/*
 *  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 <linux/linkage.h>
#include <asm/asmmacro.h>
#include <asm/core.h>

/*
 * 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
ENTRY(__strnlen_user)

        abi_entry_default
        # 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(10f) l32i    a9, a4, 4               # 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(10f) l32i    a9, a4, 4       # 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
        abi_ret_default

# 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
        abi_ret_default
.Lz1:   # byte 1 is zero
        addi    a4, a4, 1+1     # point just beyond zero byte
        sub     a2, a4, a2      # subtract to get length
        abi_ret_default
.Lz2:   # byte 2 is zero
        addi    a4, a4, 2+1     # point just beyond zero byte
        sub     a2, a4, a2      # subtract to get length
        abi_ret_default

.L1mod2:        # address is odd
EX(10f) l8ui    a9, a4, 4               # 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(10f) l32i    a9, a4, 0       # 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
        abi_ret_default

ENDPROC(__strnlen_user)
EXPORT_SYMBOL(__strnlen_user)

        .section .fixup, "ax"
        .align  4
10:
        movi    a2, 0
        abi_ret_default