From 4e5112b45b27793a1f7929f6d7dec349e9377b24 Mon Sep 17 00:00:00 2001
From: Elaina Claus <elaina.claus@chtm.me>
Date: Fri, 5 Sep 2025 20:32:19 -0400
Subject: [PATCH] move unreal mode hackery back to stage2.nasm

---
 src/stage2/stage2.nasm | 59 +++++++++++++++++++++++++++++++++++++++++-
 1 file changed, 58 insertions(+), 1 deletion(-)

diff --git a/src/stage2/stage2.nasm b/src/stage2/stage2.nasm
index c0ec4dc..6b9025d 100755
--- a/src/stage2/stage2.nasm
+++ b/src/stage2/stage2.nasm
@@ -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