/*
 * Copyright 2021 Haiku, Inc. All rights reserved.
 * Released under the terms of the MIT License.
 */


#include <asm_defs.h>

#include <arch/x86/descriptors.h>

.text
.code32

/*
extern "C" void arch_enter_kernel(uint32_t pageDirectory, addr_t kernelArgs,
        addr_t kernelEntry, addr_t kernelStackTop,
        struct gdt_idt_descr *gdtDescriptor);
*/
FUNCTION(arch_enter_kernel):

        movl    4(%esp), %edx   // pageDirectory
        movl    8(%esp), %ecx   // kernelArgs
        movl    12(%esp), %ebx  // kernelEntry
        movl    16(%esp), %eax  // kernelStackTop
        movl    20(%esp), %esi  // gdtDescriptor

        // initialize stack
        movl    %eax, %esp

        // ensure that Paging is disabled
        movl    %cr0, %eax
        andl    $0x7fffffff, %eax
        movl    %eax, %cr0

        // ensure that PAE is disabled
        movl    %cr4, %eax
        andl    $0xffffffdf, %eax
        movl    %eax, %cr4

        // set page directory
        movl    %edx, %eax
        movl    %eax, %cr3

        // disable interrupts
        cli

        // clear direction flag
        cld

        // initialize floating point unit
        fninit

        movl    %esi, %eax
        lgdt    (%eax)

        movl    %cr0, %eax
        orl             $0x01, %eax                     // set the PE bit (0) to switch to protected mode
        orl             $0x80000000, %eax       // set the PG bit (31) to enable paging
        movl    %eax, %cr0

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

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

        //return
        movl    $-1, %eax
        ret
FUNCTION_END(arch_enter_kernel)