diff --git a/mach/vax4/libbsd4_1a/head_em.s b/mach/vax4/libbsd4_1a/head_em.s
index 24808a8e6..05d288a95 100644
--- a/mach/vax4/libbsd4_1a/head_em.s
+++ b/mach/vax4/libbsd4_1a/head_em.s
@@ -9,6 +9,7 @@
 .define	.limhp
 .define	.trppc
 .define	.trpim
+.define EXIT, BRK, WRITE
 
 	! run time startoff
 	.data2	0
@@ -29,11 +30,36 @@
 	pushl	r2
 	pushl	r1
 	calls	$3,__m_a_i_n
+EXIT:
 	movl	$Im2,ap
 	movl	r0,6(ap)
 	chmk	(ap)+
 	halt
 
+break = 17
+
+.align	1
+BRK:
+	.data2	0x0000
+	chmk	$break
+	bcc 	1f
+	jmp 	errmon
+1:
+	movl	4(ap),.limhp
+	clrl	r0
+	ret
+
+write = 4
+
+.align	1
+WRITE:
+	.data2	0x0000
+	chmk	$write
+	bcc	1f
+	jmp	errmon
+1:
+	ret
+
 	.sect .data
 Im2:
 	.data2	1
diff --git a/mach/vax4/libbsd4_2/head_em.s b/mach/vax4/libbsd4_2/head_em.s
index 861c0d23c..3f49aad35 100644
--- a/mach/vax4/libbsd4_2/head_em.s
+++ b/mach/vax4/libbsd4_2/head_em.s
@@ -9,6 +9,7 @@
 .define	.limhp
 .define	.trppc
 .define	.trpim
+.define EXIT,WRITE,BRK
 
 	! run time startoff
 	.data2	0
@@ -29,11 +30,32 @@
 	pushl	r2
 	pushl	r1
 	calls	$3,__m_a_i_n
+EXIT:
 	movl	$Im2,ap
 	movl	r0,6(ap)
 	chmk	(ap)+
 	halt
 
+DEFINE(WRITE)
+	chmk	$SYS_write
+	bcs	1f
+	ret
+1:
+	jmp	cerror
+
+DEFINE(BRK)
+	cmpl	4(ap),$endbss
+	bgeq	1f
+	movl	$endbss,4(ap)
+1:
+	chmk	$17
+	bcs	1f
+	movl	4(ap),.limhp
+	clrl	r0
+	ret
+1:
+	jmp	cerror
+
 	.sect .data
 Im2:
 	.data2	1
diff --git a/mach/vax4/libsysV_2/head_em.s b/mach/vax4/libsysV_2/head_em.s
index 24808a8e6..473164834 100644
--- a/mach/vax4/libsysV_2/head_em.s
+++ b/mach/vax4/libsysV_2/head_em.s
@@ -9,6 +9,7 @@
 .define	.limhp
 .define	.trppc
 .define	.trpim
+.define EXIT,WRITE,BRK
 
 	! run time startoff
 	.data2	0
@@ -29,11 +30,34 @@
 	pushl	r2
 	pushl	r1
 	calls	$3,__m_a_i_n
+EXIT:
 	movl	$Im2,ap
 	movl	r0,6(ap)
 	chmk	(ap)+
 	halt
 
+write = 4
+WRITE:
+	.data2	0x0000
+	chmk	$write
+	bcc 	1f
+	jmp 	cerror
+1:
+	ret
+
+
+break = 17
+
+BRK:
+	.data2	0x0000
+	chmk	$break
+	bcc 	1f
+	jmp 	cerror
+1:
+	movl	4(ap),.limhp
+	clrl	r0
+	ret
+
 	.sect .data
 Im2:
 	.data2	1