1 files changed, 132 insertions, 0 deletions
diff --git a/pkg/sentry/vfs/device.go b/pkg/sentry/vfs/device.go
new file mode 100644
index 000000000..bda5576fa
--- /dev/null
+++ b/pkg/sentry/vfs/device.go
@@ -0,0 +1,132 @@
+// Copyright 2019 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 vfs
+
+import (
+	"fmt"
+
+	"gvisor.dev/gvisor/pkg/context"
+	"gvisor.dev/gvisor/pkg/syserror"
+)
+
+// DeviceKind indicates whether a device is a block or character device.
+type DeviceKind uint32
+
+const (
+	// BlockDevice indicates a block device.
+	BlockDevice DeviceKind = iota
+
+	// CharDevice indicates a character device.
+	CharDevice
+)
+
+// String implements fmt.Stringer.String.
+func (kind DeviceKind) String() string {
+	switch kind {
+	case BlockDevice:
+		return "block"
+	case CharDevice:
+		return "character"
+	default:
+		return fmt.Sprintf("invalid device kind %d", kind)
+	}
+}
+
+type devTuple struct {
+	kind  DeviceKind
+	major uint32
+	minor uint32
+}
+
+// A Device backs device special files.
+type Device interface {
+	// Open returns a FileDescription representing this device.
+	Open(ctx context.Context, mnt *Mount, d *Dentry, opts OpenOptions) (*FileDescription, error)
+}
+
+// +stateify savable
+type registeredDevice struct {
+	dev  Device
+	opts RegisterDeviceOptions
+}
+
+// RegisterDeviceOptions contains options to
+// VirtualFilesystem.RegisterDevice().
+//
+// +stateify savable
+type RegisterDeviceOptions struct {
+	// GroupName is the name shown for this device registration in
+	// /proc/devices. If GroupName is empty, this registration will not be
+	// shown in /proc/devices.
+	GroupName string
+}
+
+// RegisterDevice registers the given Device in vfs with the given major and
+// minor device numbers.
+func (vfs *VirtualFilesystem) RegisterDevice(kind DeviceKind, major, minor uint32, dev Device, opts *RegisterDeviceOptions) error {
+	tup := devTuple{kind, major, minor}
+	vfs.devicesMu.Lock()
+	defer vfs.devicesMu.Unlock()
+	if existing, ok := vfs.devices[tup]; ok {
+		return fmt.Errorf("%s device number (%d, %d) is already registered to device type %T", kind, major, minor, existing.dev)
+	}
+	vfs.devices[tup] = &registeredDevice{
+		dev:  dev,
+		opts: *opts,
+	}
+	return nil
+}
+
+// OpenDeviceSpecialFile returns a FileDescription representing the given
+// device.
+func (vfs *VirtualFilesystem) OpenDeviceSpecialFile(ctx context.Context, mnt *Mount, d *Dentry, kind DeviceKind, major, minor uint32, opts *OpenOptions) (*FileDescription, error) {
+	tup := devTuple{kind, major, minor}
+	vfs.devicesMu.RLock()
+	defer vfs.devicesMu.RUnlock()
+	rd, ok := vfs.devices[tup]
+	if !ok {
+		return nil, syserror.ENXIO
+	}
+	return rd.dev.Open(ctx, mnt, d, *opts)
+}
+
+// GetAnonBlockDevMinor allocates and returns an unused minor device number for
+// an "anonymous" block device with major number 0.
+func (vfs *VirtualFilesystem) GetAnonBlockDevMinor() (uint32, error) {
+	vfs.anonBlockDevMinorMu.Lock()
+	defer vfs.anonBlockDevMinorMu.Unlock()
+	minor := vfs.anonBlockDevMinorNext
+	const maxDevMinor = (1 << 20) - 1
+	for minor < maxDevMinor {
+		if _, ok := vfs.anonBlockDevMinor[minor]; !ok {
+			vfs.anonBlockDevMinor[minor] = struct{}{}
+			vfs.anonBlockDevMinorNext = minor + 1
+			return minor, nil
+		}
+		minor++
+	}
+	return 0, syserror.EMFILE
+}
+
+// PutAnonBlockDevMinor deallocates a minor device number returned by a
+// previous call to GetAnonBlockDevMinor.
+func (vfs *VirtualFilesystem) PutAnonBlockDevMinor(minor uint32) {
+	vfs.anonBlockDevMinorMu.Lock()
+	defer vfs.anonBlockDevMinorMu.Unlock()
+	delete(vfs.anonBlockDevMinor, minor)
+	if minor < vfs.anonBlockDevMinorNext {
+		vfs.anonBlockDevMinorNext = minor
+	}
+}