1 files changed, 100 insertions, 0 deletions
diff --git a/arch/i386/lib/realmode.c b/arch/i386/lib/realmode.c
new file mode 100644
index 0000000..3c3c1fc
--- /dev/null
+++ b/arch/i386/lib/realmode.c
@@ -0,0 +1,100 @@
+/*
+ * (C) Copyright 2002
+ * Daniel Engström, Omicron Ceti AB, daniel@omicron.se
+ *
+ * See file CREDITS for list of people who contributed to this
+ * project.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License as
+ * published by the Free Software Foundation; either version 2 of
+ * the License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 59 Temple Place, Suite 330, Boston,
+ * MA 02111-1307 USA
+ */
+
+#include <common.h>
+#include <asm/io.h>
+#include <asm/ptrace.h>
+#include <asm/realmode.h>
+
+
+#define REALMODE_BASE    ((char*)0x7c0)
+#define REALMODE_MAILBOX ((char*)0xe00)
+
+
+extern ulong _i386boot_realmode;
+extern ulong _i386boot_realmode_size;
+extern char realmode_enter;
+
+int realmode_setup(void)
+{
+	ulong i386boot_realmode      = (ulong)&_i386boot_realmode;
+	ulong i386boot_realmode_size = (ulong)&_i386boot_realmode_size;
+
+	/* copy the realmode switch code */
+	if (i386boot_realmode_size > (REALMODE_MAILBOX-REALMODE_BASE)) {
+		printf("realmode switch too large (%ld bytes, max is %d)\n",
+		       i386boot_realmode_size, (REALMODE_MAILBOX-REALMODE_BASE));
+		return -1;
+	}
+
+	memcpy(REALMODE_BASE, (void*)i386boot_realmode, i386boot_realmode_size);
+	asm("wbinvd\n");
+
+	return 0;
+}
+
+int enter_realmode(u16 seg, u16 off, struct pt_regs *in, struct pt_regs *out)
+{
+
+	/* setup out thin bios emulation */
+	if (bios_setup()) {
+		return -1;
+	}
+
+	if (realmode_setup()) {
+		return -1;
+	}
+
+	in->eip = off;
+	in->xcs = seg;
+	if (3>(in->esp & 0xffff)) {
+		printf("Warning: entering realmode with sp < 4 will fail\n");
+	}
+
+	memcpy(REALMODE_MAILBOX, in, sizeof(struct pt_regs));
+	asm("wbinvd\n");
+
+	__asm__ volatile (
+		 "lcall $0x20,%0\n"  : :  "i" (&realmode_enter) );
+
+	asm("wbinvd\n");
+	memcpy(out, REALMODE_MAILBOX, sizeof(struct pt_regs));
+
+	return out->eax;
+}
+
+
+/* This code is supposed to access a realmode interrupt
+ * it does currently not work for me */
+int enter_realmode_int(u8 lvl, struct pt_regs *in, struct pt_regs *out)
+{
+	/* place two instructions at 0x700 */
+	writeb(0xcd, 0x700);  /* int $lvl */
+	writeb(lvl, 0x701);
+	writeb(0xcb, 0x702);  /* lret */
+	asm("wbinvd\n");
+
+	enter_realmode(0x00, 0x700, in, out);
+
+	return out->eflags&1;
+}