filesystem/bootimg.go - android_build_soong - Gitiles

 // Copyright (C) 2021 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 (
 	"fmt"
 	"strconv"
 	"strings"

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

 	"android/soong/android"
 )

 func init() {
 	android.RegisterModuleType("bootimg", BootimgFactory)
 }

 type bootimg struct {
 	android.ModuleBase

 	properties BootimgProperties

 	output     android.Path
 	installDir android.InstallPath

 	bootImageType bootImageType
 }

 type BootimgProperties struct {
 	// Set the name of the output. Defaults to <module_name>.img.
 	Stem *string

 	// Path to the linux kernel prebuilt file
 	Kernel_prebuilt *string `android:"arch_variant,path"`

 	// Filesystem module that is used as ramdisk
 	Ramdisk_module *string

 	// Path to the device tree blob (DTB) prebuilt file to add to this boot image
 	Dtb_prebuilt *string `android:"arch_variant,path"`

 	// Header version number. Must be set to one of the version numbers that are currently
 	// supported. Refer to
 	// https://source.android.com/devices/bootloader/boot-image-header
 	Header_version *string

 	// Determines the specific type of boot image this module is building. Can be boot,
 	// vendor_boot or init_boot. Defaults to boot.
 	// Refer to https://source.android.com/devices/bootloader/partitions/vendor-boot-partitions
 	// for vendor_boot.
 	// Refer to https://source.android.com/docs/core/architecture/partitions/generic-boot for
 	// init_boot.
 	Boot_image_type *string

 	// Optional kernel commandline arguments
 	Cmdline []string `android:"arch_variant"`

 	// File that contains bootconfig parameters. This can be set only when `vendor_boot` is true
 	// and `header_version` is greater than or equal to 4.
 	Bootconfig *string `android:"arch_variant,path"`

 	// The size of the partition on the device. It will be a build error if this built partition
 	// image exceeds this size.
 	Partition_size *int64

 	// When set to true, sign the image with avbtool. Default is false.
 	Use_avb *bool

 	// This can either be "default", or "make_legacy". "make_legacy" will sign the boot image
 	// like how build/make/core/Makefile does, to get bit-for-bit backwards compatibility. But
 	// we may want to reconsider if it's necessary to have two modes in the future. The default
 	// is "default"
 	Avb_mode *string

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

 	// 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_device_first"`

 	// Hash and signing algorithm for avbtool. Default is SHA256_RSA4096.
 	Avb_algorithm *string

 	// The index used to prevent rollback of the image on device.
 	Avb_rollback_index *int64

 	// The security patch passed to as the com.android.build.<type>.security_patch avb property.
 	// Replacement for the make variables BOOT_SECURITY_PATCH / INIT_BOOT_SECURITY_PATCH.
 	Security_patch *string
 }

 type bootImageType int

 const (
 	unsupported bootImageType = iota
 	boot
 	vendorBoot
 	initBoot
 )

 func toBootImageType(ctx android.ModuleContext, bootImageType string) bootImageType {
 	switch bootImageType {
 	case "boot":
 		return boot
 	case "vendor_boot":
 		return vendorBoot
 	case "init_boot":
 		return initBoot
 	default:
 		ctx.ModuleErrorf("Unknown boot_image_type %s. Must be one of \"boot\", \"vendor_boot\", or \"init_boot\"", bootImageType)
 	}
 	return unsupported
 }

 func (b bootImageType) String() string {
 	switch b {
 	case boot:
 		return "boot"
 	case vendorBoot:
 		return "vendor_boot"
 	case initBoot:
 		return "init_boot"
 	default:
 		panic("unknown boot image type")
 	}
 }

 func (b bootImageType) isBoot() bool {
 	return b == boot
 }

 func (b bootImageType) isVendorBoot() bool {
 	return b == vendorBoot
 }

 func (b bootImageType) isInitBoot() bool {
 	return b == initBoot
 }

 // bootimg is the image for the boot partition. It consists of header, kernel, ramdisk, and dtb.
 func BootimgFactory() android.Module {
 	module := &bootimg{}
 	module.AddProperties(&module.properties)
 	android.InitAndroidArchModule(module, android.DeviceSupported, android.MultilibFirst)
 	return module
 }

