1  /* Determine current working directory.  Linux version.
       2     Copyright (C) 1997-2023 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 <assert.h>
      20  #include <errno.h>
      21  #include <limits.h>
      22  #include <stdlib.h>
      23  #include <unistd.h>
      24  #include <sys/param.h>
      25  
      26  #include <sysdep.h>
      27  #include <sys/syscall.h>
      28  
      29  
      30  /* If we compile the file for use in ld.so we don't need the feature
      31     that getcwd() allocates the buffers itself.  */
      32  #if IS_IN (rtld)
      33  # define NO_ALLOCATION	1
      34  #endif
      35  
      36  
      37  /* The "proc" filesystem provides an easy method to retrieve the value.
      38     For each process, the corresponding directory contains a symbolic link
      39     named `cwd'.  Reading the content of this link immediate gives us the
      40     information.  But we have to take care for systems which do not have
      41     the proc filesystem mounted.  Use the POSIX implementation in this case.  */
      42  
      43  /* Get the code for the generic version.  */
      44  #define GETCWD_RETURN_TYPE	static char *
      45  #include <sysdeps/posix/getcwd.c>
      46  
      47  char *
      48  __getcwd (char *buf, size_t size)
      49  {
      50    char *path;
      51    char *result;
      52  
      53  #ifndef NO_ALLOCATION
      54    size_t alloc_size = size;
      55    if (size == 0)
      56      {
      57        if (buf != NULL)
      58  	{
      59  	  __set_errno (EINVAL);
      60  	  return NULL;
      61  	}
      62  
      63        alloc_size = MAX (PATH_MAX, __getpagesize ());
      64      }
      65  
      66    if (buf == NULL)
      67      {
      68        path = malloc (alloc_size);
      69        if (path == NULL)
      70  	return NULL;
      71      }
      72    else
      73  #else
      74  # define alloc_size size
      75  #endif
      76      path = buf;
      77  
      78    int retval;
      79  
      80    retval = INLINE_SYSCALL (getcwd, 2, path, alloc_size);
      81    if (retval > 0 && path[0] == '/')
      82      {
      83  #ifndef NO_ALLOCATION
      84        if (buf == NULL && size == 0)
      85  	/* Ensure that the buffer is only as large as necessary.  */
      86  	buf = realloc (path, (size_t) retval);
      87  
      88        if (buf == NULL)
      89  	/* Either buf was NULL all along, or `realloc' failed but
      90  	   we still have the original string.  */
      91  	buf = path;
      92  #endif
      93  
      94        return buf;
      95      }
      96  
      97    /* The system call either cannot handle paths longer than a page
      98       or can succeed without returning an absolute path.  Just use the
      99       generic implementation right away.  */
     100    if (retval >= 0 || errno == ENAMETOOLONG)
     101      {
     102  #ifndef NO_ALLOCATION
     103        if (buf == NULL && size == 0)
     104  	{
     105  	  free (path);
     106  	  path = NULL;
     107  	}
     108  #endif
     109  
     110        result = __getcwd_generic (path, size);
     111  
     112  #ifndef NO_ALLOCATION
     113        if (result == NULL && buf == NULL && size != 0)
     114  	free (path);
     115  #endif
     116  
     117        return result;
     118      }
     119  
     120    /* It should never happen that the `getcwd' syscall failed because
     121       the buffer is too small if we allocated the buffer ourselves
     122       large enough.  */
     123    assert (errno != ERANGE || buf != NULL || size != 0);
     124  
     125  #ifndef NO_ALLOCATION
     126    if (buf == NULL)
     127      free (path);
     128  #endif
     129  
     130    return NULL;
     131  }
     132  libc_hidden_def (__getcwd)
     133  weak_alias (__getcwd, getcwd)