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https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git
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![Dmitry Torokhov](/assets/img/avatar_default.png)
This change allows creating kernfs files and directories with arbitrary uid/gid instead of always using GLOBAL_ROOT_UID/GID by extending kernfs_create_dir_ns() and kernfs_create_file_ns() with uid/gid arguments. The "simple" kernfs_create_file() and kernfs_create_dir() are left alone and always create objects belonging to the global root. When creating symlinks ownership (uid/gid) is taken from the target kernfs object. Co-Developed-by: Tyler Hicks <tyhicks@canonical.com> Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com> Signed-off-by: Tyler Hicks <tyhicks@canonical.com> Signed-off-by: David S. Miller <davem@davemloft.net>
1027 lines
25 KiB
C
1027 lines
25 KiB
C
/*
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* fs/kernfs/file.c - kernfs 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, 2013 Tejun Heo <tj@kernel.org>
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*
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* This file is released under the GPLv2.
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*/
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#include <linux/fs.h>
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#include <linux/seq_file.h>
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#include <linux/slab.h>
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#include <linux/poll.h>
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#include <linux/pagemap.h>
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#include <linux/sched/mm.h>
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#include <linux/fsnotify.h>
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#include "kernfs-internal.h"
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/*
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* There's one kernfs_open_file for each open file and one kernfs_open_node
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* for each kernfs_node with one or more open files.
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*
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* kernfs_node->attr.open points to kernfs_open_node. attr.open is
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* protected by kernfs_open_node_lock.
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*
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* filp->private_data points to seq_file whose ->private points to
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* kernfs_open_file. kernfs_open_files are chained at
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* kernfs_open_node->files, which is protected by kernfs_open_file_mutex.
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*/
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static DEFINE_SPINLOCK(kernfs_open_node_lock);
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static DEFINE_MUTEX(kernfs_open_file_mutex);
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struct kernfs_open_node {
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atomic_t refcnt;
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atomic_t event;
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wait_queue_head_t poll;
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struct list_head files; /* goes through kernfs_open_file.list */
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};
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/*
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* kernfs_notify() may be called from any context and bounces notifications
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* through a work item. To minimize space overhead in kernfs_node, the
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* pending queue is implemented as a singly linked list of kernfs_nodes.
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* The list is terminated with the self pointer so that whether a
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* kernfs_node is on the list or not can be determined by testing the next
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* pointer for NULL.
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*/
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#define KERNFS_NOTIFY_EOL ((void *)&kernfs_notify_list)
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static DEFINE_SPINLOCK(kernfs_notify_lock);
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static struct kernfs_node *kernfs_notify_list = KERNFS_NOTIFY_EOL;
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static struct kernfs_open_file *kernfs_of(struct file *file)
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{
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return ((struct seq_file *)file->private_data)->private;
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}
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/*
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* Determine the kernfs_ops for the given kernfs_node. This function must
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* be called while holding an active reference.
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*/
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static const struct kernfs_ops *kernfs_ops(struct kernfs_node *kn)
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{
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if (kn->flags & KERNFS_LOCKDEP)
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lockdep_assert_held(kn);
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return kn->attr.ops;
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}
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/*
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* As kernfs_seq_stop() is also called after kernfs_seq_start() or
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* kernfs_seq_next() failure, it needs to distinguish whether it's stopping
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* a seq_file iteration which is fully initialized with an active reference
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* or an aborted kernfs_seq_start() due to get_active failure. The
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* position pointer is the only context for each seq_file iteration and
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* thus the stop condition should be encoded in it. As the return value is
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* directly visible to userland, ERR_PTR(-ENODEV) is the only acceptable
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* choice to indicate get_active failure.
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*
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* Unfortunately, this is complicated due to the optional custom seq_file
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* operations which may return ERR_PTR(-ENODEV) too. kernfs_seq_stop()
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* can't distinguish whether ERR_PTR(-ENODEV) is from get_active failure or
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* custom seq_file operations and thus can't decide whether put_active
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* should be performed or not only on ERR_PTR(-ENODEV).
