Handle new filetype 'linker_config'

Handle new filetype 'linker_config' which is configuration for
linkerconfig in json type and convert into protobuf in build time.

Bug: 169634881
Test: Build succeeded and cuttlefish boot succeeded
Change-Id: I56555fc738e6d6600d15a191a24f79a2ee747f52

linkerconfig/linkerconfig.go

@@ -0,0 +1,108 @@
+// Copyright (C) 2020 The Android Open Source Project
+//
+// 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 linkerconfig
+
+import (
+	"android/soong/android"
+	"android/soong/etc"
+
+	"github.com/google/blueprint/proptools"
+)
+
+var (
+	pctx = android.NewPackageContext("android/soong/linkerconfig")
+)
+
+func init() {
+	pctx.HostBinToolVariable("conv_linker_config", "conv_linker_config")
+	android.RegisterModuleType("linker_config", linkerConfigFactory)
+}
+
+type linkerConfigProperties struct {
+	// source linker configuration property file
+	Src *string `android:"path"`
+
+	// If set to true, allow module to be installed to one of the partitions.
+	// Default value is true.
+	// Installable should be marked as false for APEX configuration to avoid
+	// conflicts of configuration on /system/etc directory.
+	Installable *bool
+}
+
+type linkerConfig struct {
+	android.ModuleBase
+	properties linkerConfigProperties
+
+	outputFilePath android.OutputPath
+	installDirPath android.InstallPath
+}
+
+// Implement PrebuiltEtcModule interface to fit in APEX prebuilt list.
+var _ etc.PrebuiltEtcModule = (*linkerConfig)(nil)
+
+func (l *linkerConfig) BaseDir() string {
+	return "etc"
+}
+
+func (l *linkerConfig) SubDir() string {
+	return ""
+}
+
+func (l *linkerConfig) OutputFile() android.OutputPath {
+	return l.outputFilePath
+}
+
+func (l *linkerConfig) GenerateAndroidBuildActions(ctx android.ModuleContext) {
+	inputFile := android.PathForModuleSrc(ctx, android.String(l.properties.Src))
+	l.outputFilePath = android.PathForModuleOut(ctx, "linker.config.pb").OutputPath
+	l.installDirPath = android.PathForModuleInstall(ctx, "etc")
+	linkerConfigRule := android.NewRuleBuilder()
+	linkerConfigRule.Command().
+		BuiltTool(ctx, "conv_linker_config").
+		Flag("proto").
+		FlagWithInput("-s ", inputFile).
+		FlagWithOutput("-o ", l.outputFilePath)
+	linkerConfigRule.Build(pctx, ctx, "conv_linker_config",
+		"Generate linker config protobuf "+l.outputFilePath.String())
+
+	if proptools.BoolDefault(l.properties.Installable, true) {
+		ctx.InstallFile(l.installDirPath, l.outputFilePath.Base(), l.outputFilePath)
+	}
+}
+
+// linker_config generates protobuf file from json file. This protobuf file will be used from
+// linkerconfig while generating ld.config.txt. Format of this file can be found from
+// https://android.googlesource.com/platform/system/linkerconfig/+/master/README.md
+func linkerConfigFactory() android.Module {
+	m := &linkerConfig{}
+	m.AddProperties(&m.properties)
+	android.InitAndroidArchModule(m, android.HostAndDeviceSupported, android.MultilibFirst)
+	return m
+}
+
+func (l *linkerConfig) AndroidMkEntries() []android.AndroidMkEntries {
+	installable := proptools.BoolDefault(l.properties.Installable, true)
+	return []android.AndroidMkEntries{android.AndroidMkEntries{
+		Class:      "ETC",
+		OutputFile: android.OptionalPathForPath(l.outputFilePath),
+		ExtraEntries: []android.AndroidMkExtraEntriesFunc{
+			func(entries *android.AndroidMkEntries) {
+				entries.SetString("LOCAL_MODULE_PATH", l.installDirPath.ToMakePath().String())
+				entries.SetString("LOCAL_INSTALLED_MODULE_STEM", l.outputFilePath.Base())
+				entries.SetBoolIfTrue("LOCAL_UNINSTALLABLE_MODULE", !installable)
+			},
+		},
+	}}
+}