128 lines
3.4 KiB
Go
128 lines
3.4 KiB
Go
// Copyright 2018 Google LLC
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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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package ashmem
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import "gvisor.googlesource.com/gvisor/pkg/abi/linux"
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const maxUint64 = ^uint64(0)
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// setFunctions implements segment.Functions generated from segment.Functions for
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// uint64 Key and noValue Value. For more information, see the build file and
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// segment set implementation at pkg/segment/set.go.
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type setFunctions struct{}
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// noValue is a type of range attached value, which is irrelevant here.
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type noValue struct{}
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// MinKey implements segment.Functions.MinKey.
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func (setFunctions) MinKey() uint64 {
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return 0
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}
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// MaxKey implements segment.Functions.MaxKey.
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func (setFunctions) MaxKey() uint64 {
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return maxUint64
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}
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// ClearValue implements segment.Functions.ClearValue.
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func (setFunctions) ClearValue(*noValue) {
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return
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}
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// Merge implements segment.Functions.Merge.
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func (setFunctions) Merge(Range, noValue, Range, noValue) (noValue, bool) {
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return noValue{}, true
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}
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// Split implements segment.Functions.Split.
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func (setFunctions) Split(Range, noValue, uint64) (noValue, noValue) {
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return noValue{}, noValue{}
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}
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// PinBoard represents a set of pinned ranges in ashmem.
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//
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// segment.Set is used for implementation where segments represent
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// ranges of pinned bytes, while gaps represent ranges of unpinned
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// bytes. All ranges are page-aligned.
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//
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// +stateify savable
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type PinBoard struct {
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Set
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}
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// NewPinBoard creates a new pin board with all pages pinned.
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func NewPinBoard() *PinBoard {
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var pb PinBoard
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pb.PinRange(Range{0, maxUint64})
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return &pb
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}
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// PinRange pins all pages in the specified range and returns true
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// if there are any newly pinned pages.
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func (pb *PinBoard) PinRange(r Range) bool {
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pinnedPages := false
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for gap := pb.LowerBoundGap(r.Start); gap.Ok() && gap.Start() < r.End; {
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common := gap.Range().Intersect(r)
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if common.Length() == 0 {
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gap = gap.NextGap()
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continue
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}
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pinnedPages = true
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gap = pb.Insert(gap, common, noValue{}).NextGap()
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}
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return pinnedPages
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}
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// UnpinRange unpins all pages in the specified range.
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func (pb *PinBoard) UnpinRange(r Range) {
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for seg := pb.LowerBoundSegment(r.Start); seg.Ok() && seg.Start() < r.End; {
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common := seg.Range().Intersect(r)
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if common.Length() == 0 {
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seg = seg.NextSegment()
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continue
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}
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seg = pb.RemoveRange(common).NextSegment()
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}
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}
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// RangePinnedStatus returns false if there's at least one unpinned page in the
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// specified range.
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func (pb *PinBoard) RangePinnedStatus(r Range) bool {
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for gap := pb.LowerBoundGap(r.Start); gap.Ok() && gap.Start() < r.End; {
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common := gap.Range().Intersect(r)
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if common.Length() == 0 {
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gap = gap.NextGap()
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continue
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}
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return false
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}
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return true
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}
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// RangeFromAshmemPin converts ashmem's original pin structure
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// to Range.
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func RangeFromAshmemPin(ap linux.AshmemPin) Range {
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if ap.Len == 0 {
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return Range{
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uint64(ap.Offset),
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maxUint64,
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}
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}
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return Range{
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uint64(ap.Offset),
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uint64(ap.Offset) + uint64(ap.Len),
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}
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}
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