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*
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* This is worked around by factoring out the custom seq_stop() and
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* put_active part into kernfs_seq_stop_active(), skipping it from
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* kernfs_seq_stop() if ERR_PTR(-ENODEV) while invoking it directly after
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* custom seq_file operations fail with ERR_PTR(-ENODEV) - this ensures
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* that kernfs_seq_stop_active() is skipped only after get_active failure.
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*/
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static void kernfs_seq_stop_active(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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const struct kernfs_ops *ops = kernfs_ops(of->kn);
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if (ops->seq_stop)
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ops->seq_stop(sf, v);
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kernfs_put_active(of->kn);
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}
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static void *kernfs_seq_start(struct seq_file *sf, loff_t *ppos)
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{
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struct kernfs_open_file *of = sf->private;
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const struct kernfs_ops *ops;
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/*
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* @of->mutex nests outside active ref and is primarily to ensure that
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* the ops aren't called concurrently for the same open file.
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*/
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mutex_lock(&of->mutex);
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if (!kernfs_get_active(of->kn))
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return ERR_PTR(-ENODEV);
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ops = kernfs_ops(of->kn);
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if (ops->seq_start) {
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void *next = ops->seq_start(sf, ppos);
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/* see the comment above kernfs_seq_stop_active() */
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if (next == ERR_PTR(-ENODEV))
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kernfs_seq_stop_active(sf, next);
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return next;
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} else {
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/*
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* The same behavior and code as single_open(). Returns
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* !NULL if pos is at the beginning; otherwise, NULL.
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*/
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return NULL + !*ppos;
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}
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}
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static void *kernfs_seq_next(struct seq_file *sf, void *v, loff_t *ppos)
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{
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struct kernfs_open_file *of = sf->private;
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const struct kernfs_ops *ops = kernfs_ops(of->kn);
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if (ops->seq_next) {
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void *next = ops->seq_next(sf, v, ppos);
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/* see the comment above kernfs_seq_stop_active() */
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if (next == ERR_PTR(-ENODEV))
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kernfs_seq_stop_active(sf, next);
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return next;
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} else {
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/*
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* The same behavior and code as single_open(), always
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* terminate after the initial read.
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*/
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++*ppos;
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return NULL;
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}
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}
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static void kernfs_seq_stop(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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if (v != ERR_PTR(-ENODEV))
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kernfs_seq_stop_active(sf, v);
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mutex_unlock(&of->mutex);
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}
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static int kernfs_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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of->event = atomic_read(&of->kn->attr.open->event);
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return of->kn->attr.ops->seq_show(sf, v);
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}
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static const struct seq_operations kernfs_seq_ops = {
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.start = kernfs_seq_start,
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.next = kernfs_seq_next,
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.stop = kernfs_seq_stop,
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.show = kernfs_seq_show,
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};
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/*
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* As reading a bin file can have side-effects, the exact offset and bytes
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* specified in read(2) call should be passed to the read callback making
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* it difficult to use seq_file. Implement simplistic custom buffering for
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* bin files.
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*/
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static ssize_t kernfs_file_direct_read(struct kernfs_open_file *of,
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char __user *user_buf, size_t count,
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loff_t *ppos)
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{
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ssize_t len = min_t(size_t, count, PAGE_SIZE);
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const struct kernfs_ops *ops;
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char *buf;
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buf = of->prealloc_buf;
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if (buf)
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mutex_lock(&of->prealloc_mutex);
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else
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buf = kmalloc(len, GFP_KERNEL);
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if (!buf)
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return -ENOMEM;
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/*
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* @of->mutex nests outside active ref and is used both to ensure that
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* the ops aren't called concurrently for the same open file.
