CeDOS - include/cedos/mm/paging.h

include/cedos/mm/paging.h (view raw)

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/*! \file
 * Provides structures and functions to interact with and modify 
 * page directories and page tables.
 */
#ifndef PAGING_H
#define PAGING_H

#include <stdint.h>
#include "string.h"

//! Number of entries within a page table/directory.
#define PAGE_ENTRY_COUNT (uint32_t)(1 << 10)

//! Size of a single page or page table/directory.
#define PAGE_SIZE (uint32_t)(1 << 12)

typedef void* PHYS_ADDR;
typedef void* VIRT_ADDR;

//! Represents a single page entry in a page table.
typedef uint32_t PAGE_DIR_ENTRY;

//! Represents a single page table entry in a page directory.
typedef uint32_t PAGE_TABLE_ENTRY;

/*!
 * Sets cr3 to new page directory and returns the old one.
 * \param pd_new Address of new page directory that is supposed to be used.
 * \return Address of old page directory.
 */
__attribute__((always_inline)) inline PHYS_ADDR switch_page_dir(PHYS_ADDR pd_new) {
    uint32_t pd_old;
    __asm__ volatile (  "mov %%cr3, %0\n"
                        "mov %1, %%cr3" : 
                        "=a" (pd_old) :
                        "Nd" (pd_new));
    return (void*)pd_old;
}

/*!
 * Invalidates all pages, forces buffer reload.
 */
__attribute__((always_inline)) inline void inv_all_pages(void) {
    __asm__ volatile (  "mov %cr3, %eax\n"
                        "mov %eax, %cr3");
}

size_t copy_to_pdir(VIRT_ADDR src, size_t length, PHYS_ADDR pdir, VIRT_ADDR dest);

/*!
 * Maps the specified range of physical addresses to the specified virtual address.
 * \param page_dir Page directory on which to map the addresses.
 * \param dest Virtual address to which the physical address \p src is to be mapped to.
 * \param src Physical address which is to be mapped to virtual address \p dest.
 * \param page_count Number of pages to map.
 * \param flags Access flags for the memory range.
 * \return 1 on success, 0 on failure
 */
int map_range_to(PHYS_ADDR page_dir, VIRT_ADDR dest, PHYS_ADDR src, uint32_t page_count, uint32_t flags);

/*!
 * Uses a free page to generate a new page directory which maps its last entry to itself.
 * \return Address of new page directory.
 */
PHYS_ADDR create_empty_page_dir(void);

/*!
 * Initializes paging.
 * \return 1 on success, 0 on failure
 */
int paging_init(void);

#endif