Replace StubMarshallable with go_marshal's marshal dynamic generator.

FUSE introduced StubMarshallable to avoid boilerplate around types
that were either marshalled in one direction, or were dynamically
sized. The marshal dynamic generator can deal with these cases with a
small bit of stubbing per type.

This also allows FUSE types to be treated as full marshal.Marshallable
types, addressing gVisor.dev/issue/3698.

Closes #3698.

PiperOrigin-RevId: 410335216

pkg/abi/linux/fuse.go

@@ -15,7 +15,6 @@
 package linux
 
 import (
-	"gvisor.dev/gvisor/pkg/marshal"
 	"gvisor.dev/gvisor/pkg/marshal/primitive"
 )
 
@@ -353,6 +352,8 @@ type FUSEEntryOut struct {
 }
 
 // CString represents a null terminated string which can be marshalled.
+//
+// +marshal dynamic
 type CString string
 
 // MarshalBytes implements marshal.Marshallable.MarshalBytes.
@@ -362,6 +363,11 @@ func (s *CString) MarshalBytes(buf []byte) []byte {
 	return buf[s.SizeBytes():]
 }
 
+// UnmarshalBytes implements marshal.Marshallable.UnmarshalBytes.
+func (s *CString) UnmarshalBytes(buf []byte) []byte {
+	panic("Unimplemented, CString is never unmarshalled")
+}
+
 // SizeBytes implements marshal.Marshallable.SizeBytes.
 func (s *CString) SizeBytes() int {
 	// 1 extra byte for null-terminated string.
@@ -371,20 +377,23 @@ func (s *CString) SizeBytes() int {
 // FUSELookupIn is the request sent by the kernel to the daemon
 // to look up a file name.
 //
-// Dynamically-sized objects cannot be marshalled.
+// +marshal dynamic
 type FUSELookupIn struct {
-	marshal.StubMarshallable
-
 	// Name is a file name to be looked up.
 	Name CString
 }
 
-// MarshalBytes serializes r.name to the dst buffer.
+// UnmarshalBytes implements marshal.Marshallable.UnmarshalBytes.
+func (r *FUSELookupIn) UnmarshalBytes(buf []byte) []byte {
+	panic("Unimplemented, FUSELookupIn is never unmarshalled")
+}
+
+// MarshalBytes implements marshal.Marshallable.MarshalBytes.
 func (r *FUSELookupIn) MarshalBytes(buf []byte) []byte {
 	return r.Name.MarshalBytes(buf)
 }
 
-// SizeBytes is the size of the memory representation of FUSELookupIn.
+// SizeBytes implements marshal.Marshallable.SizeBytes.
 func (r *FUSELookupIn) SizeBytes() int {
 	return r.Name.SizeBytes()
 }
@@ -537,10 +546,8 @@ type FUSECreateMeta struct {
 // FUSECreateIn contains all the arguments sent by the kernel to the daemon, to
 // atomically create and open a new regular file.
 //
-// Dynamically-sized objects cannot be marshalled.
+// +marshal dynamic
 type FUSECreateIn struct {
-	marshal.StubMarshallable
-
 	// CreateMeta contains mode, rdev and umash field for FUSE_MKNODS.
 	CreateMeta FUSECreateMeta
 
@@ -548,13 +555,18 @@ type FUSECreateIn struct {
 	Name CString
 }
 
-// MarshalBytes serializes r.CreateMeta and r.Name to the dst buffer.
+// MarshalBytes implements marshal.Marshallable.MarshalBytes.
 func (r *FUSECreateIn) MarshalBytes(buf []byte) []byte {
 	buf = r.CreateMeta.MarshalBytes(buf)
 	return r.Name.MarshalBytes(buf)
 }
 
-// SizeBytes is the size of the memory representation of FUSECreateIn.
+// UnmarshalBytes implements marshal.Marshallable.UnmarshalBytes.
+func (r *FUSECreateIn) UnmarshalBytes(buf []byte) []byte {
+	panic("Unimplemented, FUSECreateIn is never unmarshalled")
+}
+
+// SizeBytes implements marshal.Marshallable.SizeBytes.
 func (r *FUSECreateIn) SizeBytes() int {
 	return r.CreateMeta.SizeBytes() + r.Name.SizeBytes()
 }
@@ -579,35 +591,35 @@ type FUSEMknodMeta struct {
 // FUSEMknodIn contains all the arguments sent by the kernel
 // to the daemon, to create a new file node.
 //
-// Dynamically-sized objects cannot be marshalled.
+// +marshal dynamic
 type FUSEMknodIn struct {
-	marshal.StubMarshallable
-
 	// MknodMeta contains mode, rdev and umash field for FUSE_MKNODS.
 	MknodMeta FUSEMknodMeta
-
 	// Name is the name of the node to create.
 	Name CString
 }
 
