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/* $NetBSD: atomic_swap.S,v 1.14 2015/05/17 20:57:11 justin Exp $ */
/*-
* Copyright (c) 2007,2012 The NetBSD Foundation, Inc.
* All rights reserved.
*
* This code is derived from software contributed to The NetBSD Foundation
* by Jason R. Thorpe and Matt Thomas.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
*
* THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
* ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
* TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
* PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
* BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
* CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
* SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
* INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
* CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
* ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
* POSSIBILITY OF SUCH DAMAGE.
*/
#include "atomic_op_asm.h"
/*
* While SWP{B} is sufficient on its own for pre-ARMv7 CPUs, on MP ARMv7 cores
* SWP{B} is disabled since it's no longer atomic among multiple CPUs. They
* will actually raise an UNDEFINED exception.
*
* So if we use the LDREX/STREX template, but use a SWP instruction followed
* by a MOV instruction (using a temporary register), that gives a handler
* for the SWP UNDEFINED exception enough information to "patch" this instance
* SWP with correct forms of LDREX/STREX. (note that this would happen even
* "read-only" pages. If the page gets tossed, we will get another exception
* and fix yet again).
*/
ENTRY_NP(_atomic_swap_32)
mov ip, r0
1:
#ifdef _ARM_ARCH_6
ldrex r0, [ip]
cmp r0, r1
#ifdef __thumb__
beq 99f
strex r3, r1, [ip]
cmp r3, #0
#else
strexne r3, r1, [ip]
cmpne r3, #0
#endif
#else
swp r0, r1, [ip]
cmp r0, r1
movsne r3, #0
cmpne r3, #0
#endif
bne 1b
#ifdef _ARM_ARCH_7
dmb
#else
mcr p15, 0, r3, c7, c10, 5 /* data memory barrier */
#endif
99:
RET
END(_atomic_swap_32)
ATOMIC_OP_ALIAS(atomic_swap_32,_atomic_swap_32)
ATOMIC_OP_ALIAS(atomic_swap_uint,_atomic_swap_32)
ATOMIC_OP_ALIAS(atomic_swap_ulong,_atomic_swap_32)
ATOMIC_OP_ALIAS(atomic_swap_ptr,_atomic_swap_32)
CRT_ALIAS(__sync_lock_test_and_set_4,_atomic_swap_32)
CRT_ALIAS(__atomic_exchange_4,_atomic_swap_32)
STRONG_ALIAS(_atomic_swap_uint,_atomic_swap_32)
STRONG_ALIAS(_atomic_swap_ulong,_atomic_swap_32)
STRONG_ALIAS(_atomic_swap_ptr,_atomic_swap_32)
#if (!defined(_KERNEL) || !defined(_RUMPKERNEL)) && !defined(_STANDALONE)
ENTRY_NP(__sync_lock_release_4)
mov r1, #0
#ifdef _ARM_ARCH_7
dmb
#else
mcr p15, 0, r1, c7, c10, 5 /* data memory barrier */
#endif
strb r1, [r0]
RET
END(__sync_lock_release_4)
#endif
ENTRY_NP(_atomic_swap_8)
mov ip, r0
1:
#ifdef _ARM_ARCH_6
ldrexb r0, [ip]
strexb r3, r1, [ip]
#else
swpb r0, r1, [ip]
mov r3, #0
#endif
cmp r3, #0
bne 1b
#ifdef _ARM_ARCH_7
dmb
#else
mcr p15, 0, ip, c7, c10, 5 /* data memory barrier */
#endif
RET
END(_atomic_swap_8)
ATOMIC_OP_ALIAS(atomic_swap_8,_atomic_swap_8)
ATOMIC_OP_ALIAS(atomic_swap_char,_atomic_swap_8)
ATOMIC_OP_ALIAS(atomic_swap_uchar,_atomic_swap_8)
CRT_ALIAS(__sync_lock_test_and_set_1,_atomic_swap_8)
CRT_ALIAS(__atomic_exchange_1,_atomic_swap_8)
STRONG_ALIAS(_atomic_swap_char,_atomic_swap_8)
STRONG_ALIAS(_atomic_swap_uchar,_atomic_swap_8)
#if (!defined(_KERNEL) || !defined(_RUMPKERNEL)) && !defined(_STANDALONE)
ENTRY_NP(__sync_lock_release_1)
mov r1, #0
#ifdef _ARM_ARCH_7
dmb
#else
mcr p15, 0, r1, c7, c10, 5 /* data memory barrier */
#endif
strb r1, [r0]
RET
END(__sync_lock_release_1)
#endif
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