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https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git
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f5c16f29bf
13c589d5b0
("sysfs: use seq_file when reading regular files") switched sysfs from custom read implementation to seq_file to enable later transition to kernfs. After the change, the buffer passed to ->show() is acquired through seq_get_buf(); unfortunately, this introduces a subtle behavior change. Before the commit, the buffer passed to ->show() was always zero as it was allocated using get_zeroed_page(). Because seq_file doesn't clear buffers on allocation and neither does seq_get_buf(), after the commit, depending on the behavior of ->show(), we may end up exposing uninitialized data to userland thus possibly altering userland visible behavior and leaking information. Fix it by explicitly clearing the buffer. Signed-off-by: Tejun Heo <tj@kernel.org> Reported-by: Ron <ron@debian.org> Fixes:13c589d5b0
("sysfs: use seq_file when reading regular files") Cc: stable <stable@vger.kernel.org> # 3.13+ Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
456 lines
11 KiB
C
456 lines
11 KiB
C
/*
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* fs/sysfs/file.c - sysfs regular (text) file implementation
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*
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* Copyright (c) 2001-3 Patrick Mochel
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* Copyright (c) 2007 SUSE Linux Products GmbH
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* Copyright (c) 2007 Tejun Heo <teheo@suse.de>
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*
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* This file is released under the GPLv2.
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*
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* Please see Documentation/filesystems/sysfs.txt for more information.
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*/
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#include <linux/module.h>
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#include <linux/kobject.h>
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#include <linux/kallsyms.h>
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#include <linux/slab.h>
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#include <linux/list.h>
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#include <linux/mutex.h>
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#include <linux/seq_file.h>
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#include "sysfs.h"
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#include "../kernfs/kernfs-internal.h"
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/*
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* Determine ktype->sysfs_ops for the given kernfs_node. This function
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* must be called while holding an active reference.
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*/
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static const struct sysfs_ops *sysfs_file_ops(struct kernfs_node *kn)
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{
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struct kobject *kobj = kn->parent->priv;
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if (kn->flags & KERNFS_LOCKDEP)
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lockdep_assert_held(kn);
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return kobj->ktype ? kobj->ktype->sysfs_ops : NULL;
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}
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/*
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* Reads on sysfs are handled through seq_file, which takes care of hairy
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* details like buffering and seeking. The following function pipes
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* sysfs_ops->show() result through seq_file.
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*/
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static int sysfs_kf_seq_show(struct seq_file *sf, void *v)
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{
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struct kernfs_open_file *of = sf->private;
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struct kobject *kobj = of->kn->parent->priv;
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const struct sysfs_ops *ops = sysfs_file_ops(of->kn);
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ssize_t count;
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char *buf;
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/* acquire buffer and ensure that it's >= PAGE_SIZE and clear */
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count = seq_get_buf(sf, &buf);
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if (count < PAGE_SIZE) {
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seq_commit(sf, -1);
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return 0;
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}
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memset(buf, 0, PAGE_SIZE);
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/*
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* Invoke show(). Control may reach here via seq file lseek even
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* if @ops->show() isn't implemented.
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*/
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if (ops->show) {
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count = ops->show(kobj, of->kn->priv, buf);
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if (count < 0)
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return count;
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}
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/*
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* The code works fine with PAGE_SIZE return but it's likely to
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* indicate truncated result or overflow in normal use cases.
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*/
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if (count >= (ssize_t)PAGE_SIZE) {
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print_symbol("fill_read_buffer: %s returned bad count\n",
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(unsigned long)ops->show);
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/* Try to struggle along */
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count = PAGE_SIZE - 1;
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}
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seq_commit(sf, count);
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return 0;
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}
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static ssize_t sysfs_kf_bin_read(struct kernfs_open_file *of, char *buf,
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size_t count, loff_t pos)
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{
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struct bin_attribute *battr = of->kn->priv;
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struct kobject *kobj = of->kn->parent->priv;
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loff_t size = file_inode(of->file)->i_size;
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if (!count)
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return 0;
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if (size) {
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if (pos > size)
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return 0;
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if (pos + count > size)
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count = size - pos;
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}
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if (!battr->read)
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return -EIO;
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return battr->read(of->file, kobj, battr, buf, pos, count);
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}
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/* kernfs write callback for regular sysfs files */
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static ssize_t sysfs_kf_write(struct kernfs_open_file *of, char *buf,
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size_t count, loff_t pos)
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{
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const struct sysfs_ops *ops = sysfs_file_ops(of->kn);
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struct kobject *kobj = of->kn->parent->priv;
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if (!count)
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return 0;
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return ops->store(kobj, of->kn->priv, buf, count);
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}
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/* kernfs write callback for bin sysfs files */
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static ssize_t sysfs_kf_bin_write(struct kernfs_open_file *of, char *buf,
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size_t count, loff_t pos)
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{
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struct bin_attribute *battr = of->kn->priv;
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struct kobject *kobj = of->kn->parent->priv;
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loff_t size = file_inode(of->file)->i_size;
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if (size) {
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if (size <= pos)
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return 0;
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count = min_t(ssize_t, count, size - pos);
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}
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if (!count)
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return 0;
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if (!battr->write)
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return -EIO;
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return battr->write(of->file, kobj, battr, buf, pos, count);
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}
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static int sysfs_kf_bin_mmap(struct kernfs_open_file *of,
