sysdeps/unix/sysv/linux/fexecve.c

   1 /* Copyright (C) 1994-2024 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    <https://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 <fd_to_filename.h>
  26 #include <sysdep.h>
  27 #include <sys/syscall.h>
  28 #include <kernel-features.h>
  29
  30
  31 /* Execute the file FD refers to, overlaying the running program image.
  32    ARGV and ENVP are passed to the new program, as for `execve'.  */
  33 int
  34 fexecve (int fd, char *const argv[], char *const envp[])
  35 {
  36   if (fd < 0 || argv == NULL || envp == NULL)
  37     {
  38       __set_errno (EINVAL);
  39       return -1;
  40     }
  41
  42 #ifdef __NR_execveat
  43   /* Avoid implicit array coercion in syscall macros.  */
  44   INLINE_SYSCALL (execveat, 5, fd, "", &argv[0], &envp[0], AT_EMPTY_PATH);
  45 # ifndef __ASSUME_EXECVEAT
  46   if (errno != ENOSYS)
  47     return -1;
  48 # endif
  49 #endif
  50
  51 #ifndef __ASSUME_EXECVEAT
  52   /* We use the /proc filesystem to get the information.  If it is not
  53      mounted we fail.  We do not need the return value.  */
  54   struct fd_to_filename filename;
  55   __execve (__fd_to_filename (fd, &filename), argv, envp);
  56
  57   int save = errno;
  58
  59   /* We come here only if the 'execve' call fails.  Determine whether
  60      /proc is mounted.  If not we return ENOSYS.  */
  61   struct __stat64_t64 st;
  62   if (__stat64_time64 ("/proc/self/fd", &st) != 0 && errno == ENOENT)
  63     save = ENOSYS;
  64
  65   __set_errno (save);
  66 #endif
  67
  68   return -1;
  69 }