diff mbox series

Linux: Add execveat system call wrapper

Message ID 20210324135402.2685623-1-ahajkova@redhat.com
State Superseded
Delegated to: Adhemerval Zanella Netto
Headers show
Series Linux: Add execveat system call wrapper | expand

Commit Message

Alexandra Hájková March 24, 2021, 1:54 p.m. UTC
From: Alexandra Hájková <ahajkova@redhat.com>

 Also add the test for the new wrapper.
---
This version:
* was updated  to use 2.24 symbol version
* "difrd < 0" check was dropped

 NEWS                                          |   5 +
 include/unistd.h                              |   4 +
 posix/Makefile                                |   4 +-
 posix/Versions                                |   3 +
 posix/execveat.c                              |  41 ++++
 posix/tst-execveat-compat.c                   |  32 ++++
 posix/tst-execveat.c                          | 180 ++++++++++++++++++
 posix/unistd.h                                |   5 +
 sysdeps/mach/hurd/i386/libc.abilist           |   1 +
 sysdeps/unix/sysv/linux/aarch64/libc.abilist  |   1 +
 sysdeps/unix/sysv/linux/alpha/libc.abilist    |   1 +
 sysdeps/unix/sysv/linux/arm/be/libc.abilist   |   1 +
 sysdeps/unix/sysv/linux/arm/le/libc.abilist   |   1 +
 sysdeps/unix/sysv/linux/csky/libc.abilist     |   1 +
 sysdeps/unix/sysv/linux/execveat.c            |  54 ++++++
 sysdeps/unix/sysv/linux/execveat_fallback.c   |  69 +++++++
 sysdeps/unix/sysv/linux/hppa/libc.abilist     |   1 +
 sysdeps/unix/sysv/linux/i386/libc.abilist     |   1 +
 sysdeps/unix/sysv/linux/ia64/libc.abilist     |   1 +
 .../sysv/linux/m68k/coldfire/libc.abilist     |   1 +
 .../unix/sysv/linux/m68k/m680x0/libc.abilist  |   1 +
 .../sysv/linux/microblaze/be/libc.abilist     |   1 +
 .../sysv/linux/microblaze/le/libc.abilist     |   1 +
 .../sysv/linux/mips/mips32/fpu/libc.abilist   |   1 +
 .../sysv/linux/mips/mips32/nofpu/libc.abilist |   1 +
 .../sysv/linux/mips/mips64/n32/libc.abilist   |   1 +
 .../sysv/linux/mips/mips64/n64/libc.abilist   |   1 +
 sysdeps/unix/sysv/linux/nios2/libc.abilist    |   1 +
 .../linux/powerpc/powerpc32/fpu/libc.abilist  |   1 +
 .../powerpc/powerpc32/nofpu/libc.abilist      |   1 +
 .../linux/powerpc/powerpc64/be/libc.abilist   |   1 +
 .../linux/powerpc/powerpc64/le/libc.abilist   |   1 +
 .../unix/sysv/linux/riscv/rv64/libc.abilist   |   1 +
 .../unix/sysv/linux/s390/s390-32/libc.abilist |   1 +
 .../unix/sysv/linux/s390/s390-64/libc.abilist |   1 +
 sysdeps/unix/sysv/linux/sh/be/libc.abilist    |   1 +
 sysdeps/unix/sysv/linux/sh/le/libc.abilist    |   1 +
 .../sysv/linux/sparc/sparc32/libc.abilist     |   1 +
 .../sysv/linux/sparc/sparc64/libc.abilist     |   1 +
 .../unix/sysv/linux/x86_64/64/libc.abilist    |   1 +
 .../unix/sysv/linux/x86_64/x32/libc.abilist   |   1 +
 41 files changed, 427 insertions(+), 1 deletion(-)
 create mode 100644 posix/execveat.c
 create mode 100644 posix/tst-execveat-compat.c
 create mode 100644 posix/tst-execveat.c
 create mode 100644 sysdeps/unix/sysv/linux/execveat.c
 create mode 100644 sysdeps/unix/sysv/linux/execveat_fallback.c

Comments

Adhemerval Zanella March 26, 2021, 8:36 p.m. UTC | #1
On 24/03/2021 10:54, Alexandra Hájková via Libc-alpha wrote:
> From: Alexandra Hájková <ahajkova@redhat.com>
> 
>  Also add the test for the new wrapper.
> ---
> This version:
> * was updated  to use 2.24 symbol version
> * "difrd < 0" check was dropped

Patch looks in general, some comments below.

> 
>  NEWS                                          |   5 +
>  include/unistd.h                              |   4 +
>  posix/Makefile                                |   4 +-
>  posix/Versions                                |   3 +
>  posix/execveat.c                              |  41 ++++
>  posix/tst-execveat-compat.c                   |  32 ++++
>  posix/tst-execveat.c                          | 180 ++++++++++++++++++
>  posix/unistd.h                                |   5 +
>  sysdeps/mach/hurd/i386/libc.abilist           |   1 +
>  sysdeps/unix/sysv/linux/aarch64/libc.abilist  |   1 +
>  sysdeps/unix/sysv/linux/alpha/libc.abilist    |   1 +
>  sysdeps/unix/sysv/linux/arm/be/libc.abilist   |   1 +
>  sysdeps/unix/sysv/linux/arm/le/libc.abilist   |   1 +
>  sysdeps/unix/sysv/linux/csky/libc.abilist     |   1 +
>  sysdeps/unix/sysv/linux/execveat.c            |  54 ++++++
>  sysdeps/unix/sysv/linux/execveat_fallback.c   |  69 +++++++
>  sysdeps/unix/sysv/linux/hppa/libc.abilist     |   1 +
>  sysdeps/unix/sysv/linux/i386/libc.abilist     |   1 +
>  sysdeps/unix/sysv/linux/ia64/libc.abilist     |   1 +
>  .../sysv/linux/m68k/coldfire/libc.abilist     |   1 +
>  .../unix/sysv/linux/m68k/m680x0/libc.abilist  |   1 +
>  .../sysv/linux/microblaze/be/libc.abilist     |   1 +
>  .../sysv/linux/microblaze/le/libc.abilist     |   1 +
>  .../sysv/linux/mips/mips32/fpu/libc.abilist   |   1 +
>  .../sysv/linux/mips/mips32/nofpu/libc.abilist |   1 +
>  .../sysv/linux/mips/mips64/n32/libc.abilist   |   1 +
>  .../sysv/linux/mips/mips64/n64/libc.abilist   |   1 +
>  sysdeps/unix/sysv/linux/nios2/libc.abilist    |   1 +
>  .../linux/powerpc/powerpc32/fpu/libc.abilist  |   1 +
>  .../powerpc/powerpc32/nofpu/libc.abilist      |   1 +
>  .../linux/powerpc/powerpc64/be/libc.abilist   |   1 +
>  .../linux/powerpc/powerpc64/le/libc.abilist   |   1 +
>  .../unix/sysv/linux/riscv/rv64/libc.abilist   |   1 +
>  .../unix/sysv/linux/s390/s390-32/libc.abilist |   1 +
>  .../unix/sysv/linux/s390/s390-64/libc.abilist |   1 +
>  sysdeps/unix/sysv/linux/sh/be/libc.abilist    |   1 +
>  sysdeps/unix/sysv/linux/sh/le/libc.abilist    |   1 +
>  .../sysv/linux/sparc/sparc32/libc.abilist     |   1 +
>  .../sysv/linux/sparc/sparc64/libc.abilist     |   1 +
>  .../unix/sysv/linux/x86_64/64/libc.abilist    |   1 +
>  .../unix/sysv/linux/x86_64/x32/libc.abilist   |   1 +
>  41 files changed, 427 insertions(+), 1 deletion(-)
>  create mode 100644 posix/execveat.c
>  create mode 100644 posix/tst-execveat-compat.c
>  create mode 100644 posix/tst-execveat.c
>  create mode 100644 sysdeps/unix/sysv/linux/execveat.c
>  create mode 100644 sysdeps/unix/sysv/linux/execveat_fallback.c
> 
> diff --git a/NEWS b/NEWS
> index aa0f10a891..a61071b494 100644
> --- a/NEWS
> +++ b/NEWS
> @@ -18,6 +18,11 @@ Major new features:
>    a dump of information related to IFUNC resolver operation and
>    glibc-hwcaps subdirectory selection.
>  
> +* The function execveat has been added and it operates similar to execve.
> +  The syscall is already used to implement fexecve without requiring /proc to
> +  be mounted.  Similar to fexecve, if the syscall is not supported a fallback
> +  which access /proc is used.
> +
>  Deprecated and removed features, and other changes affecting compatibility:
>  
>    [Add deprecations, removals and changes affecting compatibility here]

Ok.

> diff --git a/include/unistd.h b/include/unistd.h
> index 54becbc9eb..2dd901ed09 100644
> --- a/include/unistd.h
> +++ b/include/unistd.h
> @@ -192,6 +192,10 @@ extern int __libc_pause (void);
>  extern int __getlogin_r_loginuid (char *name, size_t namesize)
>       attribute_hidden;
>  
> +extern int
> +__execveat_fallback (int dirfd, const char *path, char *const argv[],
> +                   char *const envp[], int flags);

Add attribute_hidden since it is an internal function.  But I think 
this is not really required, since you include the fallback file
directly on both the testcase and the execveat.c (so there is no need
of forward declaration).

> +
>  #  if IS_IN (rtld)
>  #   include <dl-unistd.h>
>  #  endif
> diff --git a/posix/Makefile b/posix/Makefile
> index be0c72f0bb..f0ebe34c8e 100644
> --- a/posix/Makefile
> +++ b/posix/Makefile
> @@ -66,7 +66,8 @@ routines :=								      \
>  	posix_madvise							      \
>  	get_child_max sched_cpucount sched_cpualloc sched_cpufree \
>  	streams-compat \
> -	shm-directory
> +	shm-directory                                                         \
> +	execveat
>  
>  aux		:= init-posix environ
>  tests		:= test-errno tstgetopt testfnm runtests runptests \

Ok.

> @@ -118,6 +119,7 @@ endif
>  
>  tests-internal	:= bug-regex5 bug-regex20 bug-regex33 \
>  		   tst-rfc3484 tst-rfc3484-2 tst-rfc3484-3
> +tests-static-internal += tst-execveat-compat
>  tests-container := bug-ga2
>  xtests		:= tst-getaddrinfo4 tst-getaddrinfo5 tst-sched_rr_get_interval
>  ifeq (yes,$(build-shared))

Ok.

> diff --git a/posix/Versions b/posix/Versions
> index cfd3819966..b77e251e00 100644
> --- a/posix/Versions
> +++ b/posix/Versions
> @@ -147,6 +147,9 @@ libc {
>    }
>    GLIBC_2.30 {
>    }
> +  GLIBC_2.34 {
> +    execveat;
> +  }
>    GLIBC_PRIVATE {
>      __libc_fork; __libc_pread; __libc_pwrite;
>      __nanosleep_nocancel; __pause_nocancel;

Ok.

