; Project name	:	XTIDE Universal BIOS
; Description	:	Functions to access BOOTVARS struct.

; Section containing code
SECTION .text

;--------------------------------------------------------------------
; Stores POST stack pointer to BOOTVARS.
;
; BootVars_StorePostStackPointer
;	Parameters:
;		DS:		BDA and Interrupt Vector segment (zero)
;	Returns:
;		Nothing
;	Corrupts registers:
;		AX
;--------------------------------------------------------------------
ALIGN JUMP_ALIGN
BootVars_StorePostStackPointer:
	pop		ax							; Pop return address
	mov		[BOOTVARS.dwPostStack], sp
	mov		[BOOTVARS.dwPostStack+2], ss
	jmp		ax


;--------------------------------------------------------------------
; Initializes stack for boot menu usage.
; POST stack is not large enough when DPTs are stored to 30:0h.
;
; BootVars_SwitchToBootMenuStack
;	Parameters:
;		Nothing
;	Returns:
;		SS:SP:	Pointer to top of Boot Menu stack
;	Corrupts registers:
;		AX
;--------------------------------------------------------------------
ALIGN JUMP_ALIGN
BootVars_SwitchToBootMenuStack:
	pop		ax							; Pop return address
	cli									; Disable interrupts
	LOAD_BDA_SEGMENT_TO	ss, sp
	mov		sp, BOOTVARS.rgbMnuStack	; Load offset to stack
	sti									; Enable interrupts
	jmp		ax


;--------------------------------------------------------------------
; Restores SS and SP to initial boot loader values.
;
; BootVars_SwitchBackToPostStack
;	Parameters:
;		Nothing
;	Returns:
;		SS:SP:	Ptr to POST stack
;	Corrupts registers:
;		AX
;--------------------------------------------------------------------
ALIGN JUMP_ALIGN
BootVars_SwitchBackToPostStack:
	pop		ax							; Pop return address
	cli									; Disable interrupts
	LOAD_BDA_SEGMENT_TO	ss, sp
;	eLSS	sp, ss:BOOTVARS.dwPostStack	; Expanded macro to remove
										; unneeded CLI instruction
%ifndef USE_386
	mov		sp, [ss:BOOTVARS.dwPostStack]
	mov		ss, [ss:BOOTVARS.dwPostStack+2]
%else
	lss		sp, [ss:BOOTVARS.dwPostStack]
%endif
	sti									; Enable interrupts
	jmp		ax