bzero.s

来自「实现一个简单的单进程内核,。该内核启用二级虚拟页表映射」· S 代码 · 共 48 行

/*
 * Written by J.T. Conklin <[e-mail]>.
 * Public domain.
 */

#include <asm.h>

#if defined(LIBC_SCCS)
	RCSID("$NetBSD: bzero.S,v 1.8 1995/04/28 22:57:58 jtc Exp $")
#endif


ENTRY(bzero)
	pushl	%edi
	movl	S_ARG1,%edi
	movl	S_ARG2,%edx

	cld				/* set fill direction forward */
	xorl	%eax,%eax		/* set fill data to 0 */

	/*
	 * if the string is too short, it's really not worth the overhead
	 * of aligning to word boundries, etc.  So we jump to a plain
	 * unaligned set.
	 */
	cmpl	$16,%edx
	jb	L1

	movl	%edi,%ecx		/* compute misalignment */
	negl	%ecx
	andl	$3,%ecx
	subl	%ecx,%edx
	rep				/* zero until word aligned */
	stosb

	movl	%edx,%ecx		/* zero by words */
	shrl	$2,%ecx
	andl	$3,%edx
	rep
	stosl

L1:	movl	%edx,%ecx		/* zero remainder by bytes */
	rep
	stosb

	popl	%edi
	ret