; ke_helpers.asm
.code

; void KeFlushGdt(GDTR* pGdtr, uint16_t codeSel, uint16_t dataSel, uint16_t tssSel);
KeFlushGdt PROC
    ; RCX = pGdtr (pointer to limit/base struct)
    ; RDX = codeSel
    ; R8 = dataSel
    ; R9 = tssSel

    ; 1. Load the GDT
    lgdt fword ptr [rcx]

    ; 2. Reload Data Segments
    mov ax, r8w
    mov ds, ax
    mov es, ax
    mov ss, ax
    mov fs, ax
    mov gs, ax

    ; 3. Load Task Register
    mov ax, r9w
    ltr ax

    ; 4. Reload Code Segment (Far Return)
    ; In MASM64, use OFFSET to get the address of the label.
    ; We push the selector, then the offset, then issue retff / retfq.

    push rdx                     ; Push new Code Selector (RDX)
    lea  rax, [reload_cs]        ; RIP-relative address of the label
    push rax                     ; Push "return" address
    db 048h, 0CBh                ; rex_w retf (effectively retfq)

reload_cs:
    ret
KeFlushGdt ENDP

; void KeFlushIdt(IDTR* pIdtr);
KeFlushIdt PROC
    lidt fword ptr [rcx]
    ret
KeFlushIdt ENDP

; KCPU* KeReadCurrentCpuFromGs(void);
; GS:0 contains KCPU.Self while executing in the kernel.
KeReadCurrentCpuFromGs PROC
    mov rax, qword ptr gs:[0]
    ret
KeReadCurrentCpuFromGs ENDP

END