hurd: Add support for spawn_do_closefrom

sysdeps/mach/hurd/spawn_int_def.h

@@ -0,0 +1,24 @@
+/* Internal definitions for posix_spawn functionality.  Hurd version.
+   Copyright (C) 2021 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, see
+   <https://www.gnu.org/licenses/>.  */
+
+#ifndef _SPAWN_INT_DEF_H
+#define _SPAWN_INT_DEF_H
+
+#define __SPAWN_SUPPORT_CLOSEFROM 1
+
+#endif /* _SPAWN_INT_H */

sysdeps/mach/hurd/spawni.c

@@ -505,6 +505,19 @@ retry:
 	    return EBADF;
 	  }
 
+	/* Close file descriptors in the child.  */
+	error_t do_closefrom (int lowfd)
+	  {
+	    while ((unsigned int) lowfd < dtablesize)
+	      {
+		error_t err = do_close (lowfd);
+		if (err != 0 && err != EBADF)
+		  return err;
+		lowfd++;
+	      }
+	    return 0;
+	  }
+
 	/* Make sure the dtable can hold NEWFD.  */
 #define EXPAND_DTABLE(newfd)						      \
 	({								      \
@@ -615,7 +628,7 @@ retry:
 	    break;
 
 	  case spawn_do_closefrom:
-	    err = EINVAL;
+	    err = do_closefrom (action->action.closefrom_action.from);
 	    break;
 	  }