//----------------------------------------------------------------------------//
//                           GNU GPL OS/K                                     //
//                                                                            //
//  Desc:         Paging memory related functions                             //
//                                                                            //
//                                                                            //
//  Copyright © 2018-2019 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         //
//  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/>.            //
//----------------------------------------------------------------------------//

#include <kernel.h>
#include <init/boot.h>
#include <ke/idt.h>
#include <ex/malloc.h>
#include <mm/heap.h>
#include <mm/paging.h>
#include <mm/map.h>
#include <lib/buf.h>
#include <io/vga.h>

//-----------

static pml4_t MmPageMapLevel4[512] __attribute__((__aligned__(KPAGESIZE)));
static ulong *MmPhysicalPageTable __attribute__((__aligned__(KPAGESIZE)));

extern ulong _text;
extern ulong _text_end;
extern ulong _rodata;
extern ulong _rodata_end;
extern ulong _data;
extern ulong _data_end;

extern MemoryMap_t memoryMap;

static ulong MmStackGuards[2] = { 0 };
ulong MmVirtLastAddress = 0;
ulong MmPhysLastKernAddress = 0;

//-----------

//
// Creates our new page table structure and loads it
//
void MmInitPaging(void)
{
    pdpe_t *MmPDP = NULL;
    pde_t *MmPD = NULL;
    pte_t *MmPT = NULL;
    ulong index, xedni;
    ulong curAddrPML4;
    ulong curAddrPDP;
    ulong curAddrPD;
    ulong curAddrPT;

    ulong firstDirectoryAddr = 0;
    ulong lastDirectoryAddr = 0;
    ulong phDirSize = 0;

    KernLog("\tActivating paging...\n");

    // Maximum PHYSICAL address in memory
    ulong phRamSize = memoryMap.freeRamSize + memoryMap.nonfreeRamSize;

    // Difference between the end of kernel and the begin of userspace
    MmPhysLastKernAddress = (ulong)(_heap_start + _heap_max);
    ulong diffKernUsr = (ulong)USERSPACE - MmPhysLastKernAddress - KPAGESIZE;

    // Size of physical table
    phDirSize = (((phRamSize + KPAGESIZE) / KPAGESIZE)*sizeof(ulong));

    // Maximum VIRTUAL address in memory
    MmVirtLastAddress = phRamSize + diffKernUsr;

    // Alloc structures
    memzero((void *)&MmPageMapLevel4[0], 512*sizeof(ulong));
    KalAllocMemoryEx((void**)&MmPhysicalPageTable, phDirSize, M_ZEROED, KPAGESIZE);

    //DebugLog("\t\t\t\tPhysical map addr : %p\n", MmPhysicalPageTable);

    for (curAddrPML4 = 0;
         curAddrPML4 < 512 * KPAGESIZE * 0x8000000;
         curAddrPML4 += ((ulong)KPAGESIZE * 0x8000000)) {
            // Create an entry in PML4 each 512GB
            // 0x8000000 = 512 ^ 3

            index = (curAddrPML4 / ((ulong)KPAGESIZE * 0x8000000)) % 512;

            if (curAddrPML4 > phRamSize) {
                MmPageMapLevel4[index] = (pdpe_t *)0;
                //DebugLog("PML4 %d\n", index);
                continue;
            }

            MmPDP = (pdpe_t *)malloc(512*sizeof(pde_t));

            if (!firstDirectoryAddr) {
                firstDirectoryAddr = (ulong)MmPDP;
            }

            //DebugLog("\t\t\t\tPDP %d : %p\n", index, MmPDP);
            MmPageMapLevel4[index] = (pdpe_t *)((ulong)MmPDP | PRESENT | READWRITE);

            for (curAddrPDP = curAddrPML4;
                 curAddrPDP < (curAddrPML4 + ((ulong)KPAGESIZE * 0x8000000));
                 curAddrPDP += ((ulong)KPAGESIZE * 0x40000)) {
                    // Create an intry in PDP each 1GB
                    // 0x40000 = 512 ^ 2

                    index = (curAddrPDP / ((ulong)KPAGESIZE * 0x40000)) % 512;

                    if (curAddrPDP > phRamSize) {
                        MmPDP[index] = (pde_t *)0;
                        //DebugLog("PDP %d\n", index);
                        continue;
                    }

