strnlen_user.S (3724B)
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) 136 137 .section .fixup, "ax" 138 .align 4 13910: 140 movi a2, 0 141 abi_ret_default