strncpy_from_user.s

Linux内核源代码 为压缩文件 是<<Linux内核>>一书中的源代码

/*
 * Just like strncpy() except that if a fault occurs during copying,
 * -EFAULT is returned.
 *
 * Inputs:
 *	in0:	address of destination buffer
 *	in1:	address of string to be copied
 *	in2:	length of buffer in bytes
 * Outputs:
 *	r8:	-EFAULT in case of fault or number of bytes copied if no fault
 * 
 * Copyright (C) 1998-2000 Hewlett-Packard Co
 * Copyright (C) 1998-2000 David Mosberger-Tang <[e-mail]>
 *
 * 00/03/06 D. Mosberger Fixed to return proper return value (bug found by
 *			 by Andreas Schwab <[e-mail]>).
 */

#include <asm/asmmacro.h>

#define EX(x...)				\
99:	x;					\
	.section __ex_table,"a";		\
	data4 @gprel(99b);			\
	data4 .Lexit-99b;			\
	.previous

	.text
	.psr abi64
	.psr lsb
	.lsb

GLOBAL_ENTRY(__strncpy_from_user)
	alloc r2=ar.pfs,3,0,0,0
	mov r8=0
	mov r9=in1
	;;
	add r10=in1,in2
	cmp.eq p6,p0=r0,in2
(p6)	br.ret.spnt.many rp

	// XXX braindead copy loop---this needs to be optimized
.Loop1:
	EX(ld1 r8=[in1],1;; st1 [in0]=r8,1; cmp.ne p6,p7=r8,r0)
	;;
(p6)	cmp.ne.unc p8,p0=in1,r10
(p8)	br.cond.dpnt.few .Loop1
	;;
(p6)	mov r8=in2		// buffer filled up---return buffer length
(p7)	sub r8=in1,r9,1		// return string length (excluding NUL character)
	br.ret.sptk.few rp

.Lexit:
	br.ret.sptk.few rp
END(__strncpy_from_user)