Fix addrsig warnings

ld -r reorders symbols and invalidates the .llvm_addrsig section, which
then causes warnings if the resulting object is used with ld --icf=safe.
The warning is especially common when building with musl, as the
clang_rt.crt* objects have .llvm_addrsig sections, are linked into
libc_musl_crt* using ld -r, and are then linked into every other binary
and shared library with --icf=safe.

Strip the .llvm_addrsig section after ld -r to prevent the warnings.

Test: m USE_HOST_MUSL=true host-native -k
Change-Id: Ia52a4756b9ebbb62115898d0de9f8641e6fea705

cc/builder.go

@@ -125,6 +125,14 @@ var (
 		},
 		"objcopyCmd", "prefix")
 
+	// Rule to run objcopy --remove-section=.llvm_addrsig on a partially linked object
+	noAddrSig = pctx.AndroidStaticRule("noAddrSig",
+		blueprint.RuleParams{
+			Command:     "rm -f ${out} && $objcopyCmd --remove-section=.llvm_addrsig ${in} ${out}",
+			CommandDeps: []string{"$objcopyCmd"},
+		},
+		"objcopyCmd")
+
 	_ = pctx.SourcePathVariable("stripPath", "build/soong/scripts/strip.sh")
 	_ = pctx.SourcePathVariable("xzCmd", "prebuilts/build-tools/${config.HostPrebuiltTag}/bin/xz")
 	_ = pctx.SourcePathVariable("createMiniDebugInfo", "prebuilts/build-tools/${config.HostPrebuiltTag}/bin/create_minidebuginfo")
@@ -1008,6 +1016,21 @@ func transformBinaryPrefixSymbols(ctx android.ModuleContext, prefix string, inpu
 	})
 }
 
+// Generate a rule for running objcopy --remove-section=.llvm_addrsig on a partially linked object
+func transformObjectNoAddrSig(ctx android.ModuleContext, inputFile android.Path, outputFile android.WritablePath) {
+	objcopyCmd := "${config.ClangBin}/llvm-objcopy"
+
+	ctx.Build(pctx, android.BuildParams{
+		Rule:        noAddrSig,
+		Description: "remove addrsig " + outputFile.Base(),
+		Output:      outputFile,
+		Input:       inputFile,
+		Args: map[string]string{
+			"objcopyCmd": objcopyCmd,
+		},
+	})
+}
+
 // Registers a build statement to invoke `strip` (to discard symbols and data from object files).
 func transformStrip(ctx android.ModuleContext, inputFile android.Path,
 	outputFile android.WritablePath, flags StripFlags) {

cc/object.go

@@ -309,6 +309,8 @@ func (object *objectLinker) link(ctx ModuleContext,
 			})
 		}
 	} else {
+		outputAddrSig := android.PathForModuleOut(ctx, "addrsig", outputName)
+
 		if String(object.Properties.Prefix_symbols) != "" {
 			input := android.PathForModuleOut(ctx, "unprefixed", outputName)
 			transformBinaryPrefixSymbols(ctx, String(object.Properties.Prefix_symbols), input,
@@ -316,7 +318,12 @@ func (object *objectLinker) link(ctx ModuleContext,
 			output = input
 		}
 
-		transformObjsToObj(ctx, objs.objFiles, builderFlags, output, flags.LdFlagsDeps)
+		transformObjsToObj(ctx, objs.objFiles, builderFlags, outputAddrSig, flags.LdFlagsDeps)
+
+		// ld -r reorders symbols and invalidates the .llvm_addrsig section, which then causes warnings
+		// if the resulting object is used with ld --icf=safe.  Strip the .llvm_addrsig section to
+		// prevent the warnings.
+		transformObjectNoAddrSig(ctx, outputAddrSig, output)
 	}
 
 	ctx.CheckbuildFile(outputFile)

java/app_test.go

@@ -443,9 +443,9 @@ func TestUpdatableApps_JniLibShouldBeBuiltAgainstMinSdkVersion(t *testing.T) {
 	inputs := ctx.ModuleForTests("libjni", "android_arm64_armv8-a_sdk_shared").Description("link").Implicits
 	var crtbeginFound, crtendFound bool
 	expectedCrtBegin := ctx.ModuleForTests("crtbegin_so",
-		"android_arm64_armv8-a_sdk_29").Rule("partialLd").Output
+		"android_arm64_armv8-a_sdk_29").Rule("noAddrSig").Output
 	expectedCrtEnd := ctx.ModuleForTests("crtend_so",
-		"android_arm64_armv8-a_sdk_29").Rule("partialLd").Output
+		"android_arm64_armv8-a_sdk_29").Rule("noAddrSig").Output
 	implicits := []string{}
 	for _, input := range inputs {
 		implicits = append(implicits, input.String())