filesystem/filesystem.go - android_build_soong - Gitiles

 // 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 filesystem

 import (
 	"crypto/sha256"
 	"fmt"
 	"io"
 	"path/filepath"
 	"strings"

 	"android/soong/android"
 	"android/soong/cc"

 	"github.com/google/blueprint"
 	"github.com/google/blueprint/proptools"
 )

 func init() {
 	registerBuildComponents(android.InitRegistrationContext)
 }

 func registerBuildComponents(ctx android.RegistrationContext) {
 	ctx.RegisterModuleType("android_filesystem", filesystemFactory)
 	ctx.RegisterModuleType("android_system_image", systemImageFactory)
 	ctx.RegisterModuleType("avb_add_hash_footer", avbAddHashFooterFactory)
 	ctx.RegisterModuleType("avb_add_hash_footer_defaults", avbAddHashFooterDefaultsFactory)
 	ctx.RegisterModuleType("avb_gen_vbmeta_image", avbGenVbmetaImageFactory)
 	ctx.RegisterModuleType("avb_gen_vbmeta_image_defaults", avbGenVbmetaImageDefaultsFactory)
 }

 type filesystem struct {
 	android.ModuleBase
 	android.PackagingBase

 	properties filesystemProperties

 	// Function that builds extra files under the root directory and returns the files
 	buildExtraFiles func(ctx android.ModuleContext, root android.OutputPath) android.OutputPaths

 	// Function that filters PackagingSpecs returned by PackagingBase.GatherPackagingSpecs()
 	filterPackagingSpecs func(specs map[string]android.PackagingSpec)

 	output     android.OutputPath
 	installDir android.InstallPath

 	// For testing. Keeps the result of CopyDepsToZip()
 	entries []string
 }

 type symlinkDefinition struct {
 	Target *string
 	Name   *string
 }

 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"`

 	// Signing algorithm for avbtool. Default is SHA256_RSA4096.
 	Avb_algorithm *string

 	// Hash algorithm used for avbtool (for descriptors). This is passed as hash_algorithm to
 	// avbtool. Default used by avbtool is sha1.
 	Avb_hash_algorithm *string

 	// Name of the partition stored in vbmeta desc. Defaults to the name of this module.
 	Partition_name *string

 	// Type of the filesystem. Currently, ext4, cpio, and compressed_cpio are supported. Default
 	// is ext4.
 	Type *string

 	// file_contexts file to make image. Currently, only ext4 is supported.
 	File_contexts *string `android:"path"`

 	// Base directory relative to root, to which deps are installed, e.g. "system". Default is "."
 	// (root).
 	Base_dir *string

 	// Directories to be created under root. e.g. /dev, /proc, etc.
 	Dirs []string

 	// Symbolic links to be created under root with "ln -sf <target> <name>".
 	Symlinks []symlinkDefinition

 	// Seconds since unix epoch to override timestamps of file entries
 	Fake_timestamp *string

 	// When set, passed to mkuserimg_mke2fs --mke2fs_uuid & --mke2fs_hash_seed.
 	// Otherwise, they'll be set as random which might cause indeterministic build output.
 	Uuid *string

 	// Mount point for this image. Default is "/"
 	Mount_point *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).
 // The modules are placed in the filesystem image just like they are installed to the ordinary
 // partitions like system.img. For example, cc_library modules are placed under ./lib[64] directory.
 func filesystemFactory() android.Module {
 	module := &filesystem{}
 	initFilesystemModule(module)
 	return module
 }

 func initFilesystemModule(module *filesystem) {
 	module.AddProperties(&module.properties)
 	android.InitPackageModule(module)
 	android.InitAndroidMultiTargetsArchModule(module, android.DeviceSupported, android.MultilibCommon)
 }

 var dependencyTag = struct {
 	blueprint.BaseDependencyTag
 	android.PackagingItemAlwaysDepTag
 }{}

 func (f *filesystem) DepsMutator(ctx android.BottomUpMutatorContext) {
 	f.AddDeps(ctx, dependencyTag)
 }

 type fsType int

 const (
 	ext4Type fsType = iota
 	compressedCpioType
 	cpioType // uncompressed
 	unknown
 )

 func (f *filesystem) fsType(ctx android.ModuleContext) fsType {
 	typeStr := proptools.StringDefault(f.properties.Type, "ext4")
 	switch typeStr {
 	case "ext4":
 		return ext4Type
 	case "compressed_cpio":
 		return compressedCpioType
 	case "cpio":
 		return cpioType
 	default:
 		ctx.PropertyErrorf("type", "%q not supported", typeStr)
 		return unknown
 	}
 }

 func (f *filesystem) installFileName() string {
 	return f.BaseModuleName() + ".img"
 }

 var pctx = android.NewPackageContext("android/soong/filesystem")

 func (f *filesystem) GenerateAndroidBuildActions(ctx android.ModuleContext) {
 	switch f.fsType(ctx) {
 	case ext4Type:
 		f.output = f.buildImageUsingBuildImage(ctx)
 	case compressedCpioType:
 		f.output = f.buildCpioImage(ctx, true)
 	case cpioType:
 		f.output = f.buildCpioImage(ctx, false)
 	default:
 		return
 	}

 	f.installDir = android.PathForModuleInstall(ctx, "etc")
 	ctx.InstallFile(f.installDir, f.installFileName(), f.output)
 }

