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// Copyright 2018 The gVisor Authors.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
package pagetables
import (
"unsafe"
"gvisor.dev/gvisor/pkg/hostarch"
)
// newAlignedPTEs returns a set of aligned PTEs.
func newAlignedPTEs() *PTEs {
ptes := new(PTEs)
offset := physicalFor(ptes) & (hostarch.PageSize - 1)
if offset == 0 {
// Already aligned.
return ptes
}
// Need to force an aligned allocation.
unaligned := make([]byte, (2*hostarch.PageSize)-1)
offset = uintptr(unsafe.Pointer(&unaligned[0])) & (hostarch.PageSize - 1)
if offset != 0 {
offset = hostarch.PageSize - offset
}
return (*PTEs)(unsafe.Pointer(&unaligned[offset]))
}
// physicalFor returns the "physical" address for PTEs.
//
//go:nosplit
func physicalFor(ptes *PTEs) uintptr {
return uintptr(unsafe.Pointer(ptes))
}
// fromPhysical returns the PTEs from the "physical" address.
//
//go:nosplit
func fromPhysical(physical uintptr) *PTEs {
return (*PTEs)(unsafe.Pointer(physical))
}
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