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BITS 64
org 0x00100000 ;Space for a small stack?

;**************
;*** HEADER ***
;**************

section .header
DOS_HEADER:
        dw 0x5a4d ;DOS Magic number
   times 29 dw 0 ;Zeroes
   dd 0x00000080 ;Address of PE header

DOS_STUB:
        ; I don't know how to write this as text, so you get zeroes
   times 32 dw 0

PE_HEADER:
        dd 0x00004550 ;PE Magic number
   dw 0x8664 ;Building for x86 architecture
   dw 2 ;Two sections (.text, .data)
   dd 0x632F9A00 ;number of seconds between 00:00:00 1st January 1970 and 00:00:00 1st June 2023
   dd 0x0 ;No symbol table
   dd 0x0 ;No symbols in the non-existent symbol table!
   dw oSize ;The size of the entire optional header. See the OPTIONAL_HEADER_END label for the calculation.
   dw 0x1002 ;Is a valid image file, is a system file. No other fancy characteristics.

oSize equ OPTIONAL_HEADER_END - OPTIONAL_HEADER_STANDARD_FIELDS

OPTIONAL_HEADER_STANDARD_FIELDS: ;Not actually optional
        dw 0x020b ;PE32+ Executable. I want my 64-bit registers!
   dw 0x0 ;What linker?
   dd 1024 ;The size of the code segment
   dd 1024 ;The size of the data segment
   dd 0x0 ;No .bss section. All variables to be initialised.
   dd 1024 ;The program's entry point
   dd 1024 ;The program's first instruction. Same as the start of the code execution.

OPTIONAL_HEADER_WINDOWS_FIELDS: ;
        dq 0x00100000 ;The entry point of the image
   dd 0x1024 ;The section alignment
   dd 0x1024 ;The file alignment
   dw 0x0 ;No operating system requirements
   dw 0x0 ;Stil no operating system requirements
   dw 0x0 ;Major image version number
   dw 0x1 ;Minor image version number
   dw 0x0 ;Major subsystem version. Doesn't matter, as long as it supports UEFI.
   dw 0x0 ;Minor subsystem version. Doesn't matter, as long as it supports UEFI.
   dd 0x0 ;A dedicated zero
   dd 3072 ;Image size
   dd 1024 ;Header size
   dd 0x0 ;Checksum //TODO ADD LATER
   dw 0x000A ;UEFI Subsystem number.
   dw 0x0 ;Not a DLL, so this can be zero

   ;Using PE32+ file type, so the following are dqs, not dds
   dq 0x8000 ;Amount of stack space to reserve
   dq 0x8000 ;Amount of stack space to commit immediately
   dq 0x8000 ;Amount of local heap space to reserve
   dq 0x0 ;Amount of local heap space to commit immediately. Hopefully not needed.
   dd 0x0 ;Another four bytes dedicated to being zeroes
   dd 0x0 ;Number of data dictionary entries

;OPTIONAL_HEADER_DATA_DIRECTORIES: ;

OPTIONAL_HEADER_END: ;This label is required for calculating value of oSize

        SECTION_TABLE: ;as if you don't have enough information already :\
.1: ;text section
   dq `.text` ;The name of the text section
   dd 1024 ;virtual size.
   dd 1024 ;virtual entry point address.
   dd 1024 ;actual size.
   dd 1024 ;actual entry point address.
   dd 0 ;No relocations
   dd 0 ;No line numbers
   dw 0 ;No relocations
   dw 0 ;No line numbers
   dd 0x60000020 ;Contains executable code, can be executed as code, can be read.

.2: ;data section
        dq `.data` ;The name of the data section
   dd 1024 ;virtual size.
   dd 2048 ;virtual entry point address.
   dd 1024 ;actual size.
   dd 2048 ;actual entry point address.
   dd 0 ;No relocations
   dd 0 ;No line numbers
   dw 0 ;No relocations
   dw 0 ;No line numbers
   dd 0xc0000040 ;Contains initialised data, can be read, can be written to.

times 1024 - ($-$$) db 0 ;alignment

;*****************
;*** MAIN CODE ***
;*****************

section .text follows=.header
vars:
        ;Function return codes.
   EFI_SUCCESS equ 0

   ;Offsets for loading function addresses
   OFFSET_TABLE_BOOT_SERVICES equ 96
   OFFSET_TABLE_ERROR_CONSOLE equ 80
   OFFSET_TABLE_OUTPUT_CONSOLE equ 64
   OFFSET_TABLE_RUNTIME_SERVICES equ 88
   OFFSET_BOOT_EXIT_PROGRAM equ 216
   OFFSET_BOOT_STALL equ 248
   OFFSET_CONSOLE_OUTPUT_STRING equ 8

start:
        sub rsp, 6*8+8 
        mov [r_RDX], rdx
        mov [r_RCX], rcx
        mov rcx, [rdx+OFFSET_TABLE_BOOT_SERVICES]
        mov rax, [rcx+40]
        mov rcx, pointerSize ; first argument
        call rax
        call reg_to_hex ; show function's return value
        
        jmp $
; --------- read register's content in hex
reg_to_hex:
        ; rax is argument of the content 
        ; 'quadword' that we want to show
        push rsi
        push rdi
        push rbx
        mov rdi, reg_hex_converted
        mov rcx, 64
        .loop:
                push rax
                sub rcx, 4
                sar rax, cl
                and rax, 0xf
                lea rsi, [codes + rax]
                mov rbx, 0
                mov byte bl, [rsi]
                mov word [rdi], bx
                add rdi, 2
                pop rax
                test rcx, rcx
                jnz .loop
        mov rcx, [r_RDX]
        mov rcx, [rcx + 64]
        mov rax, [rcx+8]
        mov rdx, reg_hex_converted
        call rax
        pop rbx
        pop rdi
        pop rsi
        ret

; ----------------------------------------
times 1024 - ($-$$) db 0 ;alignment
    

;************
;*** DATA ***
;************

section .data follows=.text

dataStart:
    r_RDX: dq 0
    r_RCX: dq 0
    r_RAX: dq 0
    reg_hex_converted: db __utf16__ `XXXXXXXXXXXXXXXX\r\n\0`
    codes: db '0123456789ABCDEF'
    pointerSize: dq 4096
times 1024 - ($-$$) db 0 ;alignment

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   dd 0 ;No relocations
   dw 0 ;No relocations
   dd 0 ;No relocations
   dw 0 ;No relocations

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        mov rax, [rcx+40]

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        mov rcx, pointerSize ; first argument