 // root zip will contain extra files/dirs that are not from the `deps` property.
 func (f *filesystem) buildRootZip(ctx android.ModuleContext) android.OutputPath {
 	rootDir := android.PathForModuleGen(ctx, "root").OutputPath
 	builder := android.NewRuleBuilder(pctx, ctx)
 	builder.Command().Text("rm -rf").Text(rootDir.String())
 	builder.Command().Text("mkdir -p").Text(rootDir.String())

 	// create dirs and symlinks
 	for _, dir := range f.properties.Dirs {
 		// OutputPath.Join verifies dir
 		builder.Command().Text("mkdir -p").Text(rootDir.Join(ctx, dir).String())
 	}

 	for _, symlink := range f.properties.Symlinks {
 		name := strings.TrimSpace(proptools.String(symlink.Name))
 		target := strings.TrimSpace(proptools.String(symlink.Target))

 		if name == "" {
 			ctx.PropertyErrorf("symlinks", "Name can't be empty")
 			continue
 		}

 		if target == "" {
 			ctx.PropertyErrorf("symlinks", "Target can't be empty")
 			continue
 		}

 		// OutputPath.Join verifies name. don't need to verify target.
 		dst := rootDir.Join(ctx, name)

 		builder.Command().Text("mkdir -p").Text(filepath.Dir(dst.String()))
 		builder.Command().Text("ln -sf").Text(proptools.ShellEscape(target)).Text(dst.String())
 	}

 	// create extra files if there's any
 	rootForExtraFiles := android.PathForModuleGen(ctx, "root-extra").OutputPath
 	var extraFiles android.OutputPaths
 	if f.buildExtraFiles != nil {
 		extraFiles = f.buildExtraFiles(ctx, rootForExtraFiles)
 		for _, f := range extraFiles {
 			rel, _ := filepath.Rel(rootForExtraFiles.String(), f.String())
 			if strings.HasPrefix(rel, "..") {
 				panic(fmt.Errorf("%q is not under %q\n", f, rootForExtraFiles))
 			}
 		}
 	}

 	// Zip them all
 	zipOut := android.PathForModuleGen(ctx, "root.zip").OutputPath
 	zipCommand := builder.Command().BuiltTool("soong_zip")
 	zipCommand.FlagWithOutput("-o ", zipOut).
 		FlagWithArg("-C ", rootDir.String()).
 		Flag("-L 0"). // no compression because this will be unzipped soon
 		FlagWithArg("-D ", rootDir.String()).
 		Flag("-d") // include empty directories
 	if len(extraFiles) > 0 {
 		zipCommand.FlagWithArg("-C ", rootForExtraFiles.String())
 		for _, f := range extraFiles {
 			zipCommand.FlagWithInput("-f ", f)
 		}
 	}

 	builder.Command().Text("rm -rf").Text(rootDir.String())

 	builder.Build("zip_root", fmt.Sprintf("zipping root contents for %s", ctx.ModuleName()))
 	return zipOut
 }

 func (f *filesystem) buildImageUsingBuildImage(ctx android.ModuleContext) android.OutputPath {
 	depsZipFile := android.PathForModuleOut(ctx, "deps.zip").OutputPath
 	f.entries = f.CopyDepsToZip(ctx, f.gatherFilteredPackagingSpecs(ctx), depsZipFile)

 	builder := android.NewRuleBuilder(pctx, ctx)
 	depsBase := proptools.StringDefault(f.properties.Base_dir, ".")
 	rebasedDepsZip := android.PathForModuleOut(ctx, "rebased_deps.zip").OutputPath
 	builder.Command().
 		BuiltTool("zip2zip").
 		FlagWithInput("-i ", depsZipFile).
 		FlagWithOutput("-o ", rebasedDepsZip).
 		Text("**/*:" + proptools.ShellEscape(depsBase)) // zip2zip verifies depsBase

 	rootDir := android.PathForModuleOut(ctx, "root").OutputPath
 	rootZip := f.buildRootZip(ctx)
 	builder.Command().
 		BuiltTool("zipsync").
 		FlagWithArg("-d ", rootDir.String()). // zipsync wipes this. No need to clear.
 		Input(rootZip).
 		Input(rebasedDepsZip)

