Determine GC type based on BUILT_KERNEL_VERSION_FILE.

How it works:
1. build/make/core/Makefile generates a txt file with the kernel
   version, which is taken from an explicit BOARD_KERNEL_VERSION value,
   or extracted from the kernel image on the source tree, or extracted
   from the kernel image extracted from the prebuilt boot.img.
   The file is saved at
   $ANDROID_PRODUCT_OUT/obj/PACKAGING/check_vintf_all_intermediates/kernel_version.txt.
2. If PRODUCT_ENABLE_UFFD_GC is "default", meaning the GC type needs to
   be determined by the kernel version, build/make/core/Makefile copies
   kernel_version.txt to
   out/soong/dexpreopt/kernel_version_for_uffd_gc.txt.
3. build/soong/dexpreopt/config.go writes the the UFFD GC flag to
   out/soong/dexpreopt/uffd_gc_flag.txt. The flag is determined by an
   explicit PRODUCT_ENABLE_UFFD_GC value or by contruct_uffd_gc_flag.py,
   which reads kernel_version_for_uffd_gc.txt and determines the flag
   accordingly.
4. dex2oat takes the UFFD GC flag from uffd_gc_flag.txt.
5. post_process_props.py mangles ro.dalvik.vm.enable_uffd_gc based on
   the same logic.

Bug: 321751629
Bug: 319554951
Bug: 318763448
Bug: 319648491
Test: m --no-skip-soong-tests nothing
Test: atest uffd_gc_utils_test
Test: Build with `OVERRIDE_ENABLE_UFFD_GC=default m` for device with no
  UFFD support -
  1. Check the existence of `-Xgc:CMC` in
     out/soong/dexpreopt_arm64/dex_bootjars/android/system/framework/arm64/boot.invocation
     (dex2oat invocation for a boot image)
  2. Check the existence of `-Xgc:CMC` in
     out/soong/.intermediates/packages/apps/Settings/Settings/android_common/dexpreopt/Settings/oat/arm64/package.invocation
     (dex2oat invocation for an app defined in .bp)
  3. Check the existence of `-Xgc:CMC` in
     $ANDROID_PRODUCT_OUT/obj/APPS/Dialer_intermediates/oat/arm64/package.invocation
     (dex2oat invocation for an app defined in .mk)
  4. Check the value of ro.dalvik.vm.enable_uffd_gc in
     $ANDROID_PRODUCT_OUT/product/etc/build.prop
Test: Build with `OVERRIDE_ENABLE_UFFD_GC=default m` for device with
  UFFD support, and do the steps above.
Test: Build with `OVERRIDE_ENABLE_UFFD_GC=true m`, and do the steps
  above.
Test: Build with `OVERRIDE_ENABLE_UFFD_GC=false m`, and do the steps
  above.

Change-Id: I035ad32233e49e2a30ce11f6c7c318a648511ef8

dexpreopt/dexpreopt_test.go

@@ -96,7 +96,7 @@ func createTestModuleConfig(name, dexLocation string, buildPath, dexPath, enforc
 func TestDexPreopt(t *testing.T) {
 	config := android.TestConfig("out", nil, "", nil)
 	ctx := android.BuilderContextForTesting(config)
-	globalSoong := globalSoongConfigForTests()
+	globalSoong := globalSoongConfigForTests(ctx)
 	global := GlobalConfigForTests(ctx)
 	module := testSystemModuleConfig(ctx, "test")
 	productPackages := android.PathForTesting("product_packages.txt")
@@ -114,12 +114,15 @@ func TestDexPreopt(t *testing.T) {
 	if rule.Installs().String() != wantInstalls.String() {
 		t.Errorf("\nwant installs:\n   %v\ngot:\n   %v", wantInstalls, rule.Installs())
 	}
+
+	android.AssertStringListContains(t, "", rule.Inputs().RelativeToTop().Strings(),
+		"out/soong/dexpreopt_test/uffd_gc_flag.txt")
 }
 
