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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