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Based on 1 normalized pattern(s): this program is free software you can redistribute it and or modify it under the terms of the gnu general public license version 2 as published by the free software foundation this program is distributed in the hope that it will be useful but without any warranty without even the implied warranty of merchantability or fitness for a particular purpose see the gnu general public license for more details you should have received a copy of the gnu general public license along with this program if not see http www gnu org licenses extracted by the scancode license scanner the SPDX license identifier GPL-2.0-only has been chosen to replace the boilerplate/reference in 503 file(s). Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Reviewed-by: Alexios Zavras <alexios.zavras@intel.com> Reviewed-by: Allison Randal <allison@lohutok.net> Reviewed-by: Enrico Weigelt <info@metux.net> Cc: linux-spdx@vger.kernel.org Link: https://lkml.kernel.org/r/20190602204653.811534538@linutronix.de Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
161 lines
4.1 KiB
ArmAsm
161 lines
4.1 KiB
ArmAsm
/* SPDX-License-Identifier: GPL-2.0-only */
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/*
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* Copyright (C) 2013 ARM Ltd.
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* Copyright (C) 2013 Linaro.
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*
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* This code is based on glibc cortex strings work originally authored by Linaro
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* be found @
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*
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* http://bazaar.launchpad.net/~linaro-toolchain-dev/cortex-strings/trunk/
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* files/head:/src/aarch64/
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*/
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#include <linux/linkage.h>
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#include <asm/assembler.h>
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/*
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* determine the length of a fixed-size string
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*
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* Parameters:
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* x0 - const string pointer
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* x1 - maximal string length
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* Returns:
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* x0 - the return length of specific string
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*/
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/* Arguments and results. */
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srcin .req x0
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len .req x0
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limit .req x1
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/* Locals and temporaries. */
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src .req x2
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data1 .req x3
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data2 .req x4
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data2a .req x5
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has_nul1 .req x6
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has_nul2 .req x7
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tmp1 .req x8
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tmp2 .req x9
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tmp3 .req x10
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tmp4 .req x11
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zeroones .req x12
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pos .req x13
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limit_wd .req x14
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#define REP8_01 0x0101010101010101
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#define REP8_7f 0x7f7f7f7f7f7f7f7f
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#define REP8_80 0x8080808080808080
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WEAK(strnlen)
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cbz limit, .Lhit_limit
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mov zeroones, #REP8_01
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bic src, srcin, #15
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ands tmp1, srcin, #15
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b.ne .Lmisaligned
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/* Calculate the number of full and partial words -1. */
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sub limit_wd, limit, #1 /* Limit != 0, so no underflow. */
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lsr limit_wd, limit_wd, #4 /* Convert to Qwords. */
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/*
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* NUL detection works on the principle that (X - 1) & (~X) & 0x80
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* (=> (X - 1) & ~(X | 0x7f)) is non-zero iff a byte is zero, and
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* can be done in parallel across the entire word.
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*/
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/*
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* The inner loop deals with two Dwords at a time. This has a
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* slightly higher start-up cost, but we should win quite quickly,
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* especially on cores with a high number of issue slots per
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* cycle, as we get much better parallelism out of the operations.
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*/
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.Lloop:
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ldp data1, data2, [src], #16
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.Lrealigned:
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sub tmp1, data1, zeroones
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orr tmp2, data1, #REP8_7f
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sub tmp3, data2, zeroones
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orr tmp4, data2, #REP8_7f
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bic has_nul1, tmp1, tmp2
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bic has_nul2, tmp3, tmp4
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subs limit_wd, limit_wd, #1
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orr tmp1, has_nul1, has_nul2
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ccmp tmp1, #0, #0, pl /* NZCV = 0000 */
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b.eq .Lloop
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cbz tmp1, .Lhit_limit /* No null in final Qword. */
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/*
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* We know there's a null in the final Qword. The easiest thing
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* to do now is work out the length of the string and return
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* MIN (len, limit).
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*/
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sub len, src, srcin
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cbz has_nul1, .Lnul_in_data2
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CPU_BE( mov data2, data1 ) /*perpare data to re-calculate the syndrome*/
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sub len, len, #8
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mov has_nul2, has_nul1
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.Lnul_in_data2:
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/*
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* For big-endian, carry propagation (if the final byte in the
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* string is 0x01) means we cannot use has_nul directly. The
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* easiest way to get the correct byte is to byte-swap the data
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* and calculate the syndrome a second time.
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*/
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CPU_BE( rev data2, data2 )
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CPU_BE( sub tmp1, data2, zeroones )
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CPU_BE( orr tmp2, data2, #REP8_7f )
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CPU_BE( bic has_nul2, tmp1, tmp2 )
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sub len, len, #8
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rev has_nul2, has_nul2
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clz pos, has_nul2
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add len, len, pos, lsr #3 /* Bits to bytes. */
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cmp len, limit
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csel len, len, limit, ls /* Return the lower value. */
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ret
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.Lmisaligned:
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/*
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* Deal with a partial first word.
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* We're doing two things in parallel here;
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* 1) Calculate the number of words (but avoiding overflow if
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* limit is near ULONG_MAX) - to do this we need to work out
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* limit + tmp1 - 1 as a 65-bit value before shifting it;
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* 2) Load and mask the initial data words - we force the bytes
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* before the ones we are interested in to 0xff - this ensures
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* early bytes will not hit any zero detection.
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*/
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ldp data1, data2, [src], #16
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sub limit_wd, limit, #1
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and tmp3, limit_wd, #15
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lsr limit_wd, limit_wd, #4
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add tmp3, tmp3, tmp1
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add limit_wd, limit_wd, tmp3, lsr #4
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neg tmp4, tmp1
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lsl tmp4, tmp4, #3 /* Bytes beyond alignment -> bits. */
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mov tmp2, #~0
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/* Big-endian. Early bytes are at MSB. */
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CPU_BE( lsl tmp2, tmp2, tmp4 ) /* Shift (tmp1 & 63). */
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/* Little-endian. Early bytes are at LSB. */
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CPU_LE( lsr tmp2, tmp2, tmp4 ) /* Shift (tmp1 & 63). */
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cmp tmp1, #8
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orr data1, data1, tmp2
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orr data2a, data2, tmp2
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csinv data1, data1, xzr, le
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csel data2, data2, data2a, le
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b .Lrealigned
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.Lhit_limit:
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mov len, limit
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ret
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ENDPIPROC(strnlen)
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EXPORT_SYMBOL_NOKASAN(strnlen)
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