-// MarshalBytes serializes r.MknodMeta and r.Name to the dst buffer.
+// MarshalBytes implements marshal.Marshallable.MarshalBytes.
 func (r *FUSEMknodIn) MarshalBytes(buf []byte) []byte {
 	buf = r.MknodMeta.MarshalBytes(buf)
 	return r.Name.MarshalBytes(buf)
 }
 
-// SizeBytes is the size of the memory representation of FUSEMknodIn.
+// UnmarshalBytes implements marshal.Marshallable.UnmarshalBytes.
+func (r *FUSEMknodIn) UnmarshalBytes(buf []byte) []byte {
+	panic("Unimplemented, FUSEMknodIn is never unmarshalled")
+}
+
+// SizeBytes implements marshal.Marshallable.SizeBytes.
 func (r *FUSEMknodIn) SizeBytes() int {
 	return r.MknodMeta.SizeBytes() + r.Name.SizeBytes()
 }
 
-// FUSESymLinkIn is the request sent by the kernel to the daemon,
+// FUSESymlinkIn is the request sent by the kernel to the daemon,
 // to create a symbolic link.
 //
-// Dynamically-sized objects cannot be marshalled.
-type FUSESymLinkIn struct {
-	marshal.StubMarshallable
-
+// +marshal dynamic
+type FUSESymlinkIn struct {
 	// Name of symlink to create.
 	Name CString
 
@@ -615,26 +627,38 @@ type FUSESymLinkIn struct {
 	Target CString
 }
 
-// MarshalBytes serializes r.Name and r.Target to the dst buffer.
-func (r *FUSESymLinkIn) MarshalBytes(buf []byte) []byte {
+// MarshalBytes implements marshal.Marshallable.MarshalBytes.
+func (r *FUSESymlinkIn) MarshalBytes(buf []byte) []byte {
 	buf = r.Name.MarshalBytes(buf)
 	return r.Target.MarshalBytes(buf)
 }
 
-// SizeBytes is the size of the memory representation of FUSESymLinkIn.
-func (r *FUSESymLinkIn) SizeBytes() int {
+// UnmarshalBytes implements marshal.Marshallable.UnmarshalBytes.
+func (r *FUSESymlinkIn) UnmarshalBytes(buf []byte) []byte {
+	panic("Unimplemented, FUSEMknodIn is never unmarshalled")
+}
+
+// SizeBytes implements marshal.Marshallable.SizeBytes.
+func (r *FUSESymlinkIn) SizeBytes() int {
 	return r.Name.SizeBytes() + r.Target.SizeBytes()
 }
 
 // FUSEEmptyIn is used by operations without request body.
-type FUSEEmptyIn struct{ marshal.StubMarshallable }
+//
+// +marshal dynamic
+type FUSEEmptyIn struct{}
 
-// MarshalBytes do nothing for marshal.
+// MarshalBytes implements marshal.Marshallable.MarshalBytes.
 func (r *FUSEEmptyIn) MarshalBytes(buf []byte) []byte {
 	return buf
 }
 
-// SizeBytes is 0 for empty request.
+// UnmarshalBytes implements marshal.Marshallable.UnmarshalBytes.
+func (r *FUSEEmptyIn) UnmarshalBytes(buf []byte) []byte {
+	panic("Unimplemented, FUSEEmptyIn is never unmarshalled")
+}
+
+// SizeBytes implements marshal.Marshallable.SizeBytes.
 func (r *FUSEEmptyIn) SizeBytes() int {
 	return 0
 }
@@ -646,7 +670,6 @@ func (r *FUSEEmptyIn) SizeBytes() int {
 type FUSEMkdirMeta struct {
 	// Mode of the directory of create.
 	Mode uint32
-
 	// Umask is the user file creation mask.
 	Umask uint32
 }
@@ -654,24 +677,26 @@ type FUSEMkdirMeta struct {
 // FUSEMkdirIn contains all the arguments sent by the kernel
 // to the daemon, to create a new directory.
 //
-// Dynamically-sized objects cannot be marshalled.
+// +marshal dynamic
 type FUSEMkdirIn struct {
-	marshal.StubMarshallable
-
 	// MkdirMeta contains Mode and Umask of the directory to create.
 	MkdirMeta FUSEMkdirMeta
-
 	// Name of the directory to create.
 	Name CString
 }
 
