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 <asm/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.text 29.begin literal 30.align 4 31.Lmask0: 32 .byte 0xff, 0x00, 0x00, 0x00 33.Lmask1: 34 .byte 0x00, 0xff, 0x00, 0x00 35.Lmask2: 36 .byte 0x00, 0x00, 0xff, 0x00 37.Lmask3: 38 .byte 0x00, 0x00, 0x00, 0xff 39.end literal 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.align 4 57.global __strncpy_user 58.type __strncpy_user,@function 59__strncpy_user: 60 entry sp, 16 # minimal stack frame 61 # a2/ dst, a3/ src, a4/ len 62 mov a11, a2 # leave dst in return value register 63 beqz a4, .Lret # if len is zero 64 l32r a5, .Lmask0 # mask for byte 0 65 l32r a6, .Lmask1 # mask for byte 1 66 l32r a7, .Lmask2 # mask for byte 2 67 l32r a8, .Lmask3 # mask for byte 3 68 bbsi.l a3, 0, .Lsrc1mod2 # if only 8-bit aligned 69 bbsi.l a3, 1, .Lsrc2mod4 # if only 16-bit aligned 70.Lsrcaligned: # return here when src is word-aligned 71 srli a12, a4, 2 # number of loop iterations with 4B per loop 72 movi a9, 3 73 bnone a11, a9, .Laligned 74 j .Ldstunaligned 75 76.Lsrc1mod2: # src address is odd 77 EX(l8ui, a9, a3, 0, fixup_l) # get byte 0 78 addi a3, a3, 1 # advance src pointer 79 EX(s8i, a9, a11, 0, fixup_s) # store byte 0 80 beqz a9, .Lret # if byte 0 is zero 81 addi a11, a11, 1 # advance dst pointer 82 addi a4, a4, -1 # decrement len 83 beqz a4, .Lret # if len is zero 84 bbci.l a3, 1, .Lsrcaligned # if src is now word-aligned 85 86.Lsrc2mod4: # src address is 2 mod 4 87 EX(l8ui, a9, a3, 0, fixup_l) # get byte 0 88 /* 1-cycle interlock */ 89 EX(s8i, a9, a11, 0, fixup_s) # store byte 0 90 beqz a9, .Lret # if byte 0 is zero 91 addi a11, a11, 1 # advance dst pointer 92 addi a4, a4, -1 # decrement len 93 beqz a4, .Lret # if len is zero 94 EX(l8ui, a9, a3, 1, fixup_l) # get byte 0 95 addi a3, a3, 2 # advance src pointer 96 EX(s8i, a9, a11, 0, fixup_s) # store byte 0 97 beqz a9, .Lret # if byte 0 is zero 98 addi a11, a11, 1 # advance dst pointer 99 addi a4, a4, -1 # decrement len 100 bnez a4, .Lsrcaligned # if len is nonzero 101.Lret: 102 sub a2, a11, a2 # compute strlen 103 retw 104 105/* 106 * dst is word-aligned, src is word-aligned 107 */ 108 .align 4 # 1 mod 4 alignment for LOOPNEZ 109 .byte 0 # (0 mod 4 alignment for LBEG) 110.Laligned: 111#if XCHAL_HAVE_LOOPS 112 loopnez a12, .Loop1done 113#else 114 beqz a12, .Loop1done 115 slli a12, a12, 2 116 add a12, a12, a11 # a12 = end of last 4B chunck 117#endif 118.Loop1: 119 EX(l32i, a9, a3, 0, fixup_l) # get word from src 120 addi a3, a3, 4 # advance src pointer 121 bnone a9, a5, .Lz0 # if byte 0 is zero 122 bnone a9, a6, .Lz1 # if byte 1 is zero 123 bnone a9, a7, .Lz2 # if byte 2 is