diff --git a/dexpreopt/config.go b/dexpreopt/config.go
index 6163952..fe6317c 100644
--- a/dexpreopt/config.go
+++ b/dexpreopt/config.go
@@ -98,7 +98,9 @@
 	// measure, as it masks real errors and affects performance.
 	RelaxUsesLibraryCheck bool
 
-	EnableUffdGc bool // preopt with the assumption that userfaultfd GC will be used on device.
+	// "true" to force preopt with CMC GC (a.k.a., UFFD GC); "false" to force preopt with CC GC;
+	// "default" to determine the GC type based on the kernel version file.
+	EnableUffdGc string
 }
 
 var allPlatformSystemServerJarsKey = android.NewOnceKey("allPlatformSystemServerJars")
@@ -154,6 +156,7 @@
 	Zip2zip          android.Path
 	ManifestCheck    android.Path
 	ConstructContext android.Path
+	UffdGcFlag       android.WritablePath
 }
 
 type ModuleConfig struct {
@@ -537,6 +540,7 @@
 		Zip2zip:          ctx.Config().HostToolPath(ctx, "zip2zip"),
 		ManifestCheck:    ctx.Config().HostToolPath(ctx, "manifest_check"),
 		ConstructContext: ctx.Config().HostToolPath(ctx, "construct_context"),
+		UffdGcFlag:       getUffdGcFlagPath(ctx),
 	}
 }
 
@@ -588,6 +592,7 @@
 	Zip2zip          string
 	ManifestCheck    string
 	ConstructContext string
+	UffdGcFlag       string
 }
 
 // ParseGlobalSoongConfig parses the given data assumed to be read from the
@@ -609,6 +614,7 @@
 		Zip2zip:          constructPath(ctx, jc.Zip2zip),
 		ManifestCheck:    constructPath(ctx, jc.ManifestCheck),
 		ConstructContext: constructPath(ctx, jc.ConstructContext),
+		UffdGcFlag:       constructWritablePath(ctx, jc.UffdGcFlag),
 	}
 
 	return config, nil
@@ -633,12 +639,15 @@
 }
 
 func (s *globalSoongConfigSingleton) GenerateBuildActions(ctx android.SingletonContext) {
-	checkBootJarsConfigConsistency(ctx, GetGlobalConfig(ctx), ctx.Config())
+	global := GetGlobalConfig(ctx)
+	checkBootJarsConfigConsistency(ctx, global, ctx.Config())
 
-	if GetGlobalConfig(ctx).DisablePreopt {
+	if global.DisablePreopt {
 		return
 	}
 
+	buildUffdGcFlag(ctx, global)
+
 	config := GetCachedGlobalSoongConfig(ctx)
 	if config == nil {
 		// No module has enabled dexpreopting, so we assume there will be no calls
@@ -654,6 +663,7 @@
 		Zip2zip:          config.Zip2zip.String(),
 		ManifestCheck:    config.ManifestCheck.String(),
 		ConstructContext: config.ConstructContext.String(),
+		UffdGcFlag:       config.UffdGcFlag.String(),
 	}
 
 	data, err := json.Marshal(jc)
@@ -684,9 +694,32 @@
 		config.Zip2zip.String(),
 		config.ManifestCheck.String(),
 		config.ConstructContext.String(),
+		config.UffdGcFlag.String(),
 	}, " "))
 }
 
+func buildUffdGcFlag(ctx android.BuilderContext, global *GlobalConfig) {
+	uffdGcFlag := getUffdGcFlagPath(ctx)
+
+	if global.EnableUffdGc == "true" {
+		android.WriteFileRuleVerbatim(ctx, uffdGcFlag, "--runtime-arg -Xgc:CMC")
+	} else if global.EnableUffdGc == "false" {
+		android.WriteFileRuleVerbatim(ctx, uffdGcFlag, "")
+	} else if global.EnableUffdGc == "default" {
+		// Generated by `build/make/core/Makefile`.
+		kernelVersionFile := android.PathForOutput(ctx, "dexpreopt/kernel_version_for_uffd_gc.txt")
+		// Determine the UFFD GC flag by the kernel version file.
+		rule := android.NewRuleBuilder(pctx, ctx)
+		rule.Command().
+			Tool(ctx.Config().HostToolPath(ctx, "construct_uffd_gc_flag")).
+			Input(kernelVersionFile).
+			Output(uffdGcFlag)
+		rule.Restat().Build("dexpreopt_uffd_gc_flag", "dexpreopt_uffd_gc_flag")
+	} else {
+		panic(fmt.Sprintf("Unknown value of PRODUCT_ENABLE_UFFD_GC: %s", global.EnableUffdGc))
+	}
+}
+
 func GlobalConfigForTests(ctx android.PathContext) *GlobalConfig {
 	return &GlobalConfig{
 		DisablePreopt:                  false,
@@ -731,7 +764,7 @@
 	}
 }
 
-func globalSoongConfigForTests() *GlobalSoongConfig {
+func globalSoongConfigForTests(ctx android.BuilderContext) *GlobalSoongConfig {
 	return &GlobalSoongConfig{
 		Profman:          android.PathForTesting("profman"),
 		Dex2oat:          android.PathForTesting("dex2oat"),
@@ -740,5 +773,19 @@
 		Zip2zip:          android.PathForTesting("zip2zip"),
 		ManifestCheck:    android.PathForTesting("manifest_check"),
 		ConstructContext: android.PathForTesting("construct_context"),
+		UffdGcFlag:       android.PathForOutput(ctx, "dexpreopt_test", "uffd_gc_flag.txt"),
 	}
 }
+
+func GetDexpreoptDirName(ctx android.PathContext) string {
+	prefix := "dexpreopt_"
+	targets := ctx.Config().Targets[android.Android]
+	if len(targets) > 0 {
+		return prefix + targets[0].Arch.ArchType.String()
+	}
+	return prefix + "unknown_target"
+}
+
+func getUffdGcFlagPath(ctx android.PathContext) android.WritablePath {
+	return android.PathForOutput(ctx, "dexpreopt/uffd_gc_flag.txt")
+}