go_marshal: Implement automatic generation of ABI marshalling code.

This CL implements go_marshal, a code generation utility for
automatically serializing and deserializing ABI structs.

The go_marshal tool automatically generates implementations of the new
marshal interface. Unlike binary.Marshal/Unmarshal, the generated
interface implementations use no runtime reflection, and translates to
a single memcpy for most structs. See go_marshal/README.md for
details.

PiperOrigin-RevId: 268065475

2 files changed, 74 insertions, 0 deletions

diff --git a/tools/go_marshal/marshal/BUILD b/tools/go_marshal/marshal/BUILD
new file mode 100644
index 000000000..47dda97a1
--- /dev/null
+++ b/tools/go_marshal/marshal/BUILD
@@ -0,0 +1,14 @@
+load("@io_bazel_rules_go//go:def.bzl", "go_library")
+
+package(licenses = ["notice"])
+
+go_library(
+    name = "marshal",
+    srcs = [
+        "marshal.go",
+    ],
+    importpath = "gvisor.dev/gvisor/tools/go_marshal/marshal",
+    visibility = [
+        "//:sandbox",
+    ],
+)
diff --git a/tools/go_marshal/marshal/marshal.go b/tools/go_marshal/marshal/marshal.go
new file mode 100644
index 000000000..a313a27ed
--- /dev/null
+++ b/tools/go_marshal/marshal/marshal.go
@@ -0,0 +1,60 @@
+// Copyright 2019 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 defines the Marshallable interface for
+// serialize/deserializing go data structures to/from memory, according to the
+// Linux ABI.
+//
+// Implementations of this interface are typically automatically generated by
+// tools/go_marshal. See the go_marshal README for details.
+package marshal
+
+// Marshallable represents a type that can be marshalled to and from memory.
+type Marshallable interface {
+	// SizeBytes is the size of the memory representation of a type in
+	// marshalled form.
+	SizeBytes() int
+
+	// MarshalBytes serializes a copy of a type to dst. dst must be at least
+	// SizeBytes() long.
+	MarshalBytes(dst []byte)
+
+	// UnmarshalBytes deserializes a type from src. src must be at least
+	// SizeBytes() long.
+	UnmarshalBytes(src []byte)
+
+	// Packed returns true if the marshalled size of the type is the same as the
+	// size it occupies in memory. This happens when the type has no fields
+	// starting at unaligned addresses (should always be true by default for ABI
+	// structs, verified by automatically generated tests when using
+	// go_marshal), and has no fields marked `marshal:"unaligned"`.
+	Packed() bool
+
+	// MarshalUnsafe serializes a type by bulk copying its in-memory
+	// representation to the dst buffer. This is only safe to do when the type
+	// has no implicit padding, see Marshallable.Packed. When Packed would
+	// return false, MarshalUnsafe should fall back to the safer but slower
+	// MarshalBytes.
+	MarshalUnsafe(dst []byte)
+
+	// UnmarshalUnsafe deserializes a type directly to the underlying memory
+	// allocated for the object by the runtime.
+	//
+	// This allows much faster unmarshalling of types which have no implicit
+	// padding, see Marshallable.Packed. When Packed would return false,
+	// UnmarshalUnsafe should fall back to the safer but slower unmarshal
+	// mechanism implemented in UnmarshalBytes (usually by calling
+	// UnmarshalBytes directly).
+	UnmarshalUnsafe(src []byte)
+}