Strip libgcc to only keep fallback symbols

We use libgcc as fallback for symbols not present in libclang_rt
builtins, however we didn't know what exact symbols were being used,
some may not be intended to fallback.

Create libgcc_stripped, which only contains unwind symbols from libgcc.

Bug: 29275768
Test: bionic-unit-tests
Change-Id: I5b349fa6138e51663bf3b67109b880b4356da8e8

Android.bp

@@ -482,6 +482,117 @@ toolchain_library {
     },
 }
 
+toolchain_library {
+    name: "libgcc_stripped",
+    defaults: ["linux_bionic_supported"],
+    vendor_available: true,
+    recovery_available: true,
+
+    arch: {
+        arm: {
+            src: "prebuilts/gcc/linux-x86/arm/arm-linux-androideabi-4.9/lib/gcc/arm-linux-androideabi/4.9.x/libgcc.a",
+            strip: {
+                keep_symbols_list: [
+                    // unwind-arm.o
+                    "_Unwind_Complete",
+                    "_Unwind_DeleteException",
+                    "_Unwind_GetCFA",
+                    "_Unwind_VRS_Get",
+                    "_Unwind_VRS_Pop",
+                    "_Unwind_VRS_Set",
+                    "__aeabi_unwind_cpp_pr0",
+                    "__aeabi_unwind_cpp_pr1",
+                    "__aeabi_unwind_cpp_pr2",
+                    "__gnu_Unwind_Backtrace",
+                    "__gnu_Unwind_ForcedUnwind",
+                    "__gnu_Unwind_RaiseException",
+                    "__gnu_Unwind_Resume",
+                    "__gnu_Unwind_Resume_or_Rethrow",
+
+                    // libunwind.o
+                    "_Unwind_Backtrace",
+                    "_Unwind_ForcedUnwind",
+                    "_Unwind_RaiseException",
+                    "_Unwind_Resume",
+                    "_Unwind_Resume_or_Rethrow",
+                    "___Unwind_Backtrace",
+                    "___Unwind_ForcedUnwind",
+                    "___Unwind_RaiseException",
+                    "___Unwind_Resume",
+                    "___Unwind_Resume_or_Rethrow",
+                    "__gnu_Unwind_Restore_VFP",
+                    "__gnu_Unwind_Restore_VFP_D",
+                    "__gnu_Unwind_Restore_VFP_D_16_to_31",
+                    "__gnu_Unwind_Restore_WMMXC",
+                    "__gnu_Unwind_Restore_WMMXD",
+                    "__gnu_Unwind_Save_VFP",
+                    "__gnu_Unwind_Save_VFP_D",
+                    "__gnu_Unwind_Save_VFP_D_16_to_31",
+                    "__gnu_Unwind_Save_WMMXC",
+                    "__gnu_Unwind_Save_WMMXD",
+                    "__restore_core_regs",
+                    "restore_core_regs",
+
+                    // pr-support.o
+                    "_Unwind_GetDataRelBase",
+                    "_Unwind_GetLanguageSpecificData",
+                    "_Unwind_GetRegionStart",
+                    "_Unwind_GetTextRelBase",
+                    "__gnu_unwind_execute",
+                    "__gnu_unwind_frame",
+                ],
+                use_gnu_strip: true,
+            },
+        },
+        arm64: {
+            src: "prebuilts/gcc/linux-x86/aarch64/aarch64-linux-android-4.9/lib/gcc/aarch64-linux-android/4.9.x/libgcc.a",
+        },
+        x86: {
+            src: "prebuilts/gcc/linux-x86/x86/x86_64-linux-android-4.9/lib/gcc/x86_64-linux-android/4.9.x/32/libgcc.a",
+
+        },
+        x86_64: {
+            src: "prebuilts/gcc/linux-x86/x86/x86_64-linux-android-4.9/lib/gcc/x86_64-linux-android/4.9.x/libgcc.a",
+        },
+    },
+    strip: {
+        keep_symbols_list: [
+            // unwind-dw2.o
+            "_Unwind_Backtrace",
+            "_Unwind_DeleteException",
+            "_Unwind_FindEnclosingFunction",
+            "_Unwind_ForcedUnwind",
+            "_Unwind_GetCFA",
+            "_Unwind_GetDataRelBase",
+            "_Unwind_GetGR",
+            "_Unwind_GetIP",
+            "_Unwind_GetIPInfo",
+            "_Unwind_GetLanguageSpecificData",
+            "_Unwind_GetRegionStart",
+            "_Unwind_GetTextRelBase",
+            "_Unwind_RaiseException",
+            "_Unwind_Resume",
+            "_Unwind_Resume_or_Rethrow",
+            "_Unwind_SetGR",
+            "_Unwind_SetIP",
+            "__frame_state_for",
+
+            // unwind-dw2-fde-dip.o
+            "_Unwind_Find_FDE",
+            "__deregister_frame",
+            "__deregister_frame_info",
+            "__deregister_frame_info_bases",
+            "__register_frame",
+            "__register_frame_info",
+            "__register_frame_info_bases",
+            "__register_frame_info_table",
+            "__register_frame_info_table_bases",
+            "__register_frame_table",
+        ],
+        use_gnu_strip: true,
+    },
+}
+
 toolchain_library {
     name: "libwinpthread",
     host_supported: true,

