linux-imx

// SPDX-License-Identifier: GPL-2.0

/*

 *  linux/fs/namei.c

 *

 *  Copyright (C) 1991, 1992  Linus Torvalds

 */

​

/*

 * Some corrections by tytso.

 */

​

/* [Feb 1997 T. Schoebel-Theuer] Complete rewrite of the pathname

 * lookup logic.

 */

/* [Feb-Apr 2000, AV] Rewrite to the new namespace architecture.

 */

​

#include <linux/init.h>

#include <linux/export.h>

#include <linux/kernel.h>

#include <linux/slab.h>

#include <linux/fs.h>

#include <linux/namei.h>

#include <linux/pagemap.h>

#include <linux/fsnotify.h>

#include <linux/personality.h>

#include <linux/security.h>

#include <linux/ima.h>

#include <linux/syscalls.h>

#include <linux/mount.h>

#include <linux/audit.h>

#include <linux/capability.h>

#include <linux/file.h>

#include <linux/fcntl.h>

#include <linux/device_cgroup.h>

#include <linux/fs_struct.h>

#include <linux/posix_acl.h>

#include <linux/hash.h>

#include <linux/bitops.h>

#include <linux/init_task.h>

#include <linux/uaccess.h>

​

#include "internal.h"

#include "mount.h"

​

/* [Feb-1997 T. Schoebel-Theuer]

 * Fundamental changes in the pathname lookup mechanisms (namei)

 * were necessary because of omirr.  The reason is that omirr needs

 * to know the _real_ pathname, not the user-supplied one, in case

 * of symlinks (and also when transname replacements occur).

 *

 * The new code replaces the old recursive symlink resolution with

 * an iterative one (in case of non-nested symlink chains).  It does

 * this with calls to <fs>_follow_link().

 * As a side effect, dir_namei(), _namei() and follow_link() are now 

 * replaced with a single function lookup_dentry() that can handle all 

 * the special cases of the former code.

 *

 * With the new dcache, the pathname is stored at each inode, at least as

 * long as the refcount of the inode is positive.  As a side effect, the

 * size of the dcache depends on the inode cache and thus is dynamic.

 *

 * [29-Apr-1998 C. Scott Ananian] Updated above description of symlink

 * resolution to correspond with current state of the code.

 *

 * Note that the symlink resolution is not *completely* iterative.

 * There is still a significant amount of tail- and mid- recursion in

 * the algorithm.  Also, note that <fs>_readlink() is not used in

 * lookup_dentry(): lookup_dentry() on the result of <fs>_readlink()

 * may return different results than <fs>_follow_link().  Many virtual

 * filesystems (including /proc) exhibit this behavior.

 */

​

/* [24-Feb-97 T. Schoebel-Theuer] Side effects caused by new implementation:

 * New symlink semantics: when open() is called with flags O_CREAT | O_EXCL

 * and the name already exists in form of a symlink, try to create the new

 * name indicated by the symlink. The old code always complained that the

 * name already exists, due to not following the symlink even if its target

 * is nonexistent.  The new semantics affects also mknod() and link() when

 * the name is a symlink pointing to a non-existent name.

 *

 * I don't know which semantics is the right one, since I have no access

 * to standards. But I found by trial that HP-UX 9.0 has the full "new"

 * semantics implemented, while SunOS 4.1.1 and Solaris (SunOS 5.4) have the

 * "old" one. Personally, I think the new semantics is much more logical.

 * Note that "ln old new" where "new" is a symlink pointing to a non-existing

 * file does succeed in both HP-UX and SunOs, but not in Solaris

 * and in the old Linux semantics.

 */

​

/* [16-Dec-97 Kevin Buhr] For security reasons, we change some symlink

 * semantics.  See the comments in "open_namei" and "do_link" below.