zero 124 EX(s32i, a9, a11, 0, fixup_s) # store word to dst 125 bnone a9, a8, .Lz3 # if byte 3 is zero 126 addi a11, a11, 4 # advance dst pointer 127#if !XCHAL_HAVE_LOOPS 128 blt a11, a12, .Loop1 129#endif 130 131.Loop1done: 132 bbci.l a4, 1, .L100 133 # copy 2 bytes 134 EX(l16ui, a9, a3, 0, fixup_l) 135 addi a3, a3, 2 # advance src pointer 136#ifdef __XTENSA_EB__ 137 bnone a9, a7, .Lz0 # if byte 2 is zero 138 bnone a9, a8, .Lz1 # if byte 3 is zero 139#else 140 bnone a9, a5, .Lz0 # if byte 0 is zero 141 bnone a9, a6, .Lz1 # if byte 1 is zero 142#endif 143 EX(s16i, a9, a11, 0, fixup_s) 144 addi a11, a11, 2 # advance dst pointer 145.L100: 146 bbci.l a4, 0, .Lret 147 EX(l8ui, a9, a3, 0, fixup_l) 148 /* slot */ 149 EX(s8i, a9, a11, 0, fixup_s) 150 beqz a9, .Lret # if byte is zero 151 addi a11, a11, 1-3 # advance dst ptr 1, but also cancel 152 # the effect of adding 3 in .Lz3 code 153 /* fall thru to .Lz3 and "retw" */ 154 155.Lz3: # byte 3 is zero 156 addi a11, a11, 3 # advance dst pointer 157 sub a2, a11, a2 # compute strlen 158 retw 159.Lz0: # byte 0 is zero 160#ifdef __XTENSA_EB__ 161 movi a9, 0 162#endif /* __XTENSA_EB__ */ 163 EX(s8i, a9, a11, 0, fixup_s) 164 sub a2, a11, a2 # compute strlen 165 retw 166.Lz1: # byte 1 is zero 167#ifdef __XTENSA_EB__ 168 extui a9, a9, 16, 16 169#endif /* __XTENSA_EB__ */ 170 EX(s16i, a9, a11, 0, fixup_s) 171 addi a11, a11, 1 # advance dst pointer 172 sub a2, a11, a2 # compute strlen 173 retw 174.Lz2: # byte 2 is zero 175#ifdef __XTENSA_EB__ 176 extui a9, a9, 16, 16 177#endif /* __XTENSA_EB__ */ 178 EX(s16i, a9, a11, 0, fixup_s) 179 movi a9, 0 180 EX(s8i, a9, a11, 2, fixup_s) 181 addi a11, a11, 2 # advance dst pointer 182 sub a2, a11, a2 # compute strlen 183 retw 184 185 .align 4 # 1 mod 4 alignment for LOOPNEZ 186 .byte 0 # (0 mod 4 alignment for LBEG) 187.Ldstunaligned: 188/* 189 * for now just use byte copy loop 190 */ 191#if XCHAL_HAVE_LOOPS 192 loopnez a4, .Lunalignedend 193#else 194 beqz a4, .Lunalignedend 195 add a12, a11, a4 # a12 = ending address 196#endif /* XCHAL_HAVE_LOOPS */ 197.Lnextbyte: 198 EX(l8ui, a9, a3, 0, fixup_l) 199 addi a3, a3, 1 200 EX(s8i, a9, a11, 0, fixup_s) 201 beqz a9, .Lunalignedend 202 addi a11, a11, 1 203#if !XCHAL_HAVE_LOOPS 204 blt a11, a12, .Lnextbyte 205#endif 206 207.Lunalignedend: 208 sub a2, a11, a2 # compute strlen 209 retw 210 211 212 .section .fixup, "ax" 213 .align 4 214 215 /* For now, just return -EFAULT. Future implementations might 216 * like to clear remaining kernel space, like the fixup 217 * implementation in memset(). Thus, we differentiate between 218 * load/store fixups. */ 219 220fixup_s: 221fixup_l: 222 movi a2, -EFAULT 223 retw 224 225