> diff --git a/posix/execveat.c b/posix/execveat.c
> new file mode 100644
> index 0000000000..3f0d0820e7
> --- /dev/null
> +++ b/posix/execveat.c
> @@ -0,0 +1,41 @@
> +/* Execute program relative to a directory file descriptor.
> +   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/>.  */
> +
> +#include <errno.h>
> +#include <stddef.h>
> +#include <unistd.h>
> +
> +/* Replace the current process, executing PATH relative to DIFRD with
> + * arguments ARGV and environment ENVP.
> + * ARGV and ENVP are terminated by NULL pointers.  */
> +int
> +__execveat (int dirfd, const char *path, char *const argv[], char *const envp[],
> +            int flags)
> +{
> +  if (path == NULL || argv == NULL || envp == NULL)
> +    {
> +      __set_errno (EINVAL);
> +      return -1;
> +    }
> +
> +  __set_errno (ENOSYS);
> +  return -1;
> +}
> +stub_warning (execveat)
> +
> +weak_alias (__execveat, execveat)

Ok.

> diff --git a/posix/tst-execveat-compat.c b/posix/tst-execveat-compat.c
> new file mode 100644
> index 0000000000..082c67690d
> --- /dev/null
> +++ b/posix/tst-execveat-compat.c
> @@ -0,0 +1,32 @@
> +/* Test the fallback implementation of execveat.
> +   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
> +   <http://www.gnu.org/licenses/>.  */
> +
> +/* Get the declaration of the official execveat function.  */
> +#include <unistd.h>
> +
> +/* Compile a local version of execveat.  */
> +#include <sysdeps/unix/sysv/linux/execveat_fallback.c>
> +
> +int
> +__execveat_fallback (int dirfd, const char *path, char *const argv[],
> +                     char *const envp[], int flags);

Same as before, the protype declaration here is not required.

> +
> +/* Re-use the test, but run it against copy_file_range_compat defined
> +   above.  */
> +#define execveat execveat_fallback
> +#include "tst-execveat.c"

Move this test to be Linux-only, since the fallback is only defined
for Linux.

> diff --git a/posix/tst-execveat.c b/posix/tst-execveat.c
> new file mode 100644
> index 0000000000..52779de8cd
> --- /dev/null
> +++ b/posix/tst-execveat.c
> @@ -0,0 +1,180 @@
> +/* Test execveat at the various corner cases.
> +   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/>.  */
> +
> +#include <fcntl.h>
> +#include <errno.h>
> +#include <stdlib.h>
> +#include <sys/types.h>
> +#include <dirent.h>
> +#include <support/check.h>
> +#include <support/support.h>
> +#include <support/temp_file.h>
> +#include <support/xdlfcn.h>
> +#include <support/xstdio.h>
> +#include <support/xunistd.h>
> +#include <wait.h>
> +#include <support/test-driver.h>
> +
> +int
> +call_execveat (int fd, const char *pathname, int flags, int expected_fail,
> +               int num)
> +{
> +  char *envp[] = { (char *) "FOO=3", NULL };
> +  char *argv[] = { (char *) "sh", (char *) "-c", (char *) "exit $FOO", NULL };
> +  pid_t pid;
> +  int status;
> +
> +  if (test_verbose > 0)
> +    printf ("call line number: %d\n", num);
> +
> +  pid = xfork ();
> +  if (pid == 0)
> +    {
> +      TEST_COMPARE (execveat (fd, pathname, argv, envp, flags), -1);
> +      if (errno == ENOSYS)
> +        FAIL_UNSUPPORTED ("execveat is unimplemented");
> +      else if (errno == expected_fail)
> +        {
> +          if (test_verbose > 0)
> +            printf ("expected fail: errno %d\n", errno);
> +          _exit (0);
> +        }
> +      else
> +        FAIL_EXIT1 ("execveat failed: %m (%d)", errno);
> +    }
> +  xwaitpid (pid, &status, 0);
> +
> +  if (WIFEXITED (status))
> +    {
> +      if (WEXITSTATUS (status) == EXIT_UNSUPPORTED)
> +        FAIL_UNSUPPORTED ("execveat is unimplemented");
> +      else if (expected_fail != 0)
> +        TEST_COMPARE (WEXITSTATUS (status), 0);
> +      else
> +        TEST_COMPARE (WEXITSTATUS (status), 3);
> +    }

Also log a failure for !WIFEXITED (status).

> +  return 0;
> +}> +
> +static int
> +do_test (void)
> +{
> +  DIR *dirp;
> +  int fd, fd_out;
> +  char *tmp_dir, *symlink_name, *tmp_sh;
> +  struct stat64 st;
> +
> +  dirp = opendir ("/bin");
> +  if (dirp == NULL)
> +    FAIL_EXIT1 ("failed to open /bin");
> +  fd = dirfd (dirp);
> +
> +  /* Call execveat for various fd/pathname combinations.  */
> +
> +  /* Check the pathname relative to a valid dirfd.  */
> +  call_execveat (fd, "sh", 0, 0, __LINE__);
> +  xchdir ("/bin");
> +  /* Use the special value AT_FDCWD as dirfd. Quoting open(2):
> +     If pathname is relative and dirfd is the special value AT_FDCWD, then
> +     pathname is interpreted relative to the current working directory of
> +     the calling process.  */
> +  call_execveat (AT_FDCWD, "sh", 0, 0, __LINE__);
> +  xclose (fd);

Ok.

> +#ifdef O_PATH
> +  /* Check the pathname relative to a valid dirfd with O_PATH.  */
> +  fd = xopen ("/bin", O_PATH | O_DIRECTORY, O_RDONLY);
> +  call_execveat (fd, "sh", 0, 0, __LINE__);
> +  xclose (fd);
> +
> +  /* Check absolute pathname, dirfd should be ignored.  */
> +  call_execveat (AT_FDCWD, "/bin/sh", 0, 0, __LINE__);
> +  fd = xopen ("/usr", O_PATH | O_DIRECTORY, 0);
> +  /* Same check for absolute pathname, but with input file descriptor
> +     openend with different flags.  The dirfd should be ignored.  */
> +  call_execveat (fd, "/bin/sh", 0, 0, __LINE__);
> +  xclose (fd);

Ok.

> +#endif
> +
> +  fd = xopen ("/usr", O_RDONLY, 0);
> +  /* Same check for absolute pathname, but with input file descriptor
> +     openend with different flags.  The dirfd should be ignored.  */
> +  call_execveat (fd, "/bin/sh", 0, 0, __LINE__);
> +  xclose (fd);
> +

Ok.

> +  fd = xopen ("/bin/sh", O_RDONLY, 0);
> +  /* Check relative pathname, where dirfd does not point to a directory.  */
> +  call_execveat (fd, "sh", 0, ENOTDIR, __LINE__);
> +  /* Check absolute pathname, but dirfd is a regular file.  The dirfd
> +     should be ignored.  */
> +  call_execveat (fd, "/bin/sh", 0, 0, __LINE__);
> +  xclose (fd);
> +

Ok.

> +#ifdef O_PATH
> +  /* Quoting open(2): O_PATH
> +     Obtain a file descriptor that can be used for two purposes: to
> +     indicate a location in the filesystem tree and to perform
> +     operations that act purely at the file descriptor level.  */
> +  fd = xopen ("/bin/sh", O_PATH, 0);
> +  /* Check the empty pathname.  Dirfd is a regular file with O_PATH.  */
> +  call_execveat (fd, "", 0, ENOENT, __LINE__);

Ok.

> +  /* Same check for an empty pathname, but with AT_EMPTY_PATH flag.
> +     Quoting open(2):
> +     If oldpath is an empty string, create a link to the file referenced
> +     by olddirfd (which may have been obtained using the open(2) O_PATH flag. */
> +  call_execveat (fd, "", AT_EMPTY_PATH, 0, __LINE__);
> +  call_execveat (fd, "", AT_EMPTY_PATH | AT_SYMLINK_NOFOLLOW, 0, __LINE__);
> +  xclose (fd);
> +

Ok.

> +  /* Create a temporary directory "tmp_dir" and create a symbolik link tmp_sh
> +     pointing to /bin/sh inside the tmp_dir. Open dirfd as a symbolic link.  */

Missing double space after period.

> +  tmp_dir = support_create_temp_directory ("tst-execveat_dir");
> +  symlink_name = xasprintf ("%s/symlink", tmp_dir);
> +  xsymlink ("tmp_sh", symlink_name);
> +  add_temp_file (symlink_name);
> +  tmp_sh = xasprintf ("%s/tmp_sh", tmp_dir);
> +  add_temp_file (tmp_sh);
> +  fd_out = xopen (symlink_name, O_CREAT | O_WRONLY, 0);
> +  xstat ("/bin/sh", &st);
> +  fd = xopen ("/bin/sh", O_RDONLY, 0);
> +  xcopy_file_range (fd, 0, fd_out, 0, st.st_size, 0);
> +  xfchmod (fd_out, 0700);
> +  xclose (fd);
> +  xclose (fd_out);
> +  fd_out = xopen (symlink_name, O_PATH, 0);
> +
> + /* Check the empty pathname. Dirfd is a symbolic link.  */
> +  call_execveat (fd_out, "", 0, ENOENT, __LINE__);
> +  call_execveat (fd_out, "", AT_EMPTY_PATH, 0, __LINE__);
> +  call_execveat (fd_out, "", AT_EMPTY_PATH | AT_SYMLINK_NOFOLLOW, 0,
> +                 __LINE__);
> +  xclose (fd_out);
> +  free (symlink_name);
> +  free (tmp_sh);
> +  free (tmp_dir);

Ok.

> +#endif
> +
> +  /* Call execveat with closed fd, we expect this to fail with EBADF.  */
> +  call_execveat (fd, "sh", 0, EBADF, __LINE__);
> +  /* Call execveat with closed fd, we expect this to pass because the pathname is
> +     absolute.  */
> +  call_execveat (fd, "/bin/sh", 0, 0, __LINE__);
> +
> +  return 0;
> +}
> +
> +#include <support/test-driver.c>

Ok.

> diff --git a/posix/unistd.h b/posix/unistd.h
> index 3f22763379..d9d8929f71 100644
> --- a/posix/unistd.h
> +++ b/posix/unistd.h
> @@ -295,6 +295,11 @@ extern int euidaccess (const char *__name, int __type)
>  /* An alias for `euidaccess', used by some other systems.  */
>  extern int eaccess (const char *__name, int __type)
>       __THROW __nonnull ((1));
> +
> +/* Execute program relative to a directory file descriptor.  */
> +extern int execveat (int __fd, const char *__path, char *const __argv[],
> +                     char *const __envp[], int __flags)
> +    __THROW __nonnull ((2, 3));
>  #endif
>  
>  #ifdef __USE_ATFILE

Ok.

