93 lines
3.0 KiB
Go
93 lines
3.0 KiB
Go
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// Copyright 2020 The gVisor Authors.
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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 memdev
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import (
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"sync/atomic"
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"gvisor.dev/gvisor/pkg/context"
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"gvisor.dev/gvisor/pkg/rand"
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"gvisor.dev/gvisor/pkg/safemem"
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"gvisor.dev/gvisor/pkg/sentry/vfs"
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"gvisor.dev/gvisor/pkg/usermem"
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)
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const (
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randomDevMinor = 8
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urandomDevMinor = 9
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)
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// randomDevice implements vfs.Device for /dev/random and /dev/urandom.
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type randomDevice struct{}
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// Open implements vfs.Device.Open.
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func (randomDevice) Open(ctx context.Context, mnt *vfs.Mount, vfsd *vfs.Dentry, opts vfs.OpenOptions) (*vfs.FileDescription, error) {
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fd := &randomFD{}
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if err := fd.vfsfd.Init(fd, opts.Flags, mnt, vfsd, &vfs.FileDescriptionOptions{
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UseDentryMetadata: true,
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}); err != nil {
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return nil, err
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}
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return &fd.vfsfd, nil
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}
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// randomFD implements vfs.FileDescriptionImpl for /dev/random.
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type randomFD struct {
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vfsfd vfs.FileDescription
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vfs.FileDescriptionDefaultImpl
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vfs.DentryMetadataFileDescriptionImpl
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// off is the "file offset". off is accessed using atomic memory
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// operations.
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off int64
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}
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// Release implements vfs.FileDescriptionImpl.Release.
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func (fd *randomFD) Release() {
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// noop
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}
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// PRead implements vfs.FileDescriptionImpl.PRead.
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func (fd *randomFD) PRead(ctx context.Context, dst usermem.IOSequence, offset int64, opts vfs.ReadOptions) (int64, error) {
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return dst.CopyOutFrom(ctx, safemem.FromIOReader{rand.Reader})
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}
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// Read implements vfs.FileDescriptionImpl.Read.
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func (fd *randomFD) Read(ctx context.Context, dst usermem.IOSequence, opts vfs.ReadOptions) (int64, error) {
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n, err := dst.CopyOutFrom(ctx, safemem.FromIOReader{rand.Reader})
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atomic.AddInt64(&fd.off, n)
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return n, err
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}
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// PWrite implements vfs.FileDescriptionImpl.PWrite.
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func (fd *randomFD) PWrite(ctx context.Context, src usermem.IOSequence, offset int64, opts vfs.WriteOptions) (int64, error) {
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// In Linux, this mixes the written bytes into the entropy pool; we just
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// throw them away.
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return src.NumBytes(), nil
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}
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// Write implements vfs.FileDescriptionImpl.Write.
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func (fd *randomFD) Write(ctx context.Context, src usermem.IOSequence, opts vfs.WriteOptions) (int64, error) {
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atomic.AddInt64(&fd.off, src.NumBytes())
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return src.NumBytes(), nil
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}
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// Seek implements vfs.FileDescriptionImpl.Seek.
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func (fd *randomFD) Seek(ctx context.Context, offset int64, whence int32) (int64, error) {
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// Linux: drivers/char/random.c:random_fops.llseek == urandom_fops.llseek
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// == noop_llseek
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return atomic.LoadInt64(&fd.off), nil
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}
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