/*ZealOS runs exclusively in ring 0.
Ring 0 is part of the Charter.
This demo is for you to play around
with ring 3.    ZealOS is for
recreational programming, after all.

This redirects the general protection
fault, switches to ring 3, and generates
a fault to switch back.

U8 *old_stack, *new_rip;

asm {
INT_TO_RING0::  //Set to handle general protection 0xD fault temporarily.
                INC         U64 [SYS_PROGRESS1]
                PUSH        U32 CGDT.ds         //STACKSEG
                MOV         RAX, U64 [&old_stack]
                PUSH        RAX
                PUSH        U32 0                   //FLAGS--interrupts off
                PUSH        U32 CGDT.cs64
                MOV         RAX, U64 [&new_rip]
                PUSH        RAX

U0 Ring3Demo()
    U8 *old_vect;

    "Progress1 Before:%X\n", progress1;
    old_vect = IntEntrySet(0x0D, INT_TO_RING0, IDTET_TRAP);

    TSSBusy(Gs->tss->tr_ring3, OFF);
    RAXSet(Gs->tss->tr_ring3 + 3);
    LTR     AX

    asm {
        MOV U64 [&old_stack], RSP

        LEA     RAX, [R3_CALLBACK]
        MOV     U64 [&new_rip], RAX

        MOV     AX, CGDT.ds_ring3 + 3
        MOV     DS, AX
        MOV     ES, AX

        PUSH    U32 CGDT.ds_ring3 + 3       //STACKSEG
        PUSH    U64 [&old_stack]
        PUSH    U32 0                   //FLAGS--interrupts off
        PUSH    U32 CGDT.cs64_ring3 + 3
        LEA     RAX, [R3_START]
        PUSH    RAX

        INC U64 [SYS_PROGRESS1]
        CLI //This causes general protection fault #13

        MOV AX, CGDT.ds
        MOV DS, AX
        MOV ES, AX

    TSSBusy(Gs->tss->tr, OFF);
    LTR     AX

    IntEntrySet(0x0D, old_vect, IDTET_IRQ);
    "Progress1 After :%X\n", progress1;