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struct vm_area_struct *vma)
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{
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struct bin_attribute *battr = of->kn->priv;
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struct kobject *kobj = of->kn->parent->priv;
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return battr->mmap(of->file, kobj, battr, vma);
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}
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void sysfs_notify(struct kobject *kobj, const char *dir, const char *attr)
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{
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struct kernfs_node *kn = kobj->sd, *tmp;
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if (kn && dir)
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kn = kernfs_find_and_get(kn, dir);
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else
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kernfs_get(kn);
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if (kn && attr) {
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tmp = kernfs_find_and_get(kn, attr);
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kernfs_put(kn);
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kn = tmp;
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}
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if (kn) {
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kernfs_notify(kn);
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kernfs_put(kn);
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}
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}
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EXPORT_SYMBOL_GPL(sysfs_notify);
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static const struct kernfs_ops sysfs_file_kfops_empty = {
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};
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static const struct kernfs_ops sysfs_file_kfops_ro = {
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.seq_show = sysfs_kf_seq_show,
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};
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static const struct kernfs_ops sysfs_file_kfops_wo = {
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.write = sysfs_kf_write,
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};
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static const struct kernfs_ops sysfs_file_kfops_rw = {
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.seq_show = sysfs_kf_seq_show,
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.write = sysfs_kf_write,
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};
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static const struct kernfs_ops sysfs_bin_kfops_ro = {
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.read = sysfs_kf_bin_read,
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};
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static const struct kernfs_ops sysfs_bin_kfops_wo = {
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.write = sysfs_kf_bin_write,
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};
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static const struct kernfs_ops sysfs_bin_kfops_rw = {
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.read = sysfs_kf_bin_read,
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.write = sysfs_kf_bin_write,
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};
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static const struct kernfs_ops sysfs_bin_kfops_mmap = {
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.read = sysfs_kf_bin_read,
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.write = sysfs_kf_bin_write,
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.mmap = sysfs_kf_bin_mmap,
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};
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int sysfs_add_file_mode_ns(struct kernfs_node *parent,
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const struct attribute *attr, bool is_bin,
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umode_t mode, const void *ns)
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{
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struct lock_class_key *key = NULL;
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const struct kernfs_ops *ops;
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struct kernfs_node *kn;
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loff_t size;
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if (!is_bin) {
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struct kobject *kobj = parent->priv;
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const struct sysfs_ops *sysfs_ops = kobj->ktype->sysfs_ops;
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/* every kobject with an attribute needs a ktype assigned */
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if (WARN(!sysfs_ops, KERN_ERR
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"missing sysfs attribute operations for kobject: %s\n",
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kobject_name(kobj)))
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return -EINVAL;
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if (sysfs_ops->show && sysfs_ops->store)
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ops = &sysfs_file_kfops_rw;
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else if (sysfs_ops->show)
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ops = &sysfs_file_kfops_ro;
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else if (sysfs_ops->store)
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ops = &sysfs_file_kfops_wo;
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else
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ops = &sysfs_file_kfops_empty;
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size = PAGE_SIZE;
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} else {
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struct bin_attribute *battr = (void *)attr;
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if (battr->mmap)
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ops = &sysfs_bin_kfops_mmap;
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else if (battr->read && battr->write)
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ops = &sysfs_bin_kfops_rw;
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else if (battr->read)
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ops = &sysfs_bin_kfops_ro;
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else if (battr->write)
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ops = &sysfs_bin_kfops_wo;
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else
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ops = &sysfs_file_kfops_empty;
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size = battr->size;
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}
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#ifdef CONFIG_DEBUG_LOCK_ALLOC
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if (!attr->ignore_lockdep)
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key = attr->key ?: (struct lock_class_key *)&attr->skey;
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#endif
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kn = __kernfs_create_file(parent, attr->name, mode, size, ops,
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(void *)attr, ns, true, key);
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if (IS_ERR(kn)) {
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if (PTR_ERR(kn) == -EEXIST)
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sysfs_warn_dup(parent, attr->name);
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return PTR_ERR(kn);
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}
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return 0;
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}
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int sysfs_add_file(struct kernfs_node *parent, const struct attribute *attr,
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bool is_bin)
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{
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return sysfs_add_file_mode_ns(parent, attr, is_bin, attr->mode, NULL);
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}
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/**
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* sysfs_create_file_ns - create an attribute file for an object with custom ns
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* @kobj: object we're creating for
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* @attr: attribute descriptor
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* @ns: namespace the new file should belong to
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*/
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int sysfs_create_file_ns(struct kobject *kobj, const struct attribute *attr,
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const void *ns)
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{
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BUG_ON(!kobj || !kobj->sd || !attr);
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return sysfs_add_file_mode_ns(kobj->sd, attr, false, attr->mode, ns);
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}
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EXPORT_SYMBOL_GPL(sysfs_create_file_ns);
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int sysfs_create_files(struct kobject *kobj, const struct attribute **ptr)
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{
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int err = 0;
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int i;
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for (i = 0; ptr[i] && !err; i++)
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err = sysfs_create_file(kobj, ptr[i]);
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if (err)
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while (--i >= 0)
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sysfs_remove_file(kobj, ptr[i]);
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return err;
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}
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EXPORT_SYMBOL_GPL(sysfs_create_files);
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/**
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* sysfs_add_file_to_group - add an attribute file to a pre-existing group.
