sysdeps/unix/sysv/linux/openat.c

   1 /* Copyright (C) 2005-2014 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 <fcntl.h>
  20 #include <stdarg.h>
  21 #include <stddef.h>
  22 #include <stdio.h>
  23 #include <string.h>
  24 #include <sys/stat.h>
  25 #include <kernel-features.h>
  26 #include <sysdep-cancel.h>
  27 #include <not-cancel.h>
  28
  29
  30 #ifndef OPENAT
  31 # define OPENAT openat
  32
  33 # ifndef __ASSUME_ATFCTS
  34 /* Set errno after a failed call.  If BUF is not null,
  35    it is a /proc/self/fd/ path name we just tried to use.  */
  36 void
  37 attribute_hidden
  38 __atfct_seterrno (int errval, int fd, const char *buf)
  39 {
  40   if (buf != NULL)
  41     {
  42       struct stat64 st;
  43
  44       if (errval == ENOTDIR || errval == ENOENT)
  45         {
  46           /* This can mean either the file descriptor is invalid or
  47              /proc is not mounted.  */
  48           if (__fxstat64 (_STAT_VER, fd, &st) != 0)
  49             /* errno is already set correctly.  */
  50             return;
  51
  52           /* If /proc is not mounted there is nothing we can do.  */
  53           if ((errval != ENOTDIR || S_ISDIR (st.st_mode))
  54               && (__xstat64 (_STAT_VER, "/proc/self/fd", &st) != 0
  55                   || !S_ISDIR (st.st_mode)))
  56             errval = ENOSYS;
  57         }
  58     }
  59
  60   __set_errno (errval);
  61 }
  62
  63 int __have_atfcts;
  64 # endif
  65 #endif
  66
  67
  68 #define OPENAT_NOT_CANCEL CONCAT (OPENAT)
  69 #define CONCAT(name) CONCAT2 (name)
  70 #define CONCAT2(name) __##name##_nocancel
  71
  72
  73 int
  74 OPENAT_NOT_CANCEL (fd, file, oflag, mode)
  75      int fd;
  76      const char *file;
  77      int oflag;
  78      mode_t mode;
  79 {
  80
  81   /* We have to add the O_LARGEFILE flag for openat64.  */
  82 #ifdef MORE_OFLAGS
  83   oflag |= MORE_OFLAGS;
  84 #endif
  85
  86   int res;
  87
  88 #ifdef __NR_openat
  89 # ifndef __ASSUME_ATFCTS
  90   if (__have_atfcts >= 0)
  91 # endif
  92     {
  93       res = INLINE_SYSCALL (openat, 4, fd, file, oflag, mode);
  94
  95 # ifndef __ASSUME_ATFCTS
  96       if (res == -1 && errno == ENOSYS)
  97         __have_atfcts = -1;
  98       else
  99 # endif
 100         return res;
 101     }
 102 #endif
 103
 104 #ifndef __ASSUME_ATFCTS
 105   INTERNAL_SYSCALL_DECL (err);
 106   char *buf = NULL;
 107
 108   if (fd != AT_FDCWD && file[0] != '/')
 109     {
 110       size_t filelen = strlen (file);
 111       if (__builtin_expect (filelen == 0, 0))
 112         {
 113           __set_errno (ENOENT);
 114           return -1;
 115         }
 116
 117       static const char procfd[] = "/proc/self/fd/%d/%s";
 118       /* Buffer for the path name we are going to use.  It consists of
 119          - the string /proc/self/fd/
 120          - the file descriptor number
 121          - the file name provided.
 122          The final NUL is included in the sizeof.   A bit of overhead
 123          due to the format elements compensates for possible negative
 124          numbers.  */
 125       size_t buflen = sizeof (procfd) + sizeof (int) * 3 + filelen;
 126       buf = alloca (buflen);
 127
 128       /* Note: snprintf cannot be canceled.  */
 129       __snprintf (buf, buflen, procfd, fd, file);
 130       file = buf;
 131     }
 132
 133   res = INTERNAL_SYSCALL (open, err, 3, file, oflag, mode);
 134
 135   if (__builtin_expect (INTERNAL_SYSCALL_ERROR_P (res, err), 0))
 136     {
 137       __atfct_seterrno (INTERNAL_SYSCALL_ERRNO (res, err), fd, buf);
 138       res = -1;
 139     }
 140
 141   return res;
 142 #endif
 143 }
 144
 145 #define UNDERIZE(name) UNDERIZE_1 (name)
 146 #define UNDERIZE_1(name) __##name
 147 #define __OPENAT UNDERIZE (OPENAT)
 148
 149
 150 /* Open FILE with access OFLAG.  Interpret relative paths relative to
 151    the directory associated with FD.  If OFLAG includes O_CREAT, a
 152    third argument is the file protection.  */
 153 int
 154 __OPENAT (fd, file, oflag)
 155      int fd;
 156      const char *file;
 157      int oflag;
 158 {
 159   mode_t mode = 0;
 160   if (oflag & O_CREAT)
 161     {
 162       va_list arg;
 163       va_start (arg, oflag);
 164       mode = va_arg (arg, mode_t);
 165       va_end (arg);
 166     }
 167
 168   if (SINGLE_THREAD_P)
 169     return OPENAT_NOT_CANCEL (fd, file, oflag, mode);
 170
 171   int oldtype = LIBC_CANCEL_ASYNC ();
 172
 173   int res = OPENAT_NOT_CANCEL (fd, file, oflag, mode);
 174
 175   LIBC_CANCEL_RESET (oldtype);
 176
 177   return res;
 178 }
 179 libc_hidden_def (__OPENAT)
 180 weak_alias (__OPENAT, OPENAT)