[mubios] Initialize IVT, BDA and EBDA.

Signed-off-by: Richard Qin <richard.qin.x@gmail.com>

1 files changed, 47 insertions, 0 deletions

diff --git a/mubios/core/bda.c b/mubios/core/bda.c
new file mode 100644
index 0000000..d626963
--- /dev/null
+++ b/mubios/core/bda.c
@@ -0,0 +1,47 @@
+/*
+ RCC-Project
+
+ Copyright (C) 2026 Richard Qin
+
+ This file is part of RCC-Project.
+
+ RCC-Project 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 3 of the License, or (at your option) any
+ later version.
+
+ RCC-Project 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
+ RCC-Project; see the file COPYING.  If not see
+ <http://www.gnu.org/licenses/>.
+ */
+
+#include "bios.h"
+
+extern u8 __ebda_start[];
+
+static void
+store_u16 (volatile u8 *address, u16 value)
+{
+  address[0] = (u8)(value & 0x00FFu);
+  address[0] = (u8)(value >> 8);
+}
+
+void
+bda_init (void)
+{
+  volatile u8 *bda;
+  u32 ebda_base;
+
+  bda = (volatile u8 *)MUBIOS_BDA_BASE;
+  ebda_base = (u32)__ebda_start;
+
+  store_u16 (bda + BDA_EBDA_SEGMENT_OFFSET, (u16)(ebda_base >> 4));
+
+  store_u16 (bda + BDA_EQUIPMENT_OFFSET, (u16)(ebda_base >> 4));
+
+  store_u16 (bda + BDA_CONVENTIONAL_MEMORY_OFFSET, (u16)(ebda_base >> 10));
+}