paging.h

#ifndef PAGING_H
#define PAGING_H

#include <stdbool.h>
#include <std/common.h>
#include <kernel/util/interrupts/isr.h>

typedef struct page {
    uint32_t present    :  1; //page present in memory
    uint32_t rw         :  1; //read-only if clear, readwrite if set
    uint32_t user       :  1; //kernel level only if clear
    uint32_t accessed   :  1; //has page been accessed since last refresh?
    uint32_t dirty      :  1; //has page been written to since last refresh?
    uint32_t unused     :  7; //unused/reserved bits
    uint32_t frame      : 20; //frame address, shifted right 12 bits
} page_t;

typedef struct page_table {
    page_t pages[1024];
} page_table_t;

typedef struct page_directory {
    //array of pointers to pagetables
    page_table_t* tables[1024];

    //array of pointers to pagetables above, but give their *physical*
    //location, for loading into CR3 reg
    uint32_t tablesPhysical[1024];

    //physical addr of tablesPhysical. 
    //needed once kernel heap is allocated and
    //directory may be in a different location in virtual memory
    uint32_t physicalAddr;
} page_directory_t;

//sets up environment, page directories, etc
//and, enables paging
void paging_install();

//causes passed page directory to be loaded into 
//CR3 register
void switch_page_directory(page_directory_t* new_dir);

//retrieves pointer to page required
//if make == 1, if the page-table in which this page should
//reside isn't created, create it
page_t* get_page(uint32_t address, int make, page_directory_t* dir);

//retrieves current cr3 (current paging dir)
page_directory_t* get_cr3();

//maps physical range to virtual memory
void vmem_map(uint32_t virt, uint32_t physical);

bool alloc_frame(page_t* page, int is_kernel, int is_writeable);
void free_frame(page_t* page);

//create a new page directory with all the info of src
//kernel pages are linked instead of copied
page_directory_t* clone_directory(page_directory_t* src);
//free all memory associated with a page directory dir
void free_directory(page_directory_t* dir);

void *mmap(void *addr, uint32_t length, int flags, int fd, uint32_t offset);
int munmap(void* addr, uint32_t length);

int brk(void* addr);
void* sbrk(int increment);

#endif