 	// run host_init_verifier
 	// Ideally we should have a concept of pluggable linters that verify the generated image.
 	// While such concept is not implement this will do.
 	// TODO(b/263574231): substitute with pluggable linter.
 	builder.Command().
 		BuiltTool("host_init_verifier").
 		FlagWithArg("--out_system=", rootDir.String()+"/system")

 	propFile, toolDeps := f.buildPropFile(ctx)
 	output := android.PathForModuleOut(ctx, f.installFileName()).OutputPath
 	builder.Command().BuiltTool("build_image").
 		Text(rootDir.String()). // input directory
 		Input(propFile).
 		Implicits(toolDeps).
 		Output(output).
 		Text(rootDir.String()) // directory where to find fs_config_files|dirs

 	// rootDir is not deleted. Might be useful for quick inspection.
 	builder.Build("build_filesystem_image", fmt.Sprintf("Creating filesystem %s", f.BaseModuleName()))

 	return output
 }

 func (f *filesystem) buildFileContexts(ctx android.ModuleContext) android.OutputPath {
 	builder := android.NewRuleBuilder(pctx, ctx)
 	fcBin := android.PathForModuleOut(ctx, "file_contexts.bin")
 	builder.Command().BuiltTool("sefcontext_compile").
 		FlagWithOutput("-o ", fcBin).
 		Input(android.PathForModuleSrc(ctx, proptools.String(f.properties.File_contexts)))
 	builder.Build("build_filesystem_file_contexts", fmt.Sprintf("Creating filesystem file contexts for %s", f.BaseModuleName()))
 	return fcBin.OutputPath
 }

 // Calculates avb_salt from entry list (sorted) for deterministic output.
 func (f *filesystem) salt() string {
 	return sha1sum(f.entries)
 }

 func (f *filesystem) buildPropFile(ctx android.ModuleContext) (propFile android.OutputPath, toolDeps android.Paths) {
 	type prop struct {
 		name  string
 		value string
 	}

 	var props []prop
 	var deps android.Paths
 	addStr := func(name string, value string) {
 		props = append(props, prop{name, value})
 	}
 	addPath := func(name string, path android.Path) {
 		props = append(props, prop{name, path.String()})
 		deps = append(deps, path)
 	}

 	// Type string that build_image.py accepts.
 	fsTypeStr := func(t fsType) string {
 		switch t {
 		// TODO(jiyong): add more types like f2fs, erofs, etc.
 		case ext4Type:
 			return "ext4"
 		}
 		panic(fmt.Errorf("unsupported fs type %v", t))
 	}

 	addStr("fs_type", fsTypeStr(f.fsType(ctx)))
 	addStr("mount_point", proptools.StringDefault(f.properties.Mount_point, "/"))
 	addStr("use_dynamic_partition_size", "true")
 	addPath("ext_mkuserimg", ctx.Config().HostToolPath(ctx, "mkuserimg_mke2fs"))
 	// b/177813163 deps of the host tools have to be added. Remove this.
 	for _, t := range []string{"mke2fs", "e2fsdroid", "tune2fs"} {
 		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)
 		partitionName := proptools.StringDefault(f.properties.Partition_name, f.Name())
 		addStr("partition_name", partitionName)
 		avb_add_hashtree_footer_args := "--do_not_generate_fec"
 		if hashAlgorithm := proptools.String(f.properties.Avb_hash_algorithm); hashAlgorithm != "" {
 			avb_add_hashtree_footer_args += " --hash_algorithm " + hashAlgorithm
 		}
 		securityPatchKey := "com.android.build." + partitionName + ".security_patch"
 		securityPatchValue := ctx.Config().PlatformSecurityPatch()
 		avb_add_hashtree_footer_args += " --prop " + securityPatchKey + ":" + securityPatchValue
 		addStr("avb_add_hashtree_footer_args", avb_add_hashtree_footer_args)
 		addStr("avb_salt", f.salt())
 	}

 	if proptools.String(f.properties.File_contexts) != "" {
 		addPath("selinux_fc", f.buildFileContexts(ctx))
 	}
 	if timestamp := proptools.String(f.properties.Fake_timestamp); timestamp != "" {
 		addStr("timestamp", timestamp)
 	}
 	if uuid := proptools.String(f.properties.Uuid); uuid != "" {
 		addStr("uuid", uuid)
 		addStr("hash_seed", uuid)
 	}
 	propFile = android.PathForModuleOut(ctx, "prop").OutputPath
 	builder := android.NewRuleBuilder(pctx, ctx)
 	builder.Command().Text("rm").Flag("-rf").Output(propFile)
 	for _, p := range props {
 		builder.Command().
 			Text("echo").
 			Flag(`"` + p.name + "=" + p.value + `"`).
 			Text(">>").Output(propFile)
 	}
 	builder.Build("build_filesystem_prop", fmt.Sprintf("Creating filesystem props for %s", f.BaseModuleName()))
 	return propFile, deps
 }