 func TestDexPreoptSystemOther(t *testing.T) {
 	config := android.TestConfig("out", nil, "", nil)
 	ctx := android.BuilderContextForTesting(config)
-	globalSoong := globalSoongConfigForTests()
+	globalSoong := globalSoongConfigForTests(ctx)
 	global := GlobalConfigForTests(ctx)
 	systemModule := testSystemModuleConfig(ctx, "Stest")
 	systemProductModule := testSystemProductModuleConfig(ctx, "SPtest")
@@ -180,7 +183,7 @@ func TestDexPreoptSystemOther(t *testing.T) {
 func TestDexPreoptApexSystemServerJars(t *testing.T) {
 	config := android.TestConfig("out", nil, "", nil)
 	ctx := android.BuilderContextForTesting(config)
-	globalSoong := globalSoongConfigForTests()
+	globalSoong := globalSoongConfigForTests(ctx)
 	global := GlobalConfigForTests(ctx)
 	module := testApexModuleConfig(ctx, "service-A", "com.android.apex1")
 	productPackages := android.PathForTesting("product_packages.txt")
@@ -204,7 +207,7 @@ func TestDexPreoptApexSystemServerJars(t *testing.T) {
 func TestDexPreoptStandaloneSystemServerJars(t *testing.T) {
 	config := android.TestConfig("out", nil, "", nil)
 	ctx := android.BuilderContextForTesting(config)
-	globalSoong := globalSoongConfigForTests()
+	globalSoong := globalSoongConfigForTests(ctx)
 	global := GlobalConfigForTests(ctx)
 	module := testPlatformSystemServerModuleConfig(ctx, "service-A")
 	productPackages := android.PathForTesting("product_packages.txt")
@@ -228,7 +231,7 @@ func TestDexPreoptStandaloneSystemServerJars(t *testing.T) {
 func TestDexPreoptSystemExtSystemServerJars(t *testing.T) {
 	config := android.TestConfig("out", nil, "", nil)
 	ctx := android.BuilderContextForTesting(config)
-	globalSoong := globalSoongConfigForTests()
+	globalSoong := globalSoongConfigForTests(ctx)
 	global := GlobalConfigForTests(ctx)
 	module := testSystemExtSystemServerModuleConfig(ctx, "service-A")
 	productPackages := android.PathForTesting("product_packages.txt")
@@ -252,7 +255,7 @@ func TestDexPreoptSystemExtSystemServerJars(t *testing.T) {
 func TestDexPreoptApexStandaloneSystemServerJars(t *testing.T) {
 	config := android.TestConfig("out", nil, "", nil)
 	ctx := android.BuilderContextForTesting(config)
-	globalSoong := globalSoongConfigForTests()
+	globalSoong := globalSoongConfigForTests(ctx)
 	global := GlobalConfigForTests(ctx)
 	module := testApexModuleConfig(ctx, "service-A", "com.android.apex1")
 	productPackages := android.PathForTesting("product_packages.txt")
@@ -276,7 +279,7 @@ func TestDexPreoptApexStandaloneSystemServerJars(t *testing.T) {
 func TestDexPreoptProfile(t *testing.T) {
 	config := android.TestConfig("out", nil, "", nil)
 	ctx := android.BuilderContextForTesting(config)
-	globalSoong := globalSoongConfigForTests()
+	globalSoong := globalSoongConfigForTests(ctx)
 	global := GlobalConfigForTests(ctx)
 	module := testSystemModuleConfig(ctx, "test")
 	productPackages := android.PathForTesting("product_packages.txt")
@@ -316,3 +319,55 @@ func TestDexPreoptConfigToJson(t *testing.T) {
 	after := fmt.Sprintf("%v", parsed)
 	android.AssertStringEquals(t, "The result must be the same as the original after marshalling and unmarshalling it.", before, after)
 }
+
+func TestUffdGcFlagForce(t *testing.T) {
+	for _, enableUffdGc := range []string{"true", "false"} {
+		t.Run(enableUffdGc, func(t *testing.T) {
+			preparers := android.GroupFixturePreparers(
+				PrepareForTestWithFakeDex2oatd,
+				PrepareForTestWithDexpreoptConfig,
+				FixtureSetEnableUffdGc(enableUffdGc),
+			)
+
+			result := preparers.RunTest(t)
+			ctx := result.TestContext
+
+			ctx.SingletonForTests("dexpreopt-soong-config").Output("out/soong/dexpreopt/uffd_gc_flag.txt")
+		})
+	}
+}
+
+func TestUffdGcFlagDefault(t *testing.T) {
+	preparers := android.GroupFixturePreparers(
+		PrepareForTestWithFakeDex2oatd,
+		PrepareForTestWithDexpreoptConfig,
+		FixtureSetEnableUffdGc("default"),
+	)
+
+	result := preparers.RunTest(t)
+	ctx := result.TestContext
+	config := ctx.Config()
+
+	rule := ctx.SingletonForTests("dexpreopt-soong-config").Rule("dexpreopt_uffd_gc_flag")
+
+	android.AssertStringDoesContain(t, "", rule.RuleParams.Command, "construct_uffd_gc_flag")
+	android.AssertStringPathsRelativeToTopEquals(t, "", config, []string{
+		"out/soong/dexpreopt/uffd_gc_flag.txt",
+	}, rule.AllOutputs())
+	android.AssertPathsRelativeToTopEquals(t, "", []string{
+		"out/soong/dexpreopt/kernel_version_for_uffd_gc.txt",
+	}, rule.Implicits)
+}
+
+func TestUffdGcFlagBogus(t *testing.T) {
+	preparers := android.GroupFixturePreparers(
+		PrepareForTestWithFakeDex2oatd,
+		PrepareForTestWithDexpreoptConfig,
+		FixtureSetEnableUffdGc("bogus"),
+	)
+
+	preparers.
+		ExtendWithErrorHandler(android.FixtureExpectsAtLeastOneErrorMatchingPattern(
+			"Unknown value of PRODUCT_ENABLE_UFFD_GC: bogus")).
+		RunTest(t)
+}