LinuxBionic supports arm64

LinuxBionic now supports arm64 architecture in addition to the existing
x86_64 arch. This is to make it possible to build host tools like adb,
fastboot, crosvm, etc. for Linux/ARM on regular Linux/x86 machines.

The arm64 target can be selected in various ways in Android.bp files:

   - target.host (because this is still considered as a host target)
   - target.linux (provided that the module is also enabled for host)
   - target.linux_bionic (use the OS name directly)
   - target.linux_bionic_arm64 (OS name + arch combo)
   - target.linux_arm64 (provided that the module is also for host)
   - target.not_windows
   - arch.arm64

The toolchain for the new target is almost the same as the toolchain
config for Android/ARM64. One notable difference is that the clang
triple is aarch64-linux instead of aarch64-linux-android, so that
__ANDROID__ is not defined for the new OS type.

Bug: 134795810
Test: HOST_CROSS_OS=linux_bionic HOST_CROSS_ARCH=arm64 m nothing

Change-Id: If4300583edfb6d75bd4d984b38f73b6a406b4447

android/arch.go

@@ -578,7 +578,7 @@ var (
 
 	osArchTypeMap = map[OsType][]ArchType{
 		Linux:       []ArchType{X86, X86_64},
-		LinuxBionic: []ArchType{X86_64},
+		LinuxBionic: []ArchType{Arm64, X86_64},
 		Darwin:      []ArchType{X86_64},
 		Windows:     []ArchType{X86, X86_64},
 		Android:     []ArchType{Arm, Arm64, X86, X86_64},

cc/config/Android.bp

@@ -23,6 +23,8 @@ bootstrap_go_package {
         "x86_linux_host.go",
         "x86_linux_bionic_host.go",
         "x86_windows_host.go",
+
+        "arm64_linux_host.go",
     ],
     testSrcs: [
         "tidy_test.go",

cc/config/arm64_linux_host.go

@@ -0,0 +1,94 @@
+// Copyright 2020 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 (
+	"android/soong/android"
+	"strings"
+)
+
+var (
+	// This is a host toolchain but flags for device toolchain are required
+	// as the flags are actually for Bionic-based builds.
+	linuxCrossCflags = ClangFilterUnknownCflags(append(deviceGlobalCflags,
+		// clang by default enables PIC when the clang triple is set to *-android.
+		// See toolchain/llvm-project/clang/lib/Driver/ToolChains/CommonArgs.cpp#920.
+		// However, for this host target, we don't set "-android" to avoid __ANDROID__ macro
+		// which stands for "Android device target". Keeping PIC on is required because
+		// many modules we have (e.g. Bionic) assume PIC.
+		"-fpic",
+	))
+
+	linuxCrossLdflags = ClangFilterUnknownCflags([]string{
+		"-Wl,-z,noexecstack",
+		"-Wl,-z,relro",
+		"-Wl,-z,now",
+		"-Wl,--build-id=md5",
+		"-Wl,--warn-shared-textrel",
+		"-Wl,--fatal-warnings",
+		"-Wl,--hash-style=gnu",
+		"-Wl,--no-undefined-version",
+	})
+)
+
+func init() {
+	pctx.StaticVariable("LinuxBionicArm64Cflags", strings.Join(linuxCrossCflags, " "))
+	pctx.StaticVariable("LinuxBionicArm64Ldflags", strings.Join(linuxCrossLdflags, " "))
+}
+
+// toolchain config for ARM64 Linux CrossHost. Almost everything is the same as the ARM64 Android
+// target. The overridden methods below show the differences.
+type toolchainLinuxArm64 struct {
+	toolchainArm64
+}
+
+func (toolchainLinuxArm64) ClangTriple() string {
+	// Note the absence of "-android" suffix. The compiler won't define __ANDROID__
+	return "aarch64-linux"
+}
+
+func (toolchainLinuxArm64) ClangCflags() string {
+	// The inherited flags + extra flags
+	return "${config.Arm64ClangCflags} ${config.LinuxBionicArm64Cflags}"
+}
+
+func linuxArm64ToolchainFactory(arch android.Arch) Toolchain {
+	archVariant := "armv8-a" // for host, default to armv8-a
+	toolchainClangCflags := []string{arm64ClangArchVariantCflagsVar[archVariant]}
+
+	// We don't specify CPU architecture for host. Conservatively assume
+	// the host CPU needs the fix
+	extraLdflags := "-Wl,--fix-cortex-a53-843419"
+
+	ret := toolchainLinuxArm64{}
+
+	// add the extra ld and lld flags
+	ret.toolchainArm64.ldflags = strings.Join([]string{
+		"${config.Arm64Ldflags}",
+		"${config.LinuxBionicArm64Ldflags}",
+		extraLdflags,
+	}, " ")
+	ret.toolchainArm64.lldflags = strings.Join([]string{
+		"${config.Arm64Lldflags}",
+		"${config.LinuxBionicArm64Ldflags}",
+		extraLdflags,
+	}, " ")
+	ret.toolchainArm64.toolchainClangCflags = strings.Join(toolchainClangCflags, " ")
+	return &ret
+}
+
+func init() {
+	registerToolchainFactory(android.LinuxBionic, android.Arm64, linuxArm64ToolchainFactory)
+}

rust/config/Android.bp

@@ -16,5 +16,6 @@ bootstrap_go_package {
         "x86_linux_host.go",
         "x86_device.go",
         "x86_64_device.go",
+        "arm64_linux_host.go",
     ],
 }

rust/config/arm64_device.go

@@ -75,9 +75,16 @@ func (t *toolchainArm64) Supported() bool {
 }
 
 func Arm64ToolchainFactory(arch android.Arch) Toolchain {
+	archVariant := arch.ArchVariant
+	if archVariant == "" {
+		// arch variants defaults to armv8-a. This is mostly for
+		// the host target which borrows toolchain configs from here.
+		archVariant = "armv8-a"
+	}
+
 	toolchainRustFlags := []string{
 		"${config.Arm64ToolchainRustFlags}",
-		"${config.Arm64" + arch.ArchVariant + "VariantRustFlags}",
+		"${config.Arm64" + archVariant + "VariantRustFlags}",
 	}
 
 	toolchainRustFlags = append(toolchainRustFlags, deviceGlobalRustFlags...)

rust/config/arm64_linux_host.go

@@ -0,0 +1,24 @@
+// Copyright 2019 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 config
+
+import (
+	"android/soong/android"
+)
+
+func init() {
+	// Linux_cross-arm64 uses the same rust toolchain as the Android-arm64
+	registerToolchainFactory(android.LinuxBionic, android.Arm64, Arm64ToolchainFactory)
+}