make unreal mode unreal again

include/BIOS/func/video.nasm

@@ -26,20 +26,20 @@ SetTextMode:
     xor ah, ah                  ; Set Video mode BIOS function
     mov al, 0x03                ; 16 color 80x25 Text mode
     int 0x10                    ; Call video interrupt
-                                ; TODO: check for carry and clear carry before call
+                                
 
     mov ah, 0x05                ; Select active display page BIOS function
     xor al, al                  ; page 0
     int 0x10                    ; call video interrupt
-                                ; TODO: check for carry and clear carry before call
 .endp:
     popf
     __CDECL16_EXIT
     ret
 
-; disables blinking text mode cursor
+; disables blinking text mode cursor via crtc pokes
+; 0x3D4/0x3D5 for color, mono at 0x3B4/0x3B5
 ALIGN 4, db 0x90
-disable_cursor:
+disable_cursor_crtc:
     __CDECL16_ENTRY
 .func:
     mov dx, 0x3D4
@@ -53,6 +53,24 @@ disable_cursor:
     __CDECL16_EXIT
     ret
 
+; disables blinking text mode cursor via BIOS int 10h, ah = 01
+ALIGN 4, db 0x90
+disable_cursor_bios:
+    __CDECL16_ENTRY
+.func:
+    push bx
+    mov  ah, 03h      ; read cursor pos & shape
+    xor  bh, bh
+    int  10h          ; CH=top scanline, CL=bottom
+
+    or   ch, 20h      ; set bit 5 = disable
+    mov  ah, 01h      ; set leaf 01h
+    int  10h
+    pop  bx
+.endp:
+    __CDECL16_EXIT
+    ret
+
 ; Prints a C-Style string (null terminated) using BIOS vga teletype call
 ; void PrintString(char* buf)
 ALIGN 4, db 0x90

include/cdecl16.inc

@@ -14,14 +14,17 @@
 ;     along with this program.  If not, see <https://www.gnu.org/licenses/>.
 
 %ifnmacro __CDECL16_ENTRY
-%macro __CDECL16_ENTRY 0
+%macro __CDECL16_ENTRY 0-1
     push bp
     mov bp, sp
-    sub sp, 0x10
 
     push si
     push di
     push bx
+
+    %if %0 = 1
+    sub  sp, %1        ; reserve locals only when needed
+    %endif
 %endmacro
 %endif
 

src/mbr/mbr.nasm

@@ -58,7 +58,7 @@ init:
     cld
     rep stosb                         ; zero bss section
 
-    sub sp, 0x20                    ; local varible space
+    sub sp, 0x20                    ; local varible space (32 bytes)
     push bp                         ; setup top of stack frame
 
     xor cx, cx
@@ -96,7 +96,7 @@ main:
         mov ah, 0x41
         mov bx, 0x55AA
         mov dl, 0x80
-        
+
         clc
         int 0x13
         jnc main.find_active

src/stage2/stage2.nasm

@@ -149,7 +149,7 @@ main:
     add sp, 0x6
 
     call SetTextMode
-    call disable_cursor
+    call disable_cursor_bios
     print_string HelloPrompt_info
     
     ; enable A20 gate
@@ -185,14 +185,6 @@ main:
 hcf:
     ERROR STEVIA_DEBUG_OK
 
-; ##############################
-;
-; SYSTEM CONFIGURATION FUNCTIONS
-;
-; ##############################
-
-
-
 ; ##############################
 ;
 ; SYSTEM CONFIGURATION FUNCTIONS
@@ -201,56 +193,38 @@ hcf:
 ALIGN 4, db 0x90
 EnterUnrealMode:
     __CDECL16_ENTRY
-.func:
-    cli                         ; no interrupts
-    push ds                     ; save real mode data/stack selectors
-    push es
-    push fs
-    push gs
-    push ss
-
-    push cs                               ; save real mode code selector
-    xor ax, ax                            ;
-    pop ax                                ; save cs to ax to setup far jump
-    mov word [__UNREAL_SEGMENT], ax    
-
+    cli                                   ; no interrupts
+.func:    
     lgdt [((__STAGE2_SEGMENT << 4) + unreal_gdt_info)]                 ; load unreal gdt
 
     mov eax, cr0                          
     or al,1                               ; set pmode bit
     mov cr0, eax                          ; switch to pmode
-    jmp short $+2
+    jmp short $+2                         ; i-cache flush
 
-    ;jmp far 0x0008:EnterUnrealMode.load_cs
+    ; set cs to a pm code segment (0x8) w/ the following
+    ;jmp far 0x0008:EnterUnrealMode.set_segs
     db 0xEA                               ; jmp far imm16:imm16
-    dw EnterUnrealMode.load_cs            ; error_far_ptr
+    dw EnterUnrealMode.set_segs            ; error_far_ptr
     dw 0x0008                             ; error_far_seg
-.load_cs:
-    mov bx, 0x10                          ; select descriptor 2
-    mov ds, bx                            ; 10h = 0001_0000b
-                  
-    mov ss, bx
-    mov es, bx
-    mov fs, bx
-    mov gs, bx                            ; other data/stack to index 2 (off 0x10)
-    
+.set_segs:
+    mov ax, 0x10                          ; select descriptor 2
+    mov ds, ax                            ; 10h = 0001_0000b
+    mov es, ax                            ; es to big data
+
+    mov ss, ax                            ; big stack
+    mov fs, ax
+    mov gs, ax                            ; extra segments to big data as well
+.pm_start:
+    ; code here is running in protected mode
+.pm_end:
+    mov eax, cr0
     and al,0xFE                           ; toggle bit 1 of cr0
     mov cr0, eax                          ; back to realmode
-    jmp short $+2
-    
-    ;jmp far 0x0008:EnterUnrealMode.unload_cs
-    db 0xEA                               ; jmp far imm16:imm16
-    dw EnterUnrealMode.unload_cs          ; error_far_ptr
-__UNREAL_SEGMENT:
-    dw 0x0000                             ; error_far_seg
-EnterUnrealMode.unload_cs:
-    pop ss
-    pop gs
-    pop fs
-    pop es
-    pop ds                                ; get back old segments
-    sti
+    jmp short $+2                         ; i-cache flush
+  
 .endp:
+    sti                                   ; re-enable interupts
     __CDECL16_EXIT
     ret
 end_text:

src/vbr/vbr.nasm

@@ -72,7 +72,7 @@ init:
     cld
     rep stosb                          
     
-    sub sp, 0x20                    ; local varible space
+    sub sp, 0x20                    ; local varible space (32 bytes)
     push bp
 
     sti                             ; all done with inital setup and relocation, reenable interupts