> diff --git a/sysdeps/mach/hurd/i386/libc.abilist b/sysdeps/mach/hurd/i386/libc.abilist
> index e10a286d2e..bef66d105c 100644
> --- a/sysdeps/mach/hurd/i386/libc.abilist
> +++ b/sysdeps/mach/hurd/i386/libc.abilist
> @@ -2204,6 +2204,7 @@ GLIBC_2.33 mknodat F
>  GLIBC_2.33 stat F
>  GLIBC_2.33 stat64 F
>  GLIBC_2.34 __libc_start_main F
> +GLIBC_2.34 execveat F
>  GLIBC_2.4 __confstr_chk F
>  GLIBC_2.4 __fgets_chk F
>  GLIBC_2.4 __fgets_unlocked_chk F
> diff --git a/sysdeps/unix/sysv/linux/aarch64/libc.abilist b/sysdeps/unix/sysv/linux/aarch64/libc.abilist
> index bac795262d..51f34d0f6d 100644
> --- a/sysdeps/unix/sysv/linux/aarch64/libc.abilist
> +++ b/sysdeps/unix/sysv/linux/aarch64/libc.abilist
> @@ -2172,3 +2172,4 @@ GLIBC_2.33 mknodat F
>  GLIBC_2.33 stat F
>  GLIBC_2.33 stat64 F
>  GLIBC_2.34 __libc_start_main F
> +GLIBC_2.34 execveat F
> diff --git a/sysdeps/unix/sysv/linux/alpha/libc.abilist b/sysdeps/unix/sysv/linux/alpha/libc.abilist
> index 897f70db22..7da53174ef 100644
> --- a/sysdeps/unix/sysv/linux/alpha/libc.abilist
> +++ b/sysdeps/unix/sysv/linux/alpha/libc.abilist
> @@ -2254,6 +2254,7 @@ GLIBC_2.33 mknodat F
>  GLIBC_2.33 stat F
>  GLIBC_2.33 stat64 F
>  GLIBC_2.34 __libc_start_main F
> +GLIBC_2.34 execveat F
>  GLIBC_2.4 _IO_fprintf F
>  GLIBC_2.4 _IO_printf F
>  GLIBC_2.4 _IO_sprintf F
> diff --git a/sysdeps/unix/sysv/linux/arm/be/libc.abilist b/sysdeps/unix/sysv/linux/arm/be/libc.abilist
> index 094236f713..108c41ae24 100644
> --- a/sysdeps/unix/sysv/linux/arm/be/libc.abilist
> +++ b/sysdeps/unix/sysv/linux/arm/be/libc.abilist
> @@ -156,6 +156,7 @@ GLIBC_2.33 mknodat F
>  GLIBC_2.33 stat F
>  GLIBC_2.33 stat64 F
>  GLIBC_2.34 __libc_start_main F
> +GLIBC_2.34 execveat F
>  GLIBC_2.4 _Exit F
>  GLIBC_2.4 _IO_2_1_stderr_ D 0xa0
>  GLIBC_2.4 _IO_2_1_stdin_ D 0xa0
> diff --git a/sysdeps/unix/sysv/linux/arm/le/libc.abilist b/sysdeps/unix/sysv/linux/arm/le/libc.abilist
> index 2bb4d31e81..a995a356a4 100644
> --- a/sysdeps/unix/sysv/linux/arm/le/libc.abilist
> +++ b/sysdeps/unix/sysv/linux/arm/le/libc.abilist
> @@ -153,6 +153,7 @@ GLIBC_2.33 mknodat F
>  GLIBC_2.33 stat F
>  GLIBC_2.33 stat64 F
>  GLIBC_2.34 __libc_start_main F
> +GLIBC_2.34 execveat F
>  GLIBC_2.4 _Exit F
>  GLIBC_2.4 _IO_2_1_stderr_ D 0xa0
>  GLIBC_2.4 _IO_2_1_stdin_ D 0xa0
> diff --git a/sysdeps/unix/sysv/linux/csky/libc.abilist b/sysdeps/unix/sysv/linux/csky/libc.abilist
> index d4291fecfb..33d0dfb2b7 100644
> --- a/sysdeps/unix/sysv/linux/csky/libc.abilist
> +++ b/sysdeps/unix/sysv/linux/csky/libc.abilist
> @@ -2116,3 +2116,4 @@ GLIBC_2.33 mknodat F
>  GLIBC_2.33 stat F
>  GLIBC_2.33 stat64 F
>  GLIBC_2.34 __libc_start_main F
> +GLIBC_2.34 execveat F

Ok.

> diff --git a/sysdeps/unix/sysv/linux/execveat.c b/sysdeps/unix/sysv/linux/execveat.c
> new file mode 100644
> index 0000000000..0576f36b98
> --- /dev/null
> +++ b/sysdeps/unix/sysv/linux/execveat.c
> @@ -0,0 +1,54 @@
> +/* Execute program relative to a directory file descriptor.
> +   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/>.  */
> +
> +#include <errno.h>
> +#include <stddef.h>
> +#include <stdio.h>
> +#include <unistd.h>
> +#include <fcntl.h>
> +#include <sys/stat.h>
> +
> +#include <sysdep.h>
> +#include <sys/syscall.h>
> +#include <kernel-features.h>
> +#include <fd_to_filename.h>
> +#include <not-cancel.h>

Add a space here to outline that the execveat_fallback is not an header
(although this is not really a code guideline enforcement).

> +#ifndef __ASSUME_EXECVEAT
> +# include "execveat_fallback.c"
> +#endif
> +
> +/* Execute the file FD refers to, overlaying the running program image.
> +   ARGV and ENVP are passed to the new program, as for `execve'.  */
> +int
> +execveat (int dirfd, const char *path, char *const argv[], char *const envp[],
> +          int flags)
> +{
> +  /* Avoid implicit array coercion in syscall macros.  */
> +    INLINE_SYSCALL_CALL (execveat, dirfd, path, &argv[0], &envp[0], flags);
> +#ifndef __ASSUME_EXECVEAT
> +  if (errno != ENOSYS)
> +    return -1;
> +
> +  if ((flags & ~(AT_EMPTY_PATH | AT_SYMLINK_NOFOLLOW)) != 0)
> +      return INLINE_SYSCALL_ERROR_RETURN_VALUE (EINVAL);
> +
> +  return __execveat_fallback (dirfd, path, argv, envp, flags);
> +#endif
> +
> +  return -1;
> +}

Ok.

> diff --git a/sysdeps/unix/sysv/linux/execveat_fallback.c b/sysdeps/unix/sysv/linux/execveat_fallback.c
> new file mode 100644
> index 0000000000..c4a37d3799
> --- /dev/null
> +++ b/sysdeps/unix/sysv/linux/execveat_fallback.c
> @@ -0,0 +1,69 @@
> +/* Execute program relative to a directory file descriptor.
> +   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/>.  */
> +
> +#include <errno.h>
> +#include <stddef.h>
> +#include <stdio.h>
> +#include <unistd.h>
> +#include <fcntl.h>
> +#include <sys/stat.h>
> +
> +#include <sysdep.h>
> +#include <sys/syscall.h>
> +#include <kernel-features.h>
> +#include <fd_to_filename.h>
> +#include <not-cancel.h>
> +
> +int
> +__execveat_fallback (int dirfd, const char *path, char *const argv[],
> +                   char *const envp[], int flags)
> +{
> +    int fd;
> +
> +    if (path[0] == '\0' && (flags & AT_EMPTY_PATH) && dirfd >= 0)
> +        fd = dirfd;
> +    else
> +    {
> +        int oflags = O_CLOEXEC;
> +        if (flags & AT_SYMLINK_NOFOLLOW)
> +            oflags |= O_NOFOLLOW;
> +        fd = __openat_nocancel (dirfd, path, oflags);
> +    }
> +    if (fd < 0)
> +        return INLINE_SYSCALL_ERROR_RETURN_VALUE (EBADFD);

Wrong indentation (4 space instead of 2) and open bracket should have a
space:

  if (....)
    fd = ...
  else
    {
      ...
    }

This also applies to the rest of the file.

> +
> +    struct fd_to_filename fdfilename;
> +    const char *gfilename = __fd_to_filename (fd, &fdfilename);
> +
> +    /* We do not need the return value.  */
> +    __execve (gfilename, argv, envp);
> +
> +    int save = errno;
> +
> +    /* We come here only if the 'execve' call fails.  Determine whether
> +       /proc is mounted.  If not we return ENOSYS.  */
> +    struct stat64 st;
> +    if (__stat64 (FD_TO_FILENAME_PREFIX, &st) != 0 && errno == ENOENT)
> +        save = ENOSYS;
> +
> +    if (fd != dirfd)
> +        __close_nocancel_nostatus (fd);
> +    __set_errno (save);
> +
> +    return -1;
> +}

Ok.

