Add support for versioned stubs.

A cc_library or cc_library_shared can be configured to have stubs
variants of the lib.

cc_library_shared {
    name: "libfoo",
    srcs: ["foo.cpp"],
    stubs: {
        symbol_file: "foo.map.txt",
        versions: ["1", "2", "3"],
    },
}

then, stubs variants of libfoo for version 1, 2, and 3 are created
from foo.map.txt. Each version has the symbols from the map file where
each symbol is annotated with the version that the symbol was introduced
via the 'introduced=<ver>' syntax. The versions don't need to be in sync
with the platform versions (e.g., P for 28). The versions are local to
the library.

For another library or executable to use the versioned stubs lib, use
the new 'name#ver' syntax to specify the version:

cc_binary {
    name: "test",
    ....
    shared_libs: ["libFoo#2"],
}

Internally, a new mutator 'version' is applied to all cc.Module objects.
By default, a variant named 'impl' is created for the non-stub version.
If the versions property is set, additional variations are created per a
version with the mutable property BuildStubs set as true, which lets the
compiler and the linker to build a stubs lib from the symbol file
instead from the source files.

This feature will be used to enforce stable interfaces among APEXs. When
a lib foo in an APEX is depending on a lib bar in another APEX, then bar
should have stable interface (in C lang) and foo should be depending on
one of the stubs libs of bar. Only libraries in the same APEX as foo can
link against non-stub version of it.

Bug: 112672359
Test: m (cc_test added)

Change-Id: I2488be0b9d7b7b8d7761234dc1c9c0e3add8601c
diff --git a/cc/cc.go b/cc/cc.go
index 8b68489..0569563 100644
--- a/cc/cc.go
+++ b/cc/cc.go
@@ -39,6 +39,7 @@
 		ctx.BottomUp("vndk", vndkMutator).Parallel()
 		ctx.BottomUp("ndk_api", ndkApiMutator).Parallel()
 		ctx.BottomUp("test_per_src", testPerSrcMutator).Parallel()
+		ctx.BottomUp("version", versionMutator).Parallel()
 		ctx.BottomUp("begin", BeginMutator).Parallel()
 	})
 
@@ -945,6 +946,16 @@
 	c.begin(ctx)
 }
 
+// Split name#version into name and version
+func stubsLibNameAndVersion(name string) (string, string) {
+	if sharp := strings.LastIndex(name, "#"); sharp != -1 && sharp != len(name)-1 {
+		version := name[sharp+1:]
+		libname := name[:sharp]
+		return libname, version
+	}
+	return name, ""
+}
+
 func (c *Module) DepsMutator(actx android.BottomUpMutatorContext) {
 	ctx := &depsContext{
 		BottomUpMutatorContext: actx,
@@ -979,25 +990,28 @@
 			variantLibs = []string{}
 			nonvariantLibs = []string{}
 			for _, entry := range list {
-				if ctx.useSdk() && inList(entry, ndkPrebuiltSharedLibraries) {
-					if !inList(entry, ndkMigratedLibs) {
-						nonvariantLibs = append(nonvariantLibs, entry+".ndk."+version)
+				// strip #version suffix out
+				name, _ := stubsLibNameAndVersion(entry)
+				if ctx.useSdk() && inList(name, ndkPrebuiltSharedLibraries) {
+					if !inList(name, ndkMigratedLibs) {
+						nonvariantLibs = append(nonvariantLibs, name+".ndk."+version)
 					} else {
-						variantLibs = append(variantLibs, entry+ndkLibrarySuffix)
+						variantLibs = append(variantLibs, name+ndkLibrarySuffix)
 					}
-				} else if ctx.useVndk() && inList(entry, llndkLibraries) {
-					nonvariantLibs = append(nonvariantLibs, entry+llndkLibrarySuffix)
-				} else if (ctx.Platform() || ctx.ProductSpecific()) && inList(entry, vendorPublicLibraries) {
-					vendorPublicLib := entry + vendorPublicLibrarySuffix
+				} else if ctx.useVndk() && inList(name, llndkLibraries) {
+					nonvariantLibs = append(nonvariantLibs, name+llndkLibrarySuffix)
+				} else if (ctx.Platform() || ctx.ProductSpecific()) && inList(name, vendorPublicLibraries) {
+					vendorPublicLib := name + vendorPublicLibrarySuffix
 					if actx.OtherModuleExists(vendorPublicLib) {
 						nonvariantLibs = append(nonvariantLibs, vendorPublicLib)
 					} else {
 						// This can happen if vendor_public_library module is defined in a
 						// namespace that isn't visible to the current module. In that case,
 						// link to the original library.
-						nonvariantLibs = append(nonvariantLibs, entry)
+						nonvariantLibs = append(nonvariantLibs, name)
 					}
 				} else {
+					// put name#version back
 					nonvariantLibs = append(nonvariantLibs, entry)
 				}
 			}
@@ -1009,6 +1023,15 @@
 		deps.ReexportSharedLibHeaders, _ = rewriteNdkLibs(deps.ReexportSharedLibHeaders)
 	}
 