 type bootimgDep struct {
 	blueprint.BaseDependencyTag
 	kind string
 }

 var bootimgRamdiskDep = bootimgDep{kind: "ramdisk"}

 func (b *bootimg) DepsMutator(ctx android.BottomUpMutatorContext) {
 	ramdisk := proptools.String(b.properties.Ramdisk_module)
 	if ramdisk != "" {
 		ctx.AddDependency(ctx.Module(), bootimgRamdiskDep, ramdisk)
 	}
 }

 func (b *bootimg) installFileName() string {
 	return proptools.StringDefault(b.properties.Stem, b.BaseModuleName()+".img")
 }

 func (b *bootimg) partitionName() string {
 	return proptools.StringDefault(b.properties.Partition_name, b.BaseModuleName())
 }

 func (b *bootimg) GenerateAndroidBuildActions(ctx android.ModuleContext) {
 	b.bootImageType = toBootImageType(ctx, proptools.StringDefault(b.properties.Boot_image_type, "boot"))
 	if b.bootImageType == unsupported {
 		return
 	}

 	kernelProp := proptools.String(b.properties.Kernel_prebuilt)
 	if b.bootImageType.isVendorBoot() && kernelProp != "" {
 		ctx.PropertyErrorf("kernel_prebuilt", "vendor_boot partition can't have kernel")
 		return
 	}
 	if b.bootImageType.isBoot() && kernelProp == "" {
 		ctx.PropertyErrorf("kernel_prebuilt", "boot partition must have kernel")
 		return
 	}
 	var kernel android.Path
 	if kernelProp != "" {
 		kernel = android.PathForModuleSrc(ctx, kernelProp)
 	}

 	unsignedOutput := b.buildBootImage(ctx, kernel)

 	output := unsignedOutput
 	if proptools.Bool(b.properties.Use_avb) {
 		// This bootimg module supports 2 modes of avb signing. It is not clear to this author
 		// why there are differences, but one of them is to match the behavior of make-built boot
 		// images.
 		switch proptools.StringDefault(b.properties.Avb_mode, "default") {
 		case "default":
 			output = b.signImage(ctx, unsignedOutput)
 		case "make_legacy":
 			output = b.addAvbFooter(ctx, unsignedOutput, kernel)
 		default:
 			ctx.PropertyErrorf("avb_mode", `Unknown value for avb_mode, expected "default" or "make_legacy", got: %q`, *b.properties.Avb_mode)
 		}
 	}

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

 	ctx.SetOutputFiles([]android.Path{output}, "")
 	b.output = output
 }

 func (b *bootimg) buildBootImage(ctx android.ModuleContext, kernel android.Path) android.Path {
 	output := android.PathForModuleOut(ctx, "unsigned", b.installFileName())

 	builder := android.NewRuleBuilder(pctx, ctx)
 	cmd := builder.Command().BuiltTool("mkbootimg")

 	if kernel != nil {
 		cmd.FlagWithInput("--kernel ", kernel)
 	}

 	// These arguments are passed for boot.img and init_boot.img generation
 	if b.bootImageType.isBoot() || b.bootImageType.isInitBoot() {
 		cmd.FlagWithArg("--os_version ", ctx.Config().PlatformVersionLastStable())
 		cmd.FlagWithArg("--os_patch_level ", ctx.Config().PlatformSecurityPatch())
 	}

 	dtbName := proptools.String(b.properties.Dtb_prebuilt)
 	if dtbName != "" {
 		dtb := android.PathForModuleSrc(ctx, dtbName)
 		cmd.FlagWithInput("--dtb ", dtb)
 	}

 	cmdline := strings.Join(b.properties.Cmdline, " ")
 	if cmdline != "" {
 		flag := "--cmdline "
 		if b.bootImageType.isVendorBoot() {
 			flag = "--vendor_cmdline "
 		}
 		cmd.FlagWithArg(flag, proptools.ShellEscapeIncludingSpaces(cmdline))
 	}

