Support O_DIRECTORY open() flag

Close #3545.

cpukit/libcsupport/src/open.c

@@ -73,6 +73,7 @@ static int do_open(
   bool make = (oflag & O_CREAT) == O_CREAT;
   bool exclusive = (oflag & (O_CREAT | O_EXCL)) == (O_CREAT | O_EXCL);
   bool truncate = (oflag & O_TRUNC) == O_TRUNC;
+  bool open_dir;
   int eval_flags = RTEMS_FS_FOLLOW_LINK
     | (read_access ? RTEMS_FS_PERMS_READ : 0)
     | (write_access ? RTEMS_FS_PERMS_WRITE : 0)
@@ -86,14 +87,24 @@ static int do_open(
     create_regular_file( &ctx, mode );
   }
 
-  if ( write_access ) {
+#ifdef O_DIRECTORY
+  open_dir = ( oflag & O_DIRECTORY ) == O_DIRECTORY;
+#else
+  open_dir = false;
+#endif
+
+  if ( write_access || open_dir ) {
     const rtems_filesystem_location_info_t *currentloc =
       rtems_filesystem_eval_path_get_currentloc( &ctx );
     mode_t type = rtems_filesystem_location_type( currentloc );
 
-    if ( S_ISDIR( type ) ) {
+    if ( write_access && S_ISDIR( type ) ) {
       rtems_filesystem_eval_path_error( &ctx, EISDIR );
     }
+
+    if ( open_dir && !S_ISDIR( type ) ) {
+      rtems_filesystem_eval_path_error( &ctx, ENOTDIR );
+    }
   }
 
   rtems_filesystem_eval_path_extract_currentloc( &ctx, &iop->pathinfo );

testsuites/psxtests/psxfile01/test.c

@@ -130,6 +130,29 @@ void stat_a_file(
 
 }
 
+static void test_open_directory(void)
+{
+  static const char file[] = "somefile";
+  int status;
+  int fd;
+
+  fd = open( file, O_CREAT, S_IRWXU );
+  rtems_test_assert( fd >= 0 );
+
+  status = close( fd );
+  rtems_test_assert( status == 0 );
+
+#ifdef O_DIRECTORY
+  errno = 0;
+  fd = open( file, O_DIRECTORY, S_IRWXU );
+  rtems_test_assert( fd == -1 );
+  rtems_test_assert( errno == ENOTDIR );
+#endif
+
+  status = unlink( file );
+  rtems_test_assert( status == 0 );
+}
+
 /*
  *  Main entry point of the test
  */
@@ -161,6 +184,8 @@ int main(
 
   TEST_BEGIN();
 
+  test_open_directory();
+
   /*
    *  Grab the maximum size of an in-memory file.
    */