nivirx/stevia
1
0
Fork 0
Code Issues 1 Pull Requests Actions Packages Projects Releases 1 Wiki Activity

move far jump setup in EnterUnrealMode to right after we save CS

Browse Source
This commit is contained in:
Elaina Claus
2024-10-11 21:51:07 -04:00
parent 59678149e0
commit 60aaf5cdd9
1 changed files with 14 additions and 14 deletions
Download Patch File Download Diff File Expand all files Collapse all files

28
src/stage2/stage2.nasm
View File

@@ -284,33 +284,33 @@ EnterUnrealMode:
push gs
push ss
push cs ; save real mode code selector
lgdt [unreal_gdt_info]
push cs ; save real mode code selector
pop ax ; save cs to ax to setup far jump
mov word [ds:__UNREAL_SEGMENT], ax
mov eax, cr0 ; switch to pmode
or al,1 ; set pmode bit
mov cr0, eax
jmp $+2
lgdt [unreal_gdt_info]
mov eax, cr0
or al,1 ; set pmode bit
mov cr0, eax ; switch to pmode
jmp $+2 ; clear instruction cache
;jmp far 0x0008:EnterUnrealMode.load_cs
db 0xEA ; jmp far imm16:imm16
dw EnterUnrealMode.load_cs ; error_far_ptr
dw 0x0008 ; error_far_seg
.load_cs:
mov bx, 0x10 ; select descriptor 2
mov ds, bx ; 10h = 0001_0000b
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 desc. 2
mov gs, bx ; other data/stack to index 2 (off 0x10)
and al,0xFE ; back to realmode
mov cr0, eax ; by toggling bit again
jmp $+2
and al,0xFE ; toggle bit 1 of cr0
mov cr0, eax ; back to realmode
jmp $+2 ; clear instruction cache again
pop ax ; save cs to ax to setup far jump
mov word [ds:__UNREAL_SEGMENT], ax
;jmp far 0x0008:EnterUnrealMode.unload_cs
db 0xEA ; jmp far imm16:imm16
dw EnterUnrealMode.unload_cs ; error_far_ptr