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// Copyright 2020 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 pipefs provides the filesystem implementation backing
// Kernel.PipeMount.
package pipefs
import (
"gvisor.dev/gvisor/pkg/abi/linux"
"gvisor.dev/gvisor/pkg/context"
"gvisor.dev/gvisor/pkg/sentry/fsimpl/kernfs"
"gvisor.dev/gvisor/pkg/sentry/kernel/auth"
"gvisor.dev/gvisor/pkg/sentry/kernel/pipe"
ktime "gvisor.dev/gvisor/pkg/sentry/kernel/time"
"gvisor.dev/gvisor/pkg/sentry/vfs"
"gvisor.dev/gvisor/pkg/syserror"
"gvisor.dev/gvisor/pkg/usermem"
)
type filesystemType struct{}
// Name implements vfs.FilesystemType.Name.
func (filesystemType) Name() string {
return "pipefs"
}
// GetFilesystem implements vfs.FilesystemType.GetFilesystem.
func (filesystemType) GetFilesystem(ctx context.Context, vfsObj *vfs.VirtualFilesystem, creds *auth.Credentials, source string, opts vfs.GetFilesystemOptions) (*vfs.Filesystem, *vfs.Dentry, error) {
panic("pipefs.filesystemType.GetFilesystem should never be called")
}
// TODO(gvisor.dev/issue/1193):
//
// - kernfs does not provide a way to implement statfs, from which we
// should indicate PIPEFS_MAGIC.
//
// - kernfs does not provide a way to override names for
// vfs.FilesystemImpl.PrependPath(); pipefs inodes should use synthetic
// name fmt.Sprintf("pipe:[%d]", inode.ino).
// NewFilesystem sets up and returns a new vfs.Filesystem implemented by pipefs.
func NewFilesystem(vfsObj *vfs.VirtualFilesystem) *vfs.Filesystem {
fs := &kernfs.Filesystem{}
fs.VFSFilesystem().Init(vfsObj, filesystemType{}, fs)
return fs.VFSFilesystem()
}
// inode implements kernfs.Inode.
type inode struct {
kernfs.InodeNotDirectory
kernfs.InodeNotSymlink
kernfs.InodeNoopRefCount
pipe *pipe.VFSPipe
ino uint64
uid auth.KUID
gid auth.KGID
// We use the creation timestamp for all of atime, mtime, and ctime.
ctime ktime.Time
}
func newInode(ctx context.Context, fs *kernfs.Filesystem) *inode {
creds := auth.CredentialsFromContext(ctx)
return &inode{
pipe: pipe.NewVFSPipe(false /* isNamed */, pipe.DefaultPipeSize, usermem.PageSize),
ino: fs.NextIno(),
uid: creds.EffectiveKUID,
gid: creds.EffectiveKGID,
ctime: ktime.NowFromContext(ctx),
}
}
const pipeMode = 0600 | linux.S_IFIFO
// CheckPermissions implements kernfs.Inode.CheckPermissions.
func (i *inode) CheckPermissions(ctx context.Context, creds *auth.Credentials, ats vfs.AccessTypes) error {
return vfs.GenericCheckPermissions(creds, ats, pipeMode, i.uid, i.gid)
}
// Mode implements kernfs.Inode.Mode.
func (i *inode) Mode() linux.FileMode {
return pipeMode
}
// Stat implements kernfs.Inode.Stat.
func (i *inode) Stat(vfsfs *vfs.Filesystem, opts vfs.StatOptions) (linux.Statx, error) {
ts := linux.NsecToStatxTimestamp(i.ctime.Nanoseconds())
return linux.Statx{
Mask: linux.STATX_TYPE | linux.STATX_MODE | linux.STATX_NLINK | linux.STATX_UID | linux.STATX_GID | linux.STATX_ATIME | linux.STATX_MTIME | linux.STATX_CTIME | linux.STATX_INO | linux.STATX_SIZE | linux.STATX_BLOCKS,
Blksize: usermem.PageSize,
Nlink: 1,
UID: uint32(i.uid),
GID: uint32(i.gid),
Mode: pipeMode,
Ino: i.ino,
Size: 0,
Blocks: 0,
Atime: ts,
Ctime: ts,
Mtime: ts,
// TODO(gvisor.dev/issue/1197): Device number.
}, nil
}
// SetStat implements kernfs.Inode.SetStat.
func (i *inode) SetStat(ctx context.Context, vfsfs *vfs.Filesystem, creds *auth.Credentials, opts vfs.SetStatOptions) error {
if opts.Stat.Mask == 0 {
return nil
}
return syserror.EPERM
}
// Open implements kernfs.Inode.Open.
func (i *inode) Open(ctx context.Context, rp *vfs.ResolvingPath, vfsd *vfs.Dentry, opts vfs.OpenOptions) (*vfs.FileDescription, error) {
return i.pipe.Open(ctx, rp.Mount(), vfsd, opts.Flags)
}
// NewConnectedPipeFDs returns a pair of FileDescriptions representing the read
// and write ends of a newly-created pipe, as for pipe(2) and pipe2(2).
//
// Preconditions: mnt.Filesystem() must have been returned by NewFilesystem().
func NewConnectedPipeFDs(ctx context.Context, mnt *vfs.Mount, flags uint32) (*vfs.FileDescription, *vfs.FileDescription) {
fs := mnt.Filesystem().Impl().(*kernfs.Filesystem)
inode := newInode(ctx, fs)
var d kernfs.Dentry
d.Init(inode)
defer d.DecRef()
return inode.pipe.ReaderWriterPair(mnt, d.VFSDentry(), flags)
}
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