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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
// Address constraints.
//
// The lowerTop and upperBottom currently apply to four-level pagetables;
// additional refactoring would be necessary to support five-level pagetables.
const (
lowerTop = 0x00007fffffffffff
upperBottom = 0xffff800000000000
pteShift = 12
pmdShift = 21
pudShift = 30
pgdShift = 39
pteMask = 0x1ff << pteShift
pmdMask = 0x1ff << pmdShift
pudMask = 0x1ff << pudShift
pgdMask = 0x1ff << pgdShift
pteSize = 1 << pteShift
pmdSize = 1 << pmdShift
pudSize = 1 << pudShift
pgdSize = 1 << pgdShift
executeDisable = 1 << 63
entriesPerPage = 512
)
// InitArch does some additional initialization related to the architecture.
//
// +checkescape:hard,stack
//go:nosplit
func (p *PageTables) InitArch(allocator Allocator) {
if p.upperSharedPageTables != nil {
p.cloneUpperShared()
}
}
//go:nosplit
func pgdIndex(upperStart uintptr) uintptr {
if upperStart&(pgdSize-1) != 0 {
panic("upperStart should be pgd size aligned")
}
if upperStart >= upperBottom {
return entriesPerPage/2 + (upperStart-upperBottom)/pgdSize
}
if upperStart < lowerTop {
return upperStart / pgdSize
}
panic("upperStart should be in canonical range")
}
// cloneUpperShared clone the upper from the upper shared page tables.
//
//go:nosplit
func (p *PageTables) cloneUpperShared() {
start := pgdIndex(p.upperStart)
copy(p.root[start:entriesPerPage], p.upperSharedPageTables.root[start:entriesPerPage])
}
// PTEs is a collection of entries.
type PTEs [entriesPerPage]PTE
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