Nucleus

/*
 * This file contains the page fault handler.
 * There is an early handler which just gives out memory when requested.  This
 * is used by the kernel before it has initialised multi-tasking and the virtual
 * file system.
 */

#include <stdint.h>
#include <nucleus/cpu.h>
#include <nucleus/memory.h>
#include <nucleus/panic.h>

/* Early (pre-VFS/tasking) page fault handler */
void
early_page_fault_handler(struct InterruptFrame *frame, uint32_t err)
{
	uintptr_t addr;
	asm volatile("mov %%cr2, %0" : "=r" (addr));
	uint8_t present = err & (1 << 0);
	uint8_t write   = err & (1 << 1);
	uint8_t user    = err & (1 << 2);
	if (!PAGE_ADDR(addr))
		panic("Null dereference @ %#.8x", frame->eip);
	ASSERT(!present);
	kprintf("Allocating frame for %#.8x [%#.8x]", addr, frame->eip);
	/* Allocate a page */
	set_page(addr, alloc_frame() | PTE_PRESENT | PTE_WRITE | PTE_GLOBAL);
}