1/* 2 * arch/xtensa/lib/strncpy_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: -EFAULT if exception before terminator, N if the entire 9 * buffer filled, else strlen. 10 * 11 * Copyright (C) 2002 Tensilica Inc. 12 */ 13 14#include <variant/core.h> 15#include <linux/errno.h> 16 17/* Load or store instructions that may cause exceptions use the EX macro. */ 18 19#define EX(insn,reg1,reg2,offset,handler) \ 209: insn reg1, reg2, offset; \ 21 .section __ex_table, "a"; \ 22 .word 9b, handler; \ 23 .previous 24 25/* 26 * char *__strncpy_user(char *dst, const char *src, size_t len) 27 */ 28 29#ifdef __XTENSA_EB__ 30# define MASK0 0xff000000 31# define MASK1 0x00ff0000 32# define MASK2 0x0000ff00 33# define MASK3 0x000000ff 34#else 35# define MASK0 0x000000ff 36# define MASK1 0x0000ff00 37# define MASK2 0x00ff0000 38# define MASK3 0xff000000 39#endif 40 41# Register use 42# a0/ return address 43# a1/ stack pointer 44# a2/ return value 45# a3/ src 46# a4/ len 47# a5/ mask0 48# a6/ mask1 49# a7/ mask2 50# a8/ mask3 51# a9/ tmp 52# a10/ tmp 53# a11/ dst 54# a12/ tmp 55 56.text 57.align 4 58.global __strncpy_user 59.type __strncpy_user,@function 60__strncpy_user: 61 entry sp, 16 # minimal stack frame 62 # a2/ dst, a3/ src, a4/ len 63 mov a11, a2 # leave dst in return value register 64 beqz a4, .Lret # if len is zero 65 movi a5, MASK0 # mask for byte 0 66 movi a6, MASK1 # mask for byte 1 67 movi a7, MASK2 # mask for byte 2 68 movi a8, MASK3 # mask for byte 3 69 bbsi.l a3, 0, .Lsrc1mod2 # if only 8-bit aligned 70 bbsi.l a3, 1, .Lsrc2mod4 # if only 16-bit aligned 71.Lsrcaligned: # return here when src is word-aligned 72 srli a12, a4, 2 # number of loop iterations with 4B per loop 73 movi a9, 3 74 bnone a11, a9, .Laligned 75 j .Ldstunaligned 76 77.Lsrc1mod2: # src address is odd 78 EX(l8ui, a9, a3, 0, fixup_l) # get byte 0 79 addi a3, a3, 1 # advance src pointer 80 EX(s8i, a9, a11, 0, fixup_s) # store byte 0 81 beqz a9, .Lret # if byte 0 is zero 82 addi a11, a11, 1 # advance dst pointer 83 addi a4, a4, -1 # decrement len 84 beqz a4, .Lret # if len is zero 85 bbci.l a3, 1, .Lsrcaligned # if src is now word-aligned 86 87.Lsrc2mod4: # src address is 2 mod 4 88 EX(l8ui, a9, a3, 0, fixup_l) # get byte 0 89 /* 1-cycle interlock */ 90 EX(s8i, a9, a11, 0, fixup_s) # store byte 0 91 beqz a9, .Lret # if byte 0 is zero 92 addi a11, a11, 1 # advance dst pointer 93 addi a4, a4, -1 # decrement len 94 beqz a4, .Lret # if len is zero 95 EX(l8ui, a9, a3, 1, fixup_l) # get byte 0 96 addi a3, a3, 2 # advance src pointer 97 EX(s8i, a9, a11, 0, fixup_s) # store byte 0 98 beqz a9, .Lret # if byte 0 is zero 99 addi a11, a11, 1 # advance dst pointer 100 addi a4, a4, -1 # decrement len 101 bnez a4, .Lsrcaligned # if len is nonzero 102.Lret: 103 sub a2, a11, a2 # compute strlen 104 retw 105 106/* 107 * dst is word-aligned, src is word-aligned 108 */ 109 .align 4 # 1 mod 4 alignment for LOOPNEZ 110 .byte 0 # (0 mod 4 alignment for LBEG) 111.Laligned: 112#if XCHAL_HAVE_LOOPS 113 loopnez a12, .Loop1done 