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bool init_vm_paging() {
	page_directory_table = (uint32_t*)kmalloc(sizeof(int) * 1024);
	if ((uint32_t)page_directory_table % 4096) {
		dprintf("page_directory_table address is not aligned!\n");
		kfree(page_directory_table);
		return false;
	}

	first_page_table = (uint32_t*)kmalloc(sizeof(int) * 1024);
	if ((uint32_t)first_page_table % 4096) {
		dprintf("first_page_table address is not aligned!\n");
		kfree(first_page_table);
		return false;
	}

	for(uint32_t i = 0; i < 1024; i++) {
    	// This sets the following flags to the pages:
    	//   Supervisor: Only kernel-mode can access them
    	//   Write Enabled: It can be both read from and written to
    	//   Not Present: The page table is not present
    	page_directory_table[i] = 0x00000002;
	}

	for(uint32_t i = 0; i < 1024; i++)
	{
    	// As the address is page aligned, it will always leave 12 bits zeroed.
    	// Those bits are used by the attributes ;)
    	first_page_table[i] = (i * 0x1000) | 3; // attributes: supervisor level, read/write, present.
	}

	// attributes: supervisor level, read/write, present
	page_directory_table[0] = ((unsigned int)first_page_table) | 3;

	loadPageDirectory(page_directory_table);
	enablePaging();
	return true;
}

Code: Select all

.text
.global enablePaging
enablePaging:
push %ebp
mov %esp, %ebp
mov %cr0, %eax
or $0x80000000, %eax
mov %eax, %cr0
mov %ebp, %esp
pop %ebp <--------
ret

Code: Select all

uint16_t ss = 0; //stack start
uint32_t esp = 0; //stack end
__asm__ (
    "mov %%ss, %0" : "=r"(ss)
);
__asm__ (
    "mov %%esp, %0" : "=r"(esp)
);