 	headerVersion := proptools.String(b.properties.Header_version)
 	if headerVersion == "" {
 		ctx.PropertyErrorf("header_version", "must be set")
 		return output
 	}
 	verNum, err := strconv.Atoi(headerVersion)
 	if err != nil {
 		ctx.PropertyErrorf("header_version", "%q is not a number", headerVersion)
 		return output
 	}
 	if verNum < 3 {
 		ctx.PropertyErrorf("header_version", "must be 3 or higher for vendor_boot")
 		return output
 	}
 	cmd.FlagWithArg("--header_version ", headerVersion)

 	ramdiskName := proptools.String(b.properties.Ramdisk_module)
 	if ramdiskName != "" {
 		ramdisk := ctx.GetDirectDepWithTag(ramdiskName, bootimgRamdiskDep)
 		if filesystem, ok := ramdisk.(*filesystem); ok {
 			flag := "--ramdisk "
 			if b.bootImageType.isVendorBoot() {
 				flag = "--vendor_ramdisk "
 			}
 			cmd.FlagWithInput(flag, filesystem.OutputPath())
 		} else {
 			ctx.PropertyErrorf("ramdisk", "%q is not android_filesystem module", ramdisk.Name())
 			return output
 		}
 	}

 	bootconfig := proptools.String(b.properties.Bootconfig)
 	if bootconfig != "" {
 		if !b.bootImageType.isVendorBoot() {
 			ctx.PropertyErrorf("bootconfig", "requires vendor_boot: true")
 			return output
 		}
 		if verNum < 4 {
 			ctx.PropertyErrorf("bootconfig", "requires header_version: 4 or later")
 			return output
 		}
 		cmd.FlagWithInput("--vendor_bootconfig ", android.PathForModuleSrc(ctx, bootconfig))
 	}

 	// Output flag for boot.img and init_boot.img
 	flag := "--output "
 	if b.bootImageType.isVendorBoot() {
 		flag = "--vendor_boot "
 	}
 	cmd.FlagWithOutput(flag, output)

 	if b.properties.Partition_size != nil {
 		assertMaxImageSize(builder, output, *b.properties.Partition_size, proptools.Bool(b.properties.Use_avb))
 	}

 	builder.Build("build_bootimg", fmt.Sprintf("Creating %s", b.BaseModuleName()))
 	return output
 }

 func (b *bootimg) addAvbFooter(ctx android.ModuleContext, unsignedImage android.Path, kernel android.Path) android.Path {
 	output := android.PathForModuleOut(ctx, b.installFileName())
 	builder := android.NewRuleBuilder(pctx, ctx)
 	builder.Command().Text("cp").Input(unsignedImage).Output(output)
 	cmd := builder.Command().BuiltTool("avbtool").
 		Text("add_hash_footer").
 		FlagWithInput("--image ", output)

 	if b.properties.Partition_size != nil {
 		cmd.FlagWithArg("--partition_size ", strconv.FormatInt(*b.properties.Partition_size, 10))
 	} else {
 		cmd.Flag("--dynamic_partition_size")
 	}

 	// If you don't provide a salt, avbtool will use random bytes for the salt.
 	// This is bad for determinism (cached builds and diff tests are affected), so instead,
 	// we try to provide a salt. The requirements for a salt are not very clear, one aspect of it
 	// is that if it's unpredictable, attackers trying to change the contents of a partition need
 	// to find a new hash collision every release, because the salt changed.
 	if kernel != nil {
 		cmd.Textf(`--salt $(sha256sum "%s" | cut -d " " -f 1)`, kernel.String())
 		cmd.Implicit(kernel)
 	} else {
 		cmd.Textf(`--salt $(sha256sum "%s" "%s" | cut -d " " -f 1 | tr -d '\n')`, ctx.Config().BuildNumberFile(ctx), ctx.Config().Getenv("BUILD_DATETIME_FILE"))
 		cmd.OrderOnly(ctx.Config().BuildNumberFile(ctx))
 	}

