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/* Determine current working directory. Linux version.
Copyright (C) 1997,1998,1999,2000,2002,2003,2006,2011
Free Software Foundation, Inc.
This file is part of the GNU C Library.
Contributed by Ulrich Drepper <drepper@cygnus.com>, 1997.
The GNU C Library is free software; you can redistribute it and/or
modify it under the terms of the GNU Lesser General Public
License as published by the Free Software Foundation; either
version 2.1 of the License, or (at your option) any later version.
The GNU C Library is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
Lesser General Public License for more details.
You should have received a copy of the GNU Lesser General Public
License along with the GNU C Library; if not, see
<http://www.gnu.org/licenses/>. */
#include <assert.h>
#include <errno.h>
#include <limits.h>
#include <stdlib.h>
#include <unistd.h>
#include <sysdep.h>
#include <sys/syscall.h>
#include <bp-checks.h>
#include <kernel-features.h>
/* If we compile the file for use in ld.so we don't need the feature
that getcwd() allocates the buffers itself. */
#ifdef IS_IN_rtld
# define NO_ALLOCATION 1
#endif
#if __ASSUME_GETCWD_SYSCALL > 0
/* Kernel 2.1.92 introduced a third way to get the current working
directory: a syscall. We've got to be careful that even when
compiling under 2.1.92+ the libc still runs under older kernels. */
# define no_syscall_getcwd 0
# define have_new_dcache 1
#else
# if __NR_getcwd
/* Kernel 2.1.92 introduced a third way to get the current working
directory: a syscall. We've got to be careful that even when
compiling under 2.1.92+ the libc still runs under older kernels.
An additional problem is that the system call does not return
the path of directories longer than one page. */
static int no_syscall_getcwd;
static int have_new_dcache;
# else
# define no_syscall_getcwd 1
static int have_new_dcache = 1;
# endif
#endif
/* The "proc" filesystem provides an easy method to retrieve the value.
For each process, the corresponding directory contains a symbolic link
named `cwd'. Reading the content of this link immediate gives us the
information. But we have to take care for systems which do not have
the proc filesystem mounted. Use the POSIX implementation in this case. */
static char *generic_getcwd (char *buf, size_t size) internal_function;
char *
__getcwd (char *buf, size_t size)
{
char *path;
int n;
char *result;
if (no_syscall_getcwd && !have_new_dcache)
return generic_getcwd (buf, size);
#ifndef NO_ALLOCATION
size_t alloc_size = size;
if (size == 0)
{
if (buf != NULL)
{
__set_errno (EINVAL);
return NULL;
}
alloc_size = MAX (PATH_MAX, __getpagesize ());
}
if (buf == NULL)
{
path = malloc (alloc_size);
if (path == NULL)
return NULL;
}
else
#else
# define alloc_size size
#endif
path = buf;
#if defined __NR_getcwd || __LINUX_GETCWD_SYSCALL > 0
if (!no_syscall_getcwd)
{
int retval;
retval = INLINE_SYSCALL (getcwd, 2, CHECK_STRING (path), alloc_size);
if (retval >= 0)
{
# ifndef NO_ALLOCATION
if (buf == NULL && size == 0)
/* Ensure that the buffer is only as large as necessary. */
buf = realloc (path, (size_t) retval);
if (buf == NULL)
/* Either buf was NULL all along, or `realloc' failed but
we still have the original string. */
buf = path;
# endif
return buf;
}
/* The system call cannot handle paths longer than a page.
Neither can the magic symlink in /proc/self. Just use the
generic implementation right away. */
if (errno == ENAMETOOLONG)
{
# ifndef NO_ALLOCATION
if (buf == NULL && size == 0)
{
free (path);
path = NULL;
}
# endif
result = generic_getcwd (path, size);
# ifndef NO_ALLOCATION
if (result == NULL && buf == NULL && size != 0)
free (path);
# endif
return result;
}
# if __ASSUME_GETCWD_SYSCALL
/* It should never happen that the `getcwd' syscall failed because
the buffer is too small if we allocated the buffer ourselves
large enough. */
assert (errno != ERANGE || buf != NULL || size != 0);
# ifndef NO_ALLOCATION
if (buf == NULL)
free (path);
# endif
return NULL;
# else
if (errno == ENOSYS)
{
no_syscall_getcwd = 1;
have_new_dcache = 1; /* Now we will try the /proc method. */
}
else if (errno != ERANGE || buf != NULL)
{
# ifndef NO_ALLOCATION
if (buf == NULL)
free (path);
# endif
return NULL;
}
# endif
}
#endif
n = __readlink ("/proc/self/cwd", path, alloc_size - 1);
if (n != -1)
{
if (path[0] == '/')
{
if ((size_t) n >= alloc_size - 1)
{
#ifndef NO_ALLOCATION
if (buf == NULL)
free (path);
#endif
return NULL;
}
path[n] = '\0';
#ifndef NO_ALLOCATION
if (buf == NULL && size == 0)
/* Ensure that the buffer is only as large as necessary. */
buf = realloc (path, (size_t) n + 1);
if (buf == NULL)
/* Either buf was NULL all along, or `realloc' failed but
we still have the original string. */
buf = path;
#endif
return buf;
}
#ifndef have_new_dcache
else
have_new_dcache = 0;
#endif
}
#if __ASSUME_GETCWD_SYSCALL == 0
/* Set to have_new_dcache only if error indicates that proc doesn't
exist. */
if (errno != EACCES && errno != ENAMETOOLONG)
have_new_dcache = 0;
#endif
#ifndef NO_ALLOCATION
/* Don't put restrictions on the length of the path unless the user does. */
if (buf == NULL && size == 0)
{
free (path);
path = NULL;
}
#endif
result = generic_getcwd (path, size);
#ifndef NO_ALLOCATION
if (result == NULL && buf == NULL && size != 0)
free (path);
#endif
return result;
}
weak_alias (__getcwd, getcwd)
/* Get the code for the generic version. */
#define GETCWD_RETURN_TYPE static char * internal_function
#define __getcwd generic_getcwd
#include <sysdeps/posix/getcwd.c>
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