The BDA is at segment 0x0040 not 0x0000.

The interrupt vector table is technically at 0x0000.

5 files changed, 37 insertions, 31 deletions

diff --git a/src/biosvar.h b/src/biosvar.h
index 2fb4b8d..5c948ca 100644
--- a/src/biosvar.h
+++ b/src/biosvar.h
@@ -12,19 +12,28 @@
 
 
 /****************************************************************
- * Bios Data Area (BDA)
+ * Interupt vector table
  ****************************************************************/
 
 struct ivec {
-    u16 offset;
-    u16 seg;
+    union {
+        struct {
+            u16 offset;
+            u16 seg;
+        };
+        u32 segoff;
+    };
 };
 
+#define SET_IVT(vector, seg, off)                                       \
+    SET_FARVAR(SEG_IVT, ((struct ivec *)0)[vector].segoff, ((seg) << 16) | (off))
+
+
+/****************************************************************
+ * Bios Data Area (BDA)
+ ****************************************************************/
+
 struct bios_data_area_s {
-    // 00:00
-    struct ivec ivecs[256];
-    // 30:00
-//    u8 stack[256];
     // 40:00
     u16 port_com[4];
     u16 port_lpt[3];
diff --git a/src/config.h b/src/config.h
index 13a023a..1ff4606 100644
--- a/src/config.h
+++ b/src/config.h
@@ -107,8 +107,9 @@
 #define BUILD_START_FIXED       0xe050
 
 // Important real-mode segments
+#define SEG_IVT      0x0000
+#define SEG_BDA      0x0040
 #define SEG_BIOS     0xf000
-#define SEG_BDA      0x0000
 
 // Segment definitions in protected mode (see rombios32_gdt in romlayout.S)
 #define SEG32_MODE32_CS    (2 << 3)
diff --git a/src/kbd.c b/src/kbd.c
index 3af7033..f171cf3 100644
--- a/src/kbd.c
+++ b/src/kbd.c
@@ -83,7 +83,7 @@ void
 kbd_setup()
 {
     dprintf(3, "init keyboard\n");
-    u16 x = offsetof(struct bios_data_area_s, kbd_buf) - 0x400;
+    u16 x = offsetof(struct bios_data_area_s, kbd_buf);
     SET_BDA(kbd_mode, 0x10);
     SET_BDA(kbd_buf_head, x);
     SET_BDA(kbd_buf_tail, x);
@@ -117,8 +117,8 @@ enqueue_key(u8 scan_code, u8 ascii_code)
     if (buffer_tail == buffer_head)
         return 0;
 
-    SET_FARVAR(SEG_BDA, *(u8*)(temp_tail+0x400+0), ascii_code);
-    SET_FARVAR(SEG_BDA, *(u8*)(temp_tail+0x400+1), scan_code);
+    SET_FARVAR(SEG_BDA, *(u8*)(temp_tail+0), ascii_code);
+    SET_FARVAR(SEG_BDA, *(u8*)(temp_tail+1), scan_code);
     SET_BDA(kbd_buf_tail, buffer_tail);
     return 1;
 }
@@ -141,8 +141,8 @@ dequeue_key(struct bregs *regs, int incr, int extended)
         cpu_relax();
     }
 
-    u8 ascii_code = GET_FARVAR(SEG_BDA, *(u8*)(buffer_head+0x400+0));
-    u8 scan_code  = GET_FARVAR(SEG_BDA, *(u8*)(buffer_head+0x400+1));
+    u8 ascii_code = GET_FARVAR(SEG_BDA, *(u8*)(buffer_head+0));
+    u8 scan_code  = GET_FARVAR(SEG_BDA, *(u8*)(buffer_head+1));
     if ((ascii_code == 0xF0 && scan_code != 0)
         || (ascii_code == 0xE0 && !extended))
         ascii_code = 0;
diff --git a/src/post.c b/src/post.c
index b53bc75..c7ddb24 100644
--- a/src/post.c
+++ b/src/post.c
@@ -18,13 +18,10 @@
 #include "bregs.h" // struct bregs
 #include "boot.h" // IPL
 
-#define bda ((struct bios_data_area_s *)MAKE_FARPTR(SEG_BDA, 0))
-
 void
 __set_irq(int vector, void *loc)
 {
-    SET_BDA(ivecs[vector].seg, SEG_BIOS);
-    SET_BDA(ivecs[vector].offset, (u32)loc - BUILD_BIOS_ADDR);
+    SET_IVT(vector, SEG_BIOS, (u32)loc - BUILD_BIOS_ADDR);
 }
 
 #define set_irq(vector, func) do {              \
@@ -33,10 +30,9 @@ __set_irq(int vector, void *loc)
     } while (0)
 
 static void
-init_bda()
+init_ivt()
 {
-    dprintf(3, "init bda\n");
-    memset(bda, 0, sizeof(*bda));
+    dprintf(3, "init ivt\n");
 
     // Initialize all vectors to a dummy handler.
     int i;
@@ -66,15 +62,19 @@ init_bda()
 
     // set vector 0x79 to zero
     // this is used by 'gardian angel' protection system
-    SET_BDA(ivecs[0x79].seg, 0);
-    SET_BDA(ivecs[0x79].offset, 0);
+    SET_IVT(0x79, 0, 0);
 
     __set_irq(0x1E, &diskette_param_table2);
 }
 
 static void
-init_ebda()
+init_bda()
 {
+    dprintf(3, "init bda\n");
+
+    struct bios_data_area_s *bda = MAKE_FARPTR(SEG_BDA, 0);
+    memset(bda, 0, sizeof(*bda));
+
     int esize = DIV_ROUND_UP(sizeof(struct extended_bios_data_area_s), 1024);
     SET_BDA(mem_size_kb, 640 - esize);
     u16 eseg = FARPTR_TO_SEG((640 - esize) * 1024);
@@ -83,12 +83,8 @@ init_ebda()
     struct extended_bios_data_area_s *ebda = get_ebda_ptr();
     memset(ebda, 0, sizeof(*ebda));
     ebda->size = esize;
-    SET_BDA(ivecs[0x41].seg, eseg);
-    SET_BDA(ivecs[0x41].offset
-            , offsetof(struct extended_bios_data_area_s, fdpt[0]));
-    SET_BDA(ivecs[0x46].seg, eseg);
-    SET_BDA(ivecs[0x46].offset
-            , offsetof(struct extended_bios_data_area_s, fdpt[1]));
+    SET_IVT(0x41, eseg, offsetof(struct extended_bios_data_area_s, fdpt[0]));
+    SET_IVT(0x46, eseg, offsetof(struct extended_bios_data_area_s, fdpt[1]));
 }
 
 static void
@@ -190,8 +186,8 @@ init_boot_vectors()
 static void
 post()
 {
+    init_ivt();
     init_bda();
-    init_ebda();
 
     pic_setup();
     timer_setup();
diff --git a/src/resume.c b/src/resume.c
index 9db8cad..4ff3133 100644
--- a/src/resume.c
+++ b/src/resume.c
@@ -60,7 +60,7 @@ handle_resume(u8 status)
         // NO BREAK
     case 0x0a:
         // resume execution by jump via 40h:0067h
-#define bda ((struct bios_data_area_s *)0)
+#define bda ((struct bios_data_area_s *)MAKE_FARPTR(SEG_BDA, 0))
         asm volatile(
             "movw %%ax, %%ds\n"
             "ljmpw *%0\n"