Add directory support to nsjail genrule

Trusty build requires a lot of files. Rather than globbing all such
files (more than 10,000 files), allowing bind-mounting directories makes
nsjail much more efficient. With this change, directories can be
directly bind-mounted with dirgroup modules and dir_srcs property of
genrule module.

dirgroup module and dir_srcs property will be allowed only to Trusty
builds.

Bug: 358302178
Test: m lk.elf.x86_64 lk.elf.arm64
Change-Id: I5938a57b7fb65f8fecce4a8f40aa4aedbf991135
diff --git a/android/Android.bp b/android/Android.bp
index 44cddcc..3b54326 100644
--- a/android/Android.bp
+++ b/android/Android.bp
@@ -52,6 +52,7 @@
         "defs.go",
         "depset_generic.go",
         "deptag.go",
+        "dirgroup.go",
         "early_module_context.go",
         "expand.go",
         "filegroup.go",
diff --git a/android/dirgroup.go b/android/dirgroup.go
new file mode 100644
index 0000000..20c4d13
--- /dev/null
+++ b/android/dirgroup.go
@@ -0,0 +1,63 @@
+// Copyright 2024 Google Inc. All rights reserved.
+//
+// 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 android
+
+import (
+	"github.com/google/blueprint"
+	"github.com/google/blueprint/proptools"
+)
+
+func init() {
+	RegisterDirgroupBuildComponents(InitRegistrationContext)
+}
+
+func RegisterDirgroupBuildComponents(ctx RegistrationContext) {
+	ctx.RegisterModuleType("dirgroup", DirGroupFactory)
+}
+
+type dirGroupProperties struct {
+	// dirs lists directories that will be included in this dirgroup
+	Dirs proptools.Configurable[[]string] `android:"path"`
+}
+
+type dirGroup struct {
+	ModuleBase
+	DefaultableModuleBase
+	properties dirGroupProperties
+}
+
+type DirInfo struct {
+	// TODO(b/358302178): Use DirectoryPaths instead of Paths
+	Dirs Paths
+}
+
+var DirProvider = blueprint.NewProvider[DirInfo]()
+
+// dirgroup contains a list of dirs that are referenced by other modules
+// properties using the syntax ":<name>". dirgroup are also be used to export
+// dirs across package boundaries. Currently the only allowed usage is genrule's
+// dir_srcs property.
+func DirGroupFactory() Module {
+	module := &dirGroup{}
+	module.AddProperties(&module.properties)
+	InitAndroidModule(module)
+	InitDefaultableModule(module)
+	return module
+}
+
+func (fg *dirGroup) GenerateAndroidBuildActions(ctx ModuleContext) {
+	dirs := DirectoryPathsForModuleSrc(ctx, fg.properties.Dirs.GetOrDefault(ctx, nil))
+	SetProvider(ctx, DirProvider, DirInfo{Dirs: dirs})
+}
diff --git a/android/neverallow.go b/android/neverallow.go
index e93763b..041c9a0 100644
--- a/android/neverallow.go
+++ b/android/neverallow.go
@@ -60,6 +60,7 @@
 	AddNeverAllowRules(createCcStubsRule())
 	AddNeverAllowRules(createProhibitHeaderOnlyRule())
 	AddNeverAllowRules(createLimitNdkExportRule()...)
+	AddNeverAllowRules(createLimitDirgroupRule()...)
 }
 
 // Add a NeverAllow rule to the set of rules to apply.
@@ -275,6 +276,23 @@
 	}
 }
 
+func createLimitDirgroupRule() []Rule {
+	reason := "dirgroup module and dir_srcs property of genrule is allowed only to Trusty build rule."
+	return []Rule{
+		NeverAllow().
+			ModuleType("dirgroup").
+			WithMatcher("visibility", NotInList([]string{"//trusty/vendor/google/aosp/scripts"})).Because(reason),
+		NeverAllow().
+			ModuleType("dirgroup").
+			Without("visibility", "//trusty/vendor/google/aosp/scripts").Because(reason),
+		NeverAllow().
+			ModuleType("genrule").
+			Without("name", "lk.elf.arm64").
+			Without("name", "lk.elf.x86_64").
+			WithMatcher("dir_srcs", isSetMatcherInstance).Because(reason),
+	}
+}
+
 func neverallowMutator(ctx BottomUpMutatorContext) {
 	m, ok := ctx.Module().(Module)
 	if !ok {
diff --git a/android/paths.go b/android/paths.go
index ec05831..371aed8 100644
--- a/android/paths.go
+++ b/android/paths.go
@@ -550,6 +550,58 @@
 	return ret
 }
 
+// DirectoryPathsForModuleSrcExcludes returns a Paths{} containing the resolved references in
+// directory paths. Elements of paths are resolved as:
+//   - filepath, relative to local module directory, resolves as a filepath relative to the local
+//     source directory
+//   - other modules using the ":name" syntax. These modules must implement DirProvider.
+//
+// TODO(b/358302178): Implement DirectoryPath and change the return type.
+func DirectoryPathsForModuleSrc(ctx ModuleMissingDepsPathContext, paths []string) Paths {
+	var ret Paths
+
+	for _, path := range paths {
+		if m, t := SrcIsModuleWithTag(path); m != "" {
+			module := GetModuleFromPathDep(ctx, m, t)
+			if module == nil {
+				ctx.ModuleErrorf(`missing dependency on %q, is the property annotated with android:"path"?`, m)
+				continue
+			}
+			if t != "" {
+				ctx.ModuleErrorf("DirProvider dependency %q does not support the tag %q", module, t)
+				continue
+			}
+			mctx, ok := ctx.(OtherModuleProviderContext)
+			if !ok {
+				panic(fmt.Errorf("%s is not an OtherModuleProviderContext", ctx))
+			}
+			if dirProvider, ok := OtherModuleProvider(mctx, module, DirProvider); ok {
+				ret = append(ret, dirProvider.Dirs...)
+			} else {
+				ReportPathErrorf(ctx, "module %q does not implement DirProvider", module)
+			}
+		} else {
+			p := pathForModuleSrc(ctx, path)
+			if isDir, err := ctx.Config().fs.IsDir(p.String()); err != nil {
+				ReportPathErrorf(ctx, "%s: %s", p, err.Error())
+			} else if !isDir {
+				ReportPathErrorf(ctx, "module directory path %q is not a directory", p)
+			} else {
+				ret = append(ret, p)
+			}
+		}
+	}
+
+	seen := make(map[Path]bool, len(ret))
+	for _, path := range ret {
+		if seen[path] {
+			ReportPathErrorf(ctx, "duplicated path %q", path)
+		}
+		seen[path] = true
+	}
+	return ret
+}
+
 // OutputPaths is a slice of OutputPath objects, with helpers to operate on the collection.
 type OutputPaths []OutputPath