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* @kobj: object we're acting for.
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* @attr: attribute descriptor.
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* @group: group name.
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*/
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int sysfs_add_file_to_group(struct kobject *kobj,
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const struct attribute *attr, const char *group)
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{
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struct kernfs_node *parent;
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int error;
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if (group) {
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parent = kernfs_find_and_get(kobj->sd, group);
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} else {
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parent = kobj->sd;
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kernfs_get(parent);
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}
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if (!parent)
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return -ENOENT;
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error = sysfs_add_file(parent, attr, false);
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kernfs_put(parent);
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return error;
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}
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EXPORT_SYMBOL_GPL(sysfs_add_file_to_group);
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/**
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* sysfs_chmod_file - update the modified mode value on an object attribute.
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* @kobj: object we're acting for.
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* @attr: attribute descriptor.
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* @mode: file permissions.
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*
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*/
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int sysfs_chmod_file(struct kobject *kobj, const struct attribute *attr,
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umode_t mode)
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{
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struct kernfs_node *kn;
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struct iattr newattrs;
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int rc;
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kn = kernfs_find_and_get(kobj->sd, attr->name);
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if (!kn)
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return -ENOENT;
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newattrs.ia_mode = (mode & S_IALLUGO) | (kn->mode & ~S_IALLUGO);
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newattrs.ia_valid = ATTR_MODE;
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rc = kernfs_setattr(kn, &newattrs);
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kernfs_put(kn);
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return rc;
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}
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EXPORT_SYMBOL_GPL(sysfs_chmod_file);
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/**
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* sysfs_remove_file_ns - remove an object attribute with a custom ns tag
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* @kobj: object we're acting for
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* @attr: attribute descriptor
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* @ns: namespace tag of the file to remove
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*
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* Hash the attribute name and namespace tag and kill the victim.
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*/
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void sysfs_remove_file_ns(struct kobject *kobj, const struct attribute *attr,
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const void *ns)
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{
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struct kernfs_node *parent = kobj->sd;
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kernfs_remove_by_name_ns(parent, attr->name, ns);
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}
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EXPORT_SYMBOL_GPL(sysfs_remove_file_ns);
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/**
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* sysfs_remove_file_self - remove an object attribute from its own method
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* @kobj: object we're acting for
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* @attr: attribute descriptor
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*
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* See kernfs_remove_self() for details.
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*/
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bool sysfs_remove_file_self(struct kobject *kobj, const struct attribute *attr)
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{
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struct kernfs_node *parent = kobj->sd;
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struct kernfs_node *kn;
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bool ret;
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kn = kernfs_find_and_get(parent, attr->name);
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if (WARN_ON_ONCE(!kn))
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return false;
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ret = kernfs_remove_self(kn);
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kernfs_put(kn);
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return ret;
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}
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void sysfs_remove_files(struct kobject *kobj, const struct attribute **ptr)
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{
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int i;
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for (i = 0; ptr[i]; i++)
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sysfs_remove_file(kobj, ptr[i]);
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}
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EXPORT_SYMBOL_GPL(sysfs_remove_files);
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/**
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* sysfs_remove_file_from_group - remove an attribute file from a group.
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* @kobj: object we're acting for.
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* @attr: attribute descriptor.
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* @group: group name.
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*/
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void sysfs_remove_file_from_group(struct kobject *kobj,
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const struct attribute *attr, const char *group)
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{
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struct kernfs_node *parent;
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if (group) {
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parent = kernfs_find_and_get(kobj->sd, group);
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} else {
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parent = kobj->sd;
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kernfs_get(parent);
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}
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if (parent) {
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kernfs_remove_by_name(parent, attr->name);
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kernfs_put(parent);
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}
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}
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EXPORT_SYMBOL_GPL(sysfs_remove_file_from_group);
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/**
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* sysfs_create_bin_file - create binary file for object.
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* @kobj: object.
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* @attr: attribute descriptor.
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*/
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int sysfs_create_bin_file(struct kobject *kobj,
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const struct bin_attribute *attr)
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{
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BUG_ON(!kobj || !kobj->sd || !attr);
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return sysfs_add_file(kobj->sd, &attr->attr, true);
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}
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EXPORT_SYMBOL_GPL(sysfs_create_bin_file);
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/**
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* sysfs_remove_bin_file - remove binary file for object.
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* @kobj: object.
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* @attr: attribute descriptor.
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*/
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void sysfs_remove_bin_file(struct kobject *kobj,
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const struct bin_attribute *attr)
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{
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kernfs_remove_by_name(kobj->sd, attr->attr.name);
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}
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EXPORT_SYMBOL_GPL(sysfs_remove_bin_file);
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