memory.h

来自「Linux0.01kernel相信大家能够学到一些东西的,一起努力」· C头文件 代码 · 共 21 行

/*
 *  NOTE!!! memcpy(dest,src,n) assumes ds=es=normal data segment. This
 *  goes for all kernel functions (ds=es=kernel space, fs=local data,
 *  gs=null), as well as for all well-behaving user programs (ds=es=
 *  user data space). This is NOT a bug, as any user program that changes
 *  es deserves to die if it isn't careful.
 */
#define memcpy(dest,src,n) ({ \
void * _res = dest; \
//下面的内嵌汇编的意思是：
//	movl	_res	%edi
//	movl	src	%esi
//	movl	n	%ecx
//	cld
//	rep	movsb
__asm__ ("cld;rep;movsb" \
	::"D" ((long)(_res)),"S" ((long)(src)),"c" ((long) (n)) \
	:"di","si","cx"); \
_res; \
})