/* * arch/xtensa/lib/strnlen_user.S * * This file is subject to the terms and conditions of the GNU General * Public License. See the file "COPYING" in the main directory of * this archive for more details. * * Returns strnlen, including trailing zero terminator. * Zero indicates error. * * Copyright (C) 2002 Tensilica Inc. */ #include <asm/variant/core.h> /* Load or store instructions that may cause exceptions use the EX macro. */ #define EX(insn,reg1,reg2,offset,handler) \ 9: insn reg1, reg2, offset; \ .section __ex_table, "a"; \ .word 9b, handler; \ .previous /* * size_t __strnlen_user(const char *s, size_t len) */ #ifdef __XTENSA_EB__ # define MASK0 0xff000000 # define MASK1 0x00ff0000 # define MASK2 0x0000ff00 # define MASK3 0x000000ff #else # define MASK0 0x000000ff # define MASK1 0x0000ff00 # define MASK2 0x00ff0000 # define MASK3 0xff000000 #endif # Register use: # a2/ src # a3/ len # a4/ tmp # a5/ mask0 # a6/ mask1 # a7/ mask2 # a8/ mask3 # a9/ tmp # a10/ tmp .text .align 4 .global __strnlen_user .type __strnlen_user,@function __strnlen_user: entry sp, 16 # minimal stack frame # a2/ s, a3/ len addi a4, a2, -4 # because we overincrement at the end; # we compensate with load offsets of 4 movi a5, MASK0 # mask for byte 0 movi a6, MASK1 # mask for byte 1 movi a7, MASK2 # mask for byte 2 movi a8, MASK3 # mask for byte 3 bbsi.l a2, 0, .L1mod2 # if only 8-bit aligned bbsi.l a2, 1, .L2mod4 # if only 16-bit aligned /* * String is word-aligned. */ .Laligned: srli a10, a3, 2 # number of loop iterations with 4B per loop #if XCHAL_HAVE_LOOPS loopnez a10, .Ldone #else beqz a10, .Ldone slli a10, a10, 2 add a10, a10, a4 # a10 = end of last 4B chunk #endif /* XCHAL_HAVE_LOOPS */ .Loop: EX(l32i, a9, a4, 4, lenfixup) # get next word of string addi a4, a4, 4 # advance string pointer bnone a9, a5, .Lz0 # if byte 0 is zero bnone a9, a6, .Lz1 # if byte 1 is zero bnone a9, a7, .Lz2 # if byte 2 is zero bnone a9, a8, .Lz3 # if byte 3 is zero #if !XCHAL_HAVE_LOOPS blt a4, a10, .Loop #endif .Ldone: EX(l32i, a9, a4, 4, lenfixup) # load 4 bytes for remaining checks bbci.l a3, 1, .L100 # check two more bytes (bytes 0, 1 of word) addi a4, a4, 2 # advance string pointer bnone a9, a5, .Lz0 # if byte 0 is zero bnone a9, a6, .Lz1 # if byte 1 is zero .L100: bbci.l a3, 0, .L101 # check one more byte (byte 2 of word) # Actually, we don't need to check. Zero or nonzero, we'll add one. # Do not add an extra one for the NULL terminator since we have # exhausted the original len parameter. addi a4, a4, 1 # advance string pointer .L101: sub a2, a4, a2 # compute length retw # NOTE that in several places below, we point to the byte just after # the zero byte in order to include the NULL terminator in the count. .Lz3: # byte 3 is zero addi a4, a4, 3 # point to zero byte .Lz0: # byte 0 is zero addi a4, a4, 1 # point just beyond zero byte sub a2, a4, a2 # subtract to get length retw .Lz1: # byte 1 is zero addi a4, a4, 1+1 # point just beyond zero byte sub a2, a4, a2 # subtract to get length retw .Lz2: # byte 2 is zero addi a4, a4, 2+1 # point just beyond zero byte sub a2, a4, a2 # subtract to get length retw .L1mod2: # address is odd EX(l8ui, a9, a4, 4, lenfixup) # get byte 0 addi a4, a4, 1 # advance string pointer beqz a9, .Lz3 # if byte 0 is zero bbci.l a4, 1, .Laligned # if string pointer is now word-aligned .L2mod4: # address is 2 mod 4 addi a4, a4, 2 # advance ptr for aligned access EX(l32i, a9, a4, 0, lenfixup) # get word with first two bytes of string bnone a9, a7, .Lz2 # if byte 2 (of word, not string) is zero bany a9, a8, .Laligned # if byte 3 (of word, not string) is nonzero # byte 3 is zero addi a4, a4, 3+1 # point just beyond zero byte sub a2, a4, a2 # subtract to get length retw .section .fixup, "ax" .align 4 lenfixup: movi a2, 0 retw