1 files changed, 127 insertions, 0 deletions
diff --git a/pkg/sentry/fs/ashmem/pin_board.go b/pkg/sentry/fs/ashmem/pin_board.go
new file mode 100644
index 000000000..bdf23b371
--- /dev/null
+++ b/pkg/sentry/fs/ashmem/pin_board.go
@@ -0,0 +1,127 @@
+// 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 ashmem
+
+import "gvisor.googlesource.com/gvisor/pkg/abi/linux"
+
+const maxUint64 = ^uint64(0)
+
+// setFunctions implements segment.Functions generated from segment.Functions for
+// uint64 Key and noValue Value. For more information, see the build file and
+// segment set implementation at pkg/segment/set.go.
+type setFunctions struct{}
+
+// noValue is a type of range attached value, which is irrelevant here.
+type noValue struct{}
+
+// MinKey implements segment.Functions.MinKey.
+func (setFunctions) MinKey() uint64 {
+	return 0
+}
+
+// MaxKey implements segment.Functions.MaxKey.
+func (setFunctions) MaxKey() uint64 {
+	return maxUint64
+}
+
+// ClearValue implements segment.Functions.ClearValue.
+func (setFunctions) ClearValue(*noValue) {
+	return
+}
+
+// Merge implements segment.Functions.Merge.
+func (setFunctions) Merge(Range, noValue, Range, noValue) (noValue, bool) {
+	return noValue{}, true
+}
+
+// Split implements segment.Functions.Split.
+func (setFunctions) Split(Range, noValue, uint64) (noValue, noValue) {
+	return noValue{}, noValue{}
+}
+
+// PinBoard represents a set of pinned ranges in ashmem.
+//
+// segment.Set is used for implementation where segments represent
+// ranges of pinned bytes, while gaps represent ranges of unpinned
+// bytes. All ranges are page-aligned.
+//
+// +stateify savable
+type PinBoard struct {
+	Set
+}
+
+// NewPinBoard creates a new pin board with all pages pinned.
+func NewPinBoard() *PinBoard {
+	var pb PinBoard
+	pb.PinRange(Range{0, maxUint64})
+	return &pb
+}
+
+// PinRange pins all pages in the specified range and returns true
+// if there are any newly pinned pages.
+func (pb *PinBoard) PinRange(r Range) bool {
+	pinnedPages := false
+	for gap := pb.LowerBoundGap(r.Start); gap.Ok() && gap.Start() < r.End; {
+		common := gap.Range().Intersect(r)
+		if common.Length() == 0 {
+			gap = gap.NextGap()
+			continue
+		}
+		pinnedPages = true
+		gap = pb.Insert(gap, common, noValue{}).NextGap()
+	}
+	return pinnedPages
+}
+
+// UnpinRange unpins all pages in the specified range.
+func (pb *PinBoard) UnpinRange(r Range) {
+	for seg := pb.LowerBoundSegment(r.Start); seg.Ok() && seg.Start() < r.End; {
+		common := seg.Range().Intersect(r)
+		if common.Length() == 0 {
+			seg = seg.NextSegment()
+			continue
+		}
+		seg = pb.RemoveRange(common).NextSegment()
+	}
+}
+
+// RangePinnedStatus returns false if there's at least one unpinned page in the
+// specified range.
+func (pb *PinBoard) RangePinnedStatus(r Range) bool {
+	for gap := pb.LowerBoundGap(r.Start); gap.Ok() && gap.Start() < r.End; {
+		common := gap.Range().Intersect(r)
+		if common.Length() == 0 {
+			gap = gap.NextGap()
+			continue
+		}
+		return false
+	}
+	return true
+}
+
+// RangeFromAshmemPin converts ashmem's original pin structure
+// to Range.
+func RangeFromAshmemPin(ap linux.AshmemPin) Range {
+	if ap.Len == 0 {
+		return Range{
+			uint64(ap.Offset),
+			maxUint64,
+		}
+	}
+	return Range{
+		uint64(ap.Offset),
+		uint64(ap.Offset) + uint64(ap.Len),
+	}
+}