/**
 * PROJECT:         ExectOS
 * COPYRIGHT:       See COPYING.md in the top level directory
 * FILE:            xtldr/i686/memory.c
 * DESCRIPTION:     EFI memory management for i686 target
 * DEVELOPERS:      Rafal Kupiec <belliash@codingworkshop.eu.org>
 */

#include <xtos.h>


/**
 * Builds the actual memory mapping page table and enables paging. This routine exits EFI boot services as well.
 *
 * @param MemoryMappings
 *        Supplies a pointer to linked list containing all memory mappings.
 *
 * @param VirtualAddress
 *        Supplies a pointer to the next valid, free and available virtual address.
 *
 * @param ImageProtocol
 *        A pointer to the EFI loaded image protocol with information about where in memory the loader code was placed.
 *
 * @param PtePointer
 *        Supplies a pointer to memory area containing a Page Table Entries (PTE).
 *
 * @return This routine returns a status code.
 *
 * @since XT 1.0
 */
XTCDECL
EFI_STATUS
XtEnablePaging(IN PXTBL_PAGE_MAPPING PageMap)
{
    PCPUID_REGISTERS CpuRegisters = NULL;
    EFI_STATUS Status;

    /* Prepare CPUID registers */
    CpuRegisters->Leaf = CPUID_GET_CPU_FEATURES;
    CpuRegisters->SubLeaf = 0;
    CpuRegisters->Eax = 0;
    CpuRegisters->Ebx = 0;
    CpuRegisters->Ecx = 0;
    CpuRegisters->Edx = 0;

    /* Get CPUID */
    ArCpuId(CpuRegisters);

    /* Store PAE status from the CPUID results */
    if(!(CpuRegisters->Edx & CPUID_FEATURES_EDX_PAE))
    {
        /* No PAE support */
        XtLdrProtocol->Debug.Print(L"ERROR: PAE extension not supported by the CPU\n");
        return STATUS_EFI_UNSUPPORTED;
    }

    /* Build page map */
    Status = XtLdrProtocol->Memory.BuildPageMap(PageMap, 0xC0000000);
    if(Status != STATUS_EFI_SUCCESS)
    {
        /* Failed to build page map */
        XtLdrProtocol->Debug.Print(L"Failed to build page map (Status code: %zX)\n", Status);
        return Status;
    }

    /* Exit EFI Boot Services */
    XtLdrProtocol->Debug.Print(L"Exiting EFI boot services\n");
    Status = XtLdrProtocol->Util.ExitBootServices();
    if(Status != STATUS_EFI_SUCCESS)
    {
        /* Failed to exit boot services */
        XtLdrProtocol->Debug.Print(L"Failed to exit boot services (Status code: %zX)\n", Status);
        return STATUS_EFI_ABORTED;
    }

    /* Enable Physical Address Extension (PAE) */
    ArWriteControlRegister(4, ArReadControlRegister(4) | CR4_PAE);

    /* Write page mappings to CR3 */
    ArWriteControlRegister(3, (UINT_PTR)PageMap->PtePointer);

    /* Enable paging */
    ArWriteControlRegister(0, ArReadControlRegister(0) | CR0_PG);

    /* Return success */
    return STATUS_EFI_SUCCESS;
}