46 lines
1.3 KiB
ArmAsm
46 lines
1.3 KiB
ArmAsm
// Copyright 2020 The gVisor Authors.
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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// +build arm64
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#include "funcdata.h"
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#include "textflag.h"
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#define ID_AA64MMFR0_ASIDBITS_SHIFT 4
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#define ID_AA64MMFR0_ASIDBITS_16 2
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#define TCR_EL1_AS_BIT 36
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// GetASIDBits return the system ASID bits, 8 or 16 bits.
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//
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// func GetASIDBits() uint8
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TEXT ·GetASIDBits(SB),NOSPLIT,$0-1
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// First, check whether 16bits ASID is supported.
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// ID_AA64MMFR0_EL1.ASIDBITS[7:4] == 0010.
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WORD $0xd5380700 // MRS ID_AA64MMFR0_EL1, R0
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UBFX $ID_AA64MMFR0_ASIDBITS_SHIFT, R0, $4, R0
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CMPW $ID_AA64MMFR0_ASIDBITS_16, R0
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BNE bits_8
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// Second, check whether 16bits ASID is enabled.
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// TCR_EL1.AS[36] == 1.
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WORD $0xd5382040 // MRS TCR_EL1, R0
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TBZ $TCR_EL1_AS_BIT, R0, bits_8
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MOVD $16, R0
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B done
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bits_8:
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MOVD $8, R0
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done:
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MOVB R0, ret+0(FP)
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RET
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