> diff --git a/sysdeps/unix/sysv/linux/hppa/libc.abilist b/sysdeps/unix/sysv/linux/hppa/libc.abilist
> index 1fd2a862f6..e1430bb232 100644
> --- a/sysdeps/unix/sysv/linux/hppa/libc.abilist
> +++ b/sysdeps/unix/sysv/linux/hppa/libc.abilist
> @@ -2075,6 +2075,7 @@ GLIBC_2.33 mknodat F
>  GLIBC_2.33 stat F
>  GLIBC_2.33 stat64 F
>  GLIBC_2.34 __libc_start_main F
> +GLIBC_2.34 execveat F
>  GLIBC_2.4 __confstr_chk F
>  GLIBC_2.4 __fgets_chk F
>  GLIBC_2.4 __fgets_unlocked_chk F
> diff --git a/sysdeps/unix/sysv/linux/i386/libc.abilist b/sysdeps/unix/sysv/linux/i386/libc.abilist
> index 943331f01e..7cb2d0dd6d 100644
> --- a/sysdeps/unix/sysv/linux/i386/libc.abilist
> +++ b/sysdeps/unix/sysv/linux/i386/libc.abilist
> @@ -2242,6 +2242,7 @@ GLIBC_2.33 mknodat F
>  GLIBC_2.33 stat F
>  GLIBC_2.33 stat64 F
>  GLIBC_2.34 __libc_start_main F
> +GLIBC_2.34 execveat F
>  GLIBC_2.4 __confstr_chk F
>  GLIBC_2.4 __fgets_chk F
>  GLIBC_2.4 __fgets_unlocked_chk F
> diff --git a/sysdeps/unix/sysv/linux/ia64/libc.abilist b/sysdeps/unix/sysv/linux/ia64/libc.abilist
> index f530151bde..2171cd3cb2 100644
> --- a/sysdeps/unix/sysv/linux/ia64/libc.abilist
> +++ b/sysdeps/unix/sysv/linux/ia64/libc.abilist
> @@ -2107,6 +2107,7 @@ GLIBC_2.33 mknodat F
>  GLIBC_2.33 stat F
>  GLIBC_2.33 stat64 F
>  GLIBC_2.34 __libc_start_main F
> +GLIBC_2.34 execveat F
>  GLIBC_2.4 __confstr_chk F
>  GLIBC_2.4 __fgets_chk F
>  GLIBC_2.4 __fgets_unlocked_chk F
> diff --git a/sysdeps/unix/sysv/linux/m68k/coldfire/libc.abilist b/sysdeps/unix/sysv/linux/m68k/coldfire/libc.abilist
> index 6e76b6dcaa..388eb76abf 100644
> --- a/sysdeps/unix/sysv/linux/m68k/coldfire/libc.abilist
> +++ b/sysdeps/unix/sysv/linux/m68k/coldfire/libc.abilist
> @@ -157,6 +157,7 @@ GLIBC_2.33 mknodat F
>  GLIBC_2.33 stat F
>  GLIBC_2.33 stat64 F
>  GLIBC_2.34 __libc_start_main F
> +GLIBC_2.34 execveat F
>  GLIBC_2.4 _Exit F
>  GLIBC_2.4 _IO_2_1_stderr_ D 0x98
>  GLIBC_2.4 _IO_2_1_stdin_ D 0x98
> diff --git a/sysdeps/unix/sysv/linux/m68k/m680x0/libc.abilist b/sysdeps/unix/sysv/linux/m68k/m680x0/libc.abilist
> index 7541b8289f..067ed53f2b 100644
> --- a/sysdeps/unix/sysv/linux/m68k/m680x0/libc.abilist
> +++ b/sysdeps/unix/sysv/linux/m68k/m680x0/libc.abilist
> @@ -2187,6 +2187,7 @@ GLIBC_2.33 mknodat F
>  GLIBC_2.33 stat F
>  GLIBC_2.33 stat64 F
>  GLIBC_2.34 __libc_start_main F
> +GLIBC_2.34 execveat F
>  GLIBC_2.4 __confstr_chk F
>  GLIBC_2.4 __fgets_chk F
>  GLIBC_2.4 __fgets_unlocked_chk F
> diff --git a/sysdeps/unix/sysv/linux/microblaze/be/libc.abilist b/sysdeps/unix/sysv/linux/microblaze/be/libc.abilist
> index 6cf1936c42..a792461b45 100644
> --- a/sysdeps/unix/sysv/linux/microblaze/be/libc.abilist
> +++ b/sysdeps/unix/sysv/linux/microblaze/be/libc.abilist
> @@ -2167,3 +2167,4 @@ GLIBC_2.33 mknodat F
>  GLIBC_2.33 stat F
>  GLIBC_2.33 stat64 F
>  GLIBC_2.34 __libc_start_main F
> +GLIBC_2.34 execveat F
> diff --git a/sysdeps/unix/sysv/linux/microblaze/le/libc.abilist b/sysdeps/unix/sysv/linux/microblaze/le/libc.abilist
> index 98730ebcda..0e09fe6322 100644
> --- a/sysdeps/unix/sysv/linux/microblaze/le/libc.abilist
> +++ b/sysdeps/unix/sysv/linux/microblaze/le/libc.abilist
> @@ -2164,3 +2164,4 @@ GLIBC_2.33 mknodat F
>  GLIBC_2.33 stat F
>  GLIBC_2.33 stat64 F
>  GLIBC_2.34 __libc_start_main F
> +GLIBC_2.34 execveat F
> diff --git a/sysdeps/unix/sysv/linux/mips/mips32/fpu/libc.abilist b/sysdeps/unix/sysv/linux/mips/mips32/fpu/libc.abilist
> index 92fa6cbc73..5d1b0b3d78 100644
> --- a/sysdeps/unix/sysv/linux/mips/mips32/fpu/libc.abilist
> +++ b/sysdeps/unix/sysv/linux/mips/mips32/fpu/libc.abilist
> @@ -2158,6 +2158,7 @@ GLIBC_2.33 mknodat F
>  GLIBC_2.33 stat F
>  GLIBC_2.33 stat64 F
>  GLIBC_2.34 __libc_start_main F
> +GLIBC_2.34 execveat F
>  GLIBC_2.4 __confstr_chk F
>  GLIBC_2.4 __fgets_chk F
>  GLIBC_2.4 __fgets_unlocked_chk F
> diff --git a/sysdeps/unix/sysv/linux/mips/mips32/nofpu/libc.abilist b/sysdeps/unix/sysv/linux/mips/mips32/nofpu/libc.abilist
> index 265a49e74e..a278c0a092 100644
> --- a/sysdeps/unix/sysv/linux/mips/mips32/nofpu/libc.abilist
> +++ b/sysdeps/unix/sysv/linux/mips/mips32/nofpu/libc.abilist
> @@ -2156,6 +2156,7 @@ GLIBC_2.33 mknodat F
>  GLIBC_2.33 stat F
>  GLIBC_2.33 stat64 F
>  GLIBC_2.34 __libc_start_main F
> +GLIBC_2.34 execveat F
>  GLIBC_2.4 __confstr_chk F
>  GLIBC_2.4 __fgets_chk F
>  GLIBC_2.4 __fgets_unlocked_chk F
> diff --git a/sysdeps/unix/sysv/linux/mips/mips64/n32/libc.abilist b/sysdeps/unix/sysv/linux/mips/mips64/n32/libc.abilist
> index cfa5e1111b..054d3436eb 100644
> --- a/sysdeps/unix/sysv/linux/mips/mips64/n32/libc.abilist
> +++ b/sysdeps/unix/sysv/linux/mips/mips64/n32/libc.abilist
> @@ -2164,6 +2164,7 @@ GLIBC_2.33 mknodat F
>  GLIBC_2.33 stat F
>  GLIBC_2.33 stat64 F
>  GLIBC_2.34 __libc_start_main F
> +GLIBC_2.34 execveat F
>  GLIBC_2.4 __confstr_chk F
>  GLIBC_2.4 __fgets_chk F
>  GLIBC_2.4 __fgets_unlocked_chk F
> diff --git a/sysdeps/unix/sysv/linux/mips/mips64/n64/libc.abilist b/sysdeps/unix/sysv/linux/mips/mips64/n64/libc.abilist
> index 8c03ac52cd..c22ef9f196 100644
> --- a/sysdeps/unix/sysv/linux/mips/mips64/n64/libc.abilist
> +++ b/sysdeps/unix/sysv/linux/mips/mips64/n64/libc.abilist
> @@ -2158,6 +2158,7 @@ GLIBC_2.33 mknodat F
>  GLIBC_2.33 stat F
>  GLIBC_2.33 stat64 F
>  GLIBC_2.34 __libc_start_main F
> +GLIBC_2.34 execveat F
>  GLIBC_2.4 __confstr_chk F
>  GLIBC_2.4 __fgets_chk F
>  GLIBC_2.4 __fgets_unlocked_chk F
> diff --git a/sysdeps/unix/sysv/linux/nios2/libc.abilist b/sysdeps/unix/sysv/linux/nios2/libc.abilist
> index 17f5609e06..c356e9f863 100644
> --- a/sysdeps/unix/sysv/linux/nios2/libc.abilist
> +++ b/sysdeps/unix/sysv/linux/nios2/libc.abilist
> @@ -2205,3 +2205,4 @@ GLIBC_2.33 mknodat F
>  GLIBC_2.33 stat F
>  GLIBC_2.33 stat64 F
>  GLIBC_2.34 __libc_start_main F
> +GLIBC_2.34 execveat F
> diff --git a/sysdeps/unix/sysv/linux/powerpc/powerpc32/fpu/libc.abilist b/sysdeps/unix/sysv/linux/powerpc/powerpc32/fpu/libc.abilist
> index 76a16e2a6d..d1de01f91d 100644
> --- a/sysdeps/unix/sysv/linux/powerpc/powerpc32/fpu/libc.abilist
> +++ b/sysdeps/unix/sysv/linux/powerpc/powerpc32/fpu/libc.abilist
> @@ -2214,6 +2214,7 @@ GLIBC_2.33 mknodat F
>  GLIBC_2.33 stat F
>  GLIBC_2.33 stat64 F
>  GLIBC_2.34 __libc_start_main F
> +GLIBC_2.34 execveat F
>  GLIBC_2.4 _IO_fprintf F
>  GLIBC_2.4 _IO_printf F
>  GLIBC_2.4 _IO_sprintf F
> diff --git a/sysdeps/unix/sysv/linux/powerpc/powerpc32/nofpu/libc.abilist b/sysdeps/unix/sysv/linux/powerpc/powerpc32/nofpu/libc.abilist
> index 697f072fd4..a1d52887bb 100644
> --- a/sysdeps/unix/sysv/linux/powerpc/powerpc32/nofpu/libc.abilist
> +++ b/sysdeps/unix/sysv/linux/powerpc/powerpc32/nofpu/libc.abilist
> @@ -2247,6 +2247,7 @@ GLIBC_2.33 mknodat F
>  GLIBC_2.33 stat F
>  GLIBC_2.33 stat64 F
>  GLIBC_2.34 __libc_start_main F
> +GLIBC_2.34 execveat F
>  GLIBC_2.4 _IO_fprintf F
>  GLIBC_2.4 _IO_printf F
>  GLIBC_2.4 _IO_sprintf F
> diff --git a/sysdeps/unix/sysv/linux/powerpc/powerpc64/be/libc.abilist b/sysdeps/unix/sysv/linux/powerpc/powerpc64/be/libc.abilist
> index 2647bb51f1..10cdabb11c 100644
> --- a/sysdeps/unix/sysv/linux/powerpc/powerpc64/be/libc.abilist
> +++ b/sysdeps/unix/sysv/linux/powerpc/powerpc64/be/libc.abilist
> @@ -2077,6 +2077,7 @@ GLIBC_2.33 mknodat F
>  GLIBC_2.33 stat F
>  GLIBC_2.33 stat64 F
>  GLIBC_2.34 __libc_start_main F
> +GLIBC_2.34 execveat F
>  GLIBC_2.4 _IO_fprintf F
>  GLIBC_2.4 _IO_printf F
>  GLIBC_2.4 _IO_sprintf F
> diff --git a/sysdeps/unix/sysv/linux/powerpc/powerpc64/le/libc.abilist b/sysdeps/unix/sysv/linux/powerpc/powerpc64/le/libc.abilist
> index 036b1c8345..70792ed87b 100644
> --- a/sysdeps/unix/sysv/linux/powerpc/powerpc64/le/libc.abilist
> +++ b/sysdeps/unix/sysv/linux/powerpc/powerpc64/le/libc.abilist
> @@ -2367,3 +2367,4 @@ GLIBC_2.33 mknodat F
>  GLIBC_2.33 stat F
>  GLIBC_2.33 stat64 F
>  GLIBC_2.34 __libc_start_main F
> +GLIBC_2.34 execveat F
> diff --git a/sysdeps/unix/sysv/linux/riscv/rv64/libc.abilist b/sysdeps/unix/sysv/linux/riscv/rv64/libc.abilist
> index fb5ad9909f..9b71083136 100644
> --- a/sysdeps/unix/sysv/linux/riscv/rv64/libc.abilist
> +++ b/sysdeps/unix/sysv/linux/riscv/rv64/libc.abilist
> @@ -2134,3 +2134,4 @@ GLIBC_2.33 mknodat F
>  GLIBC_2.33 stat F
>  GLIBC_2.33 stat64 F
>  GLIBC_2.34 __libc_start_main F
> +GLIBC_2.34 execveat F
> diff --git a/sysdeps/unix/sysv/linux/s390/s390-32/libc.abilist b/sysdeps/unix/sysv/linux/s390/s390-32/libc.abilist
> index cead75acc5..aba76fbadd 100644
> --- a/sysdeps/unix/sysv/linux/s390/s390-32/libc.abilist
> +++ b/sysdeps/unix/sysv/linux/s390/s390-32/libc.abilist
> @@ -2212,6 +2212,7 @@ GLIBC_2.33 mknodat F
>  GLIBC_2.33 stat F
>  GLIBC_2.33 stat64 F
>  GLIBC_2.34 __libc_start_main F
> +GLIBC_2.34 execveat F
>  GLIBC_2.4 _IO_fprintf F
>  GLIBC_2.4 _IO_printf F
>  GLIBC_2.4 _IO_sprintf F
> diff --git a/sysdeps/unix/sysv/linux/s390/s390-64/libc.abilist b/sysdeps/unix/sysv/linux/s390/s390-64/libc.abilist
> index 31366dd7e6..6a5a765f4b 100644
> --- a/sysdeps/unix/sysv/linux/s390/s390-64/libc.abilist
> +++ b/sysdeps/unix/sysv/linux/s390/s390-64/libc.abilist
> @@ -2113,6 +2113,7 @@ GLIBC_2.33 mknodat F
>  GLIBC_2.33 stat F
>  GLIBC_2.33 stat64 F
>  GLIBC_2.34 __libc_start_main F
> +GLIBC_2.34 execveat F
>  GLIBC_2.4 _IO_fprintf F
>  GLIBC_2.4 _IO_printf F
>  GLIBC_2.4 _IO_sprintf F
> diff --git a/sysdeps/unix/sysv/linux/sh/be/libc.abilist b/sysdeps/unix/sysv/linux/sh/be/libc.abilist
> index a3a8be8910..b6629c244f 100644
> --- a/sysdeps/unix/sysv/linux/sh/be/libc.abilist
> +++ b/sysdeps/unix/sysv/linux/sh/be/libc.abilist
> @@ -2082,6 +2082,7 @@ GLIBC_2.33 mknodat F
>  GLIBC_2.33 stat F
>  GLIBC_2.33 stat64 F
>  GLIBC_2.34 __libc_start_main F
> +GLIBC_2.34 execveat F
>  GLIBC_2.4 __confstr_chk F
>  GLIBC_2.4 __fgets_chk F
>  GLIBC_2.4 __fgets_unlocked_chk F
> diff --git a/sysdeps/unix/sysv/linux/sh/le/libc.abilist b/sysdeps/unix/sysv/linux/sh/le/libc.abilist
> index 8f505c5045..e15ab4c569 100644
> --- a/sysdeps/unix/sysv/linux/sh/le/libc.abilist
> +++ b/sysdeps/unix/sysv/linux/sh/le/libc.abilist
> @@ -2079,6 +2079,7 @@ GLIBC_2.33 mknodat F
>  GLIBC_2.33 stat F
>  GLIBC_2.33 stat64 F
>  GLIBC_2.34 __libc_start_main F
> +GLIBC_2.34 execveat F
>  GLIBC_2.4 __confstr_chk F
>  GLIBC_2.4 __fgets_chk F
>  GLIBC_2.4 __fgets_unlocked_chk F
> diff --git a/sysdeps/unix/sysv/linux/sparc/sparc32/libc.abilist b/sysdeps/unix/sysv/linux/sparc/sparc32/libc.abilist
> index 53ef6304f1..11cad082d8 100644
> --- a/sysdeps/unix/sysv/linux/sparc/sparc32/libc.abilist
> +++ b/sysdeps/unix/sysv/linux/sparc/sparc32/libc.abilist
> @@ -2203,6 +2203,7 @@ GLIBC_2.33 mknodat F
>  GLIBC_2.33 stat F
>  GLIBC_2.33 stat64 F
>  GLIBC_2.34 __libc_start_main F
> +GLIBC_2.34 execveat F
>  GLIBC_2.4 _IO_fprintf F
>  GLIBC_2.4 _IO_printf F
>  GLIBC_2.4 _IO_sprintf F
> diff --git a/sysdeps/unix/sysv/linux/sparc/sparc64/libc.abilist b/sysdeps/unix/sysv/linux/sparc/sparc64/libc.abilist
> index eba0cb156d..0ff8cb8739 100644
> --- a/sysdeps/unix/sysv/linux/sparc/sparc64/libc.abilist
> +++ b/sysdeps/unix/sysv/linux/sparc/sparc64/libc.abilist
> @@ -2130,6 +2130,7 @@ GLIBC_2.33 mknodat F
>  GLIBC_2.33 stat F
>  GLIBC_2.33 stat64 F
>  GLIBC_2.34 __libc_start_main F
> +GLIBC_2.34 execveat F
>  GLIBC_2.4 __confstr_chk F
>  GLIBC_2.4 __fgets_chk F
>  GLIBC_2.4 __fgets_unlocked_chk F
> diff --git a/sysdeps/unix/sysv/linux/x86_64/64/libc.abilist b/sysdeps/unix/sysv/linux/x86_64/64/libc.abilist
> index 17ce5dfd58..040d44d3a8 100644
> --- a/sysdeps/unix/sysv/linux/x86_64/64/libc.abilist
> +++ b/sysdeps/unix/sysv/linux/x86_64/64/libc.abilist
> @@ -2089,6 +2089,7 @@ GLIBC_2.33 mknodat F
>  GLIBC_2.33 stat F
>  GLIBC_2.33 stat64 F
>  GLIBC_2.34 __libc_start_main F
> +GLIBC_2.34 execveat F
>  GLIBC_2.4 __confstr_chk F
>  GLIBC_2.4 __fgets_chk F
>  GLIBC_2.4 __fgets_unlocked_chk F
> diff --git a/sysdeps/unix/sysv/linux/x86_64/x32/libc.abilist b/sysdeps/unix/sysv/linux/x86_64/x32/libc.abilist
> index 17a1c83903..4355e06891 100644
> --- a/sysdeps/unix/sysv/linux/x86_64/x32/libc.abilist
> +++ b/sysdeps/unix/sysv/linux/x86_64/x32/libc.abilist
> @@ -2186,3 +2186,4 @@ GLIBC_2.33 mknodat F
>  GLIBC_2.33 stat F
>  GLIBC_2.33 stat64 F
>  GLIBC_2.34 __libc_start_main F
> +GLIBC_2.34 execveat F

