97 lines
3.0 KiB
Go
97 lines
3.0 KiB
Go
// Copyright 2018 Google Inc.
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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 dev
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import (
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"io"
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"math"
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"gvisor.googlesource.com/gvisor/pkg/abi/linux"
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"gvisor.googlesource.com/gvisor/pkg/sentry/context"
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"gvisor.googlesource.com/gvisor/pkg/sentry/fs"
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"gvisor.googlesource.com/gvisor/pkg/sentry/fs/fsutil"
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"gvisor.googlesource.com/gvisor/pkg/sentry/fs/ramfs"
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"gvisor.googlesource.com/gvisor/pkg/sentry/memmap"
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"gvisor.googlesource.com/gvisor/pkg/sentry/mm"
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"gvisor.googlesource.com/gvisor/pkg/sentry/platform"
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"gvisor.googlesource.com/gvisor/pkg/sentry/usermem"
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)
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type nullDevice struct {
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ramfs.Entry
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}
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func newNullDevice(ctx context.Context, owner fs.FileOwner, mode linux.FileMode) *nullDevice {
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n := &nullDevice{}
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n.InitEntry(ctx, owner, fs.FilePermsFromMode(mode))
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return n
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}
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// DeprecatedPreadv reads data from the device.
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func (n *nullDevice) DeprecatedPreadv(ctx context.Context, dst usermem.IOSequence, offset int64) (int64, error) {
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return 0, io.EOF
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}
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// DeprecatedPwritev discards writes.
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func (n *nullDevice) DeprecatedPwritev(_ context.Context, src usermem.IOSequence, offset int64) (int64, error) {
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return src.NumBytes(), nil
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}
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// Truncate should be simply ignored for character devices on linux.
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func (n *nullDevice) Truncate(context.Context, *fs.Inode, int64) error {
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return nil
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}
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type zeroDevice struct {
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nullDevice
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}
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func newZeroDevice(ctx context.Context, owner fs.FileOwner, mode linux.FileMode) *zeroDevice {
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zd := &zeroDevice{}
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zd.InitEntry(ctx, owner, fs.FilePermsFromMode(mode))
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return zd
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}
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// DeprecatedPreadv implements fs.InodeOperations.DeprecatedPreadv.
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func (zd *zeroDevice) DeprecatedPreadv(ctx context.Context, dst usermem.IOSequence, offset int64) (int64, error) {
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return dst.ZeroOut(ctx, math.MaxInt64)
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}
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// GetFile overrides ramfs.Entry.GetFile and returns a zeroFile instead.
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func (zd *zeroDevice) GetFile(ctx context.Context, dirent *fs.Dirent, flags fs.FileFlags) (*fs.File, error) {
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// Allow pread(2) and pwrite(2) on this file.
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flags.Pread = true
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flags.Pwrite = true
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return fs.NewFile(ctx, dirent, flags, &zeroFileOperations{
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FileOperations: &fsutil.Handle{HandleOperations: dirent.Inode.HandleOps()},
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}), nil
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}
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type zeroFileOperations struct {
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fs.FileOperations
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}
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// ConfigureMMap implements fs.FileOperations.ConfigureMMap.
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func (*zeroFileOperations) ConfigureMMap(ctx context.Context, file *fs.File, opts *memmap.MMapOpts) error {
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m, err := mm.NewSharedAnonMappable(opts.Length, platform.FromContext(ctx))
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if err != nil {
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return err
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}
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opts.MappingIdentity = m
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opts.Mappable = m
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return nil
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}
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