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      1 /*	$NetBSD: diskbuf.c,v 1.7 2017/01/24 11:09:14 nonaka Exp $	*/
      2 
      3 /*
      4  * Copyright (c) 1996
      5  *	Matthias Drochner.  All rights reserved.
      6  *
      7  * Redistribution and use in source and binary forms, with or without
      8  * modification, are permitted provided that the following conditions
      9  * are met:
     10  * 1. Redistributions of source code must retain the above copyright
     11  *    notice, this list of conditions and the following disclaimer.
     12  * 2. Redistributions in binary form must reproduce the above copyright
     13  *    notice, this list of conditions and the following disclaimer in the
     14  *    documentation and/or other materials provided with the distribution.
     15  *
     16  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
     17  * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
     18  * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
     19  * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
     20  * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
     21  * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
     22  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
     23  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
     24  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
     25  * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
     26  *
     27  */
     28 
     29 /* data buffer for BIOS disk / DOS I/O  */
     30 
     31 #include <sys/inttypes.h>
     32 
     33 #include <lib/libsa/stand.h>
     34 #include "diskbuf.h"
     35 
     36 char *diskbufp;		/* allocated from heap */
     37 
     38 const void *diskbuf_user;
     39 
     40 /*
     41  * Global shared "diskbuf" is used as read ahead buffer.
     42  * This MAY have to not cross a 64k boundary.
     43  * In practise it is allocated out of the heap early on...
     44  * NB a statically allocated diskbuf is not guaranteed to not
     45  * cross a 64k boundary.
     46  */
     47 char *
     48 alloc_diskbuf(const void *user)
     49 {
     50 	diskbuf_user = user;
     51 	if (!diskbufp) {
     52 		diskbufp = alloc(DISKBUFSIZE);
     53 #ifndef EFIBOOT
     54 		if (((uintptr_t)diskbufp & 0xffff) + DISKBUFSIZE > 0x10000) {
     55 			printf("diskbufp %" PRIxPTR "\n", (uintptr_t)diskbufp);
     56 			panic("diskbuf crosses 64k boundary");
     57 		}
     58 #endif
     59 	}
     60 	return diskbufp;
     61 }
     62