diff --git a/android/config.go b/android/config.go
index 101f457..3c49c1a 100644
--- a/android/config.go
+++ b/android/config.go
@@ -135,12 +135,12 @@
 }
 
 func loadConfig(config *config) error {
-	err := loadFromConfigFile(&config.FileConfigurableOptions, config.ConfigFileName)
+	err := loadFromConfigFile(&config.FileConfigurableOptions, absolutePath(config.ConfigFileName))
 	if err != nil {
 		return err
 	}
 
-	return loadFromConfigFile(&config.productVariables, config.ProductVariablesFileName)
+	return loadFromConfigFile(&config.productVariables, absolutePath(config.ProductVariablesFileName))
 }
 
 // loads configuration options from a JSON file in the cwd.
@@ -204,6 +204,17 @@
 	return nil
 }
 
+// NullConfig returns a mostly empty Config for use by standalone tools like dexpreopt_gen that
+// use the android package.
+func NullConfig(buildDir string) Config {
+	return Config{
+		config: &config{
+			buildDir: buildDir,
+			fs:       pathtools.OsFs,
+		},
+	}
+}
+
 // TestConfig returns a Config object suitable for using for tests
 func TestConfig(buildDir string, env map[string]string, bp string, fs map[string][]byte) Config {
 	envCopy := make(map[string]string)
@@ -320,7 +331,7 @@
 		buildDir:          buildDir,
 		multilibConflicts: make(map[ArchType]bool),
 
-		fs: pathtools.OsFs,
+		fs: pathtools.NewOsFs(absSrcDir),
 	}
 
 	config.deviceConfig = &deviceConfig{
@@ -350,7 +361,7 @@
 	}
 
 	inMakeFile := filepath.Join(buildDir, ".soong.in_make")
-	if _, err := os.Stat(inMakeFile); err == nil {
+	if _, err := os.Stat(absolutePath(inMakeFile)); err == nil {
 		config.inMake = true
 	}
 
@@ -398,6 +409,8 @@
 	return Config{config}, nil
 }
 
+var TestConfigOsFs = map[string][]byte{}
+
 // mockFileSystem replaces all reads with accesses to the provided map of
 // filenames to contents stored as a byte slice.
 func (c *config) mockFileSystem(bp string, fs map[string][]byte) {
@@ -901,8 +914,13 @@
 	return c.productVariables.BootJars
 }
 
-func (c *config) DexpreoptGlobalConfig() string {
-	return String(c.productVariables.DexpreoptGlobalConfig)
+func (c *config) DexpreoptGlobalConfig(ctx PathContext) ([]byte, error) {
+	if c.productVariables.DexpreoptGlobalConfig == nil {
+		return nil, nil
+	}
+	path := absolutePath(*c.productVariables.DexpreoptGlobalConfig)
+	ctx.AddNinjaFileDeps(path)
+	return ioutil.ReadFile(path)
 }
 
 func (c *config) FrameworksBaseDirExists(ctx PathContext) bool {