apex/apex_test.go

@@ -92,6 +92,13 @@ func testApex(t *testing.T, bp string) *android.TestContext {
 			recovery_available: true,
 		}
 
+		toolchain_library {
+			name: "libgcc_stripped",
+			src: "",
+			vendor_available: true,
+			recovery_available: true,
+		}
+
 		toolchain_library {
 			name: "libclang_rt.builtins-aarch64-android",
 			src: "",

cc/builder.go

@@ -255,6 +255,7 @@ type builderFlags struct {
 	groupStaticLibs bool
 
 	stripKeepSymbols       bool
+	stripKeepSymbolsList   string
 	stripKeepMiniDebugInfo bool
 	stripAddGnuDebuglink   bool
 	stripUseGnuStrip       bool
@@ -835,6 +836,9 @@ func TransformStrip(ctx android.ModuleContext, inputFile android.Path,
 	if flags.stripKeepSymbols {
 		args += " --keep-symbols"
 	}
+	if flags.stripKeepSymbolsList != "" {
+		args += " -k" + flags.stripKeepSymbolsList
+	}
 	if flags.stripUseGnuStrip {
 		args += " --use-gnu-strip"
 	}

cc/cc_test.go

@@ -1833,13 +1833,13 @@ func TestStaticLibDepExport(t *testing.T) {
 	// Check the shared version of lib2.
 	variant := "android_arm64_armv8-a_core_shared"
 	module := ctx.ModuleForTests("lib2", variant).Module().(*Module)
-	checkStaticLibs(t, []string{"lib1", "libclang_rt.builtins-aarch64-android", "libatomic", "libgcc"}, module)
+	checkStaticLibs(t, []string{"lib1", "libclang_rt.builtins-aarch64-android", "libatomic", "libgcc_stripped"}, module)
 
 	// Check the static version of lib2.
 	variant = "android_arm64_armv8-a_core_static"
 	module = ctx.ModuleForTests("lib2", variant).Module().(*Module)
 	// libc++_static is linked additionally.
-	checkStaticLibs(t, []string{"lib1", "libc++_static", "libclang_rt.builtins-aarch64-android", "libatomic", "libgcc"}, module)
+	checkStaticLibs(t, []string{"lib1", "libc++_static", "libclang_rt.builtins-aarch64-android", "libatomic", "libgcc_stripped"}, module)
 }
 
 var compilerFlagsTestCases = []struct {

cc/linker.go

@@ -228,10 +228,10 @@ func (linker *baseLinker) linkerDeps(ctx DepsContext, deps Deps) Deps {
 		// libclang_rt.builtins, libgcc and libatomic have to be last on the command line
 		if !Bool(linker.Properties.No_libcrt) {
 			deps.LateStaticLibs = append(deps.LateStaticLibs, config.BuiltinsRuntimeLibrary(ctx.toolchain()))
-		}
+			deps.LateStaticLibs = append(deps.LateStaticLibs, "libatomic")
-
+			deps.LateStaticLibs = append(deps.LateStaticLibs, "libgcc_stripped")
-		deps.LateStaticLibs = append(deps.LateStaticLibs, "libatomic")
+		} else if !Bool(linker.Properties.No_libgcc) {
-		if !Bool(linker.Properties.No_libgcc) {
+			deps.LateStaticLibs = append(deps.LateStaticLibs, "libatomic")
 			deps.LateStaticLibs = append(deps.LateStaticLibs, "libgcc")
 		}
 