                    MmPD = (pde_t *)malloc(512*sizeof(pde_t));

                    index = (curAddrPDP / ((ulong)KPAGESIZE * 0x40000)) % 512;

                    //DebugLog("\t\t\t\tPD %d : %p\n", index, MmPD);
                    MmPDP[index] = (pde_t *)((ulong)MmPD | PRESENT | READWRITE);

                    for (curAddrPD = curAddrPDP;
                         curAddrPD < (curAddrPDP + ((ulong)KPAGESIZE * 0x40000));
                         curAddrPD += ((ulong)KPAGESIZE * 0x200)) {
                            // Create an intry in PD each 2MB
                            // 0x200 = 512

                            index = (curAddrPD / ((ulong)KPAGESIZE * 0x200)) % 512;

                            if (curAddrPD > phRamSize) {
                                MmPD[index] = (pte_t *)0;
                                //DebugLog("PD %d\n", index);
                                continue;
                            }

                            if (index == 0x447c0ffe4dbf9e55)
                                KeStartPanic("ERROR");

                            MmPT = (pte_t *)malloc(512*sizeof(pte_t));

                            //DebugLog("\t\t\t\tPT %d : %p\n", index, MmPT);
                            MmPD[index] = (pte_t *)((ulong)MmPT | PRESENT | READWRITE);

                            for (curAddrPT = curAddrPD;
                                 curAddrPT < (curAddrPD + ((ulong)KPAGESIZE * 0x200));
                                 curAddrPT += (ulong)KPAGESIZE) {
                                    // Create an entry in PT each page of 4KB

                                    index = (curAddrPT / ((ulong)KPAGESIZE)) % 512;
                                    xedni = (curAddrPT / ((ulong)KPAGESIZE));

                                    // STACK GUARD PAGE */
                                    if ((ulong)curAddrPT == (ulong)BtLoaderInfo.stackEndAddr) {
                                        MmPT[index] = (ulong)curAddrPT | PRESENT;
                                        MmPhysicalPageTable[xedni] = (ulong)curAddrPT;
                                        MmStackGuards[0] = (ulong)curAddrPT;
                                        DebugLog("\tStack Guard at %p\n", curAddrPT);
                                    }
                                    else if ((ulong)curAddrPT == (ulong)BtLoaderInfo.kernelEndAddr) {
                                        MmPT[index] = (ulong)curAddrPT | PRESENT;
                                        MmPhysicalPageTable[xedni] = (ulong)curAddrPT;
                                        MmStackGuards[1] = (ulong)curAddrPT;
                                        DebugLog("\tStack Guard at %p\n", curAddrPT);
                                    }
                                    // SECTION .TEXT PROTECTION
                                    else if ((ulong)curAddrPT >= (ulong)&_text && (ulong)curAddrPT <= (ulong)&_text_end) {
                                        MmPT[index] = (ulong)curAddrPT | PRESENT;
                                        MmPhysicalPageTable[xedni] = (ulong)curAddrPT;
                                        DebugLog("\tSection .text at %p\n", curAddrPT);
                                    }
                                    // SECTION .DATA PROTECTION
                                    else if ((ulong)curAddrPT >= (ulong)&_data && (ulong)curAddrPT <= (ulong)&_data_end) {
                                        MmPT[index] = (ulong)curAddrPT | PRESENT | WRITETHR | READWRITE | NX;
                                        MmPhysicalPageTable[xedni] = (ulong)curAddrPT;
                                        DebugLog("\tSection .data at %p\n", curAddrPT);
                                    }
                                    // SECTION .RODATA PROTECTION
                                    else if ((ulong)curAddrPT >= (ulong)&_rodata && (ulong)curAddrPT <= (ulong)&_rodata_end) {
                                        MmPT[index] = (ulong)curAddrPT | PRESENT | NX;
                                        MmPhysicalPageTable[xedni] = (ulong)curAddrPT;
                                        DebugLog("\tSection .rodata at %p\n", curAddrPT);
                                    }
                                    // While we're inside the kernel pages
                                    else if ((ulong)curAddrPT <= MmPhysLastKernAddress) {
                                        MmPT[index] = (ulong)curAddrPT | PRESENT | READWRITE;
                                        MmPhysicalPageTable[xedni] = (ulong)curAddrPT;
                                    }
                            }
                    }
            }
    }
    lastDirectoryAddr = (ulong)MmPT;