 func (f *filesystem) buildCpioImage(ctx android.ModuleContext, compressed bool) android.OutputPath {
 	if proptools.Bool(f.properties.Use_avb) {
 		ctx.PropertyErrorf("use_avb", "signing compresed cpio image using avbtool is not supported."+
 			"Consider adding this to bootimg module and signing the entire boot image.")
 	}

 	if proptools.String(f.properties.File_contexts) != "" {
 		ctx.PropertyErrorf("file_contexts", "file_contexts is not supported for compressed cpio image.")
 	}

 	depsZipFile := android.PathForModuleOut(ctx, "deps.zip").OutputPath
 	f.entries = f.CopyDepsToZip(ctx, f.gatherFilteredPackagingSpecs(ctx), depsZipFile)

 	builder := android.NewRuleBuilder(pctx, ctx)
 	depsBase := proptools.StringDefault(f.properties.Base_dir, ".")
 	rebasedDepsZip := android.PathForModuleOut(ctx, "rebased_deps.zip").OutputPath
 	builder.Command().
 		BuiltTool("zip2zip").
 		FlagWithInput("-i ", depsZipFile).
 		FlagWithOutput("-o ", rebasedDepsZip).
 		Text("**/*:" + proptools.ShellEscape(depsBase)) // zip2zip verifies depsBase

 	rootDir := android.PathForModuleOut(ctx, "root").OutputPath
 	rootZip := f.buildRootZip(ctx)
 	builder.Command().
 		BuiltTool("zipsync").
 		FlagWithArg("-d ", rootDir.String()). // zipsync wipes this. No need to clear.
 		Input(rootZip).
 		Input(rebasedDepsZip)

 	output := android.PathForModuleOut(ctx, f.installFileName()).OutputPath
 	cmd := builder.Command().
 		BuiltTool("mkbootfs").
 		Text(rootDir.String()) // input directory
 	if compressed {
 		cmd.Text("|").
 			BuiltTool("lz4").
 			Flag("--favor-decSpeed"). // for faster boot
 			Flag("-12").              // maximum compression level
 			Flag("-l").               // legacy format for kernel
 			Text(">").Output(output)
 	} else {
 		cmd.Text(">").Output(output)
 	}

 	// rootDir is not deleted. Might be useful for quick inspection.
 	builder.Build("build_cpio_image", fmt.Sprintf("Creating filesystem %s", f.BaseModuleName()))

 	return output
 }

 var _ android.AndroidMkEntriesProvider = (*filesystem)(nil)

 // Implements android.AndroidMkEntriesProvider
 func (f *filesystem) AndroidMkEntries() []android.AndroidMkEntries {
 	return []android.AndroidMkEntries{android.AndroidMkEntries{
 		Class:      "ETC",
 		OutputFile: android.OptionalPathForPath(f.output),
 		ExtraEntries: []android.AndroidMkExtraEntriesFunc{
 			func(ctx android.AndroidMkExtraEntriesContext, entries *android.AndroidMkEntries) {
 				entries.SetString("LOCAL_MODULE_PATH", f.installDir.String())
 				entries.SetString("LOCAL_INSTALLED_MODULE_STEM", f.installFileName())
 			},
 		},
 	}}
 }

 var _ android.OutputFileProducer = (*filesystem)(nil)

 // Implements android.OutputFileProducer
 func (f *filesystem) OutputFiles(tag string) (android.Paths, error) {
 	if tag == "" {
 		return []android.Path{f.output}, nil
 	}
 	return nil, fmt.Errorf("unsupported module reference tag %q", tag)
 }

 // Filesystem is the public interface for the filesystem struct. Currently, it's only for the apex
 // package to have access to the output file.
 type Filesystem interface {
 	android.Module
 	OutputPath() android.Path

 	// Returns the output file that is signed by avbtool. If this module is not signed, returns
 	// nil.
 	SignedOutputPath() android.Path
 }

 var _ Filesystem = (*filesystem)(nil)

 func (f *filesystem) OutputPath() android.Path {
 	return f.output
 }

 func (f *filesystem) SignedOutputPath() android.Path {
 	if proptools.Bool(f.properties.Use_avb) {
 		return f.OutputPath()
 	}
 	return nil
 }

 // Filter the result of GatherPackagingSpecs to discard items targeting outside "system" partition.
 // Note that "apex" module installs its contents to "apex"(fake partition) as well
 // for symbol lookup by imitating "activated" paths.
 func (f *filesystem) gatherFilteredPackagingSpecs(ctx android.ModuleContext) map[string]android.PackagingSpec {
 	specs := f.PackagingBase.GatherPackagingSpecs(ctx)
 	if f.filterPackagingSpecs != nil {
 		f.filterPackagingSpecs(specs)
 	}
 	return specs
 }

 func sha1sum(values []string) string {
 	h := sha256.New()
 	for _, value := range values {
 		io.WriteString(h, value)
 	}
 	return fmt.Sprintf("%x", h.Sum(nil))
 }

