/*
 * Copyright 2021-2022 Haiku, Inc. All rights reserved.
 * Released under the terms of the MIT License.
 *
 * Copyright 2001, Travis Geiselbrecht. All rights reserved.
 * Copyright 2012, Alex Smith, alex@alex-smith.me.uk.
 * Distributed under the terms of the NewOS License.
 */

// Relocatable. Before calling, smp_trampoline_args should point
// to a struct trampoline_args (see smp.cpp). This pointer should
// be 16-byte aligned, below 1MB and identity-mapped.
.globl smp_trampoline
.globl smp_trampoline_end
.globl smp_trampoline_args

#include <asm_defs.h>

#include <arch/x86/descriptors.h>
#include "mmu.h"

.code16
smp_trampoline:
        cli

//  movl 0xdeadbeef, esi
        .byte 0x66
        .byte 0xbe
smp_trampoline_args:
        .long 0xdeadbeef

        // Set up the stack pointer for 16-bit mode
        movl %esi, %eax
        shrl $4, %eax
        movw %ax, %ss
        xorw %sp, %sp

        popl %ebx               // trampoline

        // Initialize GDT
        popl %edx               // gdt
        lgdt (%edx)

        // Switch to protected mode
        movl   %cr0, %eax
        orl    $0x01, %eax
        movl   %eax, %cr0

        pushl  $KERNEL_CODE_SELECTOR
        leal  (trampoline_32 - smp_trampoline)(%ebx), %eax
        pushl  %eax
.code32
        .byte 0x66
        lret

trampoline_32:
        // Set data segments.
        movw   $KERNEL_DATA_SELECTOR, %ax
        movw   %ax, %ds
        movw   %ax, %es
        movw   %ax, %fs
        movw   %ax, %gs
        movw   %ax, %ss

        // Set up the stack pointer for 32-bit mode
        movl    %esi, %esp
        addl    $8, %esp

        // Point CR3 to the kernel's page dir.
        popl    %eax            // page_dir
        movl    %eax, %cr3

        popl    %ebx            // kernel_entry
        popl    %ecx            // kernel_args
        popl    %edx            // current_cpu

        // Set the stack pointer, write to the sentinel and clear the stack frame
        popl    %ebp            // stack_top
        movl    $0, (%esp)      // sentinel
        movl    %ebp, %esp
        xorl    %ebp, %ebp

        movl    $0x80010021, %eax
        movl    %eax, %cr0

        cli
        cld
        fninit

        pushl   %edx            // currentCpu
        pushl   %ecx            // kernelArgs
        pushl   $0x0            // fake return address
        pushl   $KERNEL_CODE_SELECTOR
        pushl   %ebx            // kernelEntry
        lret
smp_trampoline_end: