Add Rust support to Soong.

Adds support to Soong for building rust modules. This currently only
supports x86_64 device and x86 linux host targets. The functionality
is sufficient to build crosvm.

Bug: 136189233
Test: Test module builds.
Test: crosvm builds.
Change-Id: I6ea04615834a6d673578ab10ea1a2eb04259fe09
diff --git a/rust/config/global.go b/rust/config/global.go
new file mode 100644
index 0000000..2e08a8c
--- /dev/null
+++ b/rust/config/global.go
@@ -0,0 +1,65 @@
+// 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"
+	_ "android/soong/cc/config"
+)
+
+var pctx = android.NewPackageContext("android/soong/rust/config")
+
+var (
+	RustDefaultVersion = "1.35.0"
+	RustDefaultBase    = "prebuilts/rust/"
+	DefaultEdition     = "2018"
+	Stdlibs            = []string{
+		"libarena",
+		"libfmt_macros",
+		"libgraphviz",
+		"libserialize",
+		"libstd",
+		"libsyntax",
+		"libsyntax_ext",
+		"libsyntax_pos",
+		"libterm",
+	}
+)
+
+func init() {
+	pctx.SourcePathVariable("RustDefaultBase", RustDefaultBase)
+	pctx.VariableConfigMethod("HostPrebuiltTag", android.Config.PrebuiltOS)
+
+	pctx.VariableFunc("RustBase", func(ctx android.PackageVarContext) string {
+		if override := ctx.Config().Getenv("RUST_PREBUILTS_BASE"); override != "" {
+			return override
+		}
+		return "${RustDefaultBase}"
+	})
+
+	pctx.VariableFunc("RustVersion", func(ctx android.PackageVarContext) string {
+		if override := ctx.Config().Getenv("RUST_PREBUILTS_VERSION"); override != "" {
+			return override
+		}
+		return RustDefaultVersion
+	})
+
+	pctx.StaticVariable("RustPath", "${RustBase}/${HostPrebuiltTag}/${RustVersion}")
+	pctx.StaticVariable("RustBin", "${RustPath}/bin")
+
+	pctx.ImportAs("ccConfig", "android/soong/cc/config")
+	pctx.StaticVariable("RustLinker", "${ccConfig.ClangBin}/clang++")
+	pctx.StaticVariable("RustLinkerArgs", "-B ${ccConfig.ClangBin} -fuse-ld=lld")
+}
diff --git a/rust/config/toolchain.go b/rust/config/toolchain.go
new file mode 100644
index 0000000..a36d61b
--- /dev/null
+++ b/rust/config/toolchain.go
@@ -0,0 +1,124 @@
+// 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"
+)
+
+type Toolchain interface {
+	RustTriple() string
+	ToolchainRustFlags() string
+	ToolchainLinkFlags() string
+
+	SharedLibSuffix() string
+	StaticLibSuffix() string
+	RlibSuffix() string
+	DylibSuffix() string
+	ProcMacroSuffix() string
+	ExecutableSuffix() string
+
+	Is64Bit() bool
+	Supported() bool
+}
+
+type toolchainBase struct {
+}
+
+func (toolchainBase) RustTriple() string {
+	panic("toolchainBase does not define a triple.")
+}
+
+func (toolchainBase) ToolchainRustFlags() string {
+	panic("toolchainBase does not provide rust flags.")
+}
+
+func (toolchainBase) ToolchainLinkFlags() string {
+	panic("toolchainBase does not provide link flags.")
+}
+
+func (toolchainBase) Is64Bit() bool {
+	panic("toolchainBase cannot determine datapath width.")
