void vmsim_handler(int signum , siginfo_t * info, void *context){

	w_ptr_t addr, map_addr;
	int rc, page_nr, i, page_size = w_get_page_size();
	page_table_t *page_table;
	struct page_table_entry *virt_page;
	w_prot_t prot_RW;
	int frame_index, fd, len = page_size * sizeof(char);
	off_t pos; ssize_t written;
	char buf[page_size];
	enum page_state state;
	memset(buf, 0, page_size);

	/* obtain from siginfo_t the memory location
	which caused the page fault */
	addr = info->si_addr;

	/* check if the signal is SIGSEGV */
	if(signum != SIGSEGV){
		return;
	}

	/* compute the page number which caused the page fault */
	page_table = find_between(&memmap, addr);
	DIE(page_table == NULL, "find_between");

	page_nr = (int)(addr - page_table->vms->start)/ page_size;
	virt_page = &(page_table->virtual_pages[page_nr]);
	DIE(virt_page == NULL, "virt_page");

	state = virt_page->state;

	prot_RW = ((state == STATE_NOT_ALLOC) ? PROTECTION_READ :
							PROTECTION_WRITE);

	if((state == STATE_NOT_ALLOC) || (state == STATE_IN_SWAP)){

		virt_page->prev_state = state;
		virt_page->state = STATE_IN_RAM;

		/* get frame number*/
		frame_index = get_frame_mapping(page_table);

		/* if no available frame,then swap out */
		if(frame_index == -1)
			frame_index = swap_out(page_table);

		virt_page->frame = malloc(sizeof(struct frame));
		virt_page->frame->index = frame_index;
		virt_page->frame->pte = virt_page;
		virt_page->protection = PROTECTION_READ;

		/* map page to ram */
		rc = munmap(virt_page->start, page_size);
		DIE(rc == -1, "munmap");

		map_addr = mmap(virt_page->start, page_size, prot_RW,
				 MAP_FIXED | MAP_SHARED, page_table->vms->ram_handle,
				frame_index * page_size);
		DIE(map_addr != virt_page->start, "NUUU");

		if(state == STATE_NOT_ALLOC){
			/* fill ram memory with 0'z*/
			w_set_file_pointer(page_table->vms->ram_handle,
						frame_index * page_size);
			w_write_file(page_table->vms->ram_handle, buf, page_size);

		}
		else {
			/* copy from swap to ram */
			memcpy(virt_page->start, page_table->vms->sstart +
					page_nr * page_size, page_size);

		}

		w_protect_mapping(virt_page->start, 1, virt_page->protection);
	}
	else
		//if(virt_page->state == STATE_IN_RAM &&
		if(virt_page->protection == PROTECTION_READ){

		virt_page->protection = PROTECTION_WRITE;
		w_protect_mapping(virt_page->start, 1, PROTECTION_READ | PROTECTION_WRITE);
		virt_page->dirty = TRUE;

	}

}