mirror of
https://sourceware.org/git/glibc.git
synced 2024-11-09 14:50:05 +00:00
73 lines
2.9 KiB
C
73 lines
2.9 KiB
C
/* Threshold at which to diagnose ELOOP. Generic version.
|
|
Copyright (C) 2012-2024 Free Software Foundation, Inc.
|
|
This file is part of the GNU C Library.
|
|
|
|
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
|
|
<https://www.gnu.org/licenses/>. */
|
|
|
|
#ifndef _ELOOP_THRESHOLD_H
|
|
#define _ELOOP_THRESHOLD_H 1
|
|
|
|
#include <limits.h>
|
|
#include <sys/param.h>
|
|
|
|
/* POSIX specifies SYMLOOP_MAX as the "Maximum number of symbolic
|
|
links that can be reliably traversed in the resolution of a
|
|
pathname in the absence of a loop." This makes it a minimum that
|
|
we should certainly accept. But it leaves open the possibility
|
|
that more might sometimes work--just not "reliably".
|
|
|
|
For example, Linux implements a complex policy whereby there is a
|
|
small limit on the number of direct symlink traversals (a symlink
|
|
to a symlink to a symlink), but larger limit on the total number of
|
|
symlink traversals overall. Hence the SYMLOOP_MAX number should be
|
|
the small one, but the limit library functions enforce on users
|
|
should be the larger one.
|
|
|
|
So, we use the larger of the reported SYMLOOP_MAX (if any) and our
|
|
own constant MIN_ELOOP_THRESHOLD, below. This constant should be
|
|
large enough that it never rules out a file name and directory tree
|
|
that the underlying system (i.e. calls to 'open' et al) would
|
|
resolve successfully. It should be small enough that actual loops
|
|
are detected without a huge number of iterations. */
|
|
|
|
#ifndef MIN_ELOOP_THRESHOLD
|
|
# define MIN_ELOOP_THRESHOLD 40
|
|
#endif
|
|
|
|
/* Return the maximum number of symlink traversals to permit
|
|
before diagnosing ELOOP. */
|
|
static inline unsigned int __attribute__ ((const))
|
|
__eloop_threshold (void)
|
|
{
|
|
#ifdef SYMLOOP_MAX
|
|
const int symloop_max = SYMLOOP_MAX;
|
|
#else
|
|
/* The function is marked 'const' even though we use memory and
|
|
call a function, because sysconf is required to return the
|
|
same value in every call and so it must always be safe to
|
|
call __eloop_threshold exactly once and reuse the value. */
|
|
static long int sysconf_symloop_max;
|
|
if (sysconf_symloop_max == 0)
|
|
sysconf_symloop_max = __sysconf (_SC_SYMLOOP_MAX);
|
|
const unsigned int symloop_max = (sysconf_symloop_max <= 0
|
|
? _POSIX_SYMLOOP_MAX
|
|
: sysconf_symloop_max);
|
|
#endif
|
|
|
|
return MAX (symloop_max, MIN_ELOOP_THRESHOLD);
|
|
}
|
|
|
|
#endif /* eloop-threshold.h */
|