-// MarshalBytes serializes r.MkdirMeta and r.Name to the dst buffer.
+// MarshalBytes implements marshal.Marshallable.MarshalBytes.
 func (r *FUSEMkdirIn) MarshalBytes(buf []byte) []byte {
 	buf = r.MkdirMeta.MarshalBytes(buf)
 	return r.Name.MarshalBytes(buf)
 }
 
-// SizeBytes is the size of the memory representation of FUSEMkdirIn.
+// UnmarshalBytes implements marshal.Marshallable.UnmarshalBytes.
+func (r *FUSEMkdirIn) UnmarshalBytes(buf []byte) []byte {
+	panic("Unimplemented, FUSEMkdirIn is never unmarshalled")
+}
+
+// SizeBytes implements marshal.Marshallable.SizeBytes.
 func (r *FUSEMkdirIn) SizeBytes() int {
 	return r.MkdirMeta.SizeBytes() + r.Name.SizeBytes()
 }
@@ -679,20 +704,23 @@ func (r *FUSEMkdirIn) SizeBytes() int {
 // FUSERmDirIn is the request sent by the kernel to the daemon
 // when trying to remove a directory.
 //
-// Dynamically-sized objects cannot be marshalled.
+// +marshal dynamic
 type FUSERmDirIn struct {
-	marshal.StubMarshallable
-
 	// Name is a directory name to be removed.
 	Name CString
 }
 
-// MarshalBytes serializes r.name to the dst buffer.
+// MarshalBytes implements marshal.Marshallable.MarshalBytes.
 func (r *FUSERmDirIn) MarshalBytes(buf []byte) []byte {
 	return r.Name.MarshalBytes(buf)
 }
 
-// SizeBytes is the size of the memory representation of FUSERmDirIn.
+// UnmarshalBytes implements marshal.Marshallable.UnmarshalBytes.
+func (r *FUSERmDirIn) UnmarshalBytes(buf []byte) []byte {
+	panic("Unimplemented, FUSERmDirIn is never unmarshalled")
+}
+
+// SizeBytes implements marshal.Marshallable.SizeBytes.
 func (r *FUSERmDirIn) SizeBytes() int {
 	return r.Name.SizeBytes()
 }
@@ -700,23 +728,18 @@ func (r *FUSERmDirIn) SizeBytes() int {
 // FUSEDirents is a list of Dirents received from the FUSE daemon server.
 // It is used for FUSE_READDIR.
 //
-// Dynamically-sized objects cannot be marshalled.
+// +marshal dynamic
 type FUSEDirents struct {
-	marshal.StubMarshallable
-
 	Dirents []*FUSEDirent
 }
 
 // FUSEDirent is a Dirent received from the FUSE daemon server.
 // It is used for FUSE_READDIR.
 //
-// Dynamically-sized objects cannot be marshalled.
+// +marshal dynamic
 type FUSEDirent struct {
-	marshal.StubMarshallable
-
 	// Meta contains all the static fields of FUSEDirent.
 	Meta FUSEDirentMeta
-
 	// Name is the filename of the dirent.
 	Name string
 }
@@ -728,18 +751,15 @@ type FUSEDirent struct {
 type FUSEDirentMeta struct {
 	// Inode of the dirent.
 	Ino uint64
-
 	// Offset of the dirent.
 	Off uint64
-
 	// NameLen is the length of the dirent name.
 	NameLen uint32
-
 	// Type of the dirent.
 	Type uint32
 }
 
-// SizeBytes is the size of the memory representation of FUSEDirents.
+// SizeBytes implements marshal.Marshallable.SizeBytes.
 func (r *FUSEDirents) SizeBytes() int {
 	var sizeBytes int
 	for _, dirent := range r.Dirents {
@@ -749,6 +769,11 @@ func (r *FUSEDirents) SizeBytes() int {
 	return sizeBytes
 }
 
