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 <asm/variant/core.h> 15 16/* Load or store instructions that may cause exceptions use the EX macro. */ 17 18#define EX(insn,reg1,reg2,offset,handler) \ 199: insn reg1, reg2, offset; \ 20 .section __ex_table, "a"; \ 21 .word 9b, handler; \ 22 .previous 23 24/* 25 * size_t __strnlen_user(const char *s, size_t len) 26 */ 27 28#ifdef __XTENSA_EB__ 29# define MASK0 0xff000000 30# define MASK1 0x00ff0000 31# define MASK2 0x0000ff00 32# define MASK3 0x000000ff 33#else 34# define MASK0 0x000000ff 35# define MASK1 0x0000ff00 36# define MASK2 0x00ff0000 37# define MASK3 0xff000000 38#endif 39 40# Register use: 41# a2/ src 42# a3/ len 43# a4/ tmp 44# a5/ mask0 45# a6/ mask1 46# a7/ mask2 47# a8/ mask3 48# a9/ tmp 49# a10/ tmp 50 51.text 52.align 4 53.global __strnlen_user 54.type __strnlen_user,@function 55__strnlen_user: 56 entry sp, 16 # minimal stack frame 57 # a2/ s, a3/ len 58 addi a4, a2, -4 # because we overincrement at the end; 59 # we compensate with load offsets of 4 60 movi a5, MASK0 # mask for byte 0 61 movi a6, MASK1 # mask for byte 1 62 movi a7, MASK2 # mask for byte 2 63 movi a8, MASK3 # mask for byte 3 64 bbsi.l a2, 0, .L1mod2 # if only 8-bit aligned 65 bbsi.l a2, 1, .L2mod4 # if only 16-bit aligned 66 67/* 68 * String is word-aligned. 69 */ 70.Laligned: 71 srli a10, a3, 2 # number of loop iterations with 4B per loop 72#if XCHAL_HAVE_LOOPS 73 loopnez a10, .Ldone 74#else 75 beqz a10, .Ldone 76 slli a10, a10, 2 77 add a10, a10, a4 # a10 = end of last 4B chunk 78#endif /* XCHAL_HAVE_LOOPS */ 79.Loop: 80 EX(l32i, a9, a4, 4, lenfixup) # get next word of string 81 addi a4, a4, 4 # advance string pointer 82 bnone a9, a5, .Lz0 # if byte 0 is zero 83 bnone a9, a6, .Lz1 # if byte 1 is zero 84 bnone a9, a7, .Lz2 # if byte 2 is zero 85 bnone a9, a8, .Lz3 # if byte 3 is zero 86#if !XCHAL_HAVE_LOOPS 87 blt a4, a10, .Loop 88#endif 89 90.Ldone: 91 EX(l32i, a9, a4, 4, lenfixup) # load 4 bytes for remaining checks 92 93 bbci.l a3, 1, .L100 94 # check two more bytes (bytes 0, 1 of word) 95 addi a4, a4, 2 # advance string pointer 96 bnone a9, a5, .Lz0 # if byte 0 is zero 97 bnone a9, a6, .Lz1 # if byte 1 is zero 98.L100: 99 bbci.l a3, 0, .L101 100 # check one more byte (byte 2 of word) 101 # Actually, we don't need to check. Zero or nonzero, we'll add one. 102 # Do not add an extra one for the NULL terminator since we have 103 # exhausted the original len parameter. 104 addi a4, a4, 1 # advance string pointer 105.L101: 106 sub a2, a4, a2 # compute length 107 retw 108 109# NOTE that in several places below, we point to the byte just after 110# the zero byte in order to include the NULL terminator in the count. 111 112.Lz3: # byte 3 is zero 113 addi a4, a4, 3 # point to zero byte 114.Lz0: # byte 0 is zero 115 addi a4, a4, 1 # point just beyond zero byte 116 sub a2, a4, a2 # subtract to get length 117 retw 118.Lz1: # byte 1 is zero 119 addi a4, a4, 1+1 # point just beyond zero byte 120 sub a2, a4, a2 # subtract to get length 121 retw 122.Lz2: # byte 2 is zero 123 addi a4, a4, 2+1 # point just beyond zero byte 124 sub a2, a4, a2 # subtract to get length 125 retw 126 127.L1mod2: # address is odd 128 EX(l8ui, a9, a4, 4, lenfixup) # get byte 0 129 addi a4, a4, 1 # advance string pointer 130 beqz a9, .Lz3 # if byte 0 is zero 131 bbci.l a4, 1, .Laligned # if string pointer is now word-aligned 132 133.L2mod4: # address is 2 mod 4 134 addi a4, a4, 2 # advance ptr for aligned access 135 EX(l32i, a9, a4, 0, lenfixup) # get word with first two bytes of string 136 bnone a9, a7, .Lz2 # if byte 2 (of word, not string) is zero 137 bany a9, a8, .Laligned # if byte 3 (of word, not string) is nonzero 138 # byte 3 is zero 139 addi a4, a4, 3+1 # point just beyond zero byte 140 sub a2, a4, a2 # subtract to get length 141 retw 142 143 .section .fixup, "ax" 144 .align 4 145lenfixup: 146 movi a2, 0 147 retw 148