 	cmd.FlagWithArg("--partition_name ", b.bootImageType.String())

 	if b.properties.Avb_algorithm != nil {
 		cmd.FlagWithArg("--algorithm ", proptools.NinjaAndShellEscape(*b.properties.Avb_algorithm))
 	}

 	if b.properties.Avb_private_key != nil {
 		key := android.PathForModuleSrc(ctx, proptools.String(b.properties.Avb_private_key))
 		cmd.FlagWithInput("--key ", key)
 	}

 	if !b.bootImageType.isVendorBoot() {
 		cmd.FlagWithArg("--prop ", proptools.NinjaAndShellEscape(fmt.Sprintf(
 			"com.android.build.%s.os_version:%s", b.bootImageType.String(), ctx.Config().PlatformVersionLastStable())))
 	}

 	fingerprintFile := ctx.Config().BuildFingerprintFile(ctx)
 	cmd.FlagWithArg("--prop ", fmt.Sprintf("com.android.build.%s.fingerprint:$(cat %s)", b.bootImageType.String(), fingerprintFile.String()))
 	cmd.OrderOnly(fingerprintFile)

 	if b.properties.Security_patch != nil {
 		cmd.FlagWithArg("--prop ", proptools.NinjaAndShellEscape(fmt.Sprintf(
 			"com.android.build.%s.security_patch:%s", b.bootImageType.String(), *b.properties.Security_patch)))
 	}

 	if b.properties.Avb_rollback_index != nil {
 		cmd.FlagWithArg("--rollback_index ", strconv.FormatInt(*b.properties.Avb_rollback_index, 10))
 	}

 	builder.Build("add_avb_footer", fmt.Sprintf("Adding avb footer to %s", b.BaseModuleName()))
 	return output
 }

 func (b *bootimg) signImage(ctx android.ModuleContext, unsignedImage android.Path) android.Path {
 	propFile, toolDeps := b.buildPropFile(ctx)

 	output := android.PathForModuleOut(ctx, b.installFileName())
 	builder := android.NewRuleBuilder(pctx, ctx)
 	builder.Command().Text("cp").Input(unsignedImage).Output(output)
 	builder.Command().BuiltTool("verity_utils").
 		Input(propFile).
 		Implicits(toolDeps).
 		Output(output)

 	builder.Build("sign_bootimg", fmt.Sprintf("Signing %s", b.BaseModuleName()))
 	return output
 }

 // Calculates avb_salt from some input for deterministic output.
 func (b *bootimg) salt() string {
 	var input []string
 	input = append(input, b.properties.Cmdline...)
 	input = append(input, proptools.StringDefault(b.properties.Partition_name, b.Name()))
 	input = append(input, proptools.String(b.properties.Header_version))
 	return sha1sum(input)
 }

 func (b *bootimg) buildPropFile(ctx android.ModuleContext) (android.Path, android.Paths) {
 	var sb strings.Builder
 	var deps android.Paths
 	addStr := func(name string, value string) {
 		fmt.Fprintf(&sb, "%s=%s\n", name, value)
 	}
 	addPath := func(name string, path android.Path) {
 		addStr(name, path.String())
 		deps = append(deps, path)
 	}

 	addStr("avb_hash_enable", "true")
 	addPath("avb_avbtool", ctx.Config().HostToolPath(ctx, "avbtool"))
 	algorithm := proptools.StringDefault(b.properties.Avb_algorithm, "SHA256_RSA4096")
 	addStr("avb_algorithm", algorithm)
 	key := android.PathForModuleSrc(ctx, proptools.String(b.properties.Avb_private_key))
 	addPath("avb_key_path", key)
 	addStr("avb_add_hash_footer_args", "") // TODO(jiyong): add --rollback_index
 	partitionName := proptools.StringDefault(b.properties.Partition_name, b.Name())
 	addStr("partition_name", partitionName)
 	addStr("avb_salt", b.salt())

 	propFile := android.PathForModuleOut(ctx, "prop")
 	android.WriteFileRule(ctx, propFile, sb.String())
 	return propFile, deps
 }