 // Base cc.UseCoverage

 var _ cc.UseCoverage = (*filesystem)(nil)

 func (*filesystem) IsNativeCoverageNeeded(ctx android.BaseModuleContext) bool {
 	return ctx.Device() && ctx.DeviceConfig().NativeCoverageEnabled()
 }
	// 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 filesystem

	import (
	"crypto/sha256"
	"fmt"
	"io"
	"path/filepath"
	"strings"

	"android/soong/android"
	"android/soong/cc"

	"github.com/google/blueprint"
	"github.com/google/blueprint/proptools"
	)

	func init() {
	registerBuildComponents(android.InitRegistrationContext)
	}

	func registerBuildComponents(ctx android.RegistrationContext) {
	ctx.RegisterModuleType("android_filesystem", filesystemFactory)
	ctx.RegisterModuleType("android_system_image", systemImageFactory)
	ctx.RegisterModuleType("avb_add_hash_footer", avbAddHashFooterFactory)
	ctx.RegisterModuleType("avb_add_hash_footer_defaults", avbAddHashFooterDefaultsFactory)
	ctx.RegisterModuleType("avb_gen_vbmeta_image", avbGenVbmetaImageFactory)
	ctx.RegisterModuleType("avb_gen_vbmeta_image_defaults", avbGenVbmetaImageDefaultsFactory)
	}

	type filesystem struct {
	android.ModuleBase
	android.PackagingBase

	properties filesystemProperties

	// Function that builds extra files under the root directory and returns the files
	buildExtraFiles func(ctx android.ModuleContext, root android.OutputPath) android.OutputPaths

	// Function that filters PackagingSpecs returned by PackagingBase.GatherPackagingSpecs()
	filterPackagingSpecs func(specs map[string]android.PackagingSpec)

	output android.OutputPath
	installDir android.InstallPath

	// For testing. Keeps the result of CopyDepsToZip()
	entries []string
	}

	type symlinkDefinition struct {
	Target *string
	Name *string
	}

	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"`

	// Signing algorithm for avbtool. Default is SHA256_RSA4096.
	Avb_algorithm *string

	// Hash algorithm used for avbtool (for descriptors). This is passed as hash_algorithm to
	// avbtool. Default used by avbtool is sha1.
	Avb_hash_algorithm *string

	// Name of the partition stored in vbmeta desc. Defaults to the name of this module.
	Partition_name *string

	// Type of the filesystem. Currently, ext4, cpio, and compressed_cpio are supported. Default
	// is ext4.
	Type *string

	// file_contexts file to make image. Currently, only ext4 is supported.
	File_contexts *string `android:"path"`

	// Base directory relative to root, to which deps are installed, e.g. "system". Default is "."
	// (root).
	Base_dir *string

	// Directories to be created under root. e.g. /dev, /proc, etc.
	Dirs []string

	// Symbolic links to be created under root with "ln -sf <target> <name>".
	Symlinks []symlinkDefinition

	// Seconds since unix epoch to override timestamps of file entries
	Fake_timestamp *string

	// When set, passed to mkuserimg_mke2fs --mke2fs_uuid & --mke2fs_hash_seed.
	// Otherwise, they'll be set as random which might cause indeterministic build output.
	Uuid *string

	// Mount point for this image. Default is "/"
	Mount_point *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).
	// The modules are placed in the filesystem image just like they are installed to the ordinary
	// partitions like system.img. For example, cc_library modules are placed under ./lib[64] directory.
	func filesystemFactory() android.Module {
	module := &filesystem{}
	initFilesystemModule(module)
	return module
	}

	func initFilesystemModule(module *filesystem) {
	module.AddProperties(&module.properties)
	android.InitPackageModule(module)
	android.InitAndroidMultiTargetsArchModule(module, android.DeviceSupported, android.MultilibCommon)
	}

	var dependencyTag = struct {
	blueprint.BaseDependencyTag
	android.PackagingItemAlwaysDepTag
	}{}

	func (f *filesystem) DepsMutator(ctx android.BottomUpMutatorContext) {
	f.AddDeps(ctx, dependencyTag)
	}

	type fsType int

	const (
	ext4Type fsType = iota
	compressedCpioType
	cpioType // uncompressed
	unknown
	)

	func (f *filesystem) fsType(ctx android.ModuleContext) fsType {
	typeStr := proptools.StringDefault(f.properties.Type, "ext4")
	switch typeStr {
	case "ext4":
	return ext4Type
	case "compressed_cpio":
	return compressedCpioType
	case "cpio":
	return cpioType
	default:
	ctx.PropertyErrorf("type", "%q not supported", typeStr)
	return unknown
	}
	}

	func (f *filesystem) installFileName() string {
	return f.BaseModuleName() + ".img"
	}

	var pctx = android.NewPackageContext("android/soong/filesystem")

	func (f *filesystem) GenerateAndroidBuildActions(ctx android.ModuleContext) {
	switch f.fsType(ctx) {
	case ext4Type:
	f.output = f.buildImageUsingBuildImage(ctx)
	case compressedCpioType:
	f.output = f.buildCpioImage(ctx, true)
	case cpioType:
	f.output = f.buildCpioImage(ctx, false)
	default:
	return
	}

	f.installDir = android.PathForModuleInstall(ctx, "etc")
	ctx.InstallFile(f.installDir, f.installFileName(), f.output)
	}