+	if c.linker != nil {
+		if library, ok := c.linker.(*libraryDecorator); ok {
+			if library.buildStubs() {
+				// Stubs lib does not have dependency to other libraries. Don't proceed.
+				return
+			}
+		}
+	}
+
 	for _, lib := range deps.HeaderLibs {
 		depTag := headerDepTag
 		if inList(lib, deps.ReexportHeaderLibHeaders) {
@@ -1035,19 +1058,40 @@
 		{Mutator: "link", Variation: "static"},
 	}, lateStaticDepTag, deps.LateStaticLibs...)
 
+	// shared lib names without the #version suffix
+	var sharedLibNames []string
+
 	for _, lib := range deps.SharedLibs {
+		name, version := stubsLibNameAndVersion(lib)
+		sharedLibNames = append(sharedLibNames, name)
 		depTag := sharedDepTag
 		if inList(lib, deps.ReexportSharedLibHeaders) {
 			depTag = sharedExportDepTag
 		}
-		actx.AddVariationDependencies([]blueprint.Variation{
-			{Mutator: "link", Variation: "shared"},
-		}, depTag, lib)
+		var variations []blueprint.Variation
+		variations = append(variations, blueprint.Variation{Mutator: "link", Variation: "shared"})
+		if version != "" && ctx.Os() == android.Android && !ctx.useVndk() && !c.inRecovery() {
+			variations = append(variations, blueprint.Variation{Mutator: "version", Variation: version})
+		}
+		actx.AddVariationDependencies(variations, depTag, name)
 	}
 
-	actx.AddVariationDependencies([]blueprint.Variation{
-		{Mutator: "link", Variation: "shared"},
-	}, lateSharedDepTag, deps.LateSharedLibs...)
+	for _, lib := range deps.LateSharedLibs {
+		name, version := stubsLibNameAndVersion(lib)
+		if inList(name, sharedLibNames) {
+			// This is to handle the case that some of the late shared libs (libc, libdl, libm, ...)
+			// are added also to SharedLibs with version (e.g., libc#10). If not skipped, we will be
+			// linking against both the stubs lib and the non-stubs lib at the same time.
+			continue
+		}
+		depTag := lateSharedDepTag
+		var variations []blueprint.Variation
+		variations = append(variations, blueprint.Variation{Mutator: "link", Variation: "shared"})
+		if version != "" && ctx.Os() == android.Android && !ctx.useVndk() && !c.inRecovery() {
+			variations = append(variations, blueprint.Variation{Mutator: "version", Variation: version})
+		}
+		actx.AddVariationDependencies(variations, depTag, name)
+	}
 
 	actx.AddVariationDependencies([]blueprint.Variation{
 		{Mutator: "link", Variation: "shared"},
@@ -1629,8 +1673,8 @@
 		return
 	}
 
-	if genrule, ok := mctx.Module().(*genrule.Module); ok {
-		if props, ok := genrule.Extra.(*GenruleExtraProperties); ok {
+	if g, ok := mctx.Module().(*genrule.Module); ok {
+		if props, ok := g.Extra.(*GenruleExtraProperties); ok {
 			var coreVariantNeeded bool = false
 			var vendorVariantNeeded bool = false
 			var recoveryVariantNeeded bool = false
@@ -1650,7 +1694,7 @@
 
 			if recoveryVariantNeeded {
 				primaryArch := mctx.Config().DevicePrimaryArchType()
-				moduleArch := genrule.Target().Arch.ArchType
+				moduleArch := g.Target().Arch.ArchType
 				if moduleArch != primaryArch {
 					recoveryVariantNeeded = false
 				}
@@ -1666,7 +1710,13 @@
 			if recoveryVariantNeeded {
 				variants = append(variants, recoveryMode)
 			}
-			mctx.CreateVariations(variants...)
+			mod := mctx.CreateVariations(variants...)
+			for i, v := range variants {
+				if v == recoveryMode {
+					m := mod[i].(*genrule.Module)
+					m.Extra.(*GenruleExtraProperties).InRecovery = true
+				}
+			}
 		}
 	}
 