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*/
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mutex_lock(&of->mutex);
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if (!kernfs_get_active(of->kn)) {
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len = -ENODEV;
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mutex_unlock(&of->mutex);
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goto out_free;
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}
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of->event = atomic_read(&of->kn->attr.open->event);
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ops = kernfs_ops(of->kn);
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if (ops->read)
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len = ops->read(of, buf, len, *ppos);
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else
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len = -EINVAL;
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kernfs_put_active(of->kn);
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mutex_unlock(&of->mutex);
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if (len < 0)
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goto out_free;
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if (copy_to_user(user_buf, buf, len)) {
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len = -EFAULT;
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goto out_free;
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}
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*ppos += len;
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out_free:
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if (buf == of->prealloc_buf)
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mutex_unlock(&of->prealloc_mutex);
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else
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kfree(buf);
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return len;
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}
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/**
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* kernfs_fop_read - kernfs vfs read callback
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* @file: file pointer
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* @user_buf: data to write
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* @count: number of bytes
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* @ppos: starting offset
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*/
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static ssize_t kernfs_fop_read(struct file *file, char __user *user_buf,
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size_t count, loff_t *ppos)
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{
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struct kernfs_open_file *of = kernfs_of(file);
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if (of->kn->flags & KERNFS_HAS_SEQ_SHOW)
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return seq_read(file, user_buf, count, ppos);
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else
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return kernfs_file_direct_read(of, user_buf, count, ppos);
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}
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/**
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* kernfs_fop_write - kernfs vfs write callback
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* @file: file pointer
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* @user_buf: data to write
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* @count: number of bytes
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* @ppos: starting offset
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*
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* Copy data in from userland and pass it to the matching kernfs write
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* operation.
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*
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* There is no easy way for us to know if userspace is only doing a partial
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* write, so we don't support them. We expect the entire buffer to come on
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* the first write. Hint: if you're writing a value, first read the file,
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* modify only the the value you're changing, then write entire buffer
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* back.
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*/
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static ssize_t kernfs_fop_write(struct file *file, const char __user *user_buf,
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size_t count, loff_t *ppos)
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{
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struct kernfs_open_file *of = kernfs_of(file);
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const struct kernfs_ops *ops;
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ssize_t len;
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char *buf;
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if (of->atomic_write_len) {
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len = count;
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if (len > of->atomic_write_len)
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return -E2BIG;
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} else {
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len = min_t(size_t, count, PAGE_SIZE);
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}
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buf = of->prealloc_buf;
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if (buf)
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mutex_lock(&of->prealloc_mutex);
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else
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buf = kmalloc(len + 1, GFP_KERNEL);
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if (!buf)
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return -ENOMEM;
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if (copy_from_user(buf, user_buf, len)) {
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len = -EFAULT;
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goto out_free;
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}
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buf[len] = '\0'; /* guarantee string termination */
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/*
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* @of->mutex nests outside active ref and is used both to ensure that
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* the ops aren't called concurrently for the same open file.
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*/
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mutex_lock(&of->mutex);
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if (!kernfs_get_active(of->kn)) {
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mutex_unlock(&of->mutex);
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len = -ENODEV;
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goto out_free;
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}
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ops = kernfs_ops(of->kn);
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if (ops->write)
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len = ops->write(of, buf, len, *ppos);
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else
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len = -EINVAL;
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kernfs_put_active(of->kn);
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mutex_unlock(&of->mutex);
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if (len > 0)
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*ppos += len;
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out_free:
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if (buf == of->prealloc_buf)
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mutex_unlock(&of->prealloc_mutex);
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else
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kfree(buf);
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return len;
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}
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static void kernfs_vma_open(struct vm_area_struct *vma)
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{
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struct file *file = vma->vm_file;
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struct kernfs_open_file *of = kernfs_of(file);
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if (!of->vm_ops)
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return;
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if (!kernfs_get_active(of->kn))
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return;
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if (of->vm_ops->open)
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of->vm_ops->open(vma);
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kernfs_put_active(of->kn);
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}
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static vm_fault_t kernfs_vma_fault(struct vm_fault *vmf)
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{
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struct file *file = vmf->vma->vm_file;
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struct kernfs_open_file *of = kernfs_of(file);
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vm_fault_t ret;
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if (!of->vm_ops)
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return VM_FAULT_SIGBUS;
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|
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if (!kernfs_get_active(of->kn))
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return VM_FAULT_SIGBUS;
|
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|
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ret = VM_FAULT_SIGBUS;
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if (of->vm_ops->fault)
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ret = of->vm_ops->fault(vmf);
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kernfs_put_active(of->kn);
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return ret;
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|
}
|
|
|
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static vm_fault_t kernfs_vma_page_mkwrite(struct vm_fault *vmf)
|
|
{
|
|
struct file *file = vmf->vma->vm_file;
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struct kernfs_open_file *of = kernfs_of(file);
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|
vm_fault_t ret;
|
|
|
|
if (!of->vm_ops)
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return VM_FAULT_SIGBUS;
|
|
|
|
if (!kernfs_get_active(of->kn))
|
|
return VM_FAULT_SIGBUS;
|
|
|
|
ret = 0;
|
|
if (of->vm_ops->page_mkwrite)
|
|
ret = of->vm_ops->page_mkwrite(vmf);
|
|
else
|
|
file_update_time(file);
|
|
|
|
kernfs_put_active(of->kn);
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return ret;
|
|
}
|
|
|
|
static int kernfs_vma_access(struct vm_area_struct *vma, unsigned long addr,
|
|
void *buf, int len, int write)
|
|
{
|
|
struct file *file = vma->vm_file;
|
|
struct kernfs_open_file *of = kernfs_of(file);
|
|
int ret;
|
|
|
|
if (!of->vm_ops)
|
|
return -EINVAL;
|
|
|
|
if (!kernfs_get_active(of->kn))
|
|
return -EINVAL;
|
|
|
|
ret = -EINVAL;
|
|
if (of->vm_ops->access)
|
|
ret = of->vm_ops->access(vma, addr, buf, len, write);
|
|
|
|
kernfs_put_active(of->kn);
|
|
return ret;
|
|
}
|
|
|
|
#ifdef CONFIG_NUMA
|
|
static int kernfs_vma_set_policy(struct vm_area_struct *vma,
|
|
struct mempolicy *new)
|
|
{
|
|
struct file *file = vma->vm_file;
|
|
struct kernfs_open_file *of = kernfs_of(file);
|
|
int ret;
|
|
|
|
if (!of->vm_ops)
|
|
return 0;
|
|
|
|
if (!kernfs_get_active(of->kn))
|
|
return -EINVAL;
|
|
|
|
ret = 0;
|
|
if (of->vm_ops->set_policy)
|
|
ret = of->vm_ops->set_policy(vma, new);
|
|
|
|
kernfs_put_active(of->kn);
|
|
return ret;
|
|
}
|
|
|
|
static struct mempolicy *kernfs_vma_get_policy(struct vm_area_struct *vma,
|
|
unsigned long addr)
|
|
{
|
|
struct file *file = vma->vm_file;
|
|
struct kernfs_open_file *of = kernfs_of(file);
|
|
struct mempolicy *pol;
|
|
|
|
if (!of->vm_ops)
|
|
return vma->vm_policy;
|
|
|
|
if (!kernfs_get_active(of->kn))
|
|
return vma->vm_policy;
|
|
|
|
pol = vma->vm_policy;
|
|
if (of->vm_ops->get_policy)
|
|
pol = of->vm_ops->get_policy(vma, addr);
|
|
|
|
kernfs_put_active(of->kn);
|
|
return pol;
|
|
}
|
|
|
|
#endif
|
|
|
|
static const struct vm_operations_struct kernfs_vm_ops = {
|
|
.open = kernfs_vma_open,
|
|
.fault = kernfs_vma_fault,
|
|
.page_mkwrite = kernfs_vma_page_mkwrite,
|
|
.access = kernfs_vma_access,
|
|
#ifdef CONFIG_NUMA
|
|
.set_policy = kernfs_vma_set_policy,
|
|
.get_policy = kernfs_vma_get_policy,
|
|
#endif
|
|
};
|
|
|
|
static int kernfs_fop_mmap(struct file *file, struct vm_area_struct *vma)
|
|
{
|
|
struct kernfs_open_file *of = kernfs_of(file);
|
|
const struct kernfs_ops *ops;
|
|
int rc;
|
|
|
|
/*
|
|
* mmap path and of->mutex are prone to triggering spurious lockdep
|
|
* warnings and we don't want to add spurious locking dependency
|
|
* between the two. Check whether mmap is actually implemented
|
|
* without grabbing @of->mutex by testing HAS_MMAP flag. See the
|
|
* comment in kernfs_file_open() for more details.
