linux/arch/arm64/lib/bitops.S
Mark Rutland c47d6a04e6 arm64: klib: bitops: fix unpredictable stxr usage
We're currently relying on unpredictable behaviour in our testops
(test_and_*_bit), as stxr is unpredictable when the status register and
the source register are the same

This patch changes reallocates the status register so as to bring us back into
the realm of predictable behaviour. Boot tested on an AEMv8 model.

Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
2013-04-30 15:53:01 +01:00

71 lines
1.6 KiB
ArmAsm

/*
* Based on arch/arm/lib/bitops.h
*
* Copyright (C) 2013 ARM Ltd.
*
* 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/>.
*/
#include <linux/linkage.h>
#include <asm/assembler.h>
/*
* x0: bits 5:0 bit offset
* bits 63:6 word offset
* x1: address
*/
.macro bitop, name, instr
ENTRY( \name )
and x3, x0, #63 // Get bit offset
eor x0, x0, x3 // Clear low bits
mov x2, #1
add x1, x1, x0, lsr #3 // Get word offset
lsl x3, x2, x3 // Create mask
1: ldxr x2, [x1]
\instr x2, x2, x3
stxr w0, x2, [x1]
cbnz w0, 1b
ret
ENDPROC(\name )
.endm
.macro testop, name, instr
ENTRY( \name )
and x3, x0, #63 // Get bit offset
eor x0, x0, x3 // Clear low bits
mov x2, #1
add x1, x1, x0, lsr #3 // Get word offset
lsl x4, x2, x3 // Create mask
smp_dmb ish
1: ldxr x2, [x1]
lsr x0, x2, x3 // Save old value of bit
\instr x2, x2, x4 // toggle bit
stxr w5, x2, [x1]
cbnz w5, 1b
smp_dmb ish
and x0, x0, #1
3: ret
ENDPROC(\name )
.endm
/*
* Atomic bit operations.
*/
bitop change_bit, eor
bitop clear_bit, bic
bitop set_bit, orr
testop test_and_change_bit, eor
testop test_and_clear_bit, bic
testop test_and_set_bit, orr