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move unreal mode hackery back to stage2.nasm

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This commit is contained in:
Elaina Claus
2025-09-05 20:32:19 -04:00
parent 66e8e3c7fc
commit 4e5112b45b
1 changed files with 58 additions and 1 deletions
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59
src/stage2/stage2.nasm
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@@ -198,9 +198,66 @@ hcf:
; ##############################
;
; SYSTEM CONFIGURATION FUNCTIONS
; SYSTEM CONFIGURATION FUNCTIONS & MACROS
;
; ##############################
; set ds and es segments back to the base of the loader
%ifnmacro __TINY_DS_ES
%macro __TINY_DS_ES 0
mov ax, __STAGE2_SEGMENT
mov ds, ax
mov es, ax
%endmacro
%endif
; for copying between locations in high memory
%ifnmacro __REFLAT_DS_ES
%macro __REFLAT_DS_ES 0
cli ; no interrupts
lgdt [((__STAGE2_SEGMENT << 4) + unreal_gdt_info)] ; load unreal gdt
mov eax, cr0
or eax, 1 ; set pmode bit
mov cr0, eax ; switch to pmode
jmp short $+2 ; i-cache flush
mov ax, 0x10 ; select descriptor 2
mov ds, ax
mov es, ax
mov eax, cr0
and eax, ~1 ; toggle bit 1 of cr0
mov cr0, eax ; back to realmode
jmp short $+2 ; i-cache flush
sti
%endmacro
%endif
; for copying from low memory to high memory (ds on a real segment, es in flat mode)
%ifnmacro __REFLAT_ES
%macro __REFLAT_ES 0
cli ; no interrupts
lgdt [((__STAGE2_SEGMENT << 4) + unreal_gdt_info)] ; load unreal gdt
mov eax, cr0
or eax, 1 ; set pmode bit
mov cr0, eax ; switch to pmode
jmp short $+2 ; i-cache flush
mov ax, 0x10 ; select descriptor 2
mov es, ax
mov eax, cr0
and eax, ~1 ; toggle bit 1 of cr0
mov cr0, eax ; back to realmode
jmp short $+2 ; i-cache flush
sti
%endmacro
%endif
ALIGN 4, db 0x90
EnterUnrealMode:
__BOCHS_MAGIC_DEBUG