Add LinuxBionic toolchain and switch

This adds a toolchain definition for LinuxBionic that only supports
Clang/64-bit. It pulls pieces from the x86_linux_host and x86_64_device
configs, and uses the android clang triple, with some manual overrides.

To enable building this, set your soong.config file to:

 {"Host_bionic": true}

Bug: 31559095
Test: out/soong/{Android,make-vars}-aosp_arm64.mk the same with or
      without host bionic turned on
Test: No change to out/soong/build.ninja before/after this change
Change-Id: Id97dda8bd9aa670c32aed31fbe6aaa8175e70b59

Android.bp

@@ -95,6 +95,7 @@ bootstrap_go_package {
 
         "cc/config/x86_darwin_host.go",
         "cc/config/x86_linux_host.go",
+        "cc/config/x86_linux_bionic_host.go",
         "cc/config/x86_windows_host.go",
     ],
     testSrcs: [

android/androidmk.go

@@ -164,6 +164,11 @@ func translateAndroidMkModule(ctx blueprint.SingletonContext, w io.Writer, mod b
 		return err
 	}
 
+	// Make does not understand LinuxBionic
+	if amod.Os() == LinuxBionic {
+		return nil
+	}
+
 	if data.SubName != "" {
 		name += data.SubName
 	}

android/arch.go

@@ -781,6 +781,10 @@ func decodeTargetProductVariables(config *config) (map[OsClass][]Target, error)
 		addTarget(BuildOs, *variables.HostSecondaryArch, nil, nil, nil)
 	}
 
+	if config.Host_bionic != nil && *config.Host_bionic {
+		addTarget(LinuxBionic, "x86_64", nil, nil, nil)
+	}
+
 	if variables.CrossHost != nil && *variables.CrossHost != "" {
 		crossHostOs := osByName(*variables.CrossHost)
 		if crossHostOs == NoOsType {

android/config.go

@@ -40,6 +40,7 @@ const productVariablesFileName = "soong.variables"
 type FileConfigurableOptions struct {
 	Mega_device *bool `json:",omitempty"`
 	Ndk_abis    *bool `json:",omitempty"`
+	Host_bionic *bool `json:",omitempty"`
 }
 
 func (f *FileConfigurableOptions) SetDefaultConfig() {

cc/binary.go

@@ -15,6 +15,8 @@
 package cc
 
 import (
+	"path/filepath"
+
 	"github.com/google/blueprint"
 	"github.com/google/blueprint/proptools"
 
@@ -236,7 +238,22 @@ func (binary *binaryDecorator) linkerFlags(ctx ModuleContext, flags Flags) Flags
 				if binary.Properties.DynamicLinker != "" {
 					flags.DynamicLinker = binary.Properties.DynamicLinker
 				} else {
-					flags.DynamicLinker = "/system/bin/linker"
+					switch ctx.Os() {
+					case android.Android:
+						flags.DynamicLinker = "/system/bin/linker"
+					case android.LinuxBionic:
+						// The linux kernel expects the linker to be an
+						// absolute path
+						path := android.PathForOutput(ctx,
+							"host", "linux_bionic-x86", "bin", "linker")
+						if p, err := filepath.Abs(path.String()); err == nil {
+							flags.DynamicLinker = p
+						} else {
+							ctx.ModuleErrorf("can't find path to dynamic linker: %q", err)
+						}
+					default:
+						ctx.ModuleErrorf("unknown dynamic linker")
+					}
 					if flags.Toolchain.Is64Bit() {
 						flags.DynamicLinker += "64"
 					}

