Sign android_filesystem with avbtool

Use_avb and other avb_* properties allows us to sign an
android_filesystem module with avbtool.

Bug: 172415113
Test: m

Change-Id: Ifa1ed8ded1b10170aaca9b34e6a14f0179dbab5d

filesystem/filesystem.go

@@ -20,6 +20,7 @@ import (
 	"android/soong/android"
 
 	"github.com/google/blueprint"
+	"github.com/google/blueprint/proptools"
 )
 
 func init() {
@@ -30,10 +31,24 @@ type filesystem struct {
 	android.ModuleBase
 	android.PackagingBase
 
+	properties filesystemProperties
+
 	output     android.OutputPath
 	installDir android.InstallPath
 }
 
+type filesystemProperties struct {
+	// When set to true, sign the image with avbtool. Default is false.
+	Use_avb *bool
+
+	// Path to the private key that avbtool will use to sign this filesystem image.
+	// TODO(jiyong): allow apex_key to be specified here
+	Avb_private_key *string `android:"path"`
+
+	// Hash and signing algorithm for avbtool. Default is SHA256_RSA4096.
+	Avb_algorithm *string
+}
+
 // android_filesystem packages a set of modules and their transitive dependencies into a filesystem
 // image. The filesystem images are expected to be mounted in the target device, which means the
 // modules in the filesystem image are built for the target device (i.e. Android, not Linux host).
@@ -41,6 +56,7 @@ type filesystem struct {
 // partitions like system.img. For example, cc_library modules are placed under ./lib[64] directory.
 func filesystemFactory() android.Module {
 	module := &filesystem{}
+	module.AddProperties(&module.properties)
 	android.InitPackageModule(module)
 	android.InitAndroidMultiTargetsArchModule(module, android.DeviceSupported, android.MultilibCommon)
 	return module
@@ -114,6 +130,17 @@ func (f *filesystem) buildPropFile(ctx android.ModuleContext) (propFile android.
 		deps = append(deps, ctx.Config().HostToolPath(ctx, t))
 	}
 
+	if proptools.Bool(f.properties.Use_avb) {
+		addStr("avb_hashtree_enable", "true")
+		addPath("avb_avbtool", ctx.Config().HostToolPath(ctx, "avbtool"))
+		algorithm := proptools.StringDefault(f.properties.Avb_algorithm, "SHA256_RSA4096")
+		addStr("avb_algorithm", algorithm)
+		key := android.PathForModuleSrc(ctx, proptools.String(f.properties.Avb_private_key))
+		addPath("avb_key_path", key)
+		addStr("avb_add_hashtree_footer_args", "--do_not_generate_fec")
+		addStr("partition_name", f.Name())
+	}
+
 	propFile = android.PathForModuleOut(ctx, "prop").OutputPath
 	builder := android.NewRuleBuilder(pctx, ctx)
 	builder.Command().Text("rm").Flag("-rf").Output(propFile)