|
|
*/
|
|
if (!(of->kn->flags & KERNFS_HAS_MMAP))
|
|
return -ENODEV;
|
|
|
|
mutex_lock(&of->mutex);
|
|
|
|
rc = -ENODEV;
|
|
if (!kernfs_get_active(of->kn))
|
|
goto out_unlock;
|
|
|
|
ops = kernfs_ops(of->kn);
|
|
rc = ops->mmap(of, vma);
|
|
if (rc)
|
|
goto out_put;
|
|
|
|
/*
|
|
* PowerPC's pci_mmap of legacy_mem uses shmem_zero_setup()
|
|
* to satisfy versions of X which crash if the mmap fails: that
|
|
* substitutes a new vm_file, and we don't then want bin_vm_ops.
|
|
*/
|
|
if (vma->vm_file != file)
|
|
goto out_put;
|
|
|
|
rc = -EINVAL;
|
|
if (of->mmapped && of->vm_ops != vma->vm_ops)
|
|
goto out_put;
|
|
|
|
/*
|
|
* It is not possible to successfully wrap close.
|
|
* So error if someone is trying to use close.
|
|
*/
|
|
rc = -EINVAL;
|
|
if (vma->vm_ops && vma->vm_ops->close)
|
|
goto out_put;
|
|
|
|
rc = 0;
|
|
of->mmapped = true;
|
|
of->vm_ops = vma->vm_ops;
|
|
vma->vm_ops = &kernfs_vm_ops;
|
|
out_put:
|
|
kernfs_put_active(of->kn);
|
|
out_unlock:
|
|
mutex_unlock(&of->mutex);
|
|
|
|
return rc;
|
|
}
|
|
|
|
/**
|
|
* kernfs_get_open_node - get or create kernfs_open_node
|
|
* @kn: target kernfs_node
|
|
* @of: kernfs_open_file for this instance of open
|
|
*
|
|
* If @kn->attr.open exists, increment its reference count; otherwise,
|
|
* create one. @of is chained to the files list.
|
|
*
|
|
* LOCKING:
|
|
* Kernel thread context (may sleep).
|
|
*
|
|
* RETURNS:
|
|
* 0 on success, -errno on failure.
|
|
*/
|
|
static int kernfs_get_open_node(struct kernfs_node *kn,
|
|
struct kernfs_open_file *of)
|
|
{
|
|
struct kernfs_open_node *on, *new_on = NULL;
|
|
|
|
retry:
|
|
mutex_lock(&kernfs_open_file_mutex);
|
|
spin_lock_irq(&kernfs_open_node_lock);
|
|
|
|
if (!kn->attr.open && new_on) {
|
|
kn->attr.open = new_on;
|
|
new_on = NULL;
|
|
}
|
|
|
|
on = kn->attr.open;
|
|
if (on) {
|
|
atomic_inc(&on->refcnt);
|
|
list_add_tail(&of->list, &on->files);
|
|
}
|
|
|
|
spin_unlock_irq(&kernfs_open_node_lock);
|
|
mutex_unlock(&kernfs_open_file_mutex);
|
|
|
|
if (on) {
|
|
kfree(new_on);
|
|
return 0;
|
|
}
|
|
|
|
/* not there, initialize a new one and retry */
|
|
new_on = kmalloc(sizeof(*new_on), GFP_KERNEL);
|
|
if (!new_on)
|
|
return -ENOMEM;
|
|
|
|
atomic_set(&new_on->refcnt, 0);
|
|
atomic_set(&new_on->event, 1);
|
|
init_waitqueue_head(&new_on->poll);
|
|
INIT_LIST_HEAD(&new_on->files);
|
|
goto retry;
|
|
}
|
|
|
|
/**
|
|
* kernfs_put_open_node - put kernfs_open_node
|
|
* @kn: target kernfs_nodet
|
|
* @of: associated kernfs_open_file
|
|
*
|
|
* Put @kn->attr.open and unlink @of from the files list. If
|
|
* reference count reaches zero, disassociate and free it.
|
|
*
|
|
* LOCKING:
|
|
* None.