cc/strip.go

@@ -15,15 +15,19 @@
 package cc
 
 import (
+	"strings"
+
 	"android/soong/android"
 )
 
 type StripProperties struct {
 	Strip struct {
-		None         *bool
+		None              *bool    `android:"arch_variant"`
-		All          *bool
+		All               *bool    `android:"arch_variant"`
-		Keep_symbols *bool
+		Keep_symbols      *bool    `android:"arch_variant"`
-	}
+		Keep_symbols_list []string `android:"arch_variant"`
+		Use_gnu_strip     *bool    `android:"arch_variant"`
+	} `android:"arch_variant"`
 }
 
 type stripper struct {
@@ -42,9 +46,14 @@ func (stripper *stripper) strip(ctx ModuleContext, in android.Path, out android.
 	} else {
 		if Bool(stripper.StripProperties.Strip.Keep_symbols) {
 			flags.stripKeepSymbols = true
+		} else if len(stripper.StripProperties.Strip.Keep_symbols_list) > 0 {
+			flags.stripKeepSymbolsList = strings.Join(stripper.StripProperties.Strip.Keep_symbols_list, ",")
 		} else if !Bool(stripper.StripProperties.Strip.All) {
 			flags.stripKeepMiniDebugInfo = true
 		}
+		if Bool(stripper.StripProperties.Strip.Use_gnu_strip) {
+			flags.stripUseGnuStrip = true
+		}
 		if ctx.Config().Debuggable() && !flags.stripKeepMiniDebugInfo {
 			flags.stripAddGnuDebuglink = true
 		}

cc/testing.go

@@ -69,6 +69,13 @@ func GatherRequiredDepsForTest(os android.OsType) string {
 			src: "",
 		}
 
+		toolchain_library {
+			name: "libgcc_stripped",
+			vendor_available: true,
+			recovery_available: true,
+			src: "",
+		}
+
 		cc_library {
 			name: "libc",
 			no_libgcc: true,

cc/toolchain_library.go

@@ -34,6 +34,8 @@ type toolchainLibraryProperties struct {
 type toolchainLibraryDecorator struct {
 	*libraryDecorator
 
+	stripper
+
 	Properties toolchainLibraryProperties
 }
 
@@ -45,7 +47,7 @@ func (*toolchainLibraryDecorator) linkerDeps(ctx DepsContext, deps Deps) Deps {
 func (library *toolchainLibraryDecorator) linkerProps() []interface{} {
 	var props []interface{}
 	props = append(props, library.libraryDecorator.linkerProps()...)
-	return append(props, &library.Properties)
+	return append(props, &library.Properties, &library.stripper.StripProperties)
 }
 
 // toolchain_library is used internally by the build tool to link the specified
@@ -78,7 +80,17 @@ func (library *toolchainLibraryDecorator) link(ctx ModuleContext,
 		return android.PathForSource(ctx, "")
 	}
 
-	return android.PathForSource(ctx, *library.Properties.Src)
+	srcPath := android.PathForSource(ctx, *library.Properties.Src)
+
+	if library.stripper.StripProperties.Strip.Keep_symbols_list != nil {
+		fileName := ctx.ModuleName() + staticLibraryExtension
+		outputFile := android.PathForModuleOut(ctx, fileName)
+		buildFlags := flagsToBuilderFlags(flags)
+		library.stripper.strip(ctx, srcPath, outputFile, buildFlags)
+		return outputFile
+	}
+
+	return srcPath
 }
 
 func (library *toolchainLibraryDecorator) nativeCoverage() bool {

scripts/strip.sh

@@ -24,6 +24,7 @@
 #   -i ${file}: input file (required)
 #   -o ${file}: output file (required)
 #   -d ${file}: deps file (required)
+#   -k symbols: Symbols to keep (optional)
 #   --add-gnu-debuglink
 #   --keep-mini-debug-info
 #   --keep-symbols
@@ -32,11 +33,11 @@
 
