--- linux/kernel/chr_drv/mem.c	2018/04/24 18:08:20	1.1.1.1
+++ linux/kernel/chr_drv/mem.c	2018/04/24 18:11:51	1.1.1.3
@@ -154,6 +154,17 @@ static int write_port(struct inode * ino
 	return tmp-buf;
 }
 
+static int read_zero(struct inode *node,struct file *file,char *buf,int count)
+{
+	int left;
+
+	for (left = count; left > 0; left--) {
+		put_fs_byte(0,buf);
+		buf++;
+	}
+	return count;
+}
+
 /*
  * The memory devices use the full 32 bits of the offset, and so we cannot
  * check against negative addresses: they are ok. The return value is weird,
@@ -192,6 +203,8 @@ static int mem_read(struct inode * inode
 			return 0;	/* /dev/null */
 		case 4:
 			return read_port(inode,file,buf,count);
+		case 5:
+			return read_zero(inode,file,buf,count);
 		default:
 			return -ENODEV;
 	}
@@ -210,6 +223,8 @@ static int mem_write(struct inode * inod
 			return count;	/* /dev/null */
 		case 4:
 			return write_port(inode,file,buf,count);
+		case 5:
+			return count; /* /dev/zero */
 		default:
 			return -ENODEV;
 	}
@@ -226,9 +241,10 @@ static struct file_operations mem_fops =
 	NULL		/* no special release code */
 };
 
-void chr_dev_init(void)
+long chr_dev_init(long mem_start, long mem_end)
 {
 	chrdev_fops[1] = &mem_fops;
-	tty_init();
-	lp_init();
+	mem_start = tty_init(mem_start);
+	mem_start = lp_init(mem_start);
+	return mem_start;
 }