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

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

 var _ Filesystem = (*bootimg)(nil)

 func (b *bootimg) OutputPath() android.Path {
 	return b.output
 }

 func (b *bootimg) SignedOutputPath() android.Path {
 	if proptools.Bool(b.properties.Use_avb) {
 		return b.OutputPath()
 	}
 	return nil
 }
	// Copyright (C) 2021 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 (
	"fmt"
	"strconv"
	"strings"

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

	"android/soong/android"
	)

	func init() {
	android.RegisterModuleType("bootimg", BootimgFactory)
	}

	type bootimg struct {
	android.ModuleBase

	properties BootimgProperties

	output android.Path
	installDir android.InstallPath

	bootImageType bootImageType
	}

	type BootimgProperties struct {
	// Set the name of the output. Defaults to <module_name>.img.
	Stem *string

	// Path to the linux kernel prebuilt file
	Kernel_prebuilt *string `android:"arch_variant,path"`

	// Filesystem module that is used as ramdisk
	Ramdisk_module *string

	// Path to the device tree blob (DTB) prebuilt file to add to this boot image
	Dtb_prebuilt *string `android:"arch_variant,path"`

	// Header version number. Must be set to one of the version numbers that are currently
	// supported. Refer to
	// https://source.android.com/devices/bootloader/boot-image-header
	Header_version *string

	// Determines the specific type of boot image this module is building. Can be boot,
	// vendor_boot or init_boot. Defaults to boot.
	// Refer to https://source.android.com/devices/bootloader/partitions/vendor-boot-partitions
	// for vendor_boot.
	// Refer to https://source.android.com/docs/core/architecture/partitions/generic-boot for
	// init_boot.
	Boot_image_type *string

	// Optional kernel commandline arguments
	Cmdline []string `android:"arch_variant"`

	// File that contains bootconfig parameters. This can be set only when `vendor_boot` is true
	// and `header_version` is greater than or equal to 4.
	Bootconfig *string `android:"arch_variant,path"`

	// The size of the partition on the device. It will be a build error if this built partition
	// image exceeds this size.
	Partition_size *int64

	// When set to true, sign the image with avbtool. Default is false.
	Use_avb *bool

	// This can either be "default", or "make_legacy". "make_legacy" will sign the boot image
	// like how build/make/core/Makefile does, to get bit-for-bit backwards compatibility. But
	// we may want to reconsider if it's necessary to have two modes in the future. The default
	// is "default"
	Avb_mode *string

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

	// 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_device_first"`

	// Hash and signing algorithm for avbtool. Default is SHA256_RSA4096.
	Avb_algorithm *string

	// The index used to prevent rollback of the image on device.
	Avb_rollback_index *int64

	// The security patch passed to as the com.android.build.<type>.security_patch avb property.
	// Replacement for the make variables BOOT_SECURITY_PATCH / INIT_BOOT_SECURITY_PATCH.
	Security_patch *string
	}

	type bootImageType int

	const (
	unsupported bootImageType = iota
	boot
	vendorBoot
	initBoot
	)

	func toBootImageType(ctx android.ModuleContext, bootImageType string) bootImageType {
	switch bootImageType {
	case "boot":
	return boot
	case "vendor_boot":
	return vendorBoot
	case "init_boot":
	return initBoot
	default:
	ctx.ModuleErrorf("Unknown boot_image_type %s. Must be one of \"boot\", \"vendor_boot\", or \"init_boot\"", bootImageType)
	}
	return unsupported
	}

	func (b bootImageType) String() string {
	switch b {
	case boot:
	return "boot"
	case vendorBoot:
	return "vendor_boot"
	case initBoot:
	return "init_boot"
	default:
	panic("unknown boot image type")
	}
	}

