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// Copyright 2018 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 gofer
import (
"golang.org/x/sys/unix"
"gvisor.dev/gvisor/pkg/context"
"gvisor.dev/gvisor/pkg/p9"
"gvisor.dev/gvisor/pkg/sentry/fs"
"gvisor.dev/gvisor/pkg/sentry/kernel/auth"
ktime "gvisor.dev/gvisor/pkg/sentry/kernel/time"
"gvisor.dev/gvisor/pkg/usermem"
)
// getattr returns the 9p attributes of the p9.File. On success, Mode, Size, and RDev
// are guaranteed to be masked as valid.
func getattr(ctx context.Context, file contextFile) (p9.QID, p9.AttrMask, p9.Attr, error) {
// Retrieve attributes over the wire.
qid, valid, attr, err := file.getAttr(ctx, p9.AttrMaskAll())
if err != nil {
return qid, valid, attr, err
}
// Require mode, size, and raw device id.
if !valid.Mode || !valid.Size || !valid.RDev {
return qid, valid, attr, unix.EIO
}
return qid, valid, attr, nil
}
func unstable(ctx context.Context, valid p9.AttrMask, pattr p9.Attr, mounter fs.FileOwner, client *p9.Client) fs.UnstableAttr {
return fs.UnstableAttr{
Size: int64(pattr.Size),
Usage: int64(pattr.Size),
Perms: perms(valid, pattr, client),
Owner: owner(mounter, valid, pattr),
AccessTime: atime(ctx, valid, pattr),
ModificationTime: mtime(ctx, valid, pattr),
StatusChangeTime: ctime(ctx, valid, pattr),
Links: links(valid, pattr),
}
}
func perms(valid p9.AttrMask, pattr p9.Attr, client *p9.Client) fs.FilePermissions {
if pattr.Mode.IsDir() && !p9.VersionSupportsMultiUser(client.Version()) {
// If user and group permissions bits are not supplied, use
// "other" bits to supplement them.
//
// Older Gofer's fake directories only have "other" permission,
// but will often be accessed via user or group permissions.
if pattr.Mode&0770 == 0 {
other := pattr.Mode & 07
pattr.Mode = pattr.Mode | other<<3 | other<<6
}
}
return fs.FilePermsFromP9(pattr.Mode)
}
func owner(mounter fs.FileOwner, valid p9.AttrMask, pattr p9.Attr) fs.FileOwner {
// Unless the file returned its UID and GID, it belongs to the mounting
// task's EUID/EGID.
owner := mounter
if valid.UID {
if pattr.UID.Ok() {
owner.UID = auth.KUID(pattr.UID)
} else {
owner.UID = auth.KUID(auth.OverflowUID)
}
}
if valid.GID {
if pattr.GID.Ok() {
owner.GID = auth.KGID(pattr.GID)
} else {
owner.GID = auth.KGID(auth.OverflowGID)
}
}
return owner
}
// bsize returns a block size from 9p attributes.
func bsize(pattr p9.Attr) int64 {
if pattr.BlockSize > 0 {
return int64(pattr.BlockSize)
}
// Some files, particularly those that are not on a local file system,
// may have no clue of their block size. Better not to report something
// misleading or buggy and have a safe default.
return usermem.PageSize
}
// ntype returns an fs.InodeType from 9p attributes.
func ntype(pattr p9.Attr) fs.InodeType {
switch {
case pattr.Mode.IsNamedPipe():
return fs.Pipe
case pattr.Mode.IsDir():
return fs.Directory
case pattr.Mode.IsSymlink():
return fs.Symlink
case pattr.Mode.IsCharacterDevice():
return fs.CharacterDevice
case pattr.Mode.IsBlockDevice():
return fs.BlockDevice
case pattr.Mode.IsSocket():
return fs.Socket
default:
return fs.RegularFile
}
}
// ctime returns a change time from 9p attributes.
func ctime(ctx context.Context, valid p9.AttrMask, pattr p9.Attr) ktime.Time {
if valid.CTime {
return ktime.FromUnix(int64(pattr.CTimeSeconds), int64(pattr.CTimeNanoSeconds))
}
// Approximate ctime with mtime if ctime isn't available.
return mtime(ctx, valid, pattr)
}
// atime returns an access time from 9p attributes.
func atime(ctx context.Context, valid p9.AttrMask, pattr p9.Attr) ktime.Time {
if valid.ATime {
return ktime.FromUnix(int64(pattr.ATimeSeconds), int64(pattr.ATimeNanoSeconds))
}
return ktime.NowFromContext(ctx)
}
// mtime returns a modification time from 9p attributes.
func mtime(ctx context.Context, valid p9.AttrMask, pattr p9.Attr) ktime.Time {
if valid.MTime {
return ktime.FromUnix(int64(pattr.MTimeSeconds), int64(pattr.MTimeNanoSeconds))
}
return ktime.NowFromContext(ctx)
}
// links returns a hard link count from 9p attributes.
func links(valid p9.AttrMask, pattr p9.Attr) uint64 {
// For gofer file systems that support link count (such as a local file gofer),
// we return the link count reported by the underlying file system.
if valid.NLink {
return pattr.NLink
}
// This node is likely backed by a file system that doesn't support links.
//
// We could readdir() and count children directories to provide an accurate
// link count. However this may be expensive since the gofer may be backed by remote
// storage. Instead, simply return 2 links for directories and 1 for everything else
// since no one relies on an accurate link count for gofer-based file systems.
switch ntype(pattr) {
case fs.Directory:
return 2
default:
return 1
}
}
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