peekb.c

来自「一个类linux的dos下开发的操作系统.」· C语言 代码 · 共 15 行

__inline__ unsigned char peekb(unsigned short sel, unsigned long off)
{
	unsigned char ret_val;

	__asm__ __volatile__("mov %1,%%es\n"
		"es\n"
		"movb (%2),%b0"
		: "=a"(ret_val)
/* xxx - "r" means any reg, but you want one of the regs than can be used
in an address without a prefix: EBP, EBX, ESI, EDI.
Can this be done with a list of registers? */
		: "m"(sel), "r"(off));
	return ret_val;
}