    MmLoadPML4((void *)MmPageMapLevel4);
    MmEnableWriteProtect();

    DebugLog("\tPage table size : %u MB\n", (lastDirectoryAddr - firstDirectoryAddr + phDirSize)/MB);
}

//
// Get a page from an address
//
static pte_t *MmGetPageDescriptorFromVirtual(void *virtualAddr)
{
    ulong virtAddrPage = (ulong)virtualAddr & ( ~((KPAGESIZE - 1) | NX));

    if (virtAddrPage > MmVirtLastAddress) {
        KeStartPanic("MmSetPage() Out of bound of the address space !");
    }

    pdpe_t *pdp = (pdpe_t*)((ulong)MmPageMapLevel4[(virtAddrPage / ((ulong)KPAGESIZE * 0x8000000)) % 512] & ~((KPAGESIZE - 1) | NX | NX));
    //DebugLog("pdp\t: %p\n", pdp);
    pde_t *pd = (pde_t*)( (ulong)pdp[(virtAddrPage / ((ulong)KPAGESIZE * 0x40000)) % 512] & ~((KPAGESIZE - 1) | NX));
    //DebugLog("pd\t: %p\n", pd);
    pte_t *pt = (pte_t*)( (ulong)pd[(virtAddrPage / ((ulong)KPAGESIZE * 0x200)) % 512] & ~((KPAGESIZE - 1) | NX));
    //DebugLog("pt\t: %p\n", pt);

    pte_t *page = &pt[(virtAddrPage / ((ulong)KPAGESIZE)) % 512];
    //DebugLog("page (with flags): %p\n", page);

    return page;
}


//
// Translates a virtual address to its physical equivalent
//
void *MmTransVirtToPhyAddr(void* virtualAddr)
{
    ulong virtAddrPage = (ulong)virtualAddr & ( ~((KPAGESIZE - 1) | NX));
    pte_t *page = MmGetPageDescriptorFromVirtual(virtualAddr);

    if (*page == (*page & ~((KPAGESIZE - 1) | NX))) {
        return NULL;
    }

    return (void*)((*page & ~((KPAGESIZE - 1) | NX))+ ((ulong)virtualAddr - (ulong)virtAddrPage));
}

void *MmTransPhyToVirtAddr(void* physicalAddr)
{
    ulong phyAddrPage = (ulong)physicalAddr & ( ~((KPAGESIZE - 1) | NX));
    return (void*)( MmPhysicalPageTable[(ulong)physicalAddr
                   / ((ulong)KPAGESIZE)
                   ] + ((ulong)physicalAddr - phyAddrPage));
}

//
// Add flags to a page
//
void MmSetPage(void* virtualAddr, ulong flags)
{
    pte_t *page = MmGetPageDescriptorFromVirtual(virtualAddr);

    *page |= flags;

    KeFlushTlbSingle(*page);
}

//
// Remove flags of a page
//
void MmUnsetPage(void* virtualAddr, ulong flags)
{
    pte_t *page = MmGetPageDescriptorFromVirtual(virtualAddr);

    *page &= (~flags);

    KeFlushTlbSingle(*page);
}

//
// Map a page in memory
//
void MmMapPage(void* virtualAddr, void* physicalAddr, ulong flags)
{
    pte_t *page = MmGetPageDescriptorFromVirtual(virtualAddr);

    *page = ((ulong)physicalAddr & ~((KPAGESIZE - 1) | NX)) | flags;

    MmPhysicalPageTable[(ulong)physicalAddr
                   / ((ulong)KPAGESIZE)
                   ] = (ulong)virtualAddr;

    KeFlushTlbSingle(*page);

    if ((ulong)virtualAddr > MmVirtLastAddress)
        MmVirtLastAddress = (ulong)virtualAddr;
}

