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

1 files changed, 158 insertions, 0 deletions

diff --git a/tools/go_marshal/defs.bzl b/tools/go_marshal/defs.bzl
new file mode 100644
index 000000000..60a992b7f
--- /dev/null
+++ b/tools/go_marshal/defs.bzl
@@ -0,0 +1,158 @@
+"""Marshal is a tool for generating marshalling interfaces for Go types.
+
+The recommended way is to use the go_library rule defined below with mostly
+identical configuration as the native go_library rule.
+
+load("//tools/go_marshal:defs.bzl", "go_library")
+
+go_library(
+    name = "foo",
+    srcs = ["foo.go"],
+)
+
+Under the hood, the go_marshal rule is used to generate a file that will
+appear in a Go target; the output file should appear explicitly in a srcs list.
+For example (the above is still the preferred way):
+
+load("//tools/go_marshal:defs.bzl", "go_marshal")
+
+go_marshal(
+    name = "foo_abi",
+    srcs = ["foo.go"],
+    out = "foo_abi.go",
+    package = "foo",
+)
+
+go_library(
+    name = "foo",
+    srcs = [
+        "foo.go",
+        "foo_abi.go",
+    ],
+    deps = [
+       "//tools/go_marshal:marshal",
+       "//pkg/sentry/platform/safecopy",
+       "//pkg/sentry/usermem",
+    ],
+)
+"""
+
+load("@io_bazel_rules_go//go:def.bzl", _go_library = "go_library", _go_test = "go_test")
+
+def _go_marshal_impl(ctx):
+    """Execute the go_marshal tool."""
+    output = ctx.outputs.lib
+    output_test = ctx.outputs.test
+    (build_dir, _, _) = ctx.build_file_path.rpartition("/BUILD")
+
+    decl = "/".join(["gvisor.dev/gvisor", build_dir])
+
+    # Run the marshal command.
+    args = ["-output=%s" % output.path]
+    args += ["-pkg=%s" % ctx.attr.package]
+    args += ["-output_test=%s" % output_test.path]
+    args += ["-declarationPkg=%s" % decl]
+
+    if ctx.attr.debug:
+        args += ["-debug"]
+
+    args += ["--"]
+    for src in ctx.attr.srcs:
+        args += [f.path for f in src.files.to_list()]
+    ctx.actions.run(
+        inputs = ctx.files.srcs,
+        outputs = [output, output_test],
+        mnemonic = "GoMarshal",
+        progress_message = "go_marshal: %s" % ctx.label,
+        arguments = args,
+        executable = ctx.executable._tool,
+    )
+
+# Generates save and restore logic from a set of Go files.
+#
+# Args:
+#   name: the name of the rule.
+#   srcs: the input source files. These files should include all structs in the
+#         package that need to be saved.
+#   imports: an optional list of extra, non-aliased, Go-style absolute import
+#            paths.
+#   out: the name of the generated file output. This must not conflict with any
+#        other files and must be added to the srcs of the relevant go_library.
+#   package: the package name for the input sources.
+go_marshal = rule(
+    implementation = _go_marshal_impl,
+    attrs = {
+        "srcs": attr.label_list(mandatory = True, allow_files = True),
+        "libname": attr.string(mandatory = True),
+        "imports": attr.string_list(mandatory = False),
+        "package": attr.string(mandatory = True),
+        "debug": attr.bool(doc = "enable debugging output from the go_marshal tool"),
+        "_tool": attr.label(executable = True, cfg = "host", default = Label("//tools/go_marshal:go_marshal")),
+    },
+    outputs = {
+        "lib": "%{name}_unsafe.go",
+        "test": "%{name}_test.go",
+    },
+)
+
+def go_library(name, srcs, deps = [], imports = [], debug = False, **kwargs):
+    """wraps the standard go_library and does mashalling interface generation.
+
+    Args:
+      name: Same as native go_library.
+      srcs: Same as native go_library.
+      deps: Same as native go_library.
+      imports: Extra import paths to pass to the go_marshal tool.
+      debug: Enables debugging output from the go_marshal tool.
+      **kwargs: Remaining args to pass to the native go_library rule unmodified.
+    """
+    go_marshal(
+        name = name + "_abi_autogen",
+        libname = name,
+        srcs = [src for src in srcs if src.endswith(".go")],
+        debug = debug,
+        imports = imports,
+        package = name,
+    )
+
+    extra_deps = [
+        "//tools/go_marshal/marshal",
+        "//pkg/sentry/platform/safecopy",
+        "//pkg/sentry/usermem",
+    ]
+
+    all_srcs = srcs + [name + "_abi_autogen_unsafe.go"]
+    all_deps = deps + []  #  + extra_deps
+
+    for extra in extra_deps:
+        if extra not in deps:
+            all_deps.append(extra)
+
+    _go_library(
+        name = name,
+        srcs = all_srcs,
+        deps = all_deps,
+        **kwargs
+    )
+
+    # Don't pass importpath arg to go_test.
+    kwargs.pop("importpath", "")
+
+    _go_test(
+        name = name + "_abi_autogen_test",
+        srcs = [name + "_abi_autogen_test.go"],
+        # Generated test has a fixed set of dependencies since we generate these
+        # tests. They should only depend on the library generated above, and the
+        # Marshallable interface.
+        deps = [
+            ":" + name,
+            "//tools/go_marshal/analysis",
+        ],
+        **kwargs
+    )
+
+def go_test(**kwargs):
+    """Wraps the standard go_test."""
+    _go_test(
+        **kwargs
+    )