	func (b bootImageType) isBoot() bool {
	return b == boot
	}

	func (b bootImageType) isVendorBoot() bool {
	return b == vendorBoot
	}

	func (b bootImageType) isInitBoot() bool {
	return b == initBoot
	}

	// bootimg is the image for the boot partition. It consists of header, kernel, ramdisk, and dtb.
	func BootimgFactory() android.Module {
	module := &bootimg{}
	module.AddProperties(&module.properties)
	android.InitAndroidArchModule(module, android.DeviceSupported, android.MultilibFirst)
	return module
	}

	type bootimgDep struct {
	blueprint.BaseDependencyTag
	kind string
	}

	var bootimgRamdiskDep = bootimgDep{kind: "ramdisk"}

	func (b *bootimg) DepsMutator(ctx android.BottomUpMutatorContext) {
	ramdisk := proptools.String(b.properties.Ramdisk_module)
	if ramdisk != "" {
	ctx.AddDependency(ctx.Module(), bootimgRamdiskDep, ramdisk)
	}
	}

	func (b *bootimg) installFileName() string {
	return proptools.StringDefault(b.properties.Stem, b.BaseModuleName()+".img")
	}

	func (b *bootimg) partitionName() string {
	return proptools.StringDefault(b.properties.Partition_name, b.BaseModuleName())
	}

	func (b *bootimg) GenerateAndroidBuildActions(ctx android.ModuleContext) {
	b.bootImageType = toBootImageType(ctx, proptools.StringDefault(b.properties.Boot_image_type, "boot"))
	if b.bootImageType == unsupported {
	return
	}

	kernelProp := proptools.String(b.properties.Kernel_prebuilt)
	if b.bootImageType.isVendorBoot() && kernelProp != "" {
	ctx.PropertyErrorf("kernel_prebuilt", "vendor_boot partition can't have kernel")
	return
	}
	if b.bootImageType.isBoot() && kernelProp == "" {
	ctx.PropertyErrorf("kernel_prebuilt", "boot partition must have kernel")
	return
	}
	var kernel android.Path
	if kernelProp != "" {
	kernel = android.PathForModuleSrc(ctx, kernelProp)
	}

	unsignedOutput := b.buildBootImage(ctx, kernel)

	output := unsignedOutput
	if proptools.Bool(b.properties.Use_avb) {
	// This bootimg module supports 2 modes of avb signing. It is not clear to this author
	// why there are differences, but one of them is to match the behavior of make-built boot
	// images.
	switch proptools.StringDefault(b.properties.Avb_mode, "default") {
	case "default":
	output = b.signImage(ctx, unsignedOutput)
	case "make_legacy":
	output = b.addAvbFooter(ctx, unsignedOutput, kernel)
	default:
	ctx.PropertyErrorf("avb_mode", `Unknown value for avb_mode, expected "default" or "make_legacy", got: %q`, *b.properties.Avb_mode)
	}
	}

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

	ctx.SetOutputFiles([]android.Path{output}, "")
	b.output = output
	}

	func (b *bootimg) buildBootImage(ctx android.ModuleContext, kernel android.Path) android.Path {
	output := android.PathForModuleOut(ctx, "unsigned", b.installFileName())

	builder := android.NewRuleBuilder(pctx, ctx)
	cmd := builder.Command().BuiltTool("mkbootimg")

	if kernel != nil {
	cmd.FlagWithInput("--kernel ", kernel)
	}

	// These arguments are passed for boot.img and init_boot.img generation
	if b.bootImageType.isBoot() \|\| b.bootImageType.isInitBoot() {
	cmd.FlagWithArg("--os_version ", ctx.Config().PlatformVersionLastStable())
	cmd.FlagWithArg("--os_patch_level ", ctx.Config().PlatformSecurityPatch())
	}

	dtbName := proptools.String(b.properties.Dtb_prebuilt)
	if dtbName != "" {
	dtb := android.PathForModuleSrc(ctx, dtbName)
	cmd.FlagWithInput("--dtb ", dtb)
	}

