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    /**PageTables are so different that we have different types

     *   for level 0 and level1 page table entries

     */  

typedef struct {

    unsigned destriptor_type     : 2;

    unsigned machine_depend      : 3; // Alf: ???? v Architecture previev neni vyznam definovan

    unsigned domain              : 4;

    unsigned should_be_zero      : 1:

    unsigned coarse_table_addr   : 22;

} __attribute__ ((packed)) pte_level0_t;

//TODO Alf: Comments

typedef struct {

    unsigned destriptor_type     : 2;

    unsigned bufferable          : 1;

    unsigned cacheable           : 1;

    unsigned access_permission_0 : 2;

    unsigned access_permission_1 : 2;

    unsigned access_permission_2 : 2;

    unsigned access_permission_3 : 2;

    unsigned frame_base_addr     : 20;

} __attribute__ ((packed)) pte__level1_t;

/// Page table level 1 access permission constants

/// User no acess, kernel no access

#define pte_ap_user_no_kernel_no 0

/// User no acess, kernel read/write

#define pte_ap_user_no_kernel_rw 1

/// User read only, kernel read/write

#define pte_ap_user_ro_kernel_rw 2

/// User read/write, kernel read/write

#define pte_ap_user_rw_kernel_rw 2

/// Value of descriptor_type in pte_level0_t and pte_level1_t that signal not present flag 

#define pte_descriptor_not_preset 0 

/// Value of descriptor_type in pte_level0_t that signal a coarse page table format

#define pte_descriptor_coarse_table 1

/// Value of descriptor_type in pte_level1_t that signal a small page table entry format

#define pte_descriptor_small_page 2