global smp_bootstrap_corecount;

[bits 16]
smp_trampoline:
cli
hlt
hlt

xor ax, ax
mov ds, ax
lgdt [.gdt_descriptor_p]
mov eax, cr0
or eax, 0x1
mov cr0, eax ; now in long mode

jmp 0x8:.smp_protected


;________________________________________________________________________________________

;TODO find how to use old gdt
.gdt_start_p: ; we need to start with a null gdt
dd 0
dd 0

.gdt_code_p:
dw 0xffff
dw 0x0000
db 0x00
db 10011010b 
db 11001111b
db 0x0000

.gdt_data_p:
dw 0xffff
dw 0x0000
db 0x00
db 10010010b 
db 11001111b
db 0x0000

.gdt_end_p:

.gdt_descriptor_p: 
  dw .gdt_end_p - .gdt_start_p - 1 
dq .gdt_start_p

SMP_PROTECTED_CODE_SEGMENT equ .gdt_code_p - .gdt_start_p
SMP_PROTECTED_DATA_SEGMENT equ .gdt_data_p - .gdt_start_p

;________________________________________________________________________________________

.smp_protected

[bits 32]
mov ax, SMP_PROTECTED_DATA_SEGMENT
mov ds, ax
mov ss, ax
mov es, ax
mov fs, ax
mov gs, ax

mov eax, 0x10000 ;TODO clarify _why_ this is a thing
mov cr3, eax

;setting up misc features
mov eax, cr4         
; PAE, OSFXSR, OSXMMEXCPT
or eax, 1 << 5 | 1 << 9 | 1 << 10
mov cr4, eax         


;set NX and LME
mov eax, 0x80000001
cpuid
and edx, 1 << 20
shr edx, 9
  
mov ecx, 0xc0000080
rdmsr
or eax, 1 << 8 | 1 << 11
or eax, edx
wrmsr

;enable paging 
mov eax, cr0
or eax, 1 << 31 | 1 << 0; 
and ax, ~(1 << 2)
mov cr0, eax

jmp SMP_LONG_CODE_SEGMENT:.counter

;________________________________________________________________________________________

[bits 64]
;TODO do we really need all this?
.gdt_start_l:
;and now we set up a temporary GDT creating a 1:1 mapping
dw 0xffff
dw 0
db 0 ;this is the invalid GDT
db 0
db 1
db 0

;now for the code GDT:
.gdt_code_l:
dw 0 ; segment limit 15:00 (I don't think this matters in 64 bit mode!)
dw 0 ; base address 15:00
db 0 ; base address 23:16
db 10011010b  
db 00100000b 
db 0

.gdt_data_l:
dw 0 
dw 0 
db 0 
db 10010010b  
db 00100000b  
db 0

.gdt_end_l: ; later calculates offset in defs below


.descriptor_l: 
  dw .gdt_end_l - .gdt_start_l - 1 
dq .gdt_start_l

SMP_LONG_CODE_SEGMENT equ .gdt_code_l - .gdt_start_l
SMP_LONG_DATA_SEGMENT equ .gdt_data_l - .gdt_start_l

.counter:
mov rax, [smp_bootstrap_corecount]
inc QWORD [rax]
cli
hlt
;TODO set up stack; enter kernel

smp_bootstrap_corecount: db 0