	cmdline := strings.Join(b.properties.Cmdline, " ")
	if cmdline != "" {
	flag := "--cmdline "
	if b.bootImageType.isVendorBoot() {
	flag = "--vendor_cmdline "
	}
	cmd.FlagWithArg(flag, proptools.ShellEscapeIncludingSpaces(cmdline))
	}

	headerVersion := proptools.String(b.properties.Header_version)
	if headerVersion == "" {
	ctx.PropertyErrorf("header_version", "must be set")
	return output
	}
	verNum, err := strconv.Atoi(headerVersion)
	if err != nil {
	ctx.PropertyErrorf("header_version", "%q is not a number", headerVersion)
	return output
	}
	if verNum < 3 {
	ctx.PropertyErrorf("header_version", "must be 3 or higher for vendor_boot")
	return output
	}
	cmd.FlagWithArg("--header_version ", headerVersion)

	ramdiskName := proptools.String(b.properties.Ramdisk_module)
	if ramdiskName != "" {
	ramdisk := ctx.GetDirectDepWithTag(ramdiskName, bootimgRamdiskDep)
	if filesystem, ok := ramdisk.(*filesystem); ok {
	flag := "--ramdisk "
	if b.bootImageType.isVendorBoot() {
	flag = "--vendor_ramdisk "
	}
	cmd.FlagWithInput(flag, filesystem.OutputPath())
	} else {
	ctx.PropertyErrorf("ramdisk", "%q is not android_filesystem module", ramdisk.Name())
	return output
	}
	}

	bootconfig := proptools.String(b.properties.Bootconfig)
	if bootconfig != "" {
	if !b.bootImageType.isVendorBoot() {
	ctx.PropertyErrorf("bootconfig", "requires vendor_boot: true")
	return output
	}
	if verNum < 4 {
	ctx.PropertyErrorf("bootconfig", "requires header_version: 4 or later")
	return output
	}
	cmd.FlagWithInput("--vendor_bootconfig ", android.PathForModuleSrc(ctx, bootconfig))
	}

	// Output flag for boot.img and init_boot.img
	flag := "--output "
	if b.bootImageType.isVendorBoot() {
	flag = "--vendor_boot "
	}
	cmd.FlagWithOutput(flag, output)

	if b.properties.Partition_size != nil {
	assertMaxImageSize(builder, output, *b.properties.Partition_size, proptools.Bool(b.properties.Use_avb))
	}

	builder.Build("build_bootimg", fmt.Sprintf("Creating %s", b.BaseModuleName()))
	return output
	}

	func (b *bootimg) addAvbFooter(ctx android.ModuleContext, unsignedImage android.Path, kernel android.Path) android.Path {
	output := android.PathForModuleOut(ctx, b.installFileName())
	builder := android.NewRuleBuilder(pctx, ctx)
	builder.Command().Text("cp").Input(unsignedImage).Output(output)
	cmd := builder.Command().BuiltTool("avbtool").
	Text("add_hash_footer").
	FlagWithInput("--image ", output)

	if b.properties.Partition_size != nil {
	cmd.FlagWithArg("--partition_size ", strconv.FormatInt(*b.properties.Partition_size, 10))
	} else {
	cmd.Flag("--dynamic_partition_size")
	}

	// If you don't provide a salt, avbtool will use random bytes for the salt.
	// This is bad for determinism (cached builds and diff tests are affected), so instead,
	// we try to provide a salt. The requirements for a salt are not very clear, one aspect of it
	// is that if it's unpredictable, attackers trying to change the contents of a partition need
	// to find a new hash collision every release, because the salt changed.
	if kernel != nil {
	cmd.Textf(`--salt $(sha256sum "%s" \| cut -d " " -f 1)`, kernel.String())
	cmd.Implicit(kernel)
	} else {
	cmd.Textf(`--salt $(sha256sum "%s" "%s" \| cut -d " " -f 1 \| tr -d '\n')`, ctx.Config().BuildNumberFile(ctx), ctx.Config().Getenv("BUILD_DATETIME_FILE"))
	cmd.OrderOnly(ctx.Config().BuildNumberFile(ctx))
	}

