OSDev.org

Code: Select all

//setup TSS
	void* stack = kmalloc(1024);
	void* tss = kmalloc(104);
	*(uint32_t*)(tss+4) = (uint32_t)stack;
	*(uint32_t*)(tss+8) = 0x10; //kernel data descriptor
	
	gdt_set_entry(5, create_gdt_entry(104, (uint32_t)tss, 0x89, 0x4));
	load_gdt(6);
	__asm__ __volatile__("ltr %%ax" : : "a" (0x28));
	
	void* program = (void*)0x00000000;
	void* userstack = (void*)0xBFFFF000;
	
	if(!vmmngr_alloc_page((virtual_addr)program))
		PrintString("Fail\n");
	else
	{
		pt_entry_add_attrib(vmmngr_ptable_lookup_entry(get_ptable_address((virtual_addr)program), (virtual_addr)program), PTE_USER); //make it a user page
		
		if(!vmmngr_alloc_page((virtual_addr)userstack))
			PrintString("Failed to allocate stack.\n");
		else
		{
			pt_entry_add_attrib(vmmngr_ptable_lookup_entry(get_ptable_address((virtual_addr)userstack), (virtual_addr)userstack), PTE_USER); //make it a user page
		   vmmngr_flush_tlb_entry((virtual_addr)program);
	      vmmngr_flush_tlb_entry((virtual_addr)userstack);

			struct FileInfo fi;
		
			if(!GetFileInfo("test.bin", &fi, 0))
				PrintString("Failed to load file.");
			else
			{
				LoadFile("test.bin", program, 0);
            _enter_usermode();
			}
		}
	}
	

	
	

Code: Select all

bits 32

global _enter_usermode

%define UserModeESP 0xC0000000

_enter_usermode:
	cli
	mov ax, 0x23 ;user mode data selector
	mov ds, ax
	mov es, ax
	mov fs, ax
	mov gs, ax
	
	push 0x23 ;for SS
	push UserModeESP ;ESP
	pushfd ;eflags
	push 0x1B ;user mode code selector
	push 0x00 ;EIP of usermode program - prog is loaded at 0
	iret
	
	cli
	hlt
	

Code: Select all

void main(void)
{
for(;;);
}