1 files changed, 69 insertions, 0 deletions
diff --git a/lib_i386/realmode.c b/lib_i386/realmode.c
new file mode 100644
index 00000000000..372147cf246
--- /dev/null
+++ b/lib_i386/realmode.c
@@ -0,0 +1,69 @@
+/*
+ * (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>
+
+
+#define REALMODE_BASE    ((char*)0x7c0)
+#define REALMODE_MAILBOX ((char*)0xe00)
+
+
+extern char realmode_enter;
+
+
+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;
+	}
+		
+	/* 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, i386boot_realmode, i386boot_realmode_size);
+		
+	
+	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__ volatile ( 
+		 "lcall $0x20,%0\n"  : :  "i" (&realmode_enter) );
+
+	memcpy(out, REALMODE_MAILBOX, sizeof(struct pt_regs));
+
+	return out->eax;
+}
+