//
// Unmap a page in memory
//
void MmUnmapPage(void* virtualAddr)
{
    pte_t *page = MmGetPageDescriptorFromVirtual(virtualAddr);

    MmPhysicalPageTable[(ulong)(MmTransVirtToPhyAddr(virtualAddr))
               / ((ulong)KPAGESIZE)
               ] = 0;

    *page = 0;

    KeFlushTlbSingle(*page);
}

//-----------

//
// Returns the rank of the Stack Guards
//
void *MmGetStackGuards(char rank)
{
    return (void *)MmStackGuards[(int)rank];
}

//
// Page fault handler
//
static void PagingHandler(ISRFrame_t *regs)
{
    ulong StackGuardOne = (ulong)MmGetStackGuards(0);
    ulong StackGuardTwo = (ulong)MmGetStackGuards(1);
    if ((regs->cr2 >= StackGuardOne) && (regs->cr2 <= StackGuardOne + KPAGESIZE) && (regs->rsp <= regs->cr2)) {
        bprintf(BStdOut,
            "\n\n%CPANIC\n[ISR 0x8] Irrecoverable Kernel Stack Underflow\n\n"
                     "  Page Fault Error code : %#x (%b)\n"
                     "  Stack Guard bypassed    : %#x",

                     VGA_COLOR_LIGHT_RED,
                     regs->ErrorCode,
                     regs->ErrorCode,
                     StackGuardOne
                 );
    } else if ((regs->cr2 >= StackGuardTwo) && (regs->cr2 <= StackGuardTwo + KPAGESIZE) && (regs->rsp >= regs->cr2)) {
        bprintf(BStdOut,
            "\n\n%CPANIC\n[ISR 0x8] Irrecoverable Kernel Stack Overflow\n\n"
                     "  Page Fault Error code : %#x (%b)\n"
                     "  Stack Guard bypassed    : %#x",

                     VGA_COLOR_LIGHT_RED,
                     regs->ErrorCode,
                     regs->ErrorCode,
                     StackGuardTwo
                 );
    } else if (regs->cr2 == 0) {
        bprintf(BStdOut,
            "\n\n%CPANIC\n[ISR 0x8] Null vector exception !\n\n"
                     "  Page Fault Error code : %#x (%b)\n",

                     VGA_COLOR_LIGHT_RED,
                     regs->intNo,
                     regs->ErrorCode,
                     regs->ErrorCode
                 );
    } else if (regs->cr2 >= MmVirtLastAddress || regs->cr2 <= 0) {
        bprintf(BStdOut,
            "\n\n%CPANIC\n[ISR 0x8] Out of bound of the address space at %p !\n\n"
                     "  End of the address space : %p\n"
                     "  Page Fault Error code : %#x (%b)\n",

                     VGA_COLOR_LIGHT_RED,
                     regs->cr2,
                     MmVirtLastAddress,
                     regs->ErrorCode,
                     regs->ErrorCode
                 );
    } else {
        //XXX page fault
        bprintf(BStdOut, "\n\n%CPANIC\n[ISR 0x8] Irrecoverable Page Fault at %p\n\n"
                     "  Error code : 0x%x (%b)",

                     VGA_COLOR_LIGHT_RED,
                     regs->cr2,
                     regs->ErrorCode,
                     regs->ErrorCode
                 );
    }

    bprintf(BStdOut, "\n  Description : ");

    if (regs->ErrorCode & PRESENT) {
        bprintf(BStdOut, "Page-protection violation ");
    } else {
        bprintf(BStdOut, "Non present page ");
    }
    if (regs->ErrorCode & READWRITE) {
        bprintf(BStdOut, "during write access ");
    } else {
        bprintf(BStdOut, "during read access ");
    }
    if (regs->ErrorCode & (1 << 3))
        bprintf(BStdOut, "from userspace ");
    if (regs->ErrorCode & (1 << 4))
        bprintf(BStdOut, "after instruction fetching ");

    KeBrkDumpRegisters(regs);

    BStdOut->flusher(BStdOut);

    KeHaltCPU();
}

void MmActivatePageHandler(void)
{
    KeRegisterISR(PagingHandler, 0xe);
    //DebugLog("\tPage handler activated\n");
}