+// MarshalBytes implements marshal.Marshallable.MarshalBytes.
+func (r *FUSEDirents) MarshalBytes(buf []byte) []byte {
+	panic("Unimplemented, FUSEDirents is never marshalled")
+}
+
 // UnmarshalBytes deserializes FUSEDirents from the src buffer.
 func (r *FUSEDirents) UnmarshalBytes(src []byte) []byte {
 	for {
@@ -772,7 +797,7 @@ func (r *FUSEDirents) UnmarshalBytes(src []byte) []byte {
 	return src
 }
 
-// SizeBytes is the size of the memory representation of FUSEDirent.
+// SizeBytes implements marshal.Marshallable.SizeBytes.
 func (r *FUSEDirent) SizeBytes() int {
 	dataSize := r.Meta.SizeBytes() + len(r.Name)
 
@@ -782,6 +807,11 @@ func (r *FUSEDirent) SizeBytes() int {
 	return (dataSize + (FUSE_DIRENT_ALIGN - 1)) & ^(FUSE_DIRENT_ALIGN - 1)
 }
 
+// MarshalBytes implements marshal.Marshallable.MarshalBytes.
+func (r *FUSEDirent) MarshalBytes(buf []byte) []byte {
+	panic("Unimplemented, FUSEDirent is never marshalled")
+}
+
 // shiftNextDirent advances buf to the start of the next dirent, per
 // FUSE ABI. buf should begin at the start of a dirent.
 func (r *FUSEDirent) shiftNextDirent(buf []byte) []byte {
@@ -792,7 +822,7 @@ func (r *FUSEDirent) shiftNextDirent(buf []byte) []byte {
 	return buf[nextOff:]
 }
 
-// UnmarshalBytes deserializes FUSEDirent from the src buffer.
+// UnmarshalBytes implements marshal.Marshallable.UnmarshalBytes.
 func (r *FUSEDirent) UnmarshalBytes(src []byte) []byte {
 	srcP := r.Meta.UnmarshalBytes(src)
 
@@ -879,20 +909,23 @@ type FUSESetAttrIn struct {
 // FUSEUnlinkIn is the request sent by the kernel to the daemon
 // when trying to unlink a node.
 //
-// Dynamically-sized objects cannot be marshalled.
+// +marshal dynamic
 type FUSEUnlinkIn struct {
-	marshal.StubMarshallable
-
 	// Name of the node to unlink.
 	Name CString
 }
 
-// MarshalBytes serializes r.name to the dst buffer.
+// MarshalBytes implements marshal.Marshallable.MarshalBytes.
 func (r *FUSEUnlinkIn) MarshalBytes(buf []byte) []byte {
 	return r.Name.MarshalBytes(buf)
 }
 
-// SizeBytes is the size of the memory representation of FUSEUnlinkIn.
+// UnmarshalBytes implements marshal.Marshallable.UnmarshalBytes.
+func (r *FUSEUnlinkIn) UnmarshalBytes(buf []byte) []byte {
+	panic("Unimplemented, FUSEUnlinkIn is never unmarshalled")
+}
+
+// SizeBytes implements marshal.Marshallable.SizeBytes.
 func (r *FUSEUnlinkIn) SizeBytes() int {
 	return r.Name.SizeBytes()
 }

pkg/marshal/BUILD

@@ -6,7 +6,6 @@ go_library(
     name = "marshal",
     srcs = [
         "marshal.go",
-        "marshal_impl_util.go",
         "util.go",
     ],
     visibility = [