diff --git a/cc/cc_test.go b/cc/cc_test.go
index ead89f6..fba38a2 100644
--- a/cc/cc_test.go
+++ b/cc/cc_test.go
@@ -66,6 +66,7 @@
 		ctx.BottomUp("image", imageMutator).Parallel()
 		ctx.BottomUp("link", LinkageMutator).Parallel()
 		ctx.BottomUp("vndk", vndkMutator).Parallel()
+		ctx.BottomUp("version", versionMutator).Parallel()
 		ctx.BottomUp("begin", BeginMutator).Parallel()
 	})
 	ctx.Register()
@@ -205,12 +206,13 @@
 `
 
 	ctx.MockFileSystem(map[string][]byte{
-		"Android.bp": []byte(bp),
-		"foo.c":      nil,
-		"bar.c":      nil,
-		"a.proto":    nil,
-		"b.aidl":     nil,
-		"my_include": nil,
+		"Android.bp":  []byte(bp),
+		"foo.c":       nil,
+		"bar.c":       nil,
+		"a.proto":     nil,
+		"b.aidl":      nil,
+		"my_include":  nil,
+		"foo.map.txt": nil,
 	})
 
 	return ctx
@@ -1730,5 +1732,58 @@
 	if !recoveryModule.Platform() {
 		t.Errorf("recovery variant of libHalInRecovery must not specific to device, soc, or product")
 	}
+}
 
+func TestVersionedStubs(t *testing.T) {
+	ctx := testCc(t, `
+		cc_library_shared {
+			name: "libFoo",
+			stubs: {
+				symbol_file: "foo.map.txt",
+				versions: ["1", "2", "3"],
+			},
+		}
+		cc_library_shared {
+			name: "libBar",
+			shared_libs: ["libFoo#1"],
+		}`)
+
+	variants := ctx.ModuleVariantsForTests("libFoo")
+	expectedVariants := []string{
+		"android_arm64_armv8-a_core_shared",
+		"android_arm64_armv8-a_core_shared_1",
+		"android_arm64_armv8-a_core_shared_2",
+		"android_arm64_armv8-a_core_shared_3",
+		"android_arm_armv7-a-neon_core_shared",
+		"android_arm_armv7-a-neon_core_shared_1",
+		"android_arm_armv7-a-neon_core_shared_2",
+		"android_arm_armv7-a-neon_core_shared_3",
+	}
+	variantsMismatch := false
+	if len(variants) != len(expectedVariants) {
+		variantsMismatch = true
+	} else {
+		for _, v := range expectedVariants {
+			if !inList(v, variants) {
+				variantsMismatch = false
+			}
+		}
+	}
+	if variantsMismatch {
+		t.Errorf("variants of libFoo expected:\n")
+		for _, v := range expectedVariants {
+			t.Errorf("%q\n", v)
+		}
+		t.Errorf(", but got:\n")
+		for _, v := range variants {
+			t.Errorf("%q\n", v)
+		}
+	}
+
+	libBarLinkRule := ctx.ModuleForTests("libBar", "android_arm64_armv8-a_core_shared").Rule("ld")
+	libFlags := libBarLinkRule.Args["libFlags"]
+	libFoo1StubPath := "libFoo/android_arm64_armv8-a_core_shared_1/libFoo.so"
+	if !strings.Contains(libFlags, libFoo1StubPath) {
+		t.Errorf("%q is not found in %q", libFoo1StubPath, libFlags)
+	}
 }
diff --git a/cc/genrule.go b/cc/genrule.go
index a672992..decf6ea 100644
--- a/cc/genrule.go
+++ b/cc/genrule.go
@@ -26,6 +26,9 @@
 type GenruleExtraProperties struct {
 	Vendor_available   *bool
 	Recovery_available *bool
+
+	// This genrule is for recovery variant
+	InRecovery bool `blueprint:"mutated"`
 }
 
 // cc_genrule is a genrule that can depend on other cc_* objects.
diff --git a/cc/library.go b/cc/library.go
index 920292d..aafe365 100644
--- a/cc/library.go
+++ b/cc/library.go
@@ -22,6 +22,7 @@
 
