xref: /openbmc/linux/arch/mips/lib/strnlen_user.S (revision 22246614)
1/*
2 * This file is subject to the terms and conditions of the GNU General Public
3 * License.  See the file "COPYING" in the main directory of this archive
4 * for more details.
5 *
6 * Copyright (c) 1996, 1998, 1999, 2004 by Ralf Baechle
7 * Copyright (c) 1999 Silicon Graphics, Inc.
8 */
9#include <asm/asm.h>
10#include <asm/asm-offsets.h>
11#include <asm/regdef.h>
12
13#define EX(insn,reg,addr,handler)			\
149:	insn	reg, addr;				\
15	.section __ex_table,"a";			\
16	PTR	9b, handler;				\
17	.previous
18
19/*
20 * Return the size of a string including the ending NUL character upto a
21 * maximum of a1 or 0 in case of error.
22 *
23 * Note: for performance reasons we deliberately accept that a user may
24 *       make strlen_user and strnlen_user access the first few KSEG0
25 *       bytes.  There's nothing secret there.  On 64-bit accessing beyond
26 *       the maximum is a tad hairier ...
27 */
28LEAF(__strnlen_user_asm)
29	LONG_L		v0, TI_ADDR_LIMIT($28)	# pointer ok?
30	and		v0, a0
31	bnez		v0, .Lfault
32
33FEXPORT(__strnlen_user_nocheck_asm)
34	move		v0, a0
35	PTR_ADDU	a1, a0			# stop pointer
361:	beq		v0, a1, 1f		# limit reached?
37	EX(lb, t0, (v0), .Lfault)
38	PTR_ADDU	v0, 1
39	bnez		t0, 1b
401:	PTR_SUBU	v0, a0
41	jr		ra
42	END(__strnlen_user_asm)
43
44.Lfault:
45	move		v0, zero
46	jr		ra
47