sysdeps/unix/sysv/linux/openat.c

   1 /* Copyright (C) 2005, 2006, 2007, 2009 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, write to the Free
  16    Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
  17    02111-1307 USA.  */
  18
  19 #include <errno.h>
  20 #include <fcntl.h>
  21 #include <stdarg.h>
  22 #include <stddef.h>
  23 #include <stdio.h>
  24 #include <string.h>
  25 #include <sys/stat.h>
  26 #include <kernel-features.h>
  27 #include <sysdep-cancel.h>
  28 #include <not-cancel.h>
  29
  30
  31 #ifndef OPENAT
  32 # define OPENAT openat
  33 # define __OPENAT_2 __openat_2
  34
  35 # ifndef __ASSUME_ATFCTS
  36 /* Set errno after a failed call.  If BUF is not null,
  37    it is a /proc/self/fd/ path name we just tried to use.  */
  38 void
  39 attribute_hidden
  40 __atfct_seterrno (int errval, int fd, const char *buf)
  41 {
  42   if (buf != NULL)
  43     {
  44       struct stat64 st;
  45
  46       if (errval == ENOTDIR || errval == ENOENT)
  47         {
  48           /* This can mean either the file descriptor is invalid or
  49              /proc is not mounted.  */
  50           if (__fxstat64 (_STAT_VER, fd, &st) != 0)
  51             /* errno is already set correctly.  */
  52             return;
  53
  54           /* If /proc is not mounted there is nothing we can do.  */
  55           if ((errval != ENOTDIR || S_ISDIR (st.st_mode))
  56               && (__xstat64 (_STAT_VER, "/proc/self/fd", &st) != 0
  57                   || !S_ISDIR (st.st_mode)))
  58             errval = ENOSYS;
  59         }
  60     }
  61
  62   __set_errno (errval);
  63 }
  64
  65 int __have_atfcts;
  66 # endif
  67 #endif
  68
  69
  70 #define OPENAT_NOT_CANCEL CONCAT (OPENAT)
  71 #define CONCAT(name) CONCAT2 (name)
  72 #define CONCAT2(name) __##name##_nocancel
  73
  74
  75 int
  76 OPENAT_NOT_CANCEL (fd, file, oflag, mode)
  77      int fd;
  78      const char *file;
  79      int oflag;
  80      mode_t mode;
  81 {
  82
  83   /* We have to add the O_LARGEFILE flag for openat64.  */
  84 #ifdef MORE_OFLAGS
  85   oflag |= MORE_OFLAGS;
  86 #endif
  87
  88   INTERNAL_SYSCALL_DECL (err);
  89   int res;
  90
  91 #ifdef __NR_openat
  92 # ifndef __ASSUME_ATFCTS
  93   if (__have_atfcts >= 0)
  94 # endif
  95     {
  96       res = INLINE_SYSCALL (openat, 4, fd, file, oflag, mode);
  97
  98 # ifndef __ASSUME_ATFCTS
  99       if (res == -1 && errno == ENOSYS)
 100         __have_atfcts = -1;
 101       else
 102 # endif
 103         return res;
 104     }
 105 #endif
 106
 107 #ifndef __ASSUME_ATFCTS
 108   char *buf = NULL;
 109
 110   if (fd != AT_FDCWD && file[0] != '/')
 111     {
 112       size_t filelen = strlen (file);
 113       if (__builtin_expect (filelen == 0, 0))
 114         {
 115           __set_errno (ENOENT);
 116           return -1;
 117         }
 118
 119       static const char procfd[] = "/proc/self/fd/%d/%s";
 120       /* Buffer for the path name we are going to use.  It consists of
 121          - the string /proc/self/fd/
 122          - the file descriptor number
 123          - the file name provided.
 124          The final NUL is included in the sizeof.   A bit of overhead
 125          due to the format elements compensates for possible negative
 126          numbers.  */
 127       size_t buflen = sizeof (procfd) + sizeof (int) * 3 + filelen;
 128       buf = alloca (buflen);
 129
 130       /* Note: snprintf cannot be canceled.  */
 131       __snprintf (buf, buflen, procfd, fd, file);
 132       file = buf;
 133     }
 134
 135   res = INTERNAL_SYSCALL (open, err, 3, file, oflag, mode);
 136
 137   if (__builtin_expect (INTERNAL_SYSCALL_ERROR_P (res, err), 0))
 138     {
 139       __atfct_seterrno (INTERNAL_SYSCALL_ERRNO (res, err), fd, buf);
 140       res = -1;
 141     }
 142
 143   return res;
 144 #endif
 145 }
 146
 147 #define UNDERIZE(name) UNDERIZE_1 (name)
 148 #define UNDERIZE_1(name) __##name
 149 #define __OPENAT UNDERIZE (OPENAT)
 150
 151
 152 /* Open FILE with access OFLAG.  Interpret relative paths relative to
 153    the directory associated with FD.  If OFLAG includes O_CREAT, a
 154    third argument is the file protection.  */
 155 int
 156 __OPENAT (fd, file, oflag)
 157      int fd;
 158      const char *file;
 159      int oflag;
 160 {
 161   mode_t mode = 0;
 162   if (oflag & O_CREAT)
 163     {
 164       va_list arg;
 165       va_start (arg, oflag);
 166       mode = va_arg (arg, mode_t);
 167       va_end (arg);
 168     }
 169
 170   if (SINGLE_THREAD_P)
 171     return OPENAT_NOT_CANCEL (fd, file, oflag, mode);
 172
 173   int oldtype = LIBC_CANCEL_ASYNC ();
 174
 175   int res = OPENAT_NOT_CANCEL (fd, file, oflag, mode);
 176
 177   LIBC_CANCEL_RESET (oldtype);
 178
 179   return res;
 180 }
 181 libc_hidden_def (__OPENAT)
 182 weak_alias (__OPENAT, OPENAT)
 183
 184
 185 int
 186 __OPENAT_2 (fd, file, oflag)
 187      int fd;
 188      const char *file;
 189      int oflag;
 190 {
 191   if (oflag & O_CREAT)
 192 #define MSG(s) MSG2 (s)
 193 #define MSG2(s) "invalid " #s " call: O_CREAT without mode"
 194     __fortify_fail (MSG (OPENAT));
 195
 196   return __OPENAT (fd, file, oflag);
 197 }