|
|
*/
|
|
static void kernfs_put_open_node(struct kernfs_node *kn,
|
|
struct kernfs_open_file *of)
|
|
{
|
|
struct kernfs_open_node *on = kn->attr.open;
|
|
unsigned long flags;
|
|
|
|
mutex_lock(&kernfs_open_file_mutex);
|
|
spin_lock_irqsave(&kernfs_open_node_lock, flags);
|
|
|
|
if (of)
|
|
list_del(&of->list);
|
|
|
|
if (atomic_dec_and_test(&on->refcnt))
|
|
kn->attr.open = NULL;
|
|
else
|
|
on = NULL;
|
|
|
|
spin_unlock_irqrestore(&kernfs_open_node_lock, flags);
|
|
mutex_unlock(&kernfs_open_file_mutex);
|
|
|
|
kfree(on);
|
|
}
|
|
|
|
static int kernfs_fop_open(struct inode *inode, struct file *file)
|
|
{
|
|
struct kernfs_node *kn = inode->i_private;
|
|
struct kernfs_root *root = kernfs_root(kn);
|
|
const struct kernfs_ops *ops;
|
|
struct kernfs_open_file *of;
|
|
bool has_read, has_write, has_mmap;
|
|
int error = -EACCES;
|
|
|
|
if (!kernfs_get_active(kn))
|
|
return -ENODEV;
|
|
|
|
ops = kernfs_ops(kn);
|
|
|
|
has_read = ops->seq_show || ops->read || ops->mmap;
|
|
has_write = ops->write || ops->mmap;
|
|
has_mmap = ops->mmap;
|
|
|
|
/* see the flag definition for details */
|
|
if (root->flags & KERNFS_ROOT_EXTRA_OPEN_PERM_CHECK) {
|
|
if ((file->f_mode & FMODE_WRITE) &&
|
|
(!(inode->i_mode & S_IWUGO) || !has_write))
|
|
goto err_out;
|
|
|
|
if ((file->f_mode & FMODE_READ) &&
|
|
(!(inode->i_mode & S_IRUGO) || !has_read))
|
|
goto err_out;
|
|
}
|
|
|
|
/* allocate a kernfs_open_file for the file */
|
|
error = -ENOMEM;
|
|
of = kzalloc(sizeof(struct kernfs_open_file), GFP_KERNEL);
|
|
if (!of)
|
|
goto err_out;
|
|
|
|
/*
|
|
* The following is done to give a different lockdep key to
|
|
* @of->mutex for files which implement mmap. This is a rather
|
|
* crude way to avoid false positive lockdep warning around
|
|
* mm->mmap_sem - mmap nests @of->mutex under mm->mmap_sem and
|
|
* reading /sys/block/sda/trace/act_mask grabs sr_mutex, under
|
|
* which mm->mmap_sem nests, while holding @of->mutex. As each
|
|
* open file has a separate mutex, it's okay as long as those don't
|
|
* happen on the same file. At this point, we can't easily give
|
|
* each file a separate locking class. Let's differentiate on
|
|
* whether the file has mmap or not for now.
|
|
*
|
|
* Both paths of the branch look the same. They're supposed to
|
|
* look that way and give @of->mutex different static lockdep keys.
|
|
*/
|
|
if (has_mmap)
|
|
mutex_init(&of->mutex);
|
|
else
|
|
mutex_init(&of->mutex);
|
|
|
|
of->kn = kn;
|
|
of->file = file;
|
|
|
|
/*
|
|
* Write path needs to atomic_write_len outside active reference.
|
|
* Cache it in open_file. See kernfs_fop_write() for details.
|
|
*/
|
|
of->atomic_write_len = ops->atomic_write_len;
|
|
|
|
error = -EINVAL;
|
|
/*
|
|
* ->seq_show is incompatible with ->prealloc,
|
|
* as seq_read does its own allocation.
|
|
* ->read must be used instead.
|
|
*/
|
|
if (ops->prealloc && ops->seq_show)
|
|
goto err_free;
|
|
if (ops->prealloc) {
|
|
int len = of->atomic_write_len ?: PAGE_SIZE;
|
|
of->prealloc_buf = kmalloc(len + 1, GFP_KERNEL);
|
|
error = -ENOMEM;
|
|
if (!of->prealloc_buf)
|
|
goto err_free;
|
|
mutex_init(&of->prealloc_mutex);
|
|
}
|
|
|
|
/*
|
|
* Always instantiate seq_file even if read access doesn't use
|
|
* seq_file or is not requested. This unifies private data access
|
|
* and readable regular files are the vast majority anyway.