	// root zip will contain extra files/dirs that are not from the `deps` property.
	func (f *filesystem) buildRootZip(ctx android.ModuleContext) android.OutputPath {
	rootDir := android.PathForModuleGen(ctx, "root").OutputPath
	builder := android.NewRuleBuilder(pctx, ctx)
	builder.Command().Text("rm -rf").Text(rootDir.String())
	builder.Command().Text("mkdir -p").Text(rootDir.String())

	// create dirs and symlinks
	for _, dir := range f.properties.Dirs {
	// OutputPath.Join verifies dir
	builder.Command().Text("mkdir -p").Text(rootDir.Join(ctx, dir).String())
	}

	for _, symlink := range f.properties.Symlinks {
	name := strings.TrimSpace(proptools.String(symlink.Name))
	target := strings.TrimSpace(proptools.String(symlink.Target))

	if name == "" {
	ctx.PropertyErrorf("symlinks", "Name can't be empty")
	continue
	}

	if target == "" {
	ctx.PropertyErrorf("symlinks", "Target can't be empty")
	continue
	}

	// OutputPath.Join verifies name. don't need to verify target.
	dst := rootDir.Join(ctx, name)

	builder.Command().Text("mkdir -p").Text(filepath.Dir(dst.String()))
	builder.Command().Text("ln -sf").Text(proptools.ShellEscape(target)).Text(dst.String())
	}

	// create extra files if there's any
	rootForExtraFiles := android.PathForModuleGen(ctx, "root-extra").OutputPath
	var extraFiles android.OutputPaths
	if f.buildExtraFiles != nil {
	extraFiles = f.buildExtraFiles(ctx, rootForExtraFiles)
	for _, f := range extraFiles {
	rel, _ := filepath.Rel(rootForExtraFiles.String(), f.String())
	if strings.HasPrefix(rel, "..") {
	panic(fmt.Errorf("%q is not under %q\n", f, rootForExtraFiles))
	}
	}
	}

	// Zip them all
	zipOut := android.PathForModuleGen(ctx, "root.zip").OutputPath
	zipCommand := builder.Command().BuiltTool("soong_zip")
	zipCommand.FlagWithOutput("-o ", zipOut).
	FlagWithArg("-C ", rootDir.String()).
	Flag("-L 0"). // no compression because this will be unzipped soon
	FlagWithArg("-D ", rootDir.String()).
	Flag("-d") // include empty directories
	if len(extraFiles) > 0 {
	zipCommand.FlagWithArg("-C ", rootForExtraFiles.String())
	for _, f := range extraFiles {
	zipCommand.FlagWithInput("-f ", f)
	}
	}

	builder.Command().Text("rm -rf").Text(rootDir.String())

	builder.Build("zip_root", fmt.Sprintf("zipping root contents for %s", ctx.ModuleName()))
	return zipOut
	}

	func (f *filesystem) buildImageUsingBuildImage(ctx android.ModuleContext) android.OutputPath {
	depsZipFile := android.PathForModuleOut(ctx, "deps.zip").OutputPath
	f.entries = f.CopyDepsToZip(ctx, f.gatherFilteredPackagingSpecs(ctx), depsZipFile)

	builder := android.NewRuleBuilder(pctx, ctx)
	depsBase := proptools.StringDefault(f.properties.Base_dir, ".")
	rebasedDepsZip := android.PathForModuleOut(ctx, "rebased_deps.zip").OutputPath
	builder.Command().
	BuiltTool("zip2zip").
	FlagWithInput("-i ", depsZipFile).
	FlagWithOutput("-o ", rebasedDepsZip).
	Text("*/:" + proptools.ShellEscape(depsBase)) // zip2zip verifies depsBase

	rootDir := android.PathForModuleOut(ctx, "root").OutputPath
	rootZip := f.buildRootZip(ctx)
	builder.Command().
	BuiltTool("zipsync").
	FlagWithArg("-d ", rootDir.String()). // zipsync wipes this. No need to clear.
	Input(rootZip).
	Input(rebasedDepsZip)