 	"android/soong/android"
 	"android/soong/cc/config"
+	"android/soong/genrule"
 )
 
 type LibraryProperties struct {
@@ -65,6 +66,15 @@
 	}
 
 	Static_ndk_lib *bool
+
+	Stubs struct {
+		// Relative path to the symbol map. The symbol map provides the list of
+		// symbols that are exported for stubs variant of this library.
+		Symbol_file *string
+
+		// List versions to generate stubs libs for.
+		Versions []string
+	}
 }
 
 type LibraryMutatedProperties struct {
@@ -78,6 +88,11 @@
 	VariantIsShared bool `blueprint:"mutated"`
 	// This variant is static
 	VariantIsStatic bool `blueprint:"mutated"`
+
+	// This variant is a stubs lib
+	BuildStubs bool `blueprint:"mutated"`
+	// Version of the stubs lib
+	StubsVersion string `blueprint:"mutated"`
 }
 
 type FlagExporterProperties struct {
@@ -240,6 +255,8 @@
 	// Location of the linked, unstripped library for shared libraries
 	unstrippedOutputFile android.Path
 
+	versionScriptPath android.ModuleGenPath
+
 	// Decorated interafaces
 	*baseCompiler
 	*baseLinker
@@ -313,7 +330,11 @@
 		flags.YasmFlags = append(flags.YasmFlags, f)
 	}
 
-	return library.baseCompiler.compilerFlags(ctx, flags, deps)
+	flags = library.baseCompiler.compilerFlags(ctx, flags, deps)
+	if library.buildStubs() {
+		flags = addStubLibraryCompilerFlags(flags)
+	}
+	return flags
 }
 
 func extractExportIncludesFromFlags(flags []string) []string {
@@ -336,6 +357,12 @@
 }
 
 func (library *libraryDecorator) compile(ctx ModuleContext, flags Flags, deps PathDeps) Objects {
+	if library.buildStubs() {
+		objs, versionScript := compileStubLibrary(ctx, flags, String(library.Properties.Stubs.Symbol_file), library.MutatedProperties.StubsVersion, "")
+		library.versionScriptPath = versionScript
+		return objs
+	}
+
 	if !library.buildShared() && !library.buildStatic() {
 		if len(library.baseCompiler.Properties.Srcs) > 0 {
 			ctx.PropertyErrorf("srcs", "cc_library_headers must not have any srcs")
@@ -422,8 +449,10 @@
 		location = InstallInSanitizerDir
 	}
 	library.baseInstaller.location = location
-
 	library.baseLinker.linkerInit(ctx)
+	// Let baseLinker know whether this variant is for stubs or not, so that
+	// it can omit things that are not required for linking stubs.
+	library.baseLinker.dynamicProperties.BuildStubs = library.buildStubs()
 }
 
 func (library *libraryDecorator) linkerDeps(ctx DepsContext, deps Deps) Deps {
@@ -735,7 +764,8 @@
 
 	if Bool(library.Properties.Static_ndk_lib) && library.static() &&
 		!ctx.useVndk() && !ctx.inRecovery() && ctx.Device() &&
-		library.baseLinker.sanitize.isUnsanitizedVariant() {
+		library.baseLinker.sanitize.isUnsanitizedVariant() &&
+		!library.buildStubs() {
 		installPath := getNdkSysrootBase(ctx).Join(
 			ctx, "usr/lib", config.NDKTriple(ctx.toolchain()), file.Base())
 
@@ -785,6 +815,14 @@
 	library.MutatedProperties.BuildStatic = false
 }
 
+func (library *libraryDecorator) buildStubs() bool {
+	return library.MutatedProperties.BuildStubs
+}
+
+func (library *libraryDecorator) stubsVersion() string {
+	return library.MutatedProperties.StubsVersion
+}
+
 func NewLibrary(hod android.HostOrDeviceSupported) (*Module, *libraryDecorator) {
 	module := newModule(hod, android.MultilibBoth)
 
