Re: [PATCH 3/3] posix: Add posix_spawn_file_actions_closefrom

[Florian Weimer <fweimer@redhat.com>]

* Adhemerval Zanella via Libc-alpha:

> +* The posix_spawn_file_actions_closefrom_np has been added, enabling
> +  posix_spawn and posix_spawnp to close all file descriptors greater than
> +  a giver interger.  This function is a GNU extension, although Solaris also
> +  provides a similar function.

Two typos: “giver interger”

> diff --git a/posix/spawn.h b/posix/spawn.h
> index be6bd591a3..21ea563425 100644
> --- a/posix/spawn.h
> +++ b/posix/spawn.h
> @@ -213,6 +213,13 @@ extern int posix_spawn_file_actions_addchdir_np (posix_spawn_file_actions_t *
>  extern int posix_spawn_file_actions_addfchdir_np (posix_spawn_file_actions_t *,
>  						  int __fd)
>       __THROW __nonnull ((1));
> +
> +/* Add an action to close all file descriptor greater than FROM during
> +   spawn.  This affects the subsequent file actions.  */
> +extern int posix_spawn_file_actions_addclosefrom_np (posix_spawn_file_actions_t *,
> +						     int __from)
> +     __THROW __nonnull ((1));
> +
>  #endif

Line length issue (but I'm not sure how to avoid that).

> diff --git a/posix/spawn_faction_addclosefrom.c b/posix/spawn_faction_addclosefrom.c
> new file mode 100644
> index 0000000000..3a295580bc
> --- /dev/null
> +++ b/posix/spawn_faction_addclosefrom.c

> +int
> +__posix_spawn_file_actions_addclosefrom (posix_spawn_file_actions_t
> +					 *file_actions, int from)
> +{
> +#if __SPAWN_SUPPORT_CLOSEFROM
> +  struct __spawn_action *rec;
> +
> +  if (!__spawn_valid_fd (from))
> +    return EBADF;
> +
> +  /* Allocate more memory if needed.  */
> +  if (file_actions->__used == file_actions->__allocated
> +      && __posix_spawn_file_actions_realloc (file_actions) != 0)
> +    /* This can only mean we ran out of memory.  */
> +    return ENOMEM;
> +
> +  /* Add the new value.  */
> +  rec = &file_actions->__actions[file_actions->__used];
> +  rec->tag = spawn_do_closefrom;
> +  rec->action.closefrom_action.from = from;
> +
> +  /* Account for the new entry.  */
> +  ++file_actions->__used;
> +
> +  return 0;
> +#else
> +  __set_errno (EINVAL);
> +  return -1;
> +#endif
> +}

Should this return EINVAL for the fallback case?

> diff --git a/posix/spawn_int_abi.h b/posix/spawn_int_abi.h
> new file mode 100644
> index 0000000000..5fda4d3442
> --- /dev/null
> +++ b/posix/spawn_int_abi.h
> @@ -0,0 +1,27 @@
> +/* Internal ABI specific for posix_spawn functionality.  Generic version.
> +   Copyright (C) 2020 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
> +   <http://www.gnu.org/licenses/>.  */
> +
> +#ifndef _SPAWN_INT_ABI_H
> +#define _SPAWN_INT_ABI_H
> +
> +/* The closefrom file actions requires either a syscall or an arch-specific
> +   way to interact over all file descriptors and act uppon them (such
> +   /proc/self/fd on Linux).  */
> +#define __SPAWN_SUPPOR_CLOSEFROM 0
> +
> +#endif /* _SPAWN_INT_H */

I think Hurd has support for this via __getdtablesize, so perhaps this
is not needed?

In any case, ABI is a bit of a misnomer here, and this file is
uncessary, given the sysdeps/generic file.

> diff --git a/posix/tst-spawn5.c b/posix/tst-spawn5.c
> new file mode 100644
> index 0000000000..1f901d112b
> --- /dev/null
> +++ b/posix/tst-spawn5.c

> +enum
> +{
> +  maximum_fd = 100,
> +  half_fd = maximum_fd / 2,
> +};
> +static int fds[maximum_fd + 1];

The usual comments about file descriptor layout. 8-)

> +static void
> +do_test_closefrom (void)
> +{
> +  for (int i = 0; i < array_length (fds); i++)
> +    fds[i] = xopen ("/dev/null", O_WRONLY, 0);

This should perhaps check that the descriptors 57, …, 90 have actually
been opened, perhaps implicitly by checking that the resulting
descriptors end up as one block.

> +  /* Close the remmaining but the last one.  */

Typo: “remmaining”

> +  if (restart)
> +    handle_restart (argc, argv);
> +
> +  initial_argv[0] = argv[1]; /* path for ld.so  */
> +  initial_argv[1] = argv[2]; /* "--library-path"  */
> +  initial_argv[2] = argv[3]; /* the library path  */
> +  initial_argv[3] = argv[4]; /* the application name  */
> +  initial_argv[4] = (char *) "--direct";
> +  initial_argv[5] = (char *) "--restart";
> +
> +  do_test_closefrom ();
> +
> +  return 0;
> +}
> +
> +#define TEST_FUNCTION_ARGV do_test
> +#include <support/test-driver.c>

You could simplify the reinvocation logic by making this a static or a
container test.

> diff --git a/sysdeps/unix/sysv/linux/spawni.c b/sysdeps/unix/sysv/linux/spawni.c
> index f157bfffd2..f496578d19 100644
> --- a/sysdeps/unix/sysv/linux/spawni.c
> +++ b/sysdeps/unix/sysv/linux/spawni.c
> @@ -16,22 +16,17 @@
>     License along with the GNU C Library; if not, see
>     <https://www.gnu.org/licenses/>.  */
>  
> -#include <spawn.h>
> -#include <fcntl.h>
> -#include <paths.h>
> -#include <string.h>
> -#include <sys/resource.h>
> -#include <sys/wait.h>
> -#include <sys/param.h>
> -#include <sys/mman.h>
> -#include <not-cancel.h>
> +#include <arch-fd_to_filename.h>
> +#include <internal-signals.h>
> +#include <ldsodefs.h>
>  #include <local-setxid.h>
> +#include <not-cancel.h>
> +#include <paths.h>
>  #include <shlib-compat.h>
> -#include <nptl/pthreadP.h>
> -#include <dl-sysdep.h>
> -#include <libc-pointer-arith.h>
> -#include <ldsodefs.h>
> -#include "spawn_int.h"
> +#include <spawn.h>
> +#include <spawn_int.h>
> +#include <sysdep.h>
> +#include <sys/resource.h>

Suprious changes?

Thanks,
Florian
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