	// run host_init_verifier
	// Ideally we should have a concept of pluggable linters that verify the generated image.
	// While such concept is not implement this will do.
	// TODO(b/263574231): substitute with pluggable linter.
	builder.Command().
	BuiltTool("host_init_verifier").
	FlagWithArg("--out_system=", rootDir.String()+"/system")

	propFile, toolDeps := f.buildPropFile(ctx)
	output := android.PathForModuleOut(ctx, f.installFileName()).OutputPath
	builder.Command().BuiltTool("build_image").
	Text(rootDir.String()). // input directory
	Input(propFile).
	Implicits(toolDeps).
	Output(output).
	Text(rootDir.String()) // directory where to find fs_config_files\|dirs

	// rootDir is not deleted. Might be useful for quick inspection.
	builder.Build("build_filesystem_image", fmt.Sprintf("Creating filesystem %s", f.BaseModuleName()))

	return output
	}

	func (f *filesystem) buildFileContexts(ctx android.ModuleContext) android.OutputPath {
	builder := android.NewRuleBuilder(pctx, ctx)
	fcBin := android.PathForModuleOut(ctx, "file_contexts.bin")
	builder.Command().BuiltTool("sefcontext_compile").
	FlagWithOutput("-o ", fcBin).
	Input(android.PathForModuleSrc(ctx, proptools.String(f.properties.File_contexts)))
	builder.Build("build_filesystem_file_contexts", fmt.Sprintf("Creating filesystem file contexts for %s", f.BaseModuleName()))
	return fcBin.OutputPath
	}

	// Calculates avb_salt from entry list (sorted) for deterministic output.
	func (f *filesystem) salt() string {
	return sha1sum(f.entries)
	}

	func (f *filesystem) buildPropFile(ctx android.ModuleContext) (propFile android.OutputPath, toolDeps android.Paths) {
	type prop struct {
	name string
	value string
	}

	var props []prop
	var deps android.Paths
	addStr := func(name string, value string) {
	props = append(props, prop{name, value})
	}
	addPath := func(name string, path android.Path) {
	props = append(props, prop{name, path.String()})
	deps = append(deps, path)
	}

	// Type string that build_image.py accepts.
	fsTypeStr := func(t fsType) string {
	switch t {
	// TODO(jiyong): add more types like f2fs, erofs, etc.
	case ext4Type:
	return "ext4"
	}
	panic(fmt.Errorf("unsupported fs type %v", t))
	}

	addStr("fs_type", fsTypeStr(f.fsType(ctx)))
	addStr("mount_point", proptools.StringDefault(f.properties.Mount_point, "/"))
	addStr("use_dynamic_partition_size", "true")
	addPath("ext_mkuserimg", ctx.Config().HostToolPath(ctx, "mkuserimg_mke2fs"))
	// b/177813163 deps of the host tools have to be added. Remove this.
	for _, t := range []string{"mke2fs", "e2fsdroid", "tune2fs"} {
	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)
	partitionName := proptools.StringDefault(f.properties.Partition_name, f.Name())
	addStr("partition_name", partitionName)
	avb_add_hashtree_footer_args := "--do_not_generate_fec"
	if hashAlgorithm := proptools.String(f.properties.Avb_hash_algorithm); hashAlgorithm != "" {
	avb_add_hashtree_footer_args += " --hash_algorithm " + hashAlgorithm
	}
	securityPatchKey := "com.android.build." + partitionName + ".security_patch"
	securityPatchValue := ctx.Config().PlatformSecurityPatch()
	avb_add_hashtree_footer_args += " --prop " + securityPatchKey + ":" + securityPatchValue
	addStr("avb_add_hashtree_footer_args", avb_add_hashtree_footer_args)
	addStr("avb_salt", f.salt())
	}

	if proptools.String(f.properties.File_contexts) != "" {
	addPath("selinux_fc", f.buildFileContexts(ctx))
	}
	if timestamp := proptools.String(f.properties.Fake_timestamp); timestamp != "" {
	addStr("timestamp", timestamp)
	}
	if uuid := proptools.String(f.properties.Uuid); uuid != "" {
	addStr("uuid", uuid)
	addStr("hash_seed", uuid)
	}
	propFile = android.PathForModuleOut(ctx, "prop").OutputPath
	builder := android.NewRuleBuilder(pctx, ctx)
	builder.Command().Text("rm").Flag("-rf").Output(propFile)
	for _, p := range props {
	builder.Command().
	Text("echo").
	Flag(`"` + p.name + "=" + p.value + `"`).
	Text(">>").Output(propFile)
	}
	builder.Build("build_filesystem_prop", fmt.Sprintf("Creating filesystem props for %s", f.BaseModuleName()))
	return propFile, deps
	}

	func (f *filesystem) buildCpioImage(ctx android.ModuleContext, compressed bool) android.OutputPath {
	if proptools.Bool(f.properties.Use_avb) {
	ctx.PropertyErrorf("use_avb", "signing compresed cpio image using avbtool is not supported."+
	"Consider adding this to bootimg module and signing the entire boot image.")
	}

