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-rw-r--r--arch/i386/lib/realmode.c100
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
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+++ b/arch/i386/lib/realmode.c
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+/*
+ * (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;
+}