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// 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)
}
type registeredDevice struct {
dev Device
opts RegisterDeviceOptions
}
// RegisterDeviceOptions contains options to
// VirtualFilesystem.RegisterDevice().
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] = ®isteredDevice{
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
}
}
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