3 * Daniel Engström, Omicron Ceti AB, <daniel@omicron.se>
5 * See file CREDITS for list of people who contributed to this
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.
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.
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,
26 #include <asm/ptrace.h>
27 #include <asm/realmode.h>
29 #define REALMODE_MAILBOX ((char *)0xe00)
31 int realmode_setup(void)
33 ulong realmode_start = (ulong)&__realmode_start + gd->reloc_off;
34 ulong realmode_size = (ulong)&__realmode_size;
36 /* copy the realmode switch code */
37 if (realmode_size > (REALMODE_MAILBOX - (char *)REALMODE_BASE)) {
38 printf("realmode switch too large (%ld bytes, max is %d)\n",
40 (int)(REALMODE_MAILBOX - (char *)REALMODE_BASE));
44 memcpy((char *)REALMODE_BASE, (void *)realmode_start, realmode_size);
50 int enter_realmode(u16 seg, u16 off, struct pt_regs *in, struct pt_regs *out)
53 /* setup out thin bios emulation */
62 if ((in->esp & 0xffff) < 4)
63 printf("Warning: entering realmode with sp < 4 will fail\n");
65 memcpy(REALMODE_MAILBOX, in, sizeof(struct pt_regs));
69 "lcall $0x20,%0\n" : : "i" (&realmode_enter));
72 memcpy(out, REALMODE_MAILBOX, sizeof(struct pt_regs));
78 * This code is supposed to access a realmode interrupt
79 * it does currently not work for me
81 int enter_realmode_int(u8 lvl, struct pt_regs *in, struct pt_regs *out)
83 /* place two instructions at 0x700 */
84 writeb(0xcd, 0x700); /* int $lvl */
86 writeb(0xcb, 0x702); /* lret */
89 enter_realmode(0x00, 0x700, in, out);
91 return out->eflags & 0x00000001;