platform_build_soong/filesystem/system_image.go

// 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 (
	"android/soong/android"
	"android/soong/linkerconfig"
)

type systemImage struct {
	filesystem

	properties systemImageProperties
}

type systemImageProperties struct {
	// Path to the input linker config json file.
	Linker_config_src *string
}

// android_system_image is a specialization of android_filesystem for the 'system' partition.
// Currently, the only difference is the inclusion of linker.config.pb file which specifies
// the provided and the required libraries to and from APEXes.
func systemImageFactory() android.Module {
	module := &systemImage{}
	module.AddProperties(&module.properties)
	module.filesystem.buildExtraFiles = module.buildExtraFiles
	module.filesystem.filterPackagingSpecs = module.filterPackagingSpecs
	initFilesystemModule(&module.filesystem)
	return module
}

func (s *systemImage) buildExtraFiles(ctx android.ModuleContext, root android.OutputPath) android.OutputPaths {
	lc := s.buildLinkerConfigFile(ctx, root)
	// Add more files if needed
	return []android.OutputPath{lc}
}

func (s *systemImage) buildLinkerConfigFile(ctx android.ModuleContext, root android.OutputPath) android.OutputPath {
	input := android.PathForModuleSrc(ctx, android.String(s.properties.Linker_config_src))
	output := root.Join(ctx, "system", "etc", "linker.config.pb")

	// we need "Module"s for packaging items
	var otherModules []android.Module
	deps := s.gatherFilteredPackagingSpecs(ctx)
	ctx.WalkDeps(func(child, parent android.Module) bool {
		for _, ps := range child.PackagingSpecs() {
			if _, ok := deps[ps.RelPathInPackage()]; ok {
				otherModules = append(otherModules, child)
			}
		}
		return true
	})

	builder := android.NewRuleBuilder(pctx, ctx)
	linkerconfig.BuildLinkerConfig(ctx, builder, input, otherModules, output)
	builder.Build("conv_linker_config", "Generate linker config protobuf "+output.String())
	return output
}

// 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 (s *systemImage) filterPackagingSpecs(specs map[string]android.PackagingSpec) {
	for k, ps := range specs {
		if ps.Partition() != "system" {
			delete(specs, k)
		}
	}
}