It misses the abifile update for arc-linux-gnu{hf} and risc32-linux-gnu-rv32*
Alexandra Hájková April 2, 2021, 12:13 p.m. UTC | #2
Thank you for the review.

> > +  if (WIFEXITED (status))
> > +    {
> > +      if (WEXITSTATUS (status) == EXIT_UNSUPPORTED)
> > +        FAIL_UNSUPPORTED ("execveat is unimplemented");
> > +      else if (expected_fail != 0)
Isn't comparing WEXITSTATUS (status) with 0 sufficient?
> > +        TEST_COMPARE (WEXITSTATUS (status), 0);
> > +      else
> > +        TEST_COMPARE (WEXITSTATUS (status), 3);
> > +    }
>
> Also log a failure for !WIFEXITED (status).

Thank you,
Alexandra
Adhemerval Zanella April 2, 2021, 1:29 p.m. UTC | #3
On 02/04/2021 09:13, Alexandra Hájková wrote:
> Thank you for the review.
> 
>>> +  if (WIFEXITED (status))
>>> +    {
>>> +      if (WEXITSTATUS (status) == EXIT_UNSUPPORTED)
>>> +        FAIL_UNSUPPORTED ("execveat is unimplemented");
>>> +      else if (expected_fail != 0)
> Isn't comparing WEXITSTATUS (status) with 0 sufficient?

It just to handle possible return code due signaling or other possible
value, similar to what support/support_capture_subprocess_check.c does.

>>> +        TEST_COMPARE (WEXITSTATUS (status), 0);
>>> +      else
>>> +        TEST_COMPARE (WEXITSTATUS (status), 3);
>>> +    }
>>
>> Also log a failure for !WIFEXITED (status).
diff mbox series

Patch

diff --git a/NEWS b/NEWS
index aa0f10a891..a61071b494 100644
--- a/NEWS
+++ b/NEWS
@@ -18,6 +18,11 @@  Major new features:
   a dump of information related to IFUNC resolver operation and
   glibc-hwcaps subdirectory selection.
 
+* The function execveat has been added and it operates similar to execve.
+  The syscall is already used to implement fexecve without requiring /proc to
+  be mounted.  Similar to fexecve, if the syscall is not supported a fallback
+  which access /proc is used.
+
 Deprecated and removed features, and other changes affecting compatibility:
 
   [Add deprecations, removals and changes affecting compatibility here]
diff --git a/include/unistd.h b/include/unistd.h
index 54becbc9eb..2dd901ed09 100644
--- a/include/unistd.h
+++ b/include/unistd.h
@@ -192,6 +192,10 @@  extern int __libc_pause (void);
 extern int __getlogin_r_loginuid (char *name, size_t namesize)
      attribute_hidden;
 
+extern int
+__execveat_fallback (int dirfd, const char *path, char *const argv[],
+                   char *const envp[], int flags);
+
 #  if IS_IN (rtld)
 #   include <dl-unistd.h>
 #  endif
diff --git a/posix/Makefile b/posix/Makefile
index be0c72f0bb..f0ebe34c8e 100644
--- a/posix/Makefile
+++ b/posix/Makefile
@@ -66,7 +66,8 @@  routines :=								      \
 	posix_madvise							      \
 	get_child_max sched_cpucount sched_cpualloc sched_cpufree \
 	streams-compat \
-	shm-directory
+	shm-directory                                                         \
+	execveat
 
 aux		:= init-posix environ
 tests		:= test-errno tstgetopt testfnm runtests runptests \
@@ -118,6 +119,7 @@  endif
 