pkg/marshal/marshal_impl_util.go

@@ -1,78 +0,0 @@
-// 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 marshal
-
-import (
-	"io"
-
-	"gvisor.dev/gvisor/pkg/hostarch"
-)
-
-// StubMarshallable implements the Marshallable interface.
-// StubMarshallable is a convenient embeddable type for satisfying the
-// marshallable interface, but provides no actual implementation. It is
-// useful when the marshallable interface needs to be implemented manually,
-// but the caller doesn't require the full marshallable interface.
-type StubMarshallable struct{}
-
-// WriteTo implements Marshallable.WriteTo.
-func (StubMarshallable) WriteTo(w io.Writer) (n int64, err error) {
-	panic("Please implement your own WriteTo function")
-}
-
-// SizeBytes implements Marshallable.SizeBytes.
-func (StubMarshallable) SizeBytes() int {
-	panic("Please implement your own SizeBytes function")
-}
-
-// MarshalBytes implements Marshallable.MarshalBytes.
-func (StubMarshallable) MarshalBytes(dst []byte) []byte {
-	panic("Please implement your own MarshalBytes function")
-}
-
-// UnmarshalBytes implements Marshallable.UnmarshalBytes.
-func (StubMarshallable) UnmarshalBytes(src []byte) []byte {
-	panic("Please implement your own UnmarshalBytes function")
-}
-
-// Packed implements Marshallable.Packed.
-func (StubMarshallable) Packed() bool {
-	panic("Please implement your own Packed function")
-}
-
-// MarshalUnsafe implements Marshallable.MarshalUnsafe.
-func (StubMarshallable) MarshalUnsafe(dst []byte) []byte {
-	panic("Please implement your own MarshalUnsafe function")
-}
-
-// UnmarshalUnsafe implements Marshallable.UnmarshalUnsafe.
-func (StubMarshallable) UnmarshalUnsafe(src []byte) []byte {
-	panic("Please implement your own UnmarshalUnsafe function")
-}
-
-// CopyIn implements Marshallable.CopyIn.
-func (StubMarshallable) CopyIn(cc CopyContext, addr hostarch.Addr) (int, error) {
-	panic("Please implement your own CopyIn function")
-}
-
-// CopyOut implements Marshallable.CopyOut.
-func (StubMarshallable) CopyOut(cc CopyContext, addr hostarch.Addr) (int, error) {
-	panic("Please implement your own CopyOut function")
-}
-
-// CopyOutN implements Marshallable.CopyOutN.
-func (StubMarshallable) CopyOutN(cc CopyContext, addr hostarch.Addr, limit int) (int, error) {
-	panic("Please implement your own CopyOutN function")
-}

pkg/sentry/fsimpl/fuse/BUILD

@@ -42,6 +42,7 @@ go_library(
         "request_list.go",
         "request_response.go",
     ],
+    marshal = True,
     visibility = ["//pkg/sentry:internal"],
     deps = [
         "//pkg/abi/linux",

pkg/sentry/fsimpl/fuse/fusefs.go

@@ -540,7 +540,7 @@ func (i *inode) NewNode(ctx context.Context, name string, opts vfs.MknodOptions)
 
 // NewSymlink implements kernfs.Inode.NewSymlink.
 func (i *inode) NewSymlink(ctx context.Context, name, target string) (kernfs.Inode, error) {
-	in := linux.FUSESymLinkIn{
+	in := linux.FUSESymlinkIn{
 		Name:   linux.CString(name),
 		Target: linux.CString(target),
 	}

pkg/sentry/fsimpl/fuse/request_response.go

@@ -29,10 +29,8 @@ import (
 // server may implement an older version of FUSE protocol, which contains a
 // linux.FUSEInitOut with less attributes.
 //
-// Dynamically-sized objects cannot be marshalled.
+// +marshal dynamic
 type fuseInitRes struct {
-	marshal.StubMarshallable
-
 	// initOut contains the response from the FUSE server.
 	initOut linux.FUSEInitOut
 
@@ -40,6 +38,10 @@ type fuseInitRes struct {
 	initLen uint32
 }
 
+func (r *fuseInitRes) MarshalBytes(src []byte) []byte {
+	panic("Unimplemented, fuseInitRes should never be marshalled")
+}
+
 // UnmarshalBytes deserializes src to the initOut attribute in a fuseInitRes.
 func (r *fuseInitRes) UnmarshalBytes(src []byte) []byte {
 	out := &r.initOut
@@ -123,9 +125,8 @@ func (conn *connection) NewRequest(creds *auth.Credentials, pid uint32, ino uint
 
 	buf := make([]byte, hdr.Len)
 
-	// TODO(gVisor.dev/issue/3698): Use the unsafe version once go_marshal is safe to use again.
-	hdr.MarshalBytes(buf[:hdrLen])
-	payload.MarshalBytes(buf[hdrLen:])
+	hdr.MarshalUnsafe(buf[:hdrLen])
+	payload.MarshalUnsafe(buf[hdrLen:])
 
 	return &Request{
 		id:   hdr.Unique,
@@ -224,7 +225,6 @@ func (r *Response) UnmarshalPayload(m marshal.Marshallable) error {
 		return nil
 	}
 
-	// TODO(gVisor.dev/issue/3698): Use the unsafe version once go_marshal is safe to use again.
-	m.UnmarshalBytes(r.data[hdrLen:])
+	m.UnmarshalUnsafe(r.data[hdrLen:])
 	return nil
 }