; Generic high-level syscall handler
[EXTERN syscall_handler]

; Low-level interrupt based system call entry function
[GLOBAL syscall_entry]

[SECTION .text]

; The SystemV ABI for x64 uses the register `rdi`, `rsi`, `rdx`, `rcx`, `r8` and
; `r9` to pass the first six parameters of a function. Since  every syscall can
; have a maximum of 5 parameters, these register will just be forwarded (without
; requiring any additional operation), having the syscall number stored in `rdi`.
; The return value will be stored in `rax`.
ALIGN 8
syscall_entry:
	; Interrupt Context Pointer (7th Parameter)
	push rsp

	; Clear direction flag for string operations
	cld

	; Call the high-level (C++) system call handler
    sti
	call syscall_handler
    cli

	; Optional: Prevent kernel information leakage
	; by zeroing scratch registers
	mov rdi, 0
	mov rsi, 0
	mov rdx, 0
	mov rcx, 0
	mov r8,  0
	mov r9,  0
	mov r10, 0
	mov r11, 0

	; Drop 7th parameter
	add rsp, 8

	; Return from interrupt entry function
	iretq