 tests-internal	:= bug-regex5 bug-regex20 bug-regex33 \
 		   tst-rfc3484 tst-rfc3484-2 tst-rfc3484-3
+tests-static-internal += tst-execveat-compat
 tests-container := bug-ga2
 xtests		:= tst-getaddrinfo4 tst-getaddrinfo5 tst-sched_rr_get_interval
 ifeq (yes,$(build-shared))
diff --git a/posix/Versions b/posix/Versions
index cfd3819966..b77e251e00 100644
--- a/posix/Versions
+++ b/posix/Versions
@@ -147,6 +147,9 @@  libc {
   }
   GLIBC_2.30 {
   }
+  GLIBC_2.34 {
+    execveat;
+  }
   GLIBC_PRIVATE {
     __libc_fork; __libc_pread; __libc_pwrite;
     __nanosleep_nocancel; __pause_nocancel;
diff --git a/posix/execveat.c b/posix/execveat.c
new file mode 100644
index 0000000000..3f0d0820e7
--- /dev/null
+++ b/posix/execveat.c
@@ -0,0 +1,41 @@ 
+/* Execute program relative to a directory file descriptor.
+   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/>.  */
+
+#include <errno.h>
+#include <stddef.h>
+#include <unistd.h>
+
+/* Replace the current process, executing PATH relative to DIFRD with
+ * arguments ARGV and environment ENVP.
+ * ARGV and ENVP are terminated by NULL pointers.  */
+int
+__execveat (int dirfd, const char *path, char *const argv[], char *const envp[],
+            int flags)
+{
+  if (path == NULL || argv == NULL || envp == NULL)
+    {
+      __set_errno (EINVAL);
+      return -1;
+    }
+
+  __set_errno (ENOSYS);
+  return -1;
+}
+stub_warning (execveat)
+
+weak_alias (__execveat, execveat)
diff --git a/posix/tst-execveat-compat.c b/posix/tst-execveat-compat.c
new file mode 100644
index 0000000000..082c67690d
--- /dev/null
+++ b/posix/tst-execveat-compat.c
@@ -0,0 +1,32 @@ 
+/* Test the fallback implementation of execveat.
+   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
+   <http://www.gnu.org/licenses/>.  */
+
+/* Get the declaration of the official execveat function.  */
+#include <unistd.h>
+
+/* Compile a local version of execveat.  */
+#include <sysdeps/unix/sysv/linux/execveat_fallback.c>
+
+int
+__execveat_fallback (int dirfd, const char *path, char *const argv[],
+                     char *const envp[], int flags);
+
+/* Re-use the test, but run it against copy_file_range_compat defined
+   above.  */
+#define execveat execveat_fallback
+#include "tst-execveat.c"
diff --git a/posix/tst-execveat.c b/posix/tst-execveat.c
new file mode 100644
index 0000000000..52779de8cd
--- /dev/null
+++ b/posix/tst-execveat.c
@@ -0,0 +1,180 @@ 
+/* Test execveat at the various corner cases.
+   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/>.  */
+
+#include <fcntl.h>
+#include <errno.h>
+#include <stdlib.h>
+#include <sys/types.h>
+#include <dirent.h>
+#include <support/check.h>
+#include <support/support.h>
+#include <support/temp_file.h>
+#include <support/xdlfcn.h>
+#include <support/xstdio.h>
+#include <support/xunistd.h>
+#include <wait.h>
+#include <support/test-driver.h>
+
+int
+call_execveat (int fd, const char *pathname, int flags, int expected_fail,
+               int num)
+{
+  char *envp[] = { (char *) "FOO=3", NULL };
+  char *argv[] = { (char *) "sh", (char *) "-c", (char *) "exit $FOO", NULL };
+  pid_t pid;
+  int status;
+
+  if (test_verbose > 0)
+    printf ("call line number: %d\n", num);
+
+  pid = xfork ();
+  if (pid == 0)
+    {
+      TEST_COMPARE (execveat (fd, pathname, argv, envp, flags), -1);
+      if (errno == ENOSYS)
+        FAIL_UNSUPPORTED ("execveat is unimplemented");
+      else if (errno == expected_fail)
+        {
+          if (test_verbose > 0)
+            printf ("expected fail: errno %d\n", errno);
+          _exit (0);
+        }
+      else
+        FAIL_EXIT1 ("execveat failed: %m (%d)", errno);
+    }
+  xwaitpid (pid, &status, 0);
+
+  if (WIFEXITED (status))
+    {
+      if (WEXITSTATUS (status) == EXIT_UNSUPPORTED)
+        FAIL_UNSUPPORTED ("execveat is unimplemented");
+      else if (expected_fail != 0)
+        TEST_COMPARE (WEXITSTATUS (status), 0);
+      else
+        TEST_COMPARE (WEXITSTATUS (status), 3);
+    }
+  return 0;
+}
+
+static int
+do_test (void)
+{
+  DIR *dirp;
+  int fd, fd_out;
+  char *tmp_dir, *symlink_name, *tmp_sh;
+  struct stat64 st;
+
+  dirp = opendir ("/bin");
+  if (dirp == NULL)
+    FAIL_EXIT1 ("failed to open /bin");
+  fd = dirfd (dirp);
+
+  /* Call execveat for various fd/pathname combinations.  */
+
+  /* Check the pathname relative to a valid dirfd.  */
+  call_execveat (fd, "sh", 0, 0, __LINE__);
+  xchdir ("/bin");
+  /* Use the special value AT_FDCWD as dirfd. Quoting open(2):
+     If pathname is relative and dirfd is the special value AT_FDCWD, then
+     pathname is interpreted relative to the current working directory of
+     the calling process.  */
+  call_execveat (AT_FDCWD, "sh", 0, 0, __LINE__);
+  xclose (fd);
+#ifdef O_PATH
+  /* Check the pathname relative to a valid dirfd with O_PATH.  */
+  fd = xopen ("/bin", O_PATH | O_DIRECTORY, O_RDONLY);
+  call_execveat (fd, "sh", 0, 0, __LINE__);
+  xclose (fd);
+
+  /* Check absolute pathname, dirfd should be ignored.  */
+  call_execveat (AT_FDCWD, "/bin/sh", 0, 0, __LINE__);
+  fd = xopen ("/usr", O_PATH | O_DIRECTORY, 0);
+  /* Same check for absolute pathname, but with input file descriptor
+     openend with different flags.  The dirfd should be ignored.  */
+  call_execveat (fd, "/bin/sh", 0, 0, __LINE__);
+  xclose (fd);
+#endif
+
+  fd = xopen ("/usr", O_RDONLY, 0);
+  /* Same check for absolute pathname, but with input file descriptor
+     openend with different flags.  The dirfd should be ignored.  */
+  call_execveat (fd, "/bin/sh", 0, 0, __LINE__);
+  xclose (fd);
+
+  fd = xopen ("/bin/sh", O_RDONLY, 0);
+  /* Check relative pathname, where dirfd does not point to a directory.  */
+  call_execveat (fd, "sh", 0, ENOTDIR, __LINE__);
+  /* Check absolute pathname, but dirfd is a regular file.  The dirfd
+     should be ignored.  */
+  call_execveat (fd, "/bin/sh", 0, 0, __LINE__);
+  xclose (fd);
+
+#ifdef O_PATH
+  /* Quoting open(2): O_PATH
+     Obtain a file descriptor that can be used for two purposes: to
+     indicate a location in the filesystem tree and to perform
+     operations that act purely at the file descriptor level.  */
+  fd = xopen ("/bin/sh", O_PATH, 0);
+  /* Check the empty pathname.  Dirfd is a regular file with O_PATH.  */
+  call_execveat (fd, "", 0, ENOENT, __LINE__);
+  /* Same check for an empty pathname, but with AT_EMPTY_PATH flag.
+     Quoting open(2):
+     If oldpath is an empty string, create a link to the file referenced
+     by olddirfd (which may have been obtained using the open(2) O_PATH flag. */
+  call_execveat (fd, "", AT_EMPTY_PATH, 0, __LINE__);
+  call_execveat (fd, "", AT_EMPTY_PATH | AT_SYMLINK_NOFOLLOW, 0, __LINE__);
+  xclose (fd);
+
+  /* Create a temporary directory "tmp_dir" and create a symbolik link tmp_sh
+     pointing to /bin/sh inside the tmp_dir. Open dirfd as a symbolic link.  */
+  tmp_dir = support_create_temp_directory ("tst-execveat_dir");
+  symlink_name = xasprintf ("%s/symlink", tmp_dir);
+  xsymlink ("tmp_sh", symlink_name);
+  add_temp_file (symlink_name);
+  tmp_sh = xasprintf ("%s/tmp_sh", tmp_dir);
+  add_temp_file (tmp_sh);
+  fd_out = xopen (symlink_name, O_CREAT | O_WRONLY, 0);
+  xstat ("/bin/sh", &st);
+  fd = xopen ("/bin/sh", O_RDONLY, 0);
+  xcopy_file_range (fd, 0, fd_out, 0, st.st_size, 0);
+  xfchmod (fd_out, 0700);
+  xclose (fd);
+  xclose (fd_out);
+  fd_out = xopen (symlink_name, O_PATH, 0);
+
+ /* Check the empty pathname. Dirfd is a symbolic link.  */
+  call_execveat (fd_out, "", 0, ENOENT, __LINE__);
+  call_execveat (fd_out, "", AT_EMPTY_PATH, 0, __LINE__);
+  call_execveat (fd_out, "", AT_EMPTY_PATH | AT_SYMLINK_NOFOLLOW, 0,
+                 __LINE__);
+  xclose (fd_out);
+  free (symlink_name);
+  free (tmp_sh);
+  free (tmp_dir);
+#endif
+
+  /* Call execveat with closed fd, we expect this to fail with EBADF.  */
+  call_execveat (fd, "sh", 0, EBADF, __LINE__);
+  /* Call execveat with closed fd, we expect this to pass because the pathname is
+     absolute.  */
+  call_execveat (fd, "/bin/sh", 0, 0, __LINE__);
+
+  return 0;
+}
+
+#include <support/test-driver.c>
diff --git a/posix/unistd.h b/posix/unistd.h
index 3f22763379..d9d8929f71 100644
--- a/posix/unistd.h
+++ b/posix/unistd.h
@@ -295,6 +295,11 @@  extern int euidaccess (const char *__name, int __type)
 /* An alias for `euidaccess', used by some other systems.  */
 extern int eaccess (const char *__name, int __type)
      __THROW __nonnull ((1));
+
+/* Execute program relative to a directory file descriptor.  */
+extern int execveat (int __fd, const char *__path, char *const __argv[],
+                     char *const __envp[], int __flags)
+    __THROW __nonnull ((2, 3));
 #endif
 
