diff --git a/core/modules/user/src/PermissionHandler.php b/core/modules/user/src/PermissionHandler.php
index d41b05e..a574cc3 100644
--- a/core/modules/user/src/PermissionHandler.php
+++ b/core/modules/user/src/PermissionHandler.php
@@ -51,6 +51,13 @@ class PermissionHandler implements PermissionHandlerInterface {
   protected $controllerResolver;
 
   /**
+   * Array of permissions keyed by module name.
+   *
+   * @var array
+   */
+  protected $permisisonsCache;
+
+  /**
    * Constructs a new PermissionHandler.
    *
    * @param \Drupal\Core\Extension\ModuleHandlerInterface $module_handler
@@ -84,8 +91,8 @@ protected function getYamlDiscovery() {
   /**
    * {@inheritdoc}
    */
-  public function getPermissions() {
-    $all_permissions = $this->buildPermissionsYaml();
+  public function getPermissions($module_name = NULL) {
+    $all_permissions = $this->buildPermissionsYaml($module_name);
 
     return $this->sortPermissions($all_permissions);
   }
@@ -94,32 +101,49 @@ public function getPermissions() {
    * {@inheritdoc}
    */
   public function moduleProvidesPermissions($module_name) {
-    // @TODO Static cache this information, see
-    // https://www.drupal.org/node/2339487
-    $permissions = $this->getPermissions();
-
+    if (!isset($this->permisisonsCache[$module_name])) {
+      $permissions = $this->getPermissions($module_name);
+    }
+    $this->permisisonsCache[$module_name] = FALSE;
     foreach ($permissions as $permission) {
       if ($permission['provider'] == $module_name) {
-        return TRUE;
+        $this->permisisonsCache[$module_name] = TRUE;
+        break;
       }
     }
-    return FALSE;
+    return $this->permisisonsCache[$module_name];
   }
 
   /**
    * Builds all permissions provided by .permissions.yml files.
    *
-   * @return array[]
-   *   Each return permission is an array with the following keys:
-   *   - title: The title of the permission.
-   *   - description: The description of the permission, defaults to NULL.
-   *   - provider: The provider of the permission.
+   * @param string $module_name
+   *   (optional) The module to build permissions YAML for. If omitted, builds
+   *   permissions for all modules.
+   * @return \array[] Each return permission is an array with the following keys:
+   * Each return permission is an array with the following keys:
+   * - title: The title of the permission.
+   * - description: The description of the permission, defaults to NULL.
+   * - provider: The provider of the permission.
    */
-  protected function buildPermissionsYaml() {
+  protected function buildPermissionsYaml($module_name = NULL) {
     $all_permissions = array();
     $all_callback_permissions = array();
 
-    foreach ($this->getYamlDiscovery()->findAll() as $provider => $permissions) {
+    if ($module_name) {
+      // Just discover the single module.
+      $directories = $this->moduleHandler->getModuleDirectories();
+      $module_directories = [];
+      if (!empty($directories[$module_name])) {
+        $module_directories = [$module_name => $directories[$module_name]];
+      }
+      $discovery = new YamlDiscovery('permissions', $module_directories);
+    }
+    else {
+      // Use the default discovery - which handles all enabled modules.
+      $discovery = $this->getYamlDiscovery();
+    }
+    foreach ($discovery->findAll() as $provider => $permissions) {
       // The top-level 'permissions_callback' is a list of methods in controller
       // syntax, see \Drupal\Core\Controller\ControllerResolver. These methods
       // should return an array of permissions in the same structure.
diff --git a/core/modules/user/src/PermissionHandlerInterface.php b/core/modules/user/src/PermissionHandlerInterface.php
index 269af11..9a54996 100644
--- a/core/modules/user/src/PermissionHandlerInterface.php
+++ b/core/modules/user/src/PermissionHandlerInterface.php
@@ -15,6 +15,10 @@
   /**
    * Gets all available permissions.
    *
+   * @param string $module_name
+   *   (optional) The module name to get permissions for. If omitted, gets
+   *   permissions for all modules.
+   *
    * @return array
    *   An array whose keys are permission names and whose corresponding values
    *   are arrays containing the following key-value pairs:
@@ -41,7 +45,7 @@
    *     information that is specific to the permission you are defining.
    *   - provider: (optional) The provider name of the permission.
    */
-  public function getPermissions();
+  public function getPermissions($module_name = NULL);
 
   /**
    * Determines whether a module provides some permissions.
@@ -55,4 +59,3 @@ public function getPermissions();
   public function moduleProvidesPermissions($module_name);
 
 }
-
diff --git a/core/modules/user/tests/src/Unit/PermissionHandlerTest.php b/core/modules/user/tests/src/Unit/PermissionHandlerTest.php
index 1180846..cd7fbcc 100644
--- a/core/modules/user/tests/src/Unit/PermissionHandlerTest.php
+++ b/core/modules/user/tests/src/Unit/PermissionHandlerTest.php
@@ -92,7 +92,7 @@ public function testBuildPermissionsYaml() {
     vfsStreamWrapper::setRoot($root);
 
     $this->moduleHandler = $this->getMock('Drupal\Core\Extension\ModuleHandlerInterface');
-    $this->moduleHandler->expects($this->once())
+    $this->moduleHandler->expects($this->any())
       ->method('getModuleDirectories')
       ->willReturn(array(
         'module_a' => vfsStream::url('modules/module_a'),