Support building rust modules against musl libc

Add a rust toolchain for musl libc, use std library built from source,
and add default dependencies on musl libc.

Bug: 216192129
Test: m USE_HOST_MUSL=true host-native
Change-Id: Ic5ff4487db9693aeb08a13405f4d18465eecdc4b

rust/binary.go

@@ -92,12 +92,21 @@ func (binary *binaryDecorator) compilerFlags(ctx ModuleContext, flags Flags) Fla
 func (binary *binaryDecorator) compilerDeps(ctx DepsContext, deps Deps) Deps {
 	deps = binary.baseCompiler.compilerDeps(ctx, deps)
 
+	static := Bool(binary.Properties.Static_executable)
 	if ctx.toolchain().Bionic() {
-		deps = bionicDeps(ctx, deps, Bool(binary.Properties.Static_executable))
-		if Bool(binary.Properties.Static_executable) {
+		deps = bionicDeps(ctx, deps, static)
+		if static {
 			deps.CrtBegin = []string{"crtbegin_static"}
 		} else {
-			deps.CrtBegin = []string{"libc_musl_crtbegin_dynamic"}
+			deps.CrtBegin = []string{"crtbegin_dynamic"}
+		}
+		deps.CrtEnd = []string{"crtend_android"}
+	} else if ctx.Os() == android.LinuxMusl {
+		deps = muslDeps(ctx, deps, static)
+		if static {
+			deps.CrtBegin = []string{"libc_musl_crtbegin_static"}
+		} else {
+			deps.CrtBegin = []string{"libc_musl_crtbegin_dynamic", "musl_linker_script"}
 		}
 		deps.CrtEnd = []string{"libc_musl_crtend"}
 	}

rust/bindgen.go

@@ -288,6 +288,8 @@ func (b *bindgenDecorator) SourceProviderDeps(ctx DepsContext, deps Deps) Deps {
 	deps = b.BaseSourceProvider.SourceProviderDeps(ctx, deps)
 	if ctx.toolchain().Bionic() {
 		deps = bionicDeps(ctx, deps, false)
+	} else if ctx.Os() == android.LinuxMusl {
+		deps = muslDeps(ctx, deps, false)
 	}
 
 	deps.SharedLibs = append(deps.SharedLibs, b.ClangProperties.Shared_libs...)

rust/compiler.go

@@ -364,7 +364,7 @@ func (compiler *baseCompiler) compilerDeps(ctx DepsContext, deps Deps) Deps {
 	if !Bool(compiler.Properties.No_stdlibs) {
 		for _, stdlib := range config.Stdlibs {
 			// If we're building for the build host, use the prebuilt stdlibs
-			if ctx.Target().Os == ctx.Config().BuildOS {
+			if ctx.Target().Os == android.Linux || ctx.Target().Os == android.Darwin {
 				stdlib = "prebuilt_" + stdlib
 			}
 			deps.Stdlibs = append(deps.Stdlibs, stdlib)
@@ -394,6 +394,20 @@ func bionicDeps(ctx DepsContext, deps Deps, static bool) Deps {
 	return deps
 }
 
+func muslDeps(ctx DepsContext, deps Deps, static bool) Deps {
+	muslLibs := []string{"libc_musl"}
+	if static {
+		deps.StaticLibs = append(deps.StaticLibs, muslLibs...)
+	} else {
+		deps.SharedLibs = append(deps.SharedLibs, muslLibs...)
+	}
+	if libRuntimeBuiltins := config.BuiltinsRuntimeLibrary(ctx.toolchain()); libRuntimeBuiltins != "" {
+		deps.StaticLibs = append(deps.StaticLibs, libRuntimeBuiltins)
+	}
+
+	return deps
+}
+
 func (compiler *baseCompiler) crateName() string {
 	return compiler.Properties.Crate_name
 }

rust/config/x86_linux_host.go

@@ -22,12 +22,29 @@ import (
 
 var (
 	LinuxRustFlags     = []string{}
+	LinuxMuslRustFlags = []string{
+		// disable rustc's builtin fallbacks for crt objects
+		"-C link_self_contained=no",
+		// force rustc to use a dynamic musl libc
+		"-C target-feature=-crt-static",
+		"-Z link-native-libraries=no",
+	}
 	LinuxRustLinkFlags = []string{
 		"-B${cc_config.ClangBin}",
 		"-fuse-ld=lld",
 		"-Wl,--undefined-version",
+	}
+	LinuxRustGlibcLinkFlags = []string{
 		"--sysroot ${cc_config.LinuxGccRoot}/sysroot",
 	}
+	LinuxRustMuslLinkFlags = []string{
+		"--sysroot /dev/null",
+		"-nodefaultlibs",
+		"-nostdlib",
+		"-Wl,--no-dynamic-linker",
+		// for unwind
+		"-lgcc", "-lgcc_eh",
+	}
 	linuxX86Rustflags   = []string{}
 	linuxX86Linkflags   = []string{}
 	linuxX8664Rustflags = []string{}
@@ -35,15 +52,17 @@ var (
 )
 
 func init() {
-	registerToolchainFactory(android.Linux, android.X86_64, linuxX8664ToolchainFactory)
-	registerToolchainFactory(android.Linux, android.X86, linuxX86ToolchainFactory)
+	registerToolchainFactory(android.Linux, android.X86_64, linuxGlibcX8664ToolchainFactory)
+	registerToolchainFactory(android.Linux, android.X86, linuxGlibcX86ToolchainFactory)
 
