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added another __REFLAT variant

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This commit is contained in:
Elaina Claus
2025-09-05 16:28:01 -04:00
parent 31d05c35e5
commit 9a478aa4d4
2 changed files with 29 additions and 4 deletions
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29
include/cdecl16.inc
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@@ -69,6 +69,7 @@
%endmacro
%endif
; 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
@@ -77,6 +78,7 @@
%endmacro
%endif
; for copying between locations in high memory
%ifnmacro __REFLAT_DS_ES
%macro __REFLAT_DS_ES 0
cli ; no interrupts
@@ -88,8 +90,31 @@
jmp short $+2 ; i-cache flush
mov ax, 0x10 ; select descriptor 2
mov ds, ax ; 10h = 0001_0000b
mov es, ax ; es to big data
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

2
src/stage2/stage2.nasm
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@@ -226,7 +226,7 @@ EnterUnrealMode:
sti ; re-enable interupts
; set ds, es to the STAGE2_SEGMENT, for our model (generally) ds == es == cs
; fs, gs & ss are all still huge data model, and the macro "__REFLAT_DS_ES" exists
; fs, gs & ss are all still huge data model, and the macro(s) "__REFLAT_xxx" exists
; to easily access data outside of 64KiB boundries using ds/es addressing
__TINY_DS_ES