Generate NDK sysroots from the platform build.

The list of migrated libraries is currently empty. Libraries will be
migrated as follow up patches.

Test: Migrated libc to this system and everything still builds.
      build.ninja shows libraries being built and used and headers are
      collected for the sysroot.
Bug: http://b/27533932
Change-Id: Iaba00543c1390f432befe0eed768ed3fbb8a9b96

1 files changed, 250 insertions, 0 deletions

diff --git a/cc/ndk_library.go b/cc/ndk_library.go
new file mode 100644
index 00000000..562186ea
--- /dev/null
+++ b/cc/ndk_library.go
@@ -0,0 +1,250 @@
+// Copyright 2016 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 cc
+
+import (
+	"fmt"
+	"strconv"
+	"strings"
+
+	"github.com/google/blueprint"
+
+	"android/soong/android"
+)
+
+var (
+	toolPath = pctx.SourcePathVariable("toolPath", "build/soong/cc/gen_stub_libs.py")
+
+	genStubSrc = pctx.StaticRule("genStubSrc",
+		blueprint.RuleParams{
+			Command:     "$toolPath --arch $arch --api $apiLevel $in $out",
+			Description: "genStubSrc $out",
+			CommandDeps: []string{"$toolPath"},
+		}, "arch", "apiLevel")
+
+	ndkLibrarySuffix = ".ndk"
+)
+
+// Creates a stub shared library based on the provided version file.
+//
+// The name of the generated file will be based on the module name by stripping
+// the ".ndk" suffix from the module name. Module names must end with ".ndk"
+// (as a convention to allow soong to guess the NDK name of a dependency when
+// needed). "libfoo.ndk" will generate "libfoo.so.
+//
+// Example:
+//
+// ndk_library {
+//     name: "libfoo.ndk",
+//     symbol_file: "libfoo.map.txt",
+//     first_version: "9",
+// }
+//
+type libraryProperties struct {
+	// Relative path to the symbol map.
+	// An example file can be seen here: TODO(danalbert): Make an example.
+	Symbol_file string
+
+	// The first API level a library was available. A library will be generated
+	// for every API level beginning with this one.
+	First_version string
+
+	// Private property for use by the mutator that splits per-API level.
+	ApiLevel int `blueprint:"mutated"`
+}
+
+type stubCompiler struct {
+	baseCompiler
+
+	properties libraryProperties
+}
+
+// OMG GO
+func intMin(a int, b int) int {
+	if a < b {
+		return a
+	} else {
+		return b
+	}
+}
+
+func generateStubApiVariants(mctx android.BottomUpMutatorContext, c *stubCompiler) {
+	minVersion := 9 // Minimum version supported by the NDK.
+	// TODO(danalbert): Use PlatformSdkVersion when possible.
+	// This is an interesting case because for the moment we actually need 24
+	// even though the latest released version in aosp is 23. prebuilts/ndk/r11
+	// has android-24 versions of libraries, and as platform libraries get
+	// migrated the libraries in prebuilts will need to depend on them.
+	//
+	// Once everything is all moved over to the new stuff (when there isn't a
+	// prebuilts/ndk any more) then this should be fixable, but for now I think
+	// it needs to remain as-is.
+	maxVersion := 24
+	firstArchVersions := map[string]int{
+		"arm":    9,
+		"arm64":  21,
+		"mips":   9,
+		"mips64": 21,
+		"x86":    9,
+		"x86_64": 21,
+	}
+
+	// If the NDK drops support for a platform version, we don't want to have to
+	// fix up every module that was using it as its minimum version. Clip to the
+	// supported version here instead.
+	firstVersion, err := strconv.Atoi(c.properties.First_version)
+	if err != nil {
+		mctx.ModuleErrorf("Invalid first_version value (must be int): %q",
+			c.properties.First_version)
+	}
+	if firstVersion < minVersion {
+		firstVersion = minVersion
+	}
+
+	arch := mctx.Arch().ArchType.String()
+	firstArchVersion, ok := firstArchVersions[arch]
+	if !ok {
+		panic(fmt.Errorf("Arch %q not found in firstArchVersions", arch))
+	}
+	firstGenVersion := intMin(firstVersion, firstArchVersion)
+	versionStrs := make([]string, maxVersion-firstGenVersion+1)
+	for version := firstGenVersion; version <= maxVersion; version++ {
+		versionStrs[version-firstGenVersion] = strconv.Itoa(version)
