x86_64_gdt.h

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#ifndef __X86_64_GDT_H__
#define __X86_64_GDT_H__
 
#include <stdint.h>
#include <stddef.h>
 
#define GDT_ENTRY_NULL 0
#define GDT_ENTRY_KERNEL_CODE 1
#define GDT_ENTRY_KERNEL_DATA 2
#define GDT_ENTRY_USER_CODE32 3
#define GDT_ENTRY_USER_DATA 4
#define GDT_ENTRY_USER_CODE 5
#define GDT_ENTRY_KERNEL_CODE32 6
#define GDT_ENTRY_TSS 7
#define GDT_ENTRY_MAX 9     //TSS takes two entries
 
 
 
#define SEGVAL(gdtent, rpl) \
    ((gdtent << 3) | rpl)
 
#define SEGVAL_LDT(ldtent, rpl) \
    ((ldtent << 3) | 0x4 | rpl)
 
enum sregs {
    SREG_CS,
    SREG_DS,
    SREG_ES,
    SREG_FS,
    SREG_GS,
    SREG_SS
};
 
#define GDT_FLAG_GRAN 0x8
#define GDT_FLAG_32BT 0x4
#define GDT_FLAG_64BT 0x2
 
#define GDT_ACCESS_PRESENT 0x80
#define GDT_ACCESS_PRIVL(x) (x << 5)
#define GDT_ACCESS_TYPE 0x10
#define GDT_ACCESS_EX 0x8
#define GDT_ACCESS_DC 0x4
#define GDT_ACCESS_RW 0x2
#define GDT_ACCESS_AC 0x1
 
#pragma pack(push, 1)
 
typedef struct _gdt {
    uint16_t limit_low;
    uint16_t base_low;
    uint8_t  base_mid;
    uint8_t  access;
    uint8_t  flags_limit;
    uint8_t  base_high;
}gdt_entry, *pgdt_entry;
 
typedef struct _gdtr{
    uint16_t size;
    pgdt_entry gdtaddr;
}gdtr, *pgdtr;
 
#pragma pack(pop)
 
/*
 * x86_64_hal_init_gdt -- initialize the global descriptor
 * table 
 */
extern "C" void x86_64_hal_init_gdt();
 
/*
* x86_64_hal_init_gdt_ap -- initialize gdt for Application
* processors
*/
extern void x86_64_hal_init_gdt_ap();
 
extern void set_gdt_entry(gdt_entry& entry, size_t base, size_t limit, uint8_t access, uint8_t flags);
 
#endif