114#else 115 beqz a12, .Loop1done 116 slli a12, a12, 2 117 add a12, a12, a11 # a12 = end of last 4B chunck 118#endif 119.Loop1: 120 EX(l32i, a9, a3, 0, fixup_l) # get word from src 121 addi a3, a3, 4 # advance src pointer 122 bnone a9, a5, .Lz0 # if byte 0 is zero 123 bnone a9, a6, .Lz1 # if byte 1 is zero 124 bnone a9, a7, .Lz2 # if byte 2 is zero 125 EX(s32i, a9, a11, 0, fixup_s) # store word to dst 126 bnone a9, a8, .Lz3 # if byte 3 is zero 127 addi a11, a11, 4 # advance dst pointer 128#if !XCHAL_HAVE_LOOPS 129 blt a11, a12, .Loop1 130#endif 131 132.Loop1done: 133 bbci.l a4, 1, .L100 134 # copy 2 bytes 135 EX(l16ui, a9, a3, 0, fixup_l) 136 addi a3, a3, 2 # advance src pointer 137#ifdef __XTENSA_EB__ 138 bnone a9, a7, .Lz0 # if byte 2 is zero 139 bnone a9, a8, .Lz1 # if byte 3 is zero 140#else 141 bnone a9, a5, .Lz0 # if byte 0 is zero 142 bnone a9, a6, .Lz1 # if byte 1 is zero 143#endif 144 EX(s16i, a9, a11, 0, fixup_s) 145 addi a11, a11, 2 # advance dst pointer 146.L100: 147 bbci.l a4, 0, .Lret 148 EX(l8ui, a9, a3, 0, fixup_l) 149 /* slot */ 150 EX(s8i, a9, a11, 0, fixup_s) 151 beqz a9, .Lret # if byte is zero 152 addi a11, a11, 1-3 # advance dst ptr 1, but also cancel 153 # the effect of adding 3 in .Lz3 code 154 /* fall thru to .Lz3 and "retw" */ 155 156.Lz3: # byte 3 is zero 157 addi a11, a11, 3 # advance dst pointer 158 sub a2, a11, a2 # compute strlen 159 retw 160.Lz0: # byte 0 is zero 161#ifdef __XTENSA_EB__ 162 movi a9, 0 163#endif /* __XTENSA_EB__ */ 164 EX(s8i, a9, a11, 0, fixup_s) 165 sub a2, a11, a2 # compute strlen 166 retw 167.Lz1: # byte 1 is zero 168#ifdef __XTENSA_EB__ 169 extui a9, a9, 16, 16 170#endif /* __XTENSA_EB__ */ 171 EX(s16i, a9, a11, 0, fixup_s) 172 addi a11, a11, 1 # advance dst pointer 173 sub a2, a11, a2 # compute strlen 174 retw 175.Lz2: # byte 2 is zero 176#ifdef __XTENSA_EB__ 177 extui a9, a9, 16, 16 178#endif /* __XTENSA_EB__ */ 179 EX(s16i, a9, a11, 0, fixup_s) 180 movi a9, 0 181 EX(s8i, a9, a11, 2, fixup_s) 182 addi a11, a11, 2 # advance dst pointer 183 sub a2, a11, a2 # compute strlen 184 retw 185 186 .align 4 # 1 mod 4 alignment for LOOPNEZ 187 .byte 0 # (0 mod 4 alignment for LBEG) 188.Ldstunaligned: 189/* 190 * for now just use byte copy loop 191 */ 192#if XCHAL_HAVE_LOOPS 193 loopnez a4, .Lunalignedend 194#else 195 beqz a4, .Lunalignedend 196 add a12, a11, a4 # a12 = ending address 197#endif /* XCHAL_HAVE_LOOPS */ 198.Lnextbyte: 199 EX(l8ui, a9, a3, 0, fixup_l) 200 addi a3, a3, 1 201 EX(s8i, a9, a11, 0, fixup_s) 202 beqz a9, .Lunalignedend 203 addi a11, a11, 1 204#if !XCHAL_HAVE_LOOPS 205 blt a11, a12, .Lnextbyte 206#endif 207 208.Lunalignedend: 209 sub a2, a11, a2 # compute strlen 210 retw 211 212 213 .section .fixup, "ax" 214 .align 4 215 216 /* For now, just return -EFAULT. Future implementations might 217 * like to clear remaining kernel space, like the fixup 218 * implementation in memset(). Thus, we differentiate between 219 * load/store fixups. */ 220 221fixup_s: 222fixup_l: 223 movi a2, -EFAULT 224 retw 225