@@ -847,3 +885,41 @@
 		}
 	}
 }
+
+// Version mutator splits a module into the mandatory non-stubs variant
+// (which is named "impl") and zero or more stubs variants.
+func versionMutator(mctx android.BottomUpMutatorContext) {
+	if mctx.Os() != android.Android {
+		return
+	}
+
+	if m, ok := mctx.Module().(*Module); ok && !m.inRecovery() && m.linker != nil {
+		if library, ok := m.linker.(*libraryDecorator); ok && library.buildShared() {
+			versions := []string{""}
+			for _, v := range library.Properties.Stubs.Versions {
+				versions = append(versions, v)
+			}
+			modules := mctx.CreateVariations(versions...)
+			for i, m := range modules {
+				l := m.(*Module).linker.(*libraryDecorator)
+				if i == 0 {
+					l.MutatedProperties.BuildStubs = false
+					continue
+				}
+				// Mark that this variant is for stubs.
+				l.MutatedProperties.BuildStubs = true
+				l.MutatedProperties.StubsVersion = versions[i]
+				m.(*Module).Properties.HideFromMake = true
+			}
+		} else {
+			mctx.CreateVariations("")
+		}
+		return
+	}
+	if genrule, ok := mctx.Module().(*genrule.Module); ok {
+		if props, ok := genrule.Extra.(*GenruleExtraProperties); ok && !props.InRecovery {
+			mctx.CreateVariations("")
+			return
+		}
+	}
+}
diff --git a/cc/linker.go b/cc/linker.go
index 28f4747..e96bfcb 100644
--- a/cc/linker.go
+++ b/cc/linker.go
@@ -160,7 +160,8 @@
 	Properties        BaseLinkerProperties
 	MoreProperties    MoreBaseLinkerProperties
 	dynamicProperties struct {
-		RunPaths []string `blueprint:"mutated"`
+		RunPaths   []string `blueprint:"mutated"`
+		BuildStubs bool     `blueprint:"mutated"`
 	}
 
 	sanitize *sanitize
@@ -269,9 +270,13 @@
 		deps.LateStaticLibs = append(deps.LateStaticLibs, "libwinpthread")
 	}
 
-	android.ExtractSourceDeps(ctx, linker.MoreProperties.Version_script)
-	android.ExtractSourceDeps(ctx,
-		linker.MoreProperties.Target.Vendor.Version_script)
+	// Version_script is not needed when linking stubs lib where the version
+	// script is created from the symbol map file.
+	if !linker.dynamicProperties.BuildStubs {
+		android.ExtractSourceDeps(ctx, linker.MoreProperties.Version_script)
+		android.ExtractSourceDeps(ctx,
+			linker.MoreProperties.Target.Vendor.Version_script)
+	}
 
 	return deps
 }
@@ -375,28 +380,32 @@
 		flags.GroupStaticLibs = true
 	}
 
-	versionScript := ctx.ExpandOptionalSource(
-		linker.MoreProperties.Version_script, "version_script")
+	// Version_script is not needed when linking stubs lib where the version
+	// script is created from the symbol map file.
+	if !linker.dynamicProperties.BuildStubs {
+		versionScript := ctx.ExpandOptionalSource(
+			linker.MoreProperties.Version_script, "version_script")
 
-	if ctx.useVndk() && linker.MoreProperties.Target.Vendor.Version_script != nil {
-		versionScript = ctx.ExpandOptionalSource(
-			linker.MoreProperties.Target.Vendor.Version_script,
-			"target.vendor.version_script")
-	}
+		if ctx.useVndk() && linker.MoreProperties.Target.Vendor.Version_script != nil {
+			versionScript = ctx.ExpandOptionalSource(
+				linker.MoreProperties.Target.Vendor.Version_script,
+				"target.vendor.version_script")
+		}
 
-	if versionScript.Valid() {
-		if ctx.Darwin() {
-			ctx.PropertyErrorf("version_script", "Not supported on Darwin")
-		} else {
-			flags.LdFlags = append(flags.LdFlags,
-				"-Wl,--version-script,"+versionScript.String())
-			flags.LdFlagsDeps = append(flags.LdFlagsDeps, versionScript.Path())
-
-			if linker.sanitize.isSanitizerEnabled(cfi) {
-				cfiExportsMap := android.PathForSource(ctx, cfiExportsMapPath)
+		if versionScript.Valid() {
+			if ctx.Darwin() {
+				ctx.PropertyErrorf("version_script", "Not supported on Darwin")
+			} else {
 				flags.LdFlags = append(flags.LdFlags,
-					"-Wl,--version-script,"+cfiExportsMap.String())
-				flags.LdFlagsDeps = append(flags.LdFlagsDeps, cfiExportsMap)
+					"-Wl,--version-script,"+versionScript.String())
+				flags.LdFlagsDeps = append(flags.LdFlagsDeps, versionScript.Path())
+
+				if linker.sanitize.isSanitizerEnabled(cfi) {
+					cfiExportsMap := android.PathForSource(ctx, cfiExportsMapPath)
+					flags.LdFlags = append(flags.LdFlags,
+						"-Wl,--version-script,"+cfiExportsMap.String())
+					flags.LdFlagsDeps = append(flags.LdFlagsDeps, cfiExportsMap)
+				}
 			}
 		}
 	}