+	}
+
+	modules := mctx.CreateVariations(versionStrs...)
+	for i, module := range modules {
+		module.(*Module).compiler.(*stubCompiler).properties.ApiLevel = firstGenVersion + i
+	}
+}
+
+func ndkApiMutator(mctx android.BottomUpMutatorContext) {
+	if m, ok := mctx.Module().(*Module); ok {
+		if compiler, ok := m.compiler.(*stubCompiler); ok {
+			generateStubApiVariants(mctx, compiler)
+		}
+	}
+}
+
+func (c *stubCompiler) compile(ctx ModuleContext, flags Flags, deps PathDeps) android.Paths {
+	arch := ctx.Arch().ArchType.String()
+
+	if !strings.HasSuffix(ctx.ModuleName(), ndkLibrarySuffix) {
+		ctx.ModuleErrorf("ndk_library modules names must be suffixed with %q\n",
+			ndkLibrarySuffix)
+	}
+	libName := strings.TrimSuffix(ctx.ModuleName(), ndkLibrarySuffix)
+	fileBase := fmt.Sprintf("%s.%s.%d", libName, arch, c.properties.ApiLevel)
+	stubSrcName := fileBase + ".c"
+	stubSrcPath := android.PathForModuleGen(ctx, stubSrcName)
+	versionScriptName := fileBase + ".map"
+	versionScriptPath := android.PathForModuleGen(ctx, versionScriptName)
+	symbolFilePath := android.PathForModuleSrc(ctx, c.properties.Symbol_file)
+	ctx.ModuleBuild(pctx, android.ModuleBuildParams{
+		Rule:    genStubSrc,
+		Outputs: []android.WritablePath{stubSrcPath, versionScriptPath},
+		Input:   symbolFilePath,
+		Args: map[string]string{
+			"arch":     arch,
+			"apiLevel": strconv.Itoa(c.properties.ApiLevel),
+		},
+	})
+
+	flags.CFlags = append(flags.CFlags,
+		// We're knowingly doing some otherwise unsightly things with builtin
+		// functions here. We're just generating stub libraries, so ignore it.
+		"-Wno-incompatible-library-redeclaration",
+		"-Wno-builtin-requires-header",
+		"-Wno-invalid-noreturn",
+
+		// These libraries aren't actually used. Don't worry about unwinding
+		// (avoids the need to link an unwinder into a fake library).
+		"-fno-unwind-tables",
+	)
+
+	subdir := ""
+	srcs := []string{}
+	excludeSrcs := []string{}
+	extraSrcs := []android.Path{stubSrcPath}
+	extraDeps := []android.Path{}
+	return c.baseCompiler.compileObjs(ctx, flags, subdir, srcs, excludeSrcs,
+		extraSrcs, extraDeps)
+}
+
+type stubLinker struct {
+	libraryLinker
+}
+
+func (linker *stubLinker) deps(ctx BaseModuleContext, deps Deps) Deps {
+	return Deps{}
+}
+
+func (linker *stubLinker) flags(ctx ModuleContext, flags Flags) Flags {
+	linker.libraryLinker.libName = strings.TrimSuffix(ctx.ModuleName(),
+		ndkLibrarySuffix)
+	return linker.libraryLinker.flags(ctx, flags)
+}
+
+type stubInstaller struct {
+	baseInstaller
+
+	compiler *stubCompiler
+
+	installPath string
+}
+
+var _ installer = (*stubInstaller)(nil)
+
+func (installer *stubInstaller) install(ctx ModuleContext, path android.Path) {
+	arch := ctx.Target().Arch.ArchType.Name
+	apiLevel := installer.compiler.properties.ApiLevel
+
+	// arm64 isn't actually a multilib toolchain, so unlike the other LP64
+	// architectures it's just installed to lib.
+	libDir := "lib"
+	if ctx.toolchain().Is64Bit() && arch != "arm64" {
+		libDir = "lib64"
+	}
+
+	installDir := getNdkInstallBase(ctx).Join(ctx, fmt.Sprintf(
+		"platforms/android-%d/arch-%s/usr/%s", apiLevel, arch, libDir))
+	installer.installPath = ctx.InstallFile(installDir, path).String()
+}
+
+func newStubLibrary() *Module {
+	module := newModule(android.DeviceSupported, android.MultilibBoth)
+	module.stl = nil
+
+	linker := &stubLinker{}
+	linker.dynamicProperties.BuildShared = true
+	linker.dynamicProperties.BuildStatic = false
+	linker.stripper.StripProperties.Strip.None = true
+	module.linker = linker
+
+	compiler := &stubCompiler{}
+	module.compiler = compiler
+	module.installer = &stubInstaller{baseInstaller{
+		dir:   "lib",
+		dir64: "lib64",
+	}, compiler, ""}
+
+	return module
+}
+
+func ndkLibraryFactory() (blueprint.Module, []interface{}) {
+	module := newStubLibrary()
+	return android.InitAndroidArchModule(module, android.DeviceSupported, android.MultilibBoth,
+		&module.compiler.(*stubCompiler).properties)
+}