sysdeps/unix/sysv/linux/fexecve.c

   1 /* Copyright (C) 1994-2018 Free Software Foundation, Inc.
   2    This file is part of the GNU C Library.
   3
   4    The GNU C Library is free software; you can redistribute it and/or
   5    modify it under the terms of the GNU Lesser General Public
   6    License as published by the Free Software Foundation; either
   7    version 2.1 of the License, or (at your option) any later version.
   8
   9    The GNU C Library is distributed in the hope that it will be useful,
  10    but WITHOUT ANY WARRANTY; without even the implied warranty of
  11    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  12    Lesser General Public License for more details.
  13
  14    You should have received a copy of the GNU Lesser General Public
  15    License along with the GNU C Library; if not, see
  16    <http://www.gnu.org/licenses/>.  */
  17
  18 #include <errno.h>
  19 #include <stddef.h>
  20 #include <stdio.h>
  21 #include <unistd.h>
  22 #include <fcntl.h>
  23 #include <sys/stat.h>
  24
  25 #include <sysdep.h>
  26 #include <sys/syscall.h>
  27 #include <kernel-features.h>
  28
  29
  30 /* Execute the file FD refers to, overlaying the running program image.
  31    ARGV and ENVP are passed to the new program, as for `execve'.  */
  32 int
  33 fexecve (int fd, char *const argv[], char *const envp[])
  34 {
  35   if (fd < 0 || argv == NULL || envp == NULL)
  36     {
  37       __set_errno (EINVAL);
  38       return -1;
  39     }
  40
  41 #ifdef __NR_execveat
  42   /* Avoid implicit array coercion in syscall macros.  */
  43   INLINE_SYSCALL (execveat, 5, fd, "", &argv[0], &envp[0], AT_EMPTY_PATH);
  44 # ifndef __ASSUME_EXECVEAT
  45   if (errno != ENOSYS)
  46     return -1;
  47 # endif
  48 #endif
  49
  50 #ifndef __ASSUME_EXECVEAT
  51   /* We use the /proc filesystem to get the information.  If it is not
  52      mounted we fail.  */
  53   char buf[sizeof "/proc/self/fd/" + sizeof (int) * 3];
  54   __snprintf (buf, sizeof (buf), "/proc/self/fd/%d", fd);
  55
  56   /* We do not need the return value.  */
  57   __execve (buf, argv, envp);
  58
  59   int save = errno;
  60
  61   /* We come here only if the 'execve' call fails.  Determine whether
  62      /proc is mounted.  If not we return ENOSYS.  */
  63   struct stat st;
  64   if (stat ("/proc/self/fd", &st) != 0 && errno == ENOENT)
  65     save = ENOSYS;
  66
  67   __set_errno (save);
  68 #endif
  69
  70   return -1;
  71 }