sysdeps/unix/sysv/linux/openat.c

   1 /* Copyright (C) 2005-2013 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 # define __OPENAT_2 __openat_2
  33
  34 # ifndef __ASSUME_ATFCTS
  35 /* Set errno after a failed call.  If BUF is not null,
  36    it is a /proc/self/fd/ path name we just tried to use.  */
  37 void
  38 attribute_hidden
  39 __atfct_seterrno (int errval, int fd, const char *buf)
  40 {
  41   if (buf != NULL)
  42     {
  43       struct stat64 st;
  44
  45       if (errval == ENOTDIR || errval == ENOENT)
  46         {
  47           /* This can mean either the file descriptor is invalid or
  48              /proc is not mounted.  */
  49           if (__fxstat64 (_STAT_VER, fd, &st) != 0)
  50             /* errno is already set correctly.  */
  51             return;
  52
  53           /* If /proc is not mounted there is nothing we can do.  */
  54           if ((errval != ENOTDIR || S_ISDIR (st.st_mode))
  55               && (__xstat64 (_STAT_VER, "/proc/self/fd", &st) != 0
  56                   || !S_ISDIR (st.st_mode)))
  57             errval = ENOSYS;
  58         }
  59     }
  60
  61   __set_errno (errval);
  62 }
  63
  64 int __have_atfcts;
  65 # endif
  66 #endif
  67
  68
  69 #define OPENAT_NOT_CANCEL CONCAT (OPENAT)
  70 #define CONCAT(name) CONCAT2 (name)
  71 #define CONCAT2(name) __##name##_nocancel
  72
  73
  74 int
  75 OPENAT_NOT_CANCEL (fd, file, oflag, mode)
  76      int fd;
  77      const char *file;
  78      int oflag;
  79      mode_t mode;
  80 {
  81
  82   /* We have to add the O_LARGEFILE flag for openat64.  */
  83 #ifdef MORE_OFLAGS
  84   oflag |= MORE_OFLAGS;
  85 #endif
  86
  87   int res;
  88
  89 #ifdef __NR_openat
  90 # ifndef __ASSUME_ATFCTS
  91   if (__have_atfcts >= 0)
  92 # endif
  93     {
  94       res = INLINE_SYSCALL (openat, 4, fd, file, oflag, mode);
  95
  96 # ifndef __ASSUME_ATFCTS
  97       if (res == -1 && errno == ENOSYS)
  98         __have_atfcts = -1;
  99       else
 100 # endif
 101         return res;
 102     }
 103 #endif
 104
 105 #ifndef __ASSUME_ATFCTS
 106   INTERNAL_SYSCALL_DECL (err);
 107   char *buf = NULL;
 108
 109   if (fd != AT_FDCWD && file[0] != '/')
 110     {
 111       size_t filelen = strlen (file);
 112       if (__builtin_expect (filelen == 0, 0))
 113         {
 114           __set_errno (ENOENT);
 115           return -1;
 116         }
 117
 118       static const char procfd[] = "/proc/self/fd/%d/%s";
 119       /* Buffer for the path name we are going to use.  It consists of
 120          - the string /proc/self/fd/
 121          - the file descriptor number
 122          - the file name provided.
 123          The final NUL is included in the sizeof.   A bit of overhead
 124          due to the format elements compensates for possible negative
 125          numbers.  */
 126       size_t buflen = sizeof (procfd) + sizeof (int) * 3 + filelen;
 127       buf = alloca (buflen);
 128
 129       /* Note: snprintf cannot be canceled.  */
 130       __snprintf (buf, buflen, procfd, fd, file);
 131       file = buf;
 132     }
 133
 134   res = INTERNAL_SYSCALL (open, err, 3, file, oflag, mode);
 135
 136   if (__builtin_expect (INTERNAL_SYSCALL_ERROR_P (res, err), 0))
 137     {
 138       __atfct_seterrno (INTERNAL_SYSCALL_ERRNO (res, err), fd, buf);
 139       res = -1;
 140     }
 141
 142   return res;
 143 #endif
 144 }
 145
 146 #define UNDERIZE(name) UNDERIZE_1 (name)
 147 #define UNDERIZE_1(name) __##name
 148 #define __OPENAT UNDERIZE (OPENAT)
 149
 150
 151 /* Open FILE with access OFLAG.  Interpret relative paths relative to
 152    the directory associated with FD.  If OFLAG includes O_CREAT, a
 153    third argument is the file protection.  */
 154 int
 155 __OPENAT (fd, file, oflag)
 156      int fd;
 157      const char *file;
 158      int oflag;
 159 {
 160   mode_t mode = 0;
 161   if (oflag & O_CREAT)
 162     {
 163       va_list arg;
 164       va_start (arg, oflag);
 165       mode = va_arg (arg, mode_t);
 166       va_end (arg);
 167     }
 168
 169   if (SINGLE_THREAD_P)
 170     return OPENAT_NOT_CANCEL (fd, file, oflag, mode);
 171
 172   int oldtype = LIBC_CANCEL_ASYNC ();
 173
 174   int res = OPENAT_NOT_CANCEL (fd, file, oflag, mode);
 175
 176   LIBC_CANCEL_RESET (oldtype);
 177
 178   return res;
 179 }
 180 libc_hidden_def (__OPENAT)
 181 weak_alias (__OPENAT, OPENAT)
 182
 183
 184 int
 185 __OPENAT_2 (fd, file, oflag)
 186      int fd;
 187      const char *file;
 188      int oflag;
 189 {
 190   if (oflag & O_CREAT)
 191 #define MSG(s) MSG2 (s)
 192 #define MSG2(s) "invalid " #s " call: O_CREAT without mode"
 193     __fortify_fail (MSG (OPENAT));
 194
 195   return __OPENAT (fd, file, oflag);
 196 }