+}
+
+type toolchain64Bit struct {
+	toolchainBase
+}
+
+func (toolchain64Bit) Is64Bit() bool {
+	return true
+}
+
+type toolchain32Bit struct {
+	toolchainBase
+}
+
+func (toolchain32Bit) Is64Bit() bool {
+	return false
+}
+
+func (toolchain32Bit) Bionic() bool {
+	return true
+}
+
+func (toolchainBase) ExecutableSuffix() string {
+	return ""
+}
+
+func (toolchainBase) SharedLibSuffix() string {
+	return ".so"
+}
+
+func (toolchainBase) StaticLibSuffix() string {
+	return ".a"
+}
+
+func (toolchainBase) RlibSuffix() string {
+	return ".rlib"
+}
+func (toolchainBase) DylibSuffix() string {
+	return ".so"
+}
+
+func (toolchainBase) ProcMacroSuffix() string {
+	return ".so"
+}
+
+func (toolchainBase) Supported() bool {
+	return false
+}
+
+func toolchainBaseFactory() Toolchain {
+	return &toolchainBase{}
+}
+
+type toolchainFactory func(arch android.Arch) Toolchain
+
+var toolchainFactories = make(map[android.OsType]map[android.ArchType]toolchainFactory)
+
+func registerToolchainFactory(os android.OsType, arch android.ArchType, factory toolchainFactory) {
+	if toolchainFactories[os] == nil {
+		toolchainFactories[os] = make(map[android.ArchType]toolchainFactory)
+	}
+	toolchainFactories[os][arch] = factory
+}
+
+func FindToolchain(os android.OsType, arch android.Arch) Toolchain {
+	factory := toolchainFactories[os][arch.ArchType]
+	if factory == nil {
+		return toolchainBaseFactory()
+	}
+	return factory(arch)
+}
diff --git a/rust/config/x86_64_device.go b/rust/config/x86_64_device.go
new file mode 100644
index 0000000..2aca56a
--- /dev/null
+++ b/rust/config/x86_64_device.go
@@ -0,0 +1,88 @@
+// 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 (
+	"strings"
+
+	"android/soong/android"
+)
+
+var (
+	x86_64RustFlags            = []string{}
+	x86_64ArchFeatureRustFlags = map[string][]string{}
+	x86_64LinkFlags            = []string{}
+
+	x86_64ArchVariantRustFlags = map[string][]string{
+		"":            []string{},
+		"broadwell":   []string{"-C target-cpu=broadwell"},
+		"haswell":     []string{"-C target-cpu=haswell"},
+		"ivybridge":   []string{"-C target-cpu=ivybridge"},
+		"sandybridge": []string{"-C target-cpu=sandybridge"},
+		"silvermont":  []string{"-C target-cpu=silvermont"},
+		"skylake":     []string{"-C target-cpu=skylake"},
+		//TODO: Add target-cpu=stoneyridge when rustc supports it.
+		"stoneyridge": []string{""},
+	}
+)
+
+func init() {
+	registerToolchainFactory(android.Android, android.X86_64, x86_64ToolchainFactory)
+
+	pctx.StaticVariable("x86_64ToolchainRustFlags", strings.Join(x86_64RustFlags, " "))
+	pctx.StaticVariable("x86_64ToolchainLinkFlags", strings.Join(x86_64LinkFlags, " "))
+
+	for variant, rustFlags := range x86_64ArchVariantRustFlags {
+		pctx.StaticVariable("X86_64"+variant+"VariantRustFlags",
+			strings.Join(rustFlags, " "))
+	}
+
+}
+
+type toolchainX86_64 struct {
+	toolchain64Bit
+	toolchainRustFlags string
+}
+
+func (t *toolchainX86_64) RustTriple() string {
+	return "x86_64-unknown-linux-gnu"
+}
+
+func (t *toolchainX86_64) ToolchainLinkFlags() string {
+	return "${config.x86_64ToolchainLinkFlags}"
+}
+
+func (t *toolchainX86_64) ToolchainRustFlags() string {
+	return t.toolchainRustFlags
+}
+
+func (t *toolchainX86_64) RustFlags() string {
+	return "${config.x86_64ToolchainRustFlags}"
+}
+
+func x86_64ToolchainFactory(arch android.Arch) Toolchain {
+	toolchainRustFlags := []string{
+		"${config.x86_64ToolchainRustFlags}",
+		"${config.X86_64" + arch.ArchVariant + "VariantRustFlags}",
+	}
+
+	for _, feature := range arch.ArchFeatures {
+		toolchainRustFlags = append(toolchainRustFlags, x86_64ArchFeatureRustFlags[feature]...)
