3 files changed, 160 insertions, 0 deletions
diff --git a/pkg/sentry/fs/fsutil/BUILD b/pkg/sentry/fs/fsutil/BUILD
index 4965e1a5f..d4767642b 100644
--- a/pkg/sentry/fs/fsutil/BUILD
+++ b/pkg/sentry/fs/fsutil/BUILD
@@ -70,6 +70,8 @@ go_library(
         "host_file_mapper.go",
         "host_file_mapper_state.go",
         "host_file_mapper_unsafe.go",
+        "host_mappable.go",
+        "host_mappable_state.go",
         "inode.go",
         "inode_cached.go",
     ],
diff --git a/pkg/sentry/fs/fsutil/host_mappable.go b/pkg/sentry/fs/fsutil/host_mappable.go
new file mode 100644
index 000000000..4e4bcf4a4
--- /dev/null
+++ b/pkg/sentry/fs/fsutil/host_mappable.go
@@ -0,0 +1,136 @@
+// Copyright 2019 Google LLC
+//
+// 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 fsutil
+
+import (
+	"sync"
+
+	"gvisor.googlesource.com/gvisor/pkg/sentry/context"
+	"gvisor.googlesource.com/gvisor/pkg/sentry/memmap"
+	"gvisor.googlesource.com/gvisor/pkg/sentry/platform"
+	"gvisor.googlesource.com/gvisor/pkg/sentry/safemem"
+	"gvisor.googlesource.com/gvisor/pkg/sentry/usermem"
+)
+
+// HostMappable implements memmap.Mappable and platform.File over an arbitrary
+// host file descriptor.
+//
+// +stateify savable
+type HostMappable struct {
+	hostFileMapper *HostFileMapper
+
+	mu sync.Mutex `state:"nosave"`
+
+	// fd is the file descriptor to the host. Protected by mu.
+	fd int `state:"nosave"`
+
+	// mappings tracks mappings of the cached file object into
+	// memmap.MappingSpaces so it can invalidated upon save. Protected by mu.
+	mappings memmap.MappingSet
+}
+
+// NewHostMappable creates a new mappable that maps directly to host FD.
+func NewHostMappable() *HostMappable {
+	return &HostMappable{
+		hostFileMapper: NewHostFileMapper(),
+		fd:             -1,
+	}
+}
+
+func (h *HostMappable) getFD() int {
+	h.mu.Lock()
+	defer h.mu.Unlock()
+	if h.fd < 0 {
+		panic("HostMappable FD isn't set")
+	}
+	return h.fd
+}
+
+// UpdateFD sets the host FD iff FD hasn't been set before or if there are
+// no mappings.
+func (h *HostMappable) UpdateFD(fd int) {
+	h.mu.Lock()
+	defer h.mu.Unlock()
+	h.fd = fd
+}
+
+// AddMapping implements memmap.Mappable.AddMapping.
+func (h *HostMappable) AddMapping(ctx context.Context, ms memmap.MappingSpace, ar usermem.AddrRange, offset uint64, writable bool) error {
+	// Hot path. Avoid defers.
+	h.mu.Lock()
+	mapped := h.mappings.AddMapping(ms, ar, offset, writable)
+	for _, r := range mapped {
+		h.hostFileMapper.IncRefOn(r)
+	}
+	h.mu.Unlock()
+	return nil
+}
+
+// RemoveMapping implements memmap.Mappable.RemoveMapping.
+func (h *HostMappable) RemoveMapping(ctx context.Context, ms memmap.MappingSpace, ar usermem.AddrRange, offset uint64, writable bool) {
+	// Hot path. Avoid defers.
+	h.mu.Lock()
+	unmapped := h.mappings.RemoveMapping(ms, ar, offset, writable)
+	for _, r := range unmapped {
+		h.hostFileMapper.DecRefOn(r)
+	}
+	h.mu.Unlock()
+}
+
+// CopyMapping implements memmap.Mappable.CopyMapping.
+func (h *HostMappable) CopyMapping(ctx context.Context, ms memmap.MappingSpace, srcAR, dstAR usermem.AddrRange, offset uint64, writable bool) error {
+	return h.AddMapping(ctx, ms, dstAR, offset, writable)
+}
+
+// Translate implements memmap.Mappable.Translate.
+func (h *HostMappable) Translate(ctx context.Context, required, optional memmap.MappableRange, at usermem.AccessType) ([]memmap.Translation, error) {
+	return []memmap.Translation{
+		{
+			Source: optional,
+			File:   h,
+			Offset: optional.Start,
+		},
+	}, nil
+}
+
+// InvalidateUnsavable implements memmap.Mappable.InvalidateUnsavable.
+func (h *HostMappable) InvalidateUnsavable(ctx context.Context) error {
+	h.mu.Lock()
+	h.mappings.InvalidateAll(memmap.InvalidateOpts{})
+	h.mu.Unlock()
+	return nil
+}
+
+// MapInto implements platform.File.MapInto.
+func (h *HostMappable) MapInto(as platform.AddressSpace, addr usermem.Addr, fr platform.FileRange, at usermem.AccessType, precommit bool) error {
+	return as.MapFile(addr, h.getFD(), fr, at, precommit)
+}
+
+// MapInternal implements platform.File.MapInternal.
+func (h *HostMappable) MapInternal(fr platform.FileRange, at usermem.AccessType) (safemem.BlockSeq, error) {
+	return h.hostFileMapper.MapInternal(fr, h.getFD(), at.Write)
+}
+
+// IncRef implements platform.File.IncRef.
+func (h *HostMappable) IncRef(fr platform.FileRange) {
+	mr := memmap.MappableRange{Start: fr.Start, End: fr.End}
+	h.hostFileMapper.IncRefOn(mr)
+}
+
+// DecRef implements platform.File.DecRef.
+func (h *HostMappable) DecRef(fr platform.FileRange) {
+	mr := memmap.MappableRange{Start: fr.Start, End: fr.End}
+	h.hostFileMapper.DecRefOn(mr)
+}
diff --git a/pkg/sentry/fs/fsutil/host_mappable_state.go b/pkg/sentry/fs/fsutil/host_mappable_state.go
new file mode 100644
index 000000000..765f1ec87
--- /dev/null
+++ b/pkg/sentry/fs/fsutil/host_mappable_state.go
@@ -0,0 +1,22 @@
+// Copyright 2019 Google LLC
+//
+// 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 fsutil
+
+// afterLoad is invoked by stateify.
+func (h *HostMappable) afterLoad() {
+	h.mu.Lock()
+	defer h.mu.Unlock()
+	h.fd = -1
+}