 #ifdef __USE_ATFILE
diff --git a/sysdeps/mach/hurd/i386/libc.abilist b/sysdeps/mach/hurd/i386/libc.abilist
index e10a286d2e..bef66d105c 100644
--- a/sysdeps/mach/hurd/i386/libc.abilist
+++ b/sysdeps/mach/hurd/i386/libc.abilist
@@ -2204,6 +2204,7 @@  GLIBC_2.33 mknodat F
 GLIBC_2.33 stat F
 GLIBC_2.33 stat64 F
 GLIBC_2.34 __libc_start_main F
+GLIBC_2.34 execveat F
 GLIBC_2.4 __confstr_chk F
 GLIBC_2.4 __fgets_chk F
 GLIBC_2.4 __fgets_unlocked_chk F
diff --git a/sysdeps/unix/sysv/linux/aarch64/libc.abilist b/sysdeps/unix/sysv/linux/aarch64/libc.abilist
index bac795262d..51f34d0f6d 100644
--- a/sysdeps/unix/sysv/linux/aarch64/libc.abilist
+++ b/sysdeps/unix/sysv/linux/aarch64/libc.abilist
@@ -2172,3 +2172,4 @@  GLIBC_2.33 mknodat F
 GLIBC_2.33 stat F
 GLIBC_2.33 stat64 F
 GLIBC_2.34 __libc_start_main F
+GLIBC_2.34 execveat F
diff --git a/sysdeps/unix/sysv/linux/alpha/libc.abilist b/sysdeps/unix/sysv/linux/alpha/libc.abilist
index 897f70db22..7da53174ef 100644
--- a/sysdeps/unix/sysv/linux/alpha/libc.abilist
+++ b/sysdeps/unix/sysv/linux/alpha/libc.abilist
@@ -2254,6 +2254,7 @@  GLIBC_2.33 mknodat F
 GLIBC_2.33 stat F
 GLIBC_2.33 stat64 F
 GLIBC_2.34 __libc_start_main F
+GLIBC_2.34 execveat F
 GLIBC_2.4 _IO_fprintf F
 GLIBC_2.4 _IO_printf F
 GLIBC_2.4 _IO_sprintf F
diff --git a/sysdeps/unix/sysv/linux/arm/be/libc.abilist b/sysdeps/unix/sysv/linux/arm/be/libc.abilist
index 094236f713..108c41ae24 100644
--- a/sysdeps/unix/sysv/linux/arm/be/libc.abilist
+++ b/sysdeps/unix/sysv/linux/arm/be/libc.abilist
@@ -156,6 +156,7 @@  GLIBC_2.33 mknodat F
 GLIBC_2.33 stat F
 GLIBC_2.33 stat64 F
 GLIBC_2.34 __libc_start_main F
+GLIBC_2.34 execveat F
 GLIBC_2.4 _Exit F
 GLIBC_2.4 _IO_2_1_stderr_ D 0xa0
 GLIBC_2.4 _IO_2_1_stdin_ D 0xa0
diff --git a/sysdeps/unix/sysv/linux/arm/le/libc.abilist b/sysdeps/unix/sysv/linux/arm/le/libc.abilist
index 2bb4d31e81..a995a356a4 100644
--- a/sysdeps/unix/sysv/linux/arm/le/libc.abilist
+++ b/sysdeps/unix/sysv/linux/arm/le/libc.abilist
@@ -153,6 +153,7 @@  GLIBC_2.33 mknodat F
 GLIBC_2.33 stat F
 GLIBC_2.33 stat64 F
 GLIBC_2.34 __libc_start_main F
+GLIBC_2.34 execveat F
 GLIBC_2.4 _Exit F
 GLIBC_2.4 _IO_2_1_stderr_ D 0xa0
 GLIBC_2.4 _IO_2_1_stdin_ D 0xa0
diff --git a/sysdeps/unix/sysv/linux/csky/libc.abilist b/sysdeps/unix/sysv/linux/csky/libc.abilist
index d4291fecfb..33d0dfb2b7 100644
--- a/sysdeps/unix/sysv/linux/csky/libc.abilist
+++ b/sysdeps/unix/sysv/linux/csky/libc.abilist
@@ -2116,3 +2116,4 @@  GLIBC_2.33 mknodat F
 GLIBC_2.33 stat F
 GLIBC_2.33 stat64 F
 GLIBC_2.34 __libc_start_main F
+GLIBC_2.34 execveat F
diff --git a/sysdeps/unix/sysv/linux/execveat.c b/sysdeps/unix/sysv/linux/execveat.c
new file mode 100644
index 0000000000..0576f36b98
--- /dev/null
+++ b/sysdeps/unix/sysv/linux/execveat.c
@@ -0,0 +1,54 @@ 
+/* Execute program relative to a directory file descriptor.
+   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/>.  */
+
+#include <errno.h>
+#include <stddef.h>
+#include <stdio.h>
+#include <unistd.h>
+#include <fcntl.h>
+#include <sys/stat.h>
+
+#include <sysdep.h>
+#include <sys/syscall.h>
+#include <kernel-features.h>
+#include <fd_to_filename.h>
+#include <not-cancel.h>
+#ifndef __ASSUME_EXECVEAT
+# include "execveat_fallback.c"
+#endif
+
+/* Execute the file FD refers to, overlaying the running program image.
+   ARGV and ENVP are passed to the new program, as for `execve'.  */
+int
+execveat (int dirfd, const char *path, char *const argv[], char *const envp[],
+          int flags)
+{
+  /* Avoid implicit array coercion in syscall macros.  */
+    INLINE_SYSCALL_CALL (execveat, dirfd, path, &argv[0], &envp[0], flags);
+#ifndef __ASSUME_EXECVEAT
+  if (errno != ENOSYS)
+    return -1;
+
+  if ((flags & ~(AT_EMPTY_PATH | AT_SYMLINK_NOFOLLOW)) != 0)
+      return INLINE_SYSCALL_ERROR_RETURN_VALUE (EINVAL);
+
+  return __execveat_fallback (dirfd, path, argv, envp, flags);
+#endif
+
+  return -1;
+}
diff --git a/sysdeps/unix/sysv/linux/execveat_fallback.c b/sysdeps/unix/sysv/linux/execveat_fallback.c
new file mode 100644
index 0000000000..c4a37d3799
--- /dev/null
+++ b/sysdeps/unix/sysv/linux/execveat_fallback.c
@@ -0,0 +1,69 @@ 
+/* Execute program relative to a directory file descriptor.
+   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/>.  */
+
+#include <errno.h>
+#include <stddef.h>
+#include <stdio.h>
+#include <unistd.h>
+#include <fcntl.h>
+#include <sys/stat.h>
+
+#include <sysdep.h>
+#include <sys/syscall.h>
+#include <kernel-features.h>
+#include <fd_to_filename.h>
+#include <not-cancel.h>
+
+int
+__execveat_fallback (int dirfd, const char *path, char *const argv[],
+                   char *const envp[], int flags)
+{
+    int fd;
+
+    if (path[0] == '\0' && (flags & AT_EMPTY_PATH) && dirfd >= 0)
+        fd = dirfd;
+    else
+    {
+        int oflags = O_CLOEXEC;
+        if (flags & AT_SYMLINK_NOFOLLOW)
+            oflags |= O_NOFOLLOW;
+        fd = __openat_nocancel (dirfd, path, oflags);
+    }
+    if (fd < 0)
+        return INLINE_SYSCALL_ERROR_RETURN_VALUE (EBADFD);
+
+    struct fd_to_filename fdfilename;
+    const char *gfilename = __fd_to_filename (fd, &fdfilename);
+
+    /* We do not need the return value.  */
+    __execve (gfilename, argv, envp);
+
+    int save = errno;
+
+    /* We come here only if the 'execve' call fails.  Determine whether
+       /proc is mounted.  If not we return ENOSYS.  */
+    struct stat64 st;
+    if (__stat64 (FD_TO_FILENAME_PREFIX, &st) != 0 && errno == ENOENT)
+        save = ENOSYS;
+
+    if (fd != dirfd)
+        __close_nocancel_nostatus (fd);
+    __set_errno (save);
+
+    return -1;
+}
diff --git a/sysdeps/unix/sysv/linux/hppa/libc.abilist b/sysdeps/unix/sysv/linux/hppa/libc.abilist
index 1fd2a862f6..e1430bb232 100644
--- a/sysdeps/unix/sysv/linux/hppa/libc.abilist
+++ b/sysdeps/unix/sysv/linux/hppa/libc.abilist
@@ -2075,6 +2075,7 @@  GLIBC_2.33 mknodat F
 GLIBC_2.33 stat F
 GLIBC_2.33 stat64 F
 GLIBC_2.34 __libc_start_main F
+GLIBC_2.34 execveat F
 GLIBC_2.4 __confstr_chk F
 GLIBC_2.4 __fgets_chk F
 GLIBC_2.4 __fgets_unlocked_chk F
diff --git a/sysdeps/unix/sysv/linux/i386/libc.abilist b/sysdeps/unix/sysv/linux/i386/libc.abilist
index 943331f01e..7cb2d0dd6d 100644
--- a/sysdeps/unix/sysv/linux/i386/libc.abilist
+++ b/sysdeps/unix/sysv/linux/i386/libc.abilist
@@ -2242,6 +2242,7 @@  GLIBC_2.33 mknodat F
 GLIBC_2.33 stat F
 GLIBC_2.33 stat64 F
 GLIBC_2.34 __libc_start_main F
+GLIBC_2.34 execveat F
 GLIBC_2.4 __confstr_chk F
 GLIBC_2.4 __fgets_chk F
 GLIBC_2.4 __fgets_unlocked_chk F
diff --git a/sysdeps/unix/sysv/linux/ia64/libc.abilist b/sysdeps/unix/sysv/linux/ia64/libc.abilist
index f530151bde..2171cd3cb2 100644
--- a/sysdeps/unix/sysv/linux/ia64/libc.abilist
+++ b/sysdeps/unix/sysv/linux/ia64/libc.abilist
@@ -2107,6 +2107,7 @@  GLIBC_2.33 mknodat F
 GLIBC_2.33 stat F
 GLIBC_2.33 stat64 F
 GLIBC_2.34 __libc_start_main F
+GLIBC_2.34 execveat F
 GLIBC_2.4 __confstr_chk F
 GLIBC_2.4 __fgets_chk F
 GLIBC_2.4 __fgets_unlocked_chk F
diff --git a/sysdeps/unix/sysv/linux/m68k/coldfire/libc.abilist b/sysdeps/unix/sysv/linux/m68k/coldfire/libc.abilist
index 6e76b6dcaa..388eb76abf 100644
--- a/sysdeps/unix/sysv/linux/m68k/coldfire/libc.abilist
+++ b/sysdeps/unix/sysv/linux/m68k/coldfire/libc.abilist
@@ -157,6 +157,7 @@  GLIBC_2.33 mknodat F
 GLIBC_2.33 stat F
 GLIBC_2.33 stat64 F
 GLIBC_2.34 __libc_start_main F
+GLIBC_2.34 execveat F
 GLIBC_2.4 _Exit F
 GLIBC_2.4 _IO_2_1_stderr_ D 0x98
 GLIBC_2.4 _IO_2_1_stdin_ D 0x98
diff --git a/sysdeps/unix/sysv/linux/m68k/m680x0/libc.abilist b/sysdeps/unix/sysv/linux/m68k/m680x0/libc.abilist
index 7541b8289f..067ed53f2b 100644
--- a/sysdeps/unix/sysv/linux/m68k/m680x0/libc.abilist
+++ b/sysdeps/unix/sysv/linux/m68k/m680x0/libc.abilist
@@ -2187,6 +2187,7 @@  GLIBC_2.33 mknodat F
 GLIBC_2.33 stat F
 GLIBC_2.33 stat64 F
 GLIBC_2.34 __libc_start_main F
+GLIBC_2.34 execveat F
 GLIBC_2.4 __confstr_chk F
 GLIBC_2.4 __fgets_chk F
 GLIBC_2.4 __fgets_unlocked_chk F
diff --git a/sysdeps/unix/sysv/linux/microblaze/be/libc.abilist b/sysdeps/unix/sysv/linux/microblaze/be/libc.abilist
index 6cf1936c42..a792461b45 100644
--- a/sysdeps/unix/sysv/linux/microblaze/be/libc.abilist
+++ b/sysdeps/unix/sysv/linux/microblaze/be/libc.abilist
@@ -2167,3 +2167,4 @@  GLIBC_2.33 mknodat F
 GLIBC_2.33 stat F
 GLIBC_2.33 stat64 F
 GLIBC_2.34 __libc_start_main F
+GLIBC_2.34 execveat F
diff --git a/sysdeps/unix/sysv/linux/microblaze/le/libc.abilist b/sysdeps/unix/sysv/linux/microblaze/le/libc.abilist
index 98730ebcda..0e09fe6322 100644
--- a/sysdeps/unix/sysv/linux/microblaze/le/libc.abilist
+++ b/sysdeps/unix/sysv/linux/microblaze/le/libc.abilist