-	// TODO: musl rust support
-	registerToolchainFactory(android.LinuxMusl, android.X86_64, linuxX8664ToolchainFactory)
-	registerToolchainFactory(android.LinuxMusl, android.X86, linuxX86ToolchainFactory)
+	registerToolchainFactory(android.LinuxMusl, android.X86_64, linuxMuslX8664ToolchainFactory)
+	registerToolchainFactory(android.LinuxMusl, android.X86, linuxMuslX86ToolchainFactory)
 
 	pctx.StaticVariable("LinuxToolchainRustFlags", strings.Join(LinuxRustFlags, " "))
+	pctx.StaticVariable("LinuxMuslToolchainRustFlags", strings.Join(LinuxMuslRustFlags, " "))
 	pctx.StaticVariable("LinuxToolchainLinkFlags", strings.Join(LinuxRustLinkFlags, " "))
+	pctx.StaticVariable("LinuxGlibcToolchainLinkFlags", strings.Join(LinuxRustGlibcLinkFlags, " "))
+	pctx.StaticVariable("LinuxMuslToolchainLinkFlags", strings.Join(LinuxRustMuslLinkFlags, " "))
 	pctx.StaticVariable("LinuxToolchainX86RustFlags", strings.Join(linuxX86Rustflags, " "))
 	pctx.StaticVariable("LinuxToolchainX86LinkFlags", strings.Join(linuxX86Linkflags, " "))
 	pctx.StaticVariable("LinuxToolchainX8664RustFlags", strings.Join(linuxX8664Rustflags, " "))
@@ -51,19 +70,9 @@ func init() {
 
 }
 
-type toolchainLinux struct {
-	toolchainRustFlags string
-	toolchainLinkFlags string
-}
-
-type toolchainLinuxX86 struct {
-	toolchain32Bit
-	toolchainLinux
-}
-
+// Base 64-bit linux rust toolchain
 type toolchainLinuxX8664 struct {
 	toolchain64Bit
-	toolchainLinux
 }
 
 func (toolchainLinuxX8664) Supported() bool {
@@ -78,10 +87,6 @@ func (t *toolchainLinuxX8664) Name() string {
 	return "x86_64"
 }
 
-func (t *toolchainLinuxX8664) RustTriple() string {
-	return "x86_64-unknown-linux-gnu"
-}
-
 func (t *toolchainLinuxX8664) ToolchainLinkFlags() string {
 	// Prepend the lld flags from cc_config so we stay in sync with cc
 	return "${cc_config.LinuxLldflags} ${cc_config.LinuxX8664Lldflags} " +
@@ -92,8 +97,49 @@ func (t *toolchainLinuxX8664) ToolchainRustFlags() string {
 	return "${config.LinuxToolchainRustFlags} ${config.LinuxToolchainX8664RustFlags}"
 }
 
-func linuxX8664ToolchainFactory(arch android.Arch) Toolchain {
-	return toolchainLinuxX8664Singleton
+// Specialization of the 64-bit linux rust toolchain for glibc.  Adds the gnu rust triple and
+// sysroot linker flags.
+type toolchainLinuxGlibcX8664 struct {
+	toolchainLinuxX8664
+}
+
+func (t *toolchainLinuxX8664) RustTriple() string {
+	return "x86_64-unknown-linux-gnu"
+}
+
+func (t *toolchainLinuxGlibcX8664) ToolchainLinkFlags() string {
+	return t.toolchainLinuxX8664.ToolchainLinkFlags() + " " + "${config.LinuxGlibcToolchainLinkFlags}"
+}
+
+func linuxGlibcX8664ToolchainFactory(arch android.Arch) Toolchain {
+	return toolchainLinuxGlibcX8664Singleton
+}
+
+// Specialization of the 64-bit linux rust toolchain for musl.  Adds the musl rust triple and
+// linker flags to avoid using the host sysroot.
+type toolchainLinuxMuslX8664 struct {
+	toolchainLinuxX8664
+}
+
+func (t *toolchainLinuxMuslX8664) RustTriple() string {
+	return "x86_64-unknown-linux-musl"
+}
+
+func (t *toolchainLinuxMuslX8664) ToolchainLinkFlags() string {
+	return t.toolchainLinuxX8664.ToolchainLinkFlags() + " " + "${config.LinuxMuslToolchainLinkFlags}"
+}
+
+func (t *toolchainLinuxMuslX8664) ToolchainRustFlags() string {
+	return t.toolchainLinuxX8664.ToolchainRustFlags() + " " + "${config.LinuxMuslToolchainRustFlags}"
+}
+
+func linuxMuslX8664ToolchainFactory(arch android.Arch) Toolchain {
+	return toolchainLinuxMuslX8664Singleton
+}
+
+// Base 32-bit linux rust toolchain
+type toolchainLinuxX86 struct {
+	toolchain32Bit
 }
 
