guard kernel against being overwritten by config environment

drbio/biosinit.asm

@@ -515,7 +515,10 @@ dos_r70:
 	pop 	es
 load_e10:
 	call	add_comspec_to_env	; append / update COMSPEC in config env
+if BIO_SEG ge 70h
+	; relocate config environment to segment 60 if kernel is not in the way
 	call	copy_config_env_to_seg60
+endif
 	mov	ax,(MS_X_EXEC * 256)+0	; Exec the Command Processor
 	mov	bx,offset exec_env	; Get the Parameter Block Address
 	mov	dx,offset shell		; and the Command Processor

drbio/genercfg.asm

@@ -4040,15 +4040,16 @@ INITDATA ends
 
 INITENV		segment public para 'INITDATA'
 Public envstart
-envstart	db	251 dup (0)	; initial env buffer
-Public envend
+envstart	db	251 dup (0)	; <<< initial env buffer, copied to seg 60
+Public envend				; 
 envend		dw	0		; make it double null terminated
 		db	1Ah		; EOF marker env buffer
 	Public	boot_options, boot_switches
 boot_options	dw	0
 boot_switches	db	0
 ; set by BIOS to either the SHIFT states, or to F5KEY or F8KEY
-
+					; >>> end of range copied to seg 60
+					;     may not exceed 256 bytes
 EXE_LENGTH	equ	001Ch
 
 exeBuffer	label word