io/statx_generic.c

   1 /* Generic implementation of statx based on fstatat64.
   2    Copyright (C) 2018-2023 Free Software Foundation, Inc.
   3    This file is part of the GNU C Library.
   4
   5    The GNU C Library is free software; you can redistribute it and/or
   6    modify it under the terms of the GNU Lesser General Public
   7    License as published by the Free Software Foundation; either
   8    version 2.1 of the License, or (at your option) any later version.
   9
  10    The GNU C Library is distributed in the hope that it will be useful,
  11    but WITHOUT ANY WARRANTY; without even the implied warranty of
  12    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  13    Lesser General Public License for more details.
  14
  15    You should have received a copy of the GNU Lesser General Public
  16    License along with the GNU C Library; if not, see
  17    <https://www.gnu.org/licenses/>.  */
  18
  19 #include <errno.h>
  20 #include <fcntl.h>
  21 #include <string.h>
  22 #include <sys/stat.h>
  23 #include <sys/sysmacros.h>
  24
  25 /* Obtain the original definition of struct statx.  */
  26 #undef __statx_defined
  27 #define statx original_statx
  28 #include <bits/types/struct_statx.h>
  29 #undef statx
  30
  31 static inline struct statx_timestamp
  32 statx_convert_timestamp (struct timespec tv)
  33 {
  34   return (struct statx_timestamp) { tv.tv_sec, tv.tv_nsec };
  35 }
  36
  37 /* Approximate emulation of statx.  This will always fill in
  38    POSIX-mandated attributes even if the underlying file system does
  39    not actually support it (for example, GID and UID on file systems
  40    without UNIX-style permissions).  */
  41 static __attribute__ ((unused)) int
  42 statx_generic (int fd, const char *path, int flags,
  43                unsigned int mask, struct statx *buf)
  44 {
  45   /* Flags which need to be cleared before passing them to
  46      fstatat64.  */
  47   static const int clear_flags = AT_STATX_SYNC_AS_STAT;
  48
  49     /* Flags supported by our emulation.  */
  50   static const int supported_flags
  51     = AT_EMPTY_PATH | AT_NO_AUTOMOUNT | AT_SYMLINK_NOFOLLOW | clear_flags;
  52
  53   if (__glibc_unlikely ((flags & ~supported_flags) != 0))
  54     {
  55       __set_errno (EINVAL);
  56       return -1;
  57     }
  58
  59   struct stat64 st;
  60   int ret = __fstatat64 (fd, path, &st, flags & ~clear_flags);
  61   if (ret != 0)
  62     return ret;
  63
  64   /* The interface is defined in such a way that unused (padding)
  65      fields have to be cleared.  STATX_BASIC_STATS corresponds to the
  66      data which is available via fstatat64.  */
  67   struct original_statx obuf =
  68     {
  69       .stx_mask = STATX_BASIC_STATS,
  70       .stx_blksize = st.st_blksize,
  71       .stx_nlink = st.st_nlink,
  72       .stx_uid = st.st_uid,
  73       .stx_gid = st.st_gid,
  74       .stx_mode = st.st_mode,
  75       .stx_ino = st.st_ino,
  76       .stx_size = st.st_size,
  77       .stx_blocks = st.st_blocks,
  78       .stx_atime = statx_convert_timestamp (st.st_atim),
  79       .stx_ctime = statx_convert_timestamp (st.st_ctim),
  80       .stx_mtime = statx_convert_timestamp (st.st_mtim),
  81       .stx_rdev_major = major (st.st_rdev),
  82       .stx_rdev_minor = minor (st.st_rdev),
  83       .stx_dev_major = major (st.st_dev),
  84       .stx_dev_minor = minor (st.st_dev),
  85     };
  86   _Static_assert (sizeof (*buf) >= sizeof (obuf), "struct statx size");
  87   memcpy (buf, &obuf, sizeof (obuf));
  88
  89   return 0;
  90 }