strnlen_user.S

  1/*
  2 *  arch/xtensa/lib/strnlen_user.S
  3 *
  4 *  This file is subject to the terms and conditions of the GNU General
  5 *  Public License.  See the file "COPYING" in the main directory of
  6 *  this archive for more details.
  7 *
  8 *  Returns strnlen, including trailing zero terminator.
  9 *  Zero indicates error.
 10 *
 11 *  Copyright (C) 2002 Tensilica Inc.
 12 */
 13
 14#include <linux/linkage.h>
 15#include <asm/asmmacro.h>
 16#include <asm/core.h>
 17
 18/*
 19 * size_t __strnlen_user(const char *s, size_t len)
 20 */
 21
 22#ifdef __XTENSA_EB__
 23# define MASK0 0xff000000
 24# define MASK1 0x00ff0000
 25# define MASK2 0x0000ff00
 26# define MASK3 0x000000ff
 27#else
 28# define MASK0 0x000000ff
 29# define MASK1 0x0000ff00
 30# define MASK2 0x00ff0000
 31# define MASK3 0xff000000
 32#endif
 33
 34# Register use:
 35#   a2/ src
 36#   a3/ len
 37#   a4/ tmp
 38#   a5/ mask0
 39#   a6/ mask1
 40#   a7/ mask2
 41#   a8/ mask3
 42#   a9/ tmp
 43#   a10/ tmp
 44
 45.text
 46ENTRY(__strnlen_user)
 47
 48	abi_entry_default
 49	# a2/ s, a3/ len
 50	addi	a4, a2, -4	# because we overincrement at the end;
 51				# we compensate with load offsets of 4
 52	movi	a5, MASK0	# mask for byte 0
 53	movi	a6, MASK1	# mask for byte 1
 54	movi	a7, MASK2	# mask for byte 2
 55	movi	a8, MASK3	# mask for byte 3
 56	bbsi.l	a2, 0, .L1mod2	# if only  8-bit aligned
 57	bbsi.l	a2, 1, .L2mod4	# if only 16-bit aligned
 58
 59/*
 60 * String is word-aligned.
 61 */
 62.Laligned:
 63	srli	a10, a3, 2	# number of loop iterations with 4B per loop
 64#if XCHAL_HAVE_LOOPS
 65	loopnez	a10, .Ldone
 66#else
 67	beqz	a10, .Ldone
 68	slli	a10, a10, 2
 69	add	a10, a10, a4	# a10 = end of last 4B chunk
 70#endif /* XCHAL_HAVE_LOOPS */
 71.Loop:
 72EX(10f)	l32i	a9, a4, 4		# get next word of string
 73	addi	a4, a4, 4		# advance string pointer
 74	bnone	a9, a5, .Lz0		# if byte 0 is zero
 75	bnone	a9, a6, .Lz1		# if byte 1 is zero
 76	bnone	a9, a7, .Lz2		# if byte 2 is zero
 77	bnone	a9, a8, .Lz3		# if byte 3 is zero
 78#if !XCHAL_HAVE_LOOPS
 79	blt	a4, a10, .Loop
 80#endif
 81
 82.Ldone:
 83EX(10f)	l32i	a9, a4, 4	# load 4 bytes for remaining checks
 84
 85	bbci.l	a3, 1, .L100
 86	# check two more bytes (bytes 0, 1 of word)
 87	addi	a4, a4, 2	# advance string pointer
 88	bnone	a9, a5, .Lz0	# if byte 0 is zero
 89	bnone	a9, a6, .Lz1	# if byte 1 is zero
 90.L100:
 91	bbci.l	a3, 0, .L101
 92	# check one more byte (byte 2 of word)
 93	# Actually, we don't need to check.  Zero or nonzero, we'll add one.
 94	# Do not add an extra one for the NULL terminator since we have
 95	#  exhausted the original len parameter.
 96	addi	a4, a4, 1	# advance string pointer
 97.L101:
 98	sub	a2, a4, a2	# compute length
 99	abi_ret_default
100
101# NOTE that in several places below, we point to the byte just after
102# the zero byte in order to include the NULL terminator in the count.
103
104.Lz3:	# byte 3 is zero
105	addi	a4, a4, 3	# point to zero byte
106.Lz0:	# byte 0 is zero
107	addi	a4, a4, 1	# point just beyond zero byte
108	sub	a2, a4, a2	# subtract to get length
109	abi_ret_default
110.Lz1:	# byte 1 is zero
111	addi	a4, a4, 1+1	# point just beyond zero byte
112	sub	a2, a4, a2	# subtract to get length
113	abi_ret_default
114.Lz2:	# byte 2 is zero
115	addi	a4, a4, 2+1	# point just beyond zero byte
116	sub	a2, a4, a2	# subtract to get length
117	abi_ret_default
118
119.L1mod2:	# address is odd
120EX(10f)	l8ui	a9, a4, 4		# get byte 0
121	addi	a4, a4, 1		# advance string pointer
122	beqz	a9, .Lz3		# if byte 0 is zero
123	bbci.l	a4, 1, .Laligned	# if string pointer is now word-aligned
124
125.L2mod4:	# address is 2 mod 4
126	addi	a4, a4, 2	# advance ptr for aligned access
127EX(10f)	l32i	a9, a4, 0	# get word with first two bytes of string
128	bnone	a9, a7, .Lz2	# if byte 2 (of word, not string) is zero
129	bany	a9, a8, .Laligned # if byte 3 (of word, not string) is nonzero
130	# byte 3 is zero
131	addi	a4, a4, 3+1	# point just beyond zero byte
132	sub	a2, a4, a2	# subtract to get length
133	abi_ret_default
134
135ENDPROC(__strnlen_user)
136EXPORT_SYMBOL(__strnlen_user)
137
138	.section .fixup, "ax"
139	.align	4
14010:
141	movi	a2, 0
142	abi_ret_default