	if proptools.String(f.properties.File_contexts) != "" {
	ctx.PropertyErrorf("file_contexts", "file_contexts is not supported for compressed cpio image.")
	}

	depsZipFile := android.PathForModuleOut(ctx, "deps.zip").OutputPath
	f.entries = f.CopyDepsToZip(ctx, f.gatherFilteredPackagingSpecs(ctx), depsZipFile)

	builder := android.NewRuleBuilder(pctx, ctx)
	depsBase := proptools.StringDefault(f.properties.Base_dir, ".")
	rebasedDepsZip := android.PathForModuleOut(ctx, "rebased_deps.zip").OutputPath
	builder.Command().
	BuiltTool("zip2zip").
	FlagWithInput("-i ", depsZipFile).
	FlagWithOutput("-o ", rebasedDepsZip).
	Text("*/:" + proptools.ShellEscape(depsBase)) // zip2zip verifies depsBase

	rootDir := android.PathForModuleOut(ctx, "root").OutputPath
	rootZip := f.buildRootZip(ctx)
	builder.Command().
	BuiltTool("zipsync").
	FlagWithArg("-d ", rootDir.String()). // zipsync wipes this. No need to clear.
	Input(rootZip).
	Input(rebasedDepsZip)

	output := android.PathForModuleOut(ctx, f.installFileName()).OutputPath
	cmd := builder.Command().
	BuiltTool("mkbootfs").
	Text(rootDir.String()) // input directory
	if compressed {
	cmd.Text("\|").
	BuiltTool("lz4").
	Flag("--favor-decSpeed"). // for faster boot
	Flag("-12"). // maximum compression level
	Flag("-l"). // legacy format for kernel
	Text(">").Output(output)
	} else {
	cmd.Text(">").Output(output)
	}

	// rootDir is not deleted. Might be useful for quick inspection.
	builder.Build("build_cpio_image", fmt.Sprintf("Creating filesystem %s", f.BaseModuleName()))

	return output
	}

	var _ android.AndroidMkEntriesProvider = (*filesystem)(nil)

	// Implements android.AndroidMkEntriesProvider
	func (f *filesystem) AndroidMkEntries() []android.AndroidMkEntries {
	return []android.AndroidMkEntries{android.AndroidMkEntries{
	Class: "ETC",
	OutputFile: android.OptionalPathForPath(f.output),
	ExtraEntries: []android.AndroidMkExtraEntriesFunc{
	func(ctx android.AndroidMkExtraEntriesContext, entries *android.AndroidMkEntries) {
	entries.SetString("LOCAL_MODULE_PATH", f.installDir.String())
	entries.SetString("LOCAL_INSTALLED_MODULE_STEM", f.installFileName())
	},
	},
	}}
	}

	var _ android.OutputFileProducer = (*filesystem)(nil)

	// Implements android.OutputFileProducer
	func (f *filesystem) OutputFiles(tag string) (android.Paths, error) {
	if tag == "" {
	return []android.Path{f.output}, nil
	}
	return nil, fmt.Errorf("unsupported module reference tag %q", tag)
	}

	// Filesystem is the public interface for the filesystem struct. Currently, it's only for the apex
	// package to have access to the output file.
	type Filesystem interface {
	android.Module
	OutputPath() android.Path

	// Returns the output file that is signed by avbtool. If this module is not signed, returns
	// nil.
	SignedOutputPath() android.Path
	}

	var _ Filesystem = (*filesystem)(nil)

	func (f *filesystem) OutputPath() android.Path {
	return f.output
	}

	func (f *filesystem) SignedOutputPath() android.Path {
	if proptools.Bool(f.properties.Use_avb) {
	return f.OutputPath()
	}
	return nil
	}

	// Filter the result of GatherPackagingSpecs to discard items targeting outside "system" partition.
	// Note that "apex" module installs its contents to "apex"(fake partition) as well
	// for symbol lookup by imitating "activated" paths.
	func (f *filesystem) gatherFilteredPackagingSpecs(ctx android.ModuleContext) map[string]android.PackagingSpec {
	specs := f.PackagingBase.GatherPackagingSpecs(ctx)
	if f.filterPackagingSpecs != nil {
	f.filterPackagingSpecs(specs)
	}
	return specs
	}

	func sha1sum(values []string) string {
	h := sha256.New()
	for _, value := range values {
	io.WriteString(h, value)
	}
	return fmt.Sprintf("%x", h.Sum(nil))
	}

	// Base cc.UseCoverage

	var _ cc.UseCoverage = (*filesystem)(nil)

	func (*filesystem) IsNativeCoverageNeeded(ctx android.BaseModuleContext) bool {
	return ctx.Device() && ctx.DeviceConfig().NativeCoverageEnabled()
	}