#include???
#include???
#include???
#include???
#include???
#include???
#include???
#include???
#include???
#include???
#include???

#define?FATAL?do?{?fprintf（stderr?“Error?at?line?%d?file?%s?（%d）?[%s]\n“?__LINE__?__FILE__?errno?strerror（errno））;?exit（1）;?}?while（0）

#define?MAP_SIZE?4096UL
#define?MAP_MASK?（MAP_SIZE?-?1）

int?main（int?argc?char?**argv）?{
	int?fd;
	void?*map_base?*virt_addr;
	unsigned?long?read_result?writeval;
	off_t?target;
	int?access_type?=?‘w‘;

	if（argc?????		fprintf（stderr?“\nUsage:\t%s?{?address?}?[?type?[?data?]?]\n“
		“\taddress?:?memory?address?to?act?upon\n“
		“\ttype????:?access?operation?type?:?[b]yte?[h]alfword?[w]ord\n“
		“\tdata????:?data?to?be?written\n\n“
		argv[0]）;
????		exit（1）;
	}

	target?=?strtoul（argv[1]?0?0）;

	if（argc?>?2）
????		access_type?=?tolower（argv[2][0]）;

	if（（fd?=?open（“/dev/mem“?O_RDWR?|?O_SYNC））?==?-1）?
		FATAL;

	printf（“/dev/mem?opened.\n“）;
	fflush（stdout）;

	map_base?=?mmap（0?MAP_SIZE?PROT_READ?|?PROT_WRITE?MAP_SHARED?fd?target?&?~MAP_MASK）;
	if（map_base?==?（void?*）-1）
		FATAL;
	printf（“Memory?mapped?at?address?%p.\n“?map_base）;
	fflush（stdout）;

	virt_addr?=?map_base?+?（target?&?MAP_MASK）;

	switch（access_type）?{
????	case?‘b‘:
		read_result?=?*（（unsigned?char?*）?virt_addr）;
		break;
????	case?‘h‘:
		read_result?=?*（（unsigned?short?*）?virt_addr）;
		break;
????	case?‘w‘:
		read_result?=?*（（unsigned?long?*）?virt_addr）;
		break;
????	default:
		fprintf（stderr?“Illegal?data?type?‘%c‘.\n“?access_type）;
		exit（2）;
	}

	printf（“Value?at?address?0x%x?（%p）:?0x%x\n“?target?virt_addr?read_result）;
	fflush（stdout）;

	if（argc?>?3）?{
????		writeval?=?strtoul（argv[3]?0?0）;
????		switch（access_type）?{
		case?‘b‘:
	????		*（（unsigned?char?*）?virt_addr）?=?writeval;
	????		read_result?=?*（（unsigned?char?*）?virt_addr）;
	????		break;
		case?‘h‘:
	????		*（（unsigned?short?*）?virt_addr）?=?writeval;
	????		read_result?=?*（（unsigned?short?*）?virt_addr）;
	????		break;
		case?‘w‘:
	????		*（（unsigned?long?*）?virt_addr）?=?writeval;
	????		read_result?=?*（（unsigned?long?*）?virt_addr）;
	????		break;
????		}
????		printf（“Written?0x%x;?readback?0x%x\n“?writeval?read_result）;
????		fflush（stdout）;
	}

	if（munmap（map_base?MAP_SIZE）?==?-1）?FATAL;
	close（fd）;
	return?0;
}