lcopystr1:
       ldq_u   t1, 0(a0)               /* t1 = *from */
@@ -882,7 +884,7 @@
Lcopystr3:
       beq     t1, Lcopystr4           /* *from == '\0'; leave quietly */

-       ldiq    v0, ENAMETOOLONG                /* *from != '\0'; error. */
+       ldiq    v0, ENAMETOOLONG        /* *from != '\0'; error. */
       RET

Lcopystr4: