diff --git a/plat/msdos386/descr b/plat/msdos386/descr
index d7be3eb1e..b6683871b 100644
--- a/plat/msdos386/descr
+++ b/plat/msdos386/descr
@@ -46,7 +46,7 @@ name led
 	program {EM}/lib/ack/em_led
 	mapflag -l* LNAME={PLATFORMDIR}/lib*
 	mapflag -fp FLOATS={EM}/{ILIB}fp
-	args {ALIGN} {SEPID} \
+	args {ALIGN} \
 		({RTS}:.b=-u _i_main) \
 	    (.e:{HEAD}={PLATFORMDIR}/boot.o) \
 		({RTS}:.ocm.bas.b={PLATFORMDIR}/c-ansi.o) \
@@ -66,7 +66,6 @@ name led
 		           {PLATFORMDIR}/libc.a \
 		           {PLATFORMDIR}/libem.a \
 		           {PLATFORMDIR}/libend.a)
-
 	linker
 end
 name cv
diff --git a/plat/msdos386/libsys/brk.s b/plat/msdos386/libsys/brk.s
index 0e3170467..3032bc929 100644
--- a/plat/msdos386/libsys/brk.s
+++ b/plat/msdos386/libsys/brk.s
@@ -7,17 +7,12 @@
 
 .sect .text
 
-.extern realloc_ptr
-
 .define _brk
 _brk:
-	enter 0, 0
-newsize = 2*4
-
-	mov eax, newsize(ebp)
+	mov ebx, esp
+	mov eax, 1*4(ebx)
 	callf (realloc_ptr)
 	xor eax, eax
-	leave
 	ret
 
 
diff --git a/plat/msdos386/libsys/close.s b/plat/msdos386/libsys/close.s
index 5e52a638b..412307b62 100644
--- a/plat/msdos386/libsys/close.s
+++ b/plat/msdos386/libsys/close.s
@@ -16,8 +16,8 @@
 
 .define _close
 _close:
-	mov ebx, sp
-	mov ebx, 4(ebx)
+	mov ebx, esp
+	mov ebx, 1*4(esp)
 	movb ah, 0x3E
 	int 0x21
 	jmp .sys_zret
diff --git a/plat/msdos386/libsys/isatty.s b/plat/msdos386/libsys/isatty.s
index 7ed92fffd..794274bfa 100644
--- a/plat/msdos386/libsys/isatty.s
+++ b/plat/msdos386/libsys/isatty.s
@@ -16,7 +16,7 @@
 
 .define _isatty
 _isatty:
-	mov ebx, sp
+	mov ebx, esp
 	mov ebx, 4(ebx)
 	o16 mov ax, 0x4400
 	int 0x21
diff --git a/plat/msdos386/libsys/rename.s b/plat/msdos386/libsys/rename.s
index 1550b73db..4b43a0d48 100644
--- a/plat/msdos386/libsys/rename.s
+++ b/plat/msdos386/libsys/rename.s
@@ -16,12 +16,39 @@
 
 .define _rename
 _rename:
-	int 3
-	mov bx, sp
-	push di
-	mov dx, 2(bx)
-	mov di, 4(bx)
+	mov ebx, esp
+	push esi
+	push edi
+
+	! Source filename.
+
+	mov esi, 4(ebx)
+    movzx edi, (transfer_buffer_ptr)
+    mov es, (pmode_ds)
+    cld
+1:
+	lodsb
+	stosb
+	testb al, al
+	jnz 1b
+	
+	! Destination filename.
+
+	mov eax, edi
+	mov esi, 8(ebx)
+1:
+	lodsb
+	stosb
+	testb al, al
+	jnz 1b
+	
+	! Make the DOS call.
+
+	o16 mov dx, (transfer_buffer_ptr)
+	o16 mov di, ax
 	movb ah, 0x56
-	int 0x21
-	pop di
+	or ebx, 0x210000
+	callf (interrupt_ptr)
+	pop edi
+	pop esi
 	jmp .sys_zret
diff --git a/plat/msdos386/libsys/sys_exists.s b/plat/msdos386/libsys/sys_exists.s
index 8786f4c2a..f57d28b3e 100644
--- a/plat/msdos386/libsys/sys_exists.s
+++ b/plat/msdos386/libsys/sys_exists.s
@@ -16,11 +16,10 @@
 
 .define __sys_exists
 __sys_exists:
-	int 3
-	mov bx, sp
-	mov dx, 2(bx)
-	mov ax, 0x4300
+	mov ebx, esp
+	mov edx, 4(ebx)
+	mov eax, 0x4300
 	int 0x21
-	sbb ax, ax
-	inc ax
+	sbb eax, eax
+	inc eax
 	ret
diff --git a/plat/msdos386/libsys/sys_getdate.s b/plat/msdos386/libsys/sys_getdate.s
index eeb118923..981253b93 100644
--- a/plat/msdos386/libsys/sys_getdate.s
+++ b/plat/msdos386/libsys/sys_getdate.s
@@ -16,11 +16,10 @@
 
 .define __sys_getdate
 __sys_getdate:
-	int 3
 	movb ah, 0x2a
 	int 0x21
-	mov bx, sp
-	mov bx, 2(bx)
-	mov (bx), dx
-	mov 2(bx), cx
+	mov ebx, esp
+	mov ebx, 4(ebx)
+	o16 mov 0(ebx), dx
+	o16 mov 2(ebx), cx
 	ret
diff --git a/plat/msdos386/libsys/sys_gettime.s b/plat/msdos386/libsys/sys_gettime.s
index d3ea65847..a565ea860 100644
--- a/plat/msdos386/libsys/sys_gettime.s
+++ b/plat/msdos386/libsys/sys_gettime.s
@@ -16,11 +16,10 @@
 
 .define __sys_gettime
 __sys_gettime:
-	int 3
 	movb ah, 0x2c
 	int 0x21
-	mov bx, sp
-	mov bx, 2(bx)
-	mov (bx), cx
-	mov 2(bx), dx
+	mov ebx, esp
+	mov ebx, 2(ebx)
+	o16 mov 0(ebx), cx
+	o16 mov 2(ebx), dx
 	ret
diff --git a/plat/msdos386/libsys/sys_isopen.s b/plat/msdos386/libsys/sys_isopen.s
index 5da95a44e..5a5fed07c 100644
--- a/plat/msdos386/libsys/sys_isopen.s
+++ b/plat/msdos386/libsys/sys_isopen.s
@@ -17,11 +17,10 @@
 
 .define __sys_isopen
 __sys_isopen:
-	int 3
-	mov bx, sp
-	mov bx, 2(bx)
-	mov ax, 0x4400
+	mov ebx, esp
+	mov ebx, 4(bx)
+	mov eax, 0x4400
 	int 0x21
-	sbb ax, ax
-	inc ax
+	sbb eax, eax
+	inc eax
 	ret
diff --git a/plat/msdos386/libsys/sys_isreadyr.s b/plat/msdos386/libsys/sys_isreadyr.s
index ff3960b27..9a646adc8 100644
--- a/plat/msdos386/libsys/sys_isreadyr.s
+++ b/plat/msdos386/libsys/sys_isreadyr.s
@@ -17,13 +17,13 @@
 
 .define __sys_isreadyr
 __sys_isreadyr:
-	mov ebx, sp
+	mov ebx, esp
 	mov eax, 0x4406
 	mov ebx, 4(ebx)
 	int 0x21
 	jnc ok
 	movb al, 0
 ok:
-	cbw
-	cwd
+	o16 cbw
+	cwde
 	ret
diff --git a/plat/msdos386/libsys/sys_rawcreat.s b/plat/msdos386/libsys/sys_rawcreat.s
index 0d765a27d..b15df3f4f 100644
--- a/plat/msdos386/libsys/sys_rawcreat.s
+++ b/plat/msdos386/libsys/sys_rawcreat.s
@@ -16,10 +16,30 @@
 
 .define __sys_rawcreat
 __sys_rawcreat:
-	int 3
+	! Copy filename to transfer buffer.
+
+	mov ebx, esp
+	push esi
+	push edi
+	mov esi, 4(ebx)
+    movzx edi, (transfer_buffer_ptr)
+    mov es, (pmode_ds)
+    cld
+1:
+	lodsb
+	stosb
+	testb al, al
+	jnz 1b
+
+	! Make the DOS call.
+
 	movb ah, 0x3c
-	mov bx, sp
-	mov dx, 2(bx)
-	mov cx, 4(bx)
-	int 0x21
+	movzx edx, (transfer_buffer_ptr)
+	movb al, 8(ebx)
+	or ebx, 0x210000
+	callf (interrupt_ptr)
+
+	pop edi
+	pop esi
 	jmp .sys_axret
+
diff --git a/plat/msdos386/libsys/sys_rawlseek.s b/plat/msdos386/libsys/sys_rawlseek.s
index 06a7783a7..c38a1e0b1 100644
--- a/plat/msdos386/libsys/sys_rawlseek.s
+++ b/plat/msdos386/libsys/sys_rawlseek.s
@@ -16,12 +16,11 @@
 
 .define __sys_rawlseek
 __sys_rawlseek:
-	int 3
 	movb ah, 0x42
-	mov bx, sp
-	mov dx, 4(bx)
-	mov cx, 6(bx)
-	movb al, 8(bx)
-	mov bx, 2(bx)
+	mov ebx, esp
+	mov edx, 8(bx)
+	mov ecx, 12(bx)
+	movb al, 16(bx)
+	mov ebx, 4(bx)
 	int 0x21
 	jmp .sys_dxaxret
diff --git a/plat/msdos386/libsys/sys_rawopen.s b/plat/msdos386/libsys/sys_rawopen.s
index 5fae1bba4..bb4ff5acb 100644
--- a/plat/msdos386/libsys/sys_rawopen.s
+++ b/plat/msdos386/libsys/sys_rawopen.s
@@ -16,10 +16,30 @@
 
 .define __sys_rawopen
 __sys_rawopen:
-	int 3
+	! Copy filename to transfer buffer.
+
+	mov ebx, esp
+	push esi
+	push edi
+
+	mov esi, 4(ebx)
+    movzx edi, (transfer_buffer_ptr)
+    mov es, (pmode_ds)
+    cld
+1:
+	lodsb
+	stosb
+	testb al, al
+	jnz 1b
+
+	! Make the DOS call.
+
 	movb ah, 0x3d
-	mov bx, sp
-	mov dx, 2(bx)
-	movb al, 4(bx)
-	int 0x21
+	o16 mov dx, (transfer_buffer_ptr)
+	movb al, 8(ebx)
+	or ebx, 0x210000
+	callf (interrupt_ptr)
+
+	pop edi
+	pop esi
 	jmp .sys_axret
diff --git a/plat/msdos386/libsys/sys_rawread.s b/plat/msdos386/libsys/sys_rawread.s
index c54410347..f5b0c1a35 100644
--- a/plat/msdos386/libsys/sys_rawread.s
+++ b/plat/msdos386/libsys/sys_rawread.s
@@ -12,12 +12,6 @@
 
 .sect .text
 
-.extern pmode_ds
-.extern pmode_cs
-.extern rmode
-.extern transfer_buffer_ptr
-.extern interrupt_ptr
-
 ! Read bytes from a file descriptor.  These routines do not do any
 ! translation between CRLF and LF line endings.
 !
@@ -27,6 +21,8 @@
 .define __sys_rawread
 __sys_rawread:
 	enter 0, 0
+	push esi
+	push edi
 file_handle = 2*4
 write_buffer = 3*4
 amount_to_read = 4*4
@@ -43,7 +39,6 @@ amount_to_read = 4*4
 	movb ah, 0x3f
 	o16 mov dx, (transfer_buffer_ptr)
 	o16 mov bx, file_handle(ebp)
-	mov ecx, 0x80
 	or ebx, 0x210000
 	callf (interrupt_ptr)
 	jnc success
@@ -52,8 +47,8 @@ amount_to_read = 4*4
 
 	push eax
 	call __sys_seterrno
-	leave
-	ret
+	pop ecx
+	jmp exit
 success:
 
 	! Copy eax bytes out of the transfer buffer.
@@ -71,6 +66,9 @@ success:
 	loop 1b
 	pop eax
 
+exit:
+	pop edi
+	pop esi
 	leave
 	ret
 
diff --git a/plat/msdos386/libsys/sys_rawwrite.s b/plat/msdos386/libsys/sys_rawwrite.s
index 5451670fe..3ac3a7e16 100644
--- a/plat/msdos386/libsys/sys_rawwrite.s
+++ b/plat/msdos386/libsys/sys_rawwrite.s
@@ -12,12 +12,6 @@
 
 .sect .text
 
-.extern pmode_ds
-.extern pmode_cs
-.extern rmode
-.extern transfer_buffer_ptr
-.extern interrupt_ptr
-
 ! Write bytes to/to a file descriptor.  These routines do not do any
 ! translation between CRLF and LF line endings.
 !
@@ -27,6 +21,8 @@
 .define __sys_rawwrite
 __sys_rawwrite:
     enter 0, 0
+    push esi
+    push edi
 file_handle = 2*4
 read_buffer = 3*4
 amount_to_write = 4*4
@@ -59,7 +55,10 @@ amount_to_write = 4*4
 
     push eax
     call __sys_seterrno
+    pop ecx
 exit:
+    pop edi
+    pop esi
     leave
     ret
 
diff --git a/plat/msdos386/libsys/unlink.s b/plat/msdos386/libsys/unlink.s
index 912f6958d..7d023ad48 100644
--- a/plat/msdos386/libsys/unlink.s
+++ b/plat/msdos386/libsys/unlink.s
@@ -16,8 +16,29 @@
 
 .define _unlink
 _unlink:
-	mov bx, sp
-	mov dx, 2(bx)
+	! Copy filename to transfer buffer.
+
+	mov ebx, esp
+	push esi
+	push edi
+
+	mov esi, 4(ebx)
+    movzx edi, (transfer_buffer_ptr)
+    mov es, (pmode_ds)
+    cld
+1:
+	lodsb
+	stosb
+	testb al, al
+	jnz 1b
+
+	! Make the DOS call.
+
+    movzx edi, (transfer_buffer_ptr)
 	movb ah, 0x41
-	int 0x21
+	or ebx, 0x210000
+	callf (interrupt_ptr)
+
+	pop edi
+	pop esi
 	jmp .sys_zret
diff --git a/plat/msdos386/stub.s b/plat/msdos386/stub.s
index 35b9e8e40..219d66470 100644
--- a/plat/msdos386/stub.s
+++ b/plat/msdos386/stub.s
@@ -321,24 +321,21 @@ interrupt:
     mov (dpmi_ds), ax
     mov (dpmi_ss), ax
     push es
-    push ds
-    mov ax, dosstack            ! auto stack is too small
-    mov (dpmi_sp), ax
+    mov (dpmi_sp), dosstack     ! auto stack is too small
     push ds
     pop es
-    mov di, dpmi_edi
+    o32 mov edi, dpmi_edi
     mov ax, 0x300
     o32 shr ebx, 16
     int 0x31                    ! simulate DOS interrupt
-    pop ds
     pop es
-    pushf
     o32 movzx eax, (dpmi_eax)
     o32 movzx ebx, (dpmi_ebx)
     o32 movzx ecx, (dpmi_ecx)
     o32 movzx edx, (dpmi_edx)
     o32 movzx esi, (dpmi_esi)
     o32 movzx edi, (dpmi_edi)
+    push (dpmi_flags)
     popf
     ret