os-k/kaleid/kernel/mm/paging.c

#include <kernel.h>
#include <init/boot.h>

#define PAGESIZE (4 * KB)


// Page directory pointer offset
typedef ulong    pdpe_t;

// Page directory offset
typedef ulong    pde_t;

// Page table entry
typedef ulong    pte_t;

// paging.asm
void MmLoadPML4(void *);
void MmEnableWriteProtect(void);
void MmDisableWriteProtect(void);

enum
{
    MF_PRESENT      = 1 << 0,
    MF_READWRITE    = 1 << 1,
    MF_USERMODE     = 1 << 2,
    MF_WRITETHR     = 1 << 3,
    MF_CACHEDIS     = 1 << 4,
    MF_ACCESSED     = 1 << 5,
    MF_DIRTY        = 1 << 6,
    MF_HUGE         = 1 << 7,
    MF_NX           = 1 << 31
};

#define RAM_MAX 16
#define NB_4K 2

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

volatile pdpe_t MmPML4[512] __attribute__((__aligned__(4096)));

volatile pde_t MmPDP[512] __attribute__((__aligned__(4096)));

volatile pde_t MmPD[512 * RAM_MAX] __attribute__((__aligned__(4096)));

volatile pte_t MmPT[512 * NB_4K] __attribute__((__aligned__(4096)));

volatile ulong MmStackGuards[2] = { 0 };


//
// Creates our new page table structure and loads it
void MmInitPaging(void)
{
    memzero((void *)&MmPML4[0], sizeof(MmPML4));
    memzero((void *)&MmPDP[0], sizeof(MmPDP));
    memzero((void *)&MmPD[0], sizeof(MmPD));
    memzero((void *)&MmPT[0], sizeof(MmPT));

    for (int i = 0; i < 512 *  NB_4K; i++) {

        // STACK GUARD PAGE
        if ((ulong)i*4096 == (ulong)BtLoaderInfo.stackEndAddr) {
            MmPT[i] = ((ulong)i * 4096);
            MmStackGuards[0] = i;
            continue;
        }

        // STACK PAGES
        if (
            (ulong)i*4096 < (ulong)BtLoaderInfo.stackEndAddr &&
            (ulong)i*4096 > (ulong)BtLoaderInfo.kernelEndAddr
            ) {
            MmPT[i] = ((ulong)i * 4096) | MF_PRESENT | MF_READWRITE;// | MF_NX;
            continue;
        }

        // STACK GARD PAGE
        if ((ulong)i*4096 == (ulong)BtLoaderInfo.kernelEndAddr) {
            MmPT[i] = ((ulong)i * 4096);
            MmStackGuards[1] = i;
            continue;
        }

        MmPT[i] = ((ulong)i * 4096) | MF_PRESENT | MF_READWRITE;
    }

    for (int i = 0; i <  NB_4K; i++) {
        MmPD[i] = (ulong)(&MmPT[i*512])| MF_PRESENT | MF_READWRITE;
    }

    for (int i =  NB_4K; i < 512 * RAM_MAX; i++) {
        MmPD[i] = ((ulong)i * 2048 * 1024) | MF_PRESENT | MF_READWRITE | MF_HUGE;
    }

    for (int i = 0; i < RAM_MAX; i++) {
        MmPDP[i] = (ulong)(&MmPD[i*512])| MF_PRESENT | MF_READWRITE;
    }

    MmPML4[0] = (ulong)(&MmPDP[0])| MF_PRESENT | MF_READWRITE;

    MmLoadPML4((void *)MmPML4);
}