;=----------------------------------------------------------------------------=;
;                            OS on Kaleid                                      ;
;                                                                              ;
;   Desc: System call & userspace related functions                            ;
;                                                                              ;
;                                                                              ;
;   Copyright © 2018-2021 The OS/K Team                                        ;
;                                                                              ;
;   This file is part of OS/K.                                                 ;
;                                                                              ;
;   OS/K is free software: you can redistribute it and/or modify               ;
;   it under the terms of the GNU General Public License as published by       ;
;   the Free Software Foundation, either version 3 of the License, or          ;
;   (at your option) any later version.                                        ;
;                                                                              ;
;   OS/K is distributed in the hope that it will be useful,                    ;
;   but WITHOUT ANY WARRANTY; without even the implied warranty of             ;
;   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the              ;
;   GNU General Public License for more details.                               ;
;                                                                              ;
;   You should have received a copy of the GNU General Public License          ;
;   along with OS/K.  If not, see <https://www.gnu.org/licenses/>.             ;
;=----------------------------------------------------------------------------=;

[BITS 64]

%include "kaleid/kernel/ke/cpuf.inc"

global KeJumpToUserspace

KeJumpToUserspace:

    # rdi = user args
    # rsi = entry point in user space
    # rdx = user space stack

    mov rax, 0x1b ; Selector 0x18 (User Data) + RPL 3
    mov ds, ax
    mov es, ax

    # Build a fake iret frame
    push rax          # Selector 0x18 (User Data) + RPL 3
    push rdx          # User space stack
    push 0x202        # rflags = interrupt enable + reserved bit
    push 0x23         # Selector 0x20 (User Code) + RPL 3
    push rsi          # Entry point in user space
    
    xor rax, rax

    iretq