@@ -2164,3 +2164,4 @@  GLIBC_2.33 mknodat F
 GLIBC_2.33 stat F
 GLIBC_2.33 stat64 F
 GLIBC_2.34 __libc_start_main F
+GLIBC_2.34 execveat F
diff --git a/sysdeps/unix/sysv/linux/mips/mips32/fpu/libc.abilist b/sysdeps/unix/sysv/linux/mips/mips32/fpu/libc.abilist
index 92fa6cbc73..5d1b0b3d78 100644
--- a/sysdeps/unix/sysv/linux/mips/mips32/fpu/libc.abilist
+++ b/sysdeps/unix/sysv/linux/mips/mips32/fpu/libc.abilist
@@ -2158,6 +2158,7 @@  GLIBC_2.33 mknodat F
 GLIBC_2.33 stat F
 GLIBC_2.33 stat64 F
 GLIBC_2.34 __libc_start_main F
+GLIBC_2.34 execveat F
 GLIBC_2.4 __confstr_chk F
 GLIBC_2.4 __fgets_chk F
 GLIBC_2.4 __fgets_unlocked_chk F
diff --git a/sysdeps/unix/sysv/linux/mips/mips32/nofpu/libc.abilist b/sysdeps/unix/sysv/linux/mips/mips32/nofpu/libc.abilist
index 265a49e74e..a278c0a092 100644
--- a/sysdeps/unix/sysv/linux/mips/mips32/nofpu/libc.abilist
+++ b/sysdeps/unix/sysv/linux/mips/mips32/nofpu/libc.abilist
@@ -2156,6 +2156,7 @@  GLIBC_2.33 mknodat F
 GLIBC_2.33 stat F
 GLIBC_2.33 stat64 F
 GLIBC_2.34 __libc_start_main F
+GLIBC_2.34 execveat F
 GLIBC_2.4 __confstr_chk F
 GLIBC_2.4 __fgets_chk F
 GLIBC_2.4 __fgets_unlocked_chk F
diff --git a/sysdeps/unix/sysv/linux/mips/mips64/n32/libc.abilist b/sysdeps/unix/sysv/linux/mips/mips64/n32/libc.abilist
index cfa5e1111b..054d3436eb 100644
--- a/sysdeps/unix/sysv/linux/mips/mips64/n32/libc.abilist
+++ b/sysdeps/unix/sysv/linux/mips/mips64/n32/libc.abilist
@@ -2164,6 +2164,7 @@  GLIBC_2.33 mknodat F
 GLIBC_2.33 stat F
 GLIBC_2.33 stat64 F
 GLIBC_2.34 __libc_start_main F
+GLIBC_2.34 execveat F
 GLIBC_2.4 __confstr_chk F
 GLIBC_2.4 __fgets_chk F
 GLIBC_2.4 __fgets_unlocked_chk F
diff --git a/sysdeps/unix/sysv/linux/mips/mips64/n64/libc.abilist b/sysdeps/unix/sysv/linux/mips/mips64/n64/libc.abilist
index 8c03ac52cd..c22ef9f196 100644
--- a/sysdeps/unix/sysv/linux/mips/mips64/n64/libc.abilist
+++ b/sysdeps/unix/sysv/linux/mips/mips64/n64/libc.abilist
@@ -2158,6 +2158,7 @@  GLIBC_2.33 mknodat F
 GLIBC_2.33 stat F
 GLIBC_2.33 stat64 F
 GLIBC_2.34 __libc_start_main F
+GLIBC_2.34 execveat F
 GLIBC_2.4 __confstr_chk F
 GLIBC_2.4 __fgets_chk F
 GLIBC_2.4 __fgets_unlocked_chk F
diff --git a/sysdeps/unix/sysv/linux/nios2/libc.abilist b/sysdeps/unix/sysv/linux/nios2/libc.abilist
index 17f5609e06..c356e9f863 100644
--- a/sysdeps/unix/sysv/linux/nios2/libc.abilist
+++ b/sysdeps/unix/sysv/linux/nios2/libc.abilist
@@ -2205,3 +2205,4 @@  GLIBC_2.33 mknodat F
 GLIBC_2.33 stat F
 GLIBC_2.33 stat64 F
 GLIBC_2.34 __libc_start_main F
+GLIBC_2.34 execveat F
diff --git a/sysdeps/unix/sysv/linux/powerpc/powerpc32/fpu/libc.abilist b/sysdeps/unix/sysv/linux/powerpc/powerpc32/fpu/libc.abilist
index 76a16e2a6d..d1de01f91d 100644
--- a/sysdeps/unix/sysv/linux/powerpc/powerpc32/fpu/libc.abilist
+++ b/sysdeps/unix/sysv/linux/powerpc/powerpc32/fpu/libc.abilist
@@ -2214,6 +2214,7 @@  GLIBC_2.33 mknodat F
 GLIBC_2.33 stat F
 GLIBC_2.33 stat64 F
 GLIBC_2.34 __libc_start_main F
+GLIBC_2.34 execveat F
 GLIBC_2.4 _IO_fprintf F
 GLIBC_2.4 _IO_printf F
 GLIBC_2.4 _IO_sprintf F
diff --git a/sysdeps/unix/sysv/linux/powerpc/powerpc32/nofpu/libc.abilist b/sysdeps/unix/sysv/linux/powerpc/powerpc32/nofpu/libc.abilist
index 697f072fd4..a1d52887bb 100644
--- a/sysdeps/unix/sysv/linux/powerpc/powerpc32/nofpu/libc.abilist
+++ b/sysdeps/unix/sysv/linux/powerpc/powerpc32/nofpu/libc.abilist
@@ -2247,6 +2247,7 @@  GLIBC_2.33 mknodat F
 GLIBC_2.33 stat F
 GLIBC_2.33 stat64 F
 GLIBC_2.34 __libc_start_main F
+GLIBC_2.34 execveat F
 GLIBC_2.4 _IO_fprintf F
 GLIBC_2.4 _IO_printf F
 GLIBC_2.4 _IO_sprintf F
diff --git a/sysdeps/unix/sysv/linux/powerpc/powerpc64/be/libc.abilist b/sysdeps/unix/sysv/linux/powerpc/powerpc64/be/libc.abilist
index 2647bb51f1..10cdabb11c 100644
--- a/sysdeps/unix/sysv/linux/powerpc/powerpc64/be/libc.abilist
+++ b/sysdeps/unix/sysv/linux/powerpc/powerpc64/be/libc.abilist
@@ -2077,6 +2077,7 @@  GLIBC_2.33 mknodat F
 GLIBC_2.33 stat F
 GLIBC_2.33 stat64 F
 GLIBC_2.34 __libc_start_main F
+GLIBC_2.34 execveat F
 GLIBC_2.4 _IO_fprintf F
 GLIBC_2.4 _IO_printf F
 GLIBC_2.4 _IO_sprintf F
diff --git a/sysdeps/unix/sysv/linux/powerpc/powerpc64/le/libc.abilist b/sysdeps/unix/sysv/linux/powerpc/powerpc64/le/libc.abilist
index 036b1c8345..70792ed87b 100644
--- a/sysdeps/unix/sysv/linux/powerpc/powerpc64/le/libc.abilist
+++ b/sysdeps/unix/sysv/linux/powerpc/powerpc64/le/libc.abilist
@@ -2367,3 +2367,4 @@  GLIBC_2.33 mknodat F
 GLIBC_2.33 stat F
 GLIBC_2.33 stat64 F
 GLIBC_2.34 __libc_start_main F
+GLIBC_2.34 execveat F
diff --git a/sysdeps/unix/sysv/linux/riscv/rv64/libc.abilist b/sysdeps/unix/sysv/linux/riscv/rv64/libc.abilist
index fb5ad9909f..9b71083136 100644
--- a/sysdeps/unix/sysv/linux/riscv/rv64/libc.abilist
+++ b/sysdeps/unix/sysv/linux/riscv/rv64/libc.abilist
@@ -2134,3 +2134,4 @@  GLIBC_2.33 mknodat F
 GLIBC_2.33 stat F
 GLIBC_2.33 stat64 F
 GLIBC_2.34 __libc_start_main F
+GLIBC_2.34 execveat F
diff --git a/sysdeps/unix/sysv/linux/s390/s390-32/libc.abilist b/sysdeps/unix/sysv/linux/s390/s390-32/libc.abilist
index cead75acc5..aba76fbadd 100644
--- a/sysdeps/unix/sysv/linux/s390/s390-32/libc.abilist
+++ b/sysdeps/unix/sysv/linux/s390/s390-32/libc.abilist
@@ -2212,6 +2212,7 @@  GLIBC_2.33 mknodat F
 GLIBC_2.33 stat F
 GLIBC_2.33 stat64 F
 GLIBC_2.34 __libc_start_main F
+GLIBC_2.34 execveat F
 GLIBC_2.4 _IO_fprintf F
 GLIBC_2.4 _IO_printf F
 GLIBC_2.4 _IO_sprintf F
diff --git a/sysdeps/unix/sysv/linux/s390/s390-64/libc.abilist b/sysdeps/unix/sysv/linux/s390/s390-64/libc.abilist
index 31366dd7e6..6a5a765f4b 100644
--- a/sysdeps/unix/sysv/linux/s390/s390-64/libc.abilist
+++ b/sysdeps/unix/sysv/linux/s390/s390-64/libc.abilist
@@ -2113,6 +2113,7 @@  GLIBC_2.33 mknodat F
 GLIBC_2.33 stat F
 GLIBC_2.33 stat64 F
 GLIBC_2.34 __libc_start_main F
+GLIBC_2.34 execveat F
 GLIBC_2.4 _IO_fprintf F
 GLIBC_2.4 _IO_printf F
 GLIBC_2.4 _IO_sprintf F
diff --git a/sysdeps/unix/sysv/linux/sh/be/libc.abilist b/sysdeps/unix/sysv/linux/sh/be/libc.abilist
index a3a8be8910..b6629c244f 100644
--- a/sysdeps/unix/sysv/linux/sh/be/libc.abilist
+++ b/sysdeps/unix/sysv/linux/sh/be/libc.abilist
@@ -2082,6 +2082,7 @@  GLIBC_2.33 mknodat F
 GLIBC_2.33 stat F
 GLIBC_2.33 stat64 F
 GLIBC_2.34 __libc_start_main F
+GLIBC_2.34 execveat F
 GLIBC_2.4 __confstr_chk F
 GLIBC_2.4 __fgets_chk F
 GLIBC_2.4 __fgets_unlocked_chk F
diff --git a/sysdeps/unix/sysv/linux/sh/le/libc.abilist b/sysdeps/unix/sysv/linux/sh/le/libc.abilist
index 8f505c5045..e15ab4c569 100644
--- a/sysdeps/unix/sysv/linux/sh/le/libc.abilist
+++ b/sysdeps/unix/sysv/linux/sh/le/libc.abilist
@@ -2079,6 +2079,7 @@  GLIBC_2.33 mknodat F
 GLIBC_2.33 stat F
 GLIBC_2.33 stat64 F
 GLIBC_2.34 __libc_start_main F
+GLIBC_2.34 execveat F
 GLIBC_2.4 __confstr_chk F
 GLIBC_2.4 __fgets_chk F
 GLIBC_2.4 __fgets_unlocked_chk F
diff --git a/sysdeps/unix/sysv/linux/sparc/sparc32/libc.abilist b/sysdeps/unix/sysv/linux/sparc/sparc32/libc.abilist
index 53ef6304f1..11cad082d8 100644
--- a/sysdeps/unix/sysv/linux/sparc/sparc32/libc.abilist
+++ b/sysdeps/unix/sysv/linux/sparc/sparc32/libc.abilist
@@ -2203,6 +2203,7 @@  GLIBC_2.33 mknodat F
 GLIBC_2.33 stat F
 GLIBC_2.33 stat64 F
 GLIBC_2.34 __libc_start_main F
+GLIBC_2.34 execveat F
 GLIBC_2.4 _IO_fprintf F
 GLIBC_2.4 _IO_printf F
 GLIBC_2.4 _IO_sprintf F
diff --git a/sysdeps/unix/sysv/linux/sparc/sparc64/libc.abilist b/sysdeps/unix/sysv/linux/sparc/sparc64/libc.abilist
index eba0cb156d..0ff8cb8739 100644
--- a/sysdeps/unix/sysv/linux/sparc/sparc64/libc.abilist
+++ b/sysdeps/unix/sysv/linux/sparc/sparc64/libc.abilist
@@ -2130,6 +2130,7 @@  GLIBC_2.33 mknodat F
 GLIBC_2.33 stat F
 GLIBC_2.33 stat64 F
 GLIBC_2.34 __libc_start_main F
+GLIBC_2.34 execveat F
 GLIBC_2.4 __confstr_chk F
 GLIBC_2.4 __fgets_chk F
 GLIBC_2.4 __fgets_unlocked_chk F
diff --git a/sysdeps/unix/sysv/linux/x86_64/64/libc.abilist b/sysdeps/unix/sysv/linux/x86_64/64/libc.abilist
index 17ce5dfd58..040d44d3a8 100644
--- a/sysdeps/unix/sysv/linux/x86_64/64/libc.abilist
+++ b/sysdeps/unix/sysv/linux/x86_64/64/libc.abilist
@@ -2089,6 +2089,7 @@  GLIBC_2.33 mknodat F
 GLIBC_2.33 stat F
 GLIBC_2.33 stat64 F
 GLIBC_2.34 __libc_start_main F
+GLIBC_2.34 execveat F
 GLIBC_2.4 __confstr_chk F
 GLIBC_2.4 __fgets_chk F
 GLIBC_2.4 __fgets_unlocked_chk F
diff --git a/sysdeps/unix/sysv/linux/x86_64/x32/libc.abilist b/sysdeps/unix/sysv/linux/x86_64/x32/libc.abilist
index 17a1c83903..4355e06891 100644
--- a/sysdeps/unix/sysv/linux/x86_64/x32/libc.abilist
+++ b/sysdeps/unix/sysv/linux/x86_64/x32/libc.abilist
@@ -2186,3 +2186,4 @@  GLIBC_2.33 mknodat F
 GLIBC_2.33 stat F
 GLIBC_2.33 stat64 F
 GLIBC_2.34 __libc_start_main F
+GLIBC_2.34 execveat F