blob: 372147cf246afee0adbdb05021ce0140792bcb4b [file] [log] [blame]
wdenk2262cfe2002-11-18 00:14:45 +00001/*
2 * (C) Copyright 2002
3 * Daniel Engström, Omicron Ceti AB, daniel@omicron.se
4 *
5 * See file CREDITS for list of people who contributed to this
6 * project.
7 *
8 * This program is free software; you can redistribute it and/or
9 * modify it under the terms of the GNU General Public License as
10 * published by the Free Software Foundation; either version 2 of
11 * the License, or (at your option) any later version.
12 *
13 * This program is distributed in the hope that it will be useful,
14 * but WITHOUT ANY WARRANTY; without even the implied warranty of
15 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
16 * GNU General Public License for more details.
17 *
18 * You should have received a copy of the GNU General Public License
19 * along with this program; if not, write to the Free Software
20 * Foundation, Inc., 59 Temple Place, Suite 330, Boston,
21 * MA 02111-1307 USA
22 */
23
24#include <common.h>
25#include <asm/io.h>
26#include <asm/ptrace.h>
27
28
29#define REALMODE_BASE ((char*)0x7c0)
30#define REALMODE_MAILBOX ((char*)0xe00)
31
32
33extern char realmode_enter;
34
35
36int enter_realmode(u16 seg, u16 off, struct pt_regs *in, struct pt_regs *out)
37{
38
39 /* setup out thin bios emulation */
40 if (bios_setup()) {
41 return -1;
42 }
43
44 /* copy the realmode switch code */
45 if (i386boot_realmode_size > (REALMODE_MAILBOX-REALMODE_BASE)) {
46 printf("realmode switch too large (%ld bytes, max is %d)\n",
47 i386boot_realmode_size, (REALMODE_MAILBOX-REALMODE_BASE));
48 return -1;
49 }
50
51 memcpy(REALMODE_BASE, i386boot_realmode, i386boot_realmode_size);
52
53
54 in->eip = off;
55 in->xcs = seg;
56 if (3>in->esp & 0xffff) {
57 printf("Warning: entering realmode with sp < 4 will fail\n");
58 }
59
60 memcpy(REALMODE_MAILBOX, in, sizeof(struct pt_regs));
61
62 __asm__ volatile (
63 "lcall $0x20,%0\n" : : "i" (&realmode_enter) );
64
65 memcpy(out, REALMODE_MAILBOX, sizeof(struct pt_regs));
66
67 return out->eax;
68}
69