 set -o pipefail
 
-OPTSTRING=d:i:o:-:
+OPTSTRING=d:i:o:k:-:
 
 usage() {
     cat <<EOF
-Usage: strip.sh [options] -i in-file -o out-file -d deps-file
+Usage: strip.sh [options] -k symbols -i in-file -o out-file -d deps-file
 Options:
         --add-gnu-debuglink     Add a gnu-debuglink section to out-file
         --keep-mini-debug-info  Keep compressed debug info in out-file
@@ -71,6 +72,20 @@ do_strip_keep_symbols() {
     fi
 }
 
+do_strip_keep_symbol_list() {
+    if [ -z "${use_gnu_strip}" ]; then
+        echo "do_strip_keep_symbol_list does not work with llvm-objcopy"
+        echo "http://b/131631155"
+        usage
+    fi
+
+    echo "${symbols_to_keep}" | tr ',' '\n' > "${outfile}.symbolList"
+    KEEP_SYMBOLS="-w --strip-unneeded-symbol=* --keep-symbols="
+    KEEP_SYMBOLS+="${outfile}.symbolList"
+
+    "${CROSS_COMPILE}objcopy" "${infile}" "${outfile}.tmp" ${KEEP_SYMBOLS}
+}
+
 do_strip_keep_mini_debug_info() {
     rm -f "${outfile}.dynsyms" "${outfile}.funcsyms" "${outfile}.keep_symbols" "${outfile}.debug" "${outfile}.mini_debuginfo" "${outfile}.mini_debuginfo.xz"
     local fail=
@@ -124,19 +139,21 @@ do_remove_build_id() {
 
 while getopts $OPTSTRING opt; do
     case "$opt" in
-	d) depsfile="${OPTARG}" ;;
+        d) depsfile="${OPTARG}" ;;
-	i) infile="${OPTARG}" ;;
+        i) infile="${OPTARG}" ;;
-	o) outfile="${OPTARG}" ;;
+        o) outfile="${OPTARG}" ;;
-	-)
+        k) symbols_to_keep="${OPTARG}" ;;
-	    case "${OPTARG}" in
+        -)
-		add-gnu-debuglink) add_gnu_debuglink=true ;;
+            case "${OPTARG}" in
-		keep-mini-debug-info) keep_mini_debug_info=true ;;
+                add-gnu-debuglink) add_gnu_debuglink=true ;;
-		keep-symbols) keep_symbols=true ;;
+                keep-mini-debug-info) keep_mini_debug_info=true ;;
-		remove-build-id) remove_build_id=true ;;
+                keep-symbols) keep_symbols=true ;;
-		*) echo "Unknown option --${OPTARG}"; usage ;;
+                remove-build-id) remove_build_id=true ;;
-	    esac;;
+                use-gnu-strip) use_gnu_strip=true ;;
-	?) usage ;;
+                *) echo "Unknown option --${OPTARG}"; usage ;;
-	*) echo "'${opt}' '${OPTARG}'"
+            esac;;
+        ?) usage ;;
+        *) echo "'${opt}' '${OPTARG}'"
     esac
 done
 
@@ -160,6 +177,11 @@ if [ ! -z "${keep_symbols}" -a ! -z "${keep_mini_debug_info}" ]; then
     usage
 fi
 
+if [ ! -z "${symbols_to_keep}" -a ! -z "${keep_symbols}" ]; then
+    echo "--keep-symbols and -k cannot be used together"
+    usage
+fi
+
 if [ ! -z "${add_gnu_debuglink}" -a ! -z "${keep_mini_debug_info}" ]; then
     echo "--add-gnu-debuglink cannot be used with --keep-mini-debug-info"
     usage
@@ -169,6 +191,8 @@ rm -f "${outfile}.tmp"
 
 if [ ! -z "${keep_symbols}" ]; then
     do_strip_keep_symbols
+elif [ ! -z "${symbols_to_keep}" ]; then
+    do_strip_keep_symbol_list
 elif [ ! -z "${keep_mini_debug_info}" ]; then
     do_strip_keep_mini_debug_info
 else