+	}
+
+	return &toolchainX86_64{
+		toolchainRustFlags: strings.Join(toolchainRustFlags, " "),
+	}
+}
diff --git a/rust/config/x86_linux_host.go b/rust/config/x86_linux_host.go
new file mode 100644
index 0000000..cb6bf1a
--- /dev/null
+++ b/rust/config/x86_linux_host.go
@@ -0,0 +1,109 @@
+// 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 (
+	"strings"
+
+	"android/soong/android"
+)
+
+var (
+	LinuxRustFlags      = []string{}
+	LinuxRustLinkFlags  = []string{}
+	linuxX86Rustflags   = []string{}
+	linuxX86Linkflags   = []string{}
+	linuxX8664Rustflags = []string{}
+	linuxX8664Linkflags = []string{}
+)
+
+func init() {
+	registerToolchainFactory(android.Linux, android.X86_64, linuxX8664ToolchainFactory)
+	registerToolchainFactory(android.Linux, android.X86, linuxX86ToolchainFactory)
+
+	pctx.StaticVariable("LinuxToolchainRustFlags", strings.Join(LinuxRustFlags, " "))
+	pctx.StaticVariable("LinuxToolchainLinkFlags", strings.Join(LinuxRustLinkFlags, " "))
+	pctx.StaticVariable("LinuxToolchainX86RustFlags", strings.Join(linuxX86Rustflags, " "))
+	pctx.StaticVariable("LinuxToolchainX86LinkFlags", strings.Join(linuxX86Linkflags, " "))
+	pctx.StaticVariable("LinuxToolchainX8664RustFlags", strings.Join(linuxX8664Rustflags, " "))
+	pctx.StaticVariable("LinuxToolchainX8664LinkFlags", strings.Join(linuxX8664Linkflags, " "))
+
+}
+
+type toolchainLinux struct {
+	toolchainRustFlags string
+	toolchainLinkFlags string
+}
+
+type toolchainLinuxX86 struct {
+	toolchain32Bit
+	toolchainLinux
+}
+
+type toolchainLinuxX8664 struct {
+	toolchain64Bit
+	toolchainLinux
+}
+
+func (toolchainLinuxX8664) Supported() bool {
+	return true
+}
+
+func (t *toolchainLinuxX8664) Name() string {
+	return "x86_64"
+}
+
+func (t *toolchainLinuxX8664) RustTriple() string {
+	return "x86_64-unknown-linux-gnu"
+}
+
+func (t *toolchainLinuxX8664) ToolchainLinkFlags() string {
+	return "${config.LinuxToolchainLinkFlags} ${config.LinuxToolchainX8664LinkFlags}"
+}
+
+func (t *toolchainLinuxX8664) ToolchainRustFlags() string {
+	return "${config.LinuxToolchainRustFlags} ${config.LinuxToolchainX8664RustFlags}"
+}
+
+func linuxX8664ToolchainFactory(arch android.Arch) Toolchain {
+	return toolchainLinuxX8664Singleton
+}
+
+func (toolchainLinuxX86) Supported() bool {
+	return true
+}
+
+func (t *toolchainLinuxX86) Name() string {
+	return "x86"
+}
+
+func (t *toolchainLinuxX86) RustTriple() string {
+	return "i686-unknown-linux-gnu"
+}
+
+func (t *toolchainLinuxX86) ToolchainLinkFlags() string {
+	return "${config.LinuxToolchainLinkFlags} ${config.LinuxToolchainX86LinkFlags}"
+}
+
+func (t *toolchainLinuxX86) ToolchainRustFlags() string {
+	return "${config.LinuxToolchainRustFlags} ${config.LinuxToolchainX86RustFlags}"
+}
+
+func linuxX86ToolchainFactory(arch android.Arch) Toolchain {
+	return toolchainLinuxX86Singleton
+}
+
+var toolchainLinuxX8664Singleton Toolchain = &toolchainLinuxX8664{}
+var toolchainLinuxX86Singleton Toolchain = &toolchainLinuxX86{}