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/* Determine current working directory. Linux version.
Copyright (C) 1997, 1998, 1999 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 Library General Public License as
published by the Free Software Foundation; either version 2 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
Library General Public License for more details.
You should have received a copy of the GNU Library General Public
License along with the GNU C Library; see the file COPYING.LIB. If not,
write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
Boston, MA 02111-1307, USA. */
#include <assert.h>
#include <errno.h>
#include <limits.h>
#include <stdlib.h>
#include <unistd.h>
#include <sysdep.h>
#include <sys/syscall.h>
#include "kernel-features.h"
#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. */
extern int __syscall_getcwd (char *buf, unsigned long size);
# define no_syscall_getcwd 0
# define have_new_dcache 1
/* This is a trick since we don't define generic_getcwd. */
# define generic_getcwd getcwd
#else
/* 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;
# 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. */
extern int __syscall_getcwd (char *buf, unsigned long size);
static int no_syscall_getcwd;
static int have_new_dcache;
# else
# define no_syscall_getcwd 1
static int have_new_dcache = 1;
# endif
#endif
char *
__getcwd (char *buf, size_t size)
{
int save_errno;
char *path;
int n;
char *result;
size_t alloc_size = size;
if (no_syscall_getcwd && !have_new_dcache)
return generic_getcwd (buf, size);
if (size == 0)
{
if (buf != NULL)
{
__set_errno (EINVAL);
return NULL;
}
alloc_size = PATH_MAX;
}
if (buf != NULL)
path = buf;
else
{
path = malloc (alloc_size);
if (path == NULL)
return NULL;
}
save_errno = errno;
#if defined __NR_getcwd || __LINUX_GETCWD_SYSCALL > 0
if (!no_syscall_getcwd)
{
int retval;
retval = INLINE_SYSCALL (getcwd, 2, path, alloc_size);
if (retval >= 0)
{
if (buf == NULL)
{
buf = realloc (path, (size_t) retval);
if (buf == NULL)
/* `realloc' failed but we still have the original string. */
buf = path;
}
return buf;
}
# if __ASSUME_GETCWD_SYSCALL
/* It should never happen that the `getcwd' syscall failed because
the buffer is too small if we allocated the buffer outself. */
assert (errno != ERANGE || buf != NULL);
if (buf == NULL)
free (path);
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)
{
if (buf == NULL)
free (path);
return NULL;
}
__set_errno (save_errno);
# endif
}
#endif
n = __readlink ("/proc/self/cwd", path, alloc_size - 1);
if (n != -1)
{
if (path[0] == '/')
{
if (n >= alloc_size - 1)
{
if (buf == NULL)
free (path);
return NULL;
}
path[n] = '\0';
if (buf == NULL)
{
buf = realloc (path, (size_t) n + 1);
if (buf == NULL)
/* `relloc' failed but we still have the original string. */
buf = path;
}
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
/* Something went wrong. Restore the error number and use the generic
version. */
__set_errno (save_errno);
/* Don't put restrictions on the length of the path unless the user does. */
if (size == 0)
{
free (path);
path = NULL;
}
result = generic_getcwd (path, size);
if (result == NULL && buf == NULL && size != 0)
free (path);
return result;
}
weak_alias (__getcwd, getcwd)
#if __ASSUME_GETCWD_SYSCALL == 0
/* Get the code for the generic version. */
# define GETCWD_RETURN_TYPE static char * internal_function
# define __getcwd generic_getcwd
# include <sysdeps/posix/getcwd.c>
#endif
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