cc/config/x86_linux_bionic_host.go

@@ -0,0 +1,168 @@
+// 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 config
+
+import (
+	"strings"
+
+	"android/soong/android"
+)
+
+var (
+	linuxBionicCflags = ClangFilterUnknownCflags([]string{
+		"-fno-exceptions", // from build/core/combo/select.mk
+		"-Wno-multichar",  // from build/core/combo/select.mk
+
+		"-fdiagnostics-color",
+
+		"-Wa,--noexecstack",
+
+		"-fPIC",
+		"-no-canonical-prefixes",
+
+		"-U_FORTIFY_SOURCE",
+		"-D_FORTIFY_SOURCE=2",
+		"-fstack-protector-strong",
+
+		// From x86_64_device
+		"-ffunction-sections",
+		"-finline-functions",
+		"-finline-limit=300",
+		"-fno-short-enums",
+		"-funswitch-loops",
+		"-funwind-tables",
+		"-no-canonical-prefixes",
+		"-fno-canonical-system-headers",
+
+		// HOST_RELEASE_CFLAGS
+		"-O2", // from build/core/combo/select.mk
+		"-g",  // from build/core/combo/select.mk
+		"-fno-strict-aliasing", // from build/core/combo/select.mk
+
+		// Tell clang where the gcc toolchain is
+		"--gcc-toolchain=${LinuxBionicGccRoot}",
+
+		// TODO: We're not really android, but we don't have a triple yet b/31393676
+		"-U__ANDROID__",
+		"-fno-emulated-tls",
+
+		// This is normally in ClangExtraTargetCflags, but this is considered host
+		"-nostdlibinc",
+	})
+
+	linuxBionicLdflags = ClangFilterUnknownCflags([]string{
+		"-Wl,-z,noexecstack",
+		"-Wl,-z,relro",
+		"-Wl,-z,now",
+		"-Wl,--build-id=md5",
+		"-Wl,--warn-shared-textrel",
+		"-Wl,--fatal-warnings",
+		"-Wl,--gc-sections",
+		"-Wl,--hash-style=gnu",
+		"-Wl,--no-undefined-version",
+
+		// Use the device gcc toolchain
+		"--gcc-toolchain=${LinuxBionicGccRoot}",
+	})
+)
+
+func init() {
+	pctx.StaticVariable("LinuxBionicCflags", strings.Join(linuxBionicCflags, " "))
+	pctx.StaticVariable("LinuxBionicLdflags", strings.Join(linuxBionicLdflags, " "))
+
+	pctx.StaticVariable("LinuxBionicIncludeFlags", bionicHeaders("x86_64", "x86"))
+
+	// Use the device gcc toolchain for now
+	pctx.StaticVariable("LinuxBionicGccRoot", "${X86_64GccRoot}")
+}
+
+type toolchainLinuxBionic struct {
+	toolchain64Bit
+}
+
+func (t *toolchainLinuxBionic) Name() string {
+	return "x86_64"
+}
+
+func (t *toolchainLinuxBionic) GccRoot() string {
+	return "${config.LinuxBionicGccRoot}"
+}
+
+func (t *toolchainLinuxBionic) GccTriple() string {
+	return "x86_64-linux-android"
+}
+
+func (t *toolchainLinuxBionic) GccVersion() string {
+	return "4.9"
+}
+
+func (t *toolchainLinuxBionic) Cflags() string {
+	return ""
+}
+
+func (t *toolchainLinuxBionic) Cppflags() string {
+	return ""
+}
+
+func (t *toolchainLinuxBionic) Ldflags() string {
+	return ""
+}
+
+func (t *toolchainLinuxBionic) IncludeFlags() string {
+	return "${config.LinuxBionicIncludeFlags}"
+}
+
+func (t *toolchainLinuxBionic) ClangTriple() string {
+	// TODO: we don't have a triple yet b/31393676
+	return "x86_64-linux-android"
+}
+
+func (t *toolchainLinuxBionic) ClangCflags() string {
+	return "${config.LinuxBionicCflags}"
+}
+
+func (t *toolchainLinuxBionic) ClangCppflags() string {
+	return ""
+}
+
+func (t *toolchainLinuxBionic) ClangLdflags() string {
+	return "${config.LinuxBionicLdflags}"
+}
+
+func (t *toolchainLinuxBionic) ToolchainClangCflags() string {
+	return "-m64 -march=x86-64"
+}
+
+func (t *toolchainLinuxBionic) ToolchainClangLdflags() string {
+	return "-m64"
+}
+
+func (t *toolchainLinuxBionic) AvailableLibraries() []string {
+	return nil
+}
+
+func (t *toolchainLinuxBionic) Bionic() bool {
+	return true
+}
+
+var toolchainLinuxBionicSingleton Toolchain = &toolchainLinuxBionic{}
+
+func linuxBionicToolchainFactory(arch android.Arch) Toolchain {
+	return toolchainLinuxBionicSingleton
+}
+
+func init() {
+	registerToolchainFactory(android.LinuxBionic, android.X86_64, linuxBionicToolchainFactory)
+}

cc/library.go

@@ -246,7 +246,7 @@ func (library *libraryDecorator) linkerFlags(ctx ModuleContext, flags Flags) Fla
 			sharedFlag = "-shared"
 		}
 		var f []string
-		if ctx.Device() {
+		if ctx.toolchain().Bionic() {
 			f = append(f,
 				"-nostdlib",
 				"-Wl,--gc-sections",