	cmd.FlagWithArg("--partition_name ", b.bootImageType.String())

	if b.properties.Avb_algorithm != nil {
	cmd.FlagWithArg("--algorithm ", proptools.NinjaAndShellEscape(*b.properties.Avb_algorithm))
	}

	if b.properties.Avb_private_key != nil {
	key := android.PathForModuleSrc(ctx, proptools.String(b.properties.Avb_private_key))
	cmd.FlagWithInput("--key ", key)
	}

	if !b.bootImageType.isVendorBoot() {
	cmd.FlagWithArg("--prop ", proptools.NinjaAndShellEscape(fmt.Sprintf(
	"com.android.build.%s.os_version:%s", b.bootImageType.String(), ctx.Config().PlatformVersionLastStable())))
	}

	fingerprintFile := ctx.Config().BuildFingerprintFile(ctx)
	cmd.FlagWithArg("--prop ", fmt.Sprintf("com.android.build.%s.fingerprint:$(cat %s)", b.bootImageType.String(), fingerprintFile.String()))
	cmd.OrderOnly(fingerprintFile)

	if b.properties.Security_patch != nil {
	cmd.FlagWithArg("--prop ", proptools.NinjaAndShellEscape(fmt.Sprintf(
	"com.android.build.%s.security_patch:%s", b.bootImageType.String(), *b.properties.Security_patch)))
	}

	if b.properties.Avb_rollback_index != nil {
	cmd.FlagWithArg("--rollback_index ", strconv.FormatInt(*b.properties.Avb_rollback_index, 10))
	}

	builder.Build("add_avb_footer", fmt.Sprintf("Adding avb footer to %s", b.BaseModuleName()))
	return output
	}

	func (b *bootimg) signImage(ctx android.ModuleContext, unsignedImage android.Path) android.Path {
	propFile, toolDeps := b.buildPropFile(ctx)

	output := android.PathForModuleOut(ctx, b.installFileName())
	builder := android.NewRuleBuilder(pctx, ctx)
	builder.Command().Text("cp").Input(unsignedImage).Output(output)
	builder.Command().BuiltTool("verity_utils").
	Input(propFile).
	Implicits(toolDeps).
	Output(output)

	builder.Build("sign_bootimg", fmt.Sprintf("Signing %s", b.BaseModuleName()))
	return output
	}

	// Calculates avb_salt from some input for deterministic output.
	func (b *bootimg) salt() string {
	var input []string
	input = append(input, b.properties.Cmdline...)
	input = append(input, proptools.StringDefault(b.properties.Partition_name, b.Name()))
	input = append(input, proptools.String(b.properties.Header_version))
	return sha1sum(input)
	}

	func (b *bootimg) buildPropFile(ctx android.ModuleContext) (android.Path, android.Paths) {
	var sb strings.Builder
	var deps android.Paths
	addStr := func(name string, value string) {
	fmt.Fprintf(&sb, "%s=%s\n", name, value)
	}
	addPath := func(name string, path android.Path) {
	addStr(name, path.String())
	deps = append(deps, path)
	}

	addStr("avb_hash_enable", "true")
	addPath("avb_avbtool", ctx.Config().HostToolPath(ctx, "avbtool"))
	algorithm := proptools.StringDefault(b.properties.Avb_algorithm, "SHA256_RSA4096")
	addStr("avb_algorithm", algorithm)
	key := android.PathForModuleSrc(ctx, proptools.String(b.properties.Avb_private_key))
	addPath("avb_key_path", key)
	addStr("avb_add_hash_footer_args", "") // TODO(jiyong): add --rollback_index
	partitionName := proptools.StringDefault(b.properties.Partition_name, b.Name())
	addStr("partition_name", partitionName)
	addStr("avb_salt", b.salt())

	propFile := android.PathForModuleOut(ctx, "prop")
	android.WriteFileRule(ctx, propFile, sb.String())
	return propFile, deps
	}

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

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

	var _ Filesystem = (*bootimg)(nil)

	func (b *bootimg) OutputPath() android.Path {
	return b.output
	}

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