GDT Problem

[OdnetninI]

i'm rewriting the gdt code but it doesn't work because after of gdt code it isn't do nothing.

Code: Select all

[GLOBAL gdt_flush]    ; Allows the C code to call gdt_flush().

gdt_flush:
   mov eax, [esp+4]  ; Get the pointer to the GDT, passed as a parameter.
   lgdt [eax]        ; Load the new GDT pointer

   mov ax, 0x10      ; 0x10 is the offset in the GDT to our data segment
   mov ds, ax        ; Load all data segment selectors
   mov es, ax
   mov fs, ax
   mov gs, ax
   mov ss, ax
   jmp 0x08:.flush   ; 0x08 is the offset to our code segment: Far jump!
.flush:
   ret

and C

Code: Select all

struct GDT_Entry_type {
		u16 lower;
		u16 low;
		u8 middle;
		u8 ring;
		u8 granularity;
		u8 high;
	} __attribute__((packed));
	typedef struct GDT_Entry_type GDT_Entry_t;

	struct GDT_Pointer_type {
		u32 adress;
		u16 limit;
	} __attribute__((packed));
	typedef struct GDT_Pointer_type GDT_Pointer_t;

GDT_Entry_t GDT_Entry[5];
	GDT_Pointer_t GDT_Pointer;

// GDT Flush desde asm	
	extern void gdt_flush(u32);

	// GDT crear entrada
	void GDT_CreateEntry ( s32 slot, u32 base, u32 limit, u8 ring, u8 granuality ) {
		GDT_Entry [slot].low = (base & 0xFFFF);
  		GDT_Entry [slot].middle = (base >> 16) & 0xFF;
  		GDT_Entry [slot].high = (base >> 24) & 0xFF;
   		GDT_Entry [slot].lower = (limit & 0xFFFF);
  		GDT_Entry [slot].granularity = (limit >> 16) & 0x0F;
   		GDT_Entry [slot].granularity |= granuality & 0xF0;
   		GDT_Entry [slot].ring = ring;
	}

	// Iniciar GDT
	void Init_GDT ( void ) { // Iniciar el GDT
		VTM_Write ("Iniciando GDT\n");
		GDT_Pointer.limit = ( sizeof ( GDT_Entry_t ) * 5 ) - 1;
		GDT_Pointer.adress = ( u32 ) &GDT_Entry;

		GDT_CreateEntry ( 0, 0, 0, 0, 0 );
		GDT_CreateEntry ( 1, 0, 0xFFFFFFFF, 0x9A, 0xCF );
		GDT_CreateEntry ( 2, 0, 0xFFFFFFFF, 0x92, 0xCF );
		GDT_CreateEntry ( 3, 0, 0xFFFFFFFF, 0xFA, 0xCF );
		GDT_CreateEntry ( 4, 0, 0xFFFFFFFF, 0xF2, 0xCF );
		gdt_flush((u32)&GDT_Pointer);

		VTM_Write ("GDT Iniciado\n");		
	}

It doesn't write VTM_Write ("GDT Iniciado\n");

any help?

[Jezze]

Limit should come before address in your pointer struct.

[OdnetninI]

it works, thanks you.
it was very simply.