 func (toolchainLinuxX86) Supported() bool {
@@ -116,10 +162,6 @@ func (toolchainLinuxX8664) LibclangRuntimeLibraryArch() string {
 	return "x86_64"
 }
 
-func (t *toolchainLinuxX86) RustTriple() string {
-	return "i686-unknown-linux-gnu"
-}
-
 func (t *toolchainLinuxX86) ToolchainLinkFlags() string {
 	// Prepend the lld flags from cc_config so we stay in sync with cc
 	return "${cc_config.LinuxLldflags} ${cc_config.LinuxX86Lldflags} " +
@@ -130,9 +172,47 @@ func (t *toolchainLinuxX86) ToolchainRustFlags() string {
 	return "${config.LinuxToolchainRustFlags} ${config.LinuxToolchainX86RustFlags}"
 }
 
-func linuxX86ToolchainFactory(arch android.Arch) Toolchain {
-	return toolchainLinuxX86Singleton
+// Specialization of the 32-bit linux rust toolchain for glibc.  Adds the gnu rust triple and
+// sysroot linker flags.
+type toolchainLinuxGlibcX86 struct {
+	toolchainLinuxX86
 }
 
-var toolchainLinuxX8664Singleton Toolchain = &toolchainLinuxX8664{}
-var toolchainLinuxX86Singleton Toolchain = &toolchainLinuxX86{}
+func (t *toolchainLinuxGlibcX86) RustTriple() string {
+	return "i686-unknown-linux-gnu"
+}
+
+func (t *toolchainLinuxGlibcX86) ToolchainLinkFlags() string {
+	return t.toolchainLinuxX86.ToolchainLinkFlags() + " " + "${config.LinuxGlibcToolchainLinkFlags}"
+}
+
+func linuxGlibcX86ToolchainFactory(arch android.Arch) Toolchain {
+	return toolchainLinuxGlibcX86Singleton
+}
+
+// Specialization of the 32-bit linux rust toolchain for musl.  Adds the musl rust triple and
+// linker flags to avoid using the host sysroot.
+type toolchainLinuxMuslX86 struct {
+	toolchainLinuxX86
+}
+
+func (t *toolchainLinuxMuslX86) RustTriple() string {
+	return "i686-unknown-linux-musl"
+}
+
+func (t *toolchainLinuxMuslX86) ToolchainLinkFlags() string {
+	return t.toolchainLinuxX86.ToolchainLinkFlags() + " " + "${config.LinuxMuslToolchainLinkFlags}"
+}
+
+func (t *toolchainLinuxMuslX86) ToolchainRustFlags() string {
+	return t.toolchainLinuxX86.ToolchainRustFlags() + " " + "${config.LinuxMuslToolchainRustFlags}"
+}
+
+func linuxMuslX86ToolchainFactory(arch android.Arch) Toolchain {
+	return toolchainLinuxMuslX86Singleton
+}
+
+var toolchainLinuxGlibcX8664Singleton Toolchain = &toolchainLinuxGlibcX8664{}
+var toolchainLinuxGlibcX86Singleton Toolchain = &toolchainLinuxGlibcX86{}
+var toolchainLinuxMuslX8664Singleton Toolchain = &toolchainLinuxMuslX8664{}
+var toolchainLinuxMuslX86Singleton Toolchain = &toolchainLinuxMuslX86{}

rust/library.go

@@ -426,10 +426,16 @@ func (library *libraryDecorator) compilerProps() []interface{} {
 func (library *libraryDecorator) compilerDeps(ctx DepsContext, deps Deps) Deps {
 	deps = library.baseCompiler.compilerDeps(ctx, deps)
 
-	if ctx.toolchain().Bionic() && (library.dylib() || library.shared()) {
+	if library.dylib() || library.shared() {
+		if ctx.toolchain().Bionic() {
 			deps = bionicDeps(ctx, deps, false)
 			deps.CrtBegin = []string{"crtbegin_so"}
 			deps.CrtEnd = []string{"crtend_so"}
+		} else if ctx.Os() == android.LinuxMusl {
+			deps = muslDeps(ctx, deps, false)
+			deps.CrtBegin = []string{"libc_musl_crtbegin_so"}
+			deps.CrtEnd = []string{"libc_musl_crtend_so"}
+		}
 	}
 
 	return deps