LXR uboot/lib_i386/realmode.c

   1/*
   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#include <asm/realmode.h>
  28
  29
  30#define REALMODE_BASE    ((char*)0x7c0)
  31#define REALMODE_MAILBOX ((char*)0xe00)
  32
  33
  34extern ulong _i386boot_realmode;
  35extern ulong _i386boot_realmode_size;
  36extern char realmode_enter;
  37
  38int realmode_setup(void)
  39{
  40        ulong i386boot_realmode      = (ulong)&_i386boot_realmode;
  41        ulong i386boot_realmode_size = (ulong)&_i386boot_realmode_size;
  42
  43        /* copy the realmode switch code */
  44        if (i386boot_realmode_size > (REALMODE_MAILBOX-REALMODE_BASE)) {
  45                printf("realmode switch too large (%ld bytes, max is %d)\n",
  46                       i386boot_realmode_size, (REALMODE_MAILBOX-REALMODE_BASE));
  47                return -1;
  48        }
  49
  50        memcpy(REALMODE_BASE, (void*)i386boot_realmode, i386boot_realmode_size);
  51        asm("wbinvd\n");
  52
  53        return 0;
  54}
  55
  56int enter_realmode(u16 seg, u16 off, struct pt_regs *in, struct pt_regs *out)
  57{
  58
  59        /* setup out thin bios emulation */
  60        if (bios_setup()) {
  61                return -1;
  62        }
  63
  64        if (realmode_setup()) {
  65                return -1;
  66        }
  67
  68        in->eip = off;
  69        in->xcs = seg;
  70        if (3>(in->esp & 0xffff)) {
  71                printf("Warning: entering realmode with sp < 4 will fail\n");
  72        }
  73
  74        memcpy(REALMODE_MAILBOX, in, sizeof(struct pt_regs));
  75        asm("wbinvd\n");
  76
  77        __asm__ volatile (
  78                 "lcall $0x20,%0\n"  : :  "i" (&realmode_enter) );
  79
  80        asm("wbinvd\n");
  81        memcpy(out, REALMODE_MAILBOX, sizeof(struct pt_regs));
  82
  83        return out->eax;
  84}
  85
  86
  87/* This code is supposed to access a realmode interrupt
  88 * it does currently not work for me */
  89int enter_realmode_int(u8 lvl, struct pt_regs *in, struct pt_regs *out)
  90{
  91        /* place two instructions at 0x700 */
  92        writeb(0xcd, 0x700);  /* int $lvl */
  93        writeb(lvl, 0x701);
  94        writeb(0xcb, 0x702);  /* lret */
  95        asm("wbinvd\n");
  96
  97        enter_realmode(0x00, 0x700, in, out);
  98
  99        return out->eflags&1;
 100}
 101