|
|
*/
|
|
if (ops->seq_show)
|
|
error = seq_open(file, &kernfs_seq_ops);
|
|
else
|
|
error = seq_open(file, NULL);
|
|
if (error)
|
|
goto err_free;
|
|
|
|
of->seq_file = file->private_data;
|
|
of->seq_file->private = of;
|
|
|
|
/* seq_file clears PWRITE unconditionally, restore it if WRITE */
|
|
if (file->f_mode & FMODE_WRITE)
|
|
file->f_mode |= FMODE_PWRITE;
|
|
|
|
/* make sure we have open node struct */
|
|
error = kernfs_get_open_node(kn, of);
|
|
if (error)
|
|
goto err_seq_release;
|
|
|
|
if (ops->open) {
|
|
/* nobody has access to @of yet, skip @of->mutex */
|
|
error = ops->open(of);
|
|
if (error)
|
|
goto err_put_node;
|
|
}
|
|
|
|
/* open succeeded, put active references */
|
|
kernfs_put_active(kn);
|
|
return 0;
|
|
|
|
err_put_node:
|
|
kernfs_put_open_node(kn, of);
|
|
err_seq_release:
|
|
seq_release(inode, file);
|
|
err_free:
|
|
kfree(of->prealloc_buf);
|
|
kfree(of);
|
|
err_out:
|
|
kernfs_put_active(kn);
|
|
return error;
|
|
}
|
|
|
|
/* used from release/drain to ensure that ->release() is called exactly once */
|
|
static void kernfs_release_file(struct kernfs_node *kn,
|
|
struct kernfs_open_file *of)
|
|
{
|
|
/*
|
|
* @of is guaranteed to have no other file operations in flight and
|
|
* we just want to synchronize release and drain paths.
|
|
* @kernfs_open_file_mutex is enough. @of->mutex can't be used
|
|
* here because drain path may be called from places which can
|
|
* cause circular dependency.
|
|
*/
|
|
lockdep_assert_held(&kernfs_open_file_mutex);
|
|
|
|
if (!of->released) {
|
|
/*
|
|
* A file is never detached without being released and we
|
|
* need to be able to release files which are deactivated
|
|
* and being drained. Don't use kernfs_ops().
|
|
*/
|
|
kn->attr.ops->release(of);
|
|
of->released = true;
|
|
}
|
|
}
|
|
|
|
static int kernfs_fop_release(struct inode *inode, struct file *filp)
|
|
{
|
|
struct kernfs_node *kn = inode->i_private;
|
|
struct kernfs_open_file *of = kernfs_of(filp);
|
|
|
|
if (kn->flags & KERNFS_HAS_RELEASE) {
|
|
mutex_lock(&kernfs_open_file_mutex);
|
|
kernfs_release_file(kn, of);
|
|
mutex_unlock(&kernfs_open_file_mutex);
|
|
}
|
|
|
|
kernfs_put_open_node(kn, of);
|
|
seq_release(inode, filp);
|
|
kfree(of->prealloc_buf);
|
|
kfree(of);
|
|
|
|
return 0;
|
|
}
|
|
|
|
void kernfs_drain_open_files(struct kernfs_node *kn)
|
|
{
|
|
struct kernfs_open_node *on;
|
|
struct kernfs_open_file *of;
|
|
|
|
if (!(kn->flags & (KERNFS_HAS_MMAP | KERNFS_HAS_RELEASE)))
|
|
return;
|
|
|
|
spin_lock_irq(&kernfs_open_node_lock);
|
|
on = kn->attr.open;
|
|
if (on)
|
|
atomic_inc(&on->refcnt);
|
|
spin_unlock_irq(&kernfs_open_node_lock);
|
|
if (!on)
|
|
return;
|
|
|
|
mutex_lock(&kernfs_open_file_mutex);
|
|
|
|
list_for_each_entry(of, &on->files, list) {
|
|
struct inode *inode = file_inode(of->file);
|
|
|
|
if (kn->flags & KERNFS_HAS_MMAP)
|
|
unmap_mapping_range(inode->i_mapping, 0, 0, 1);
|
|
|
|
if (kn->flags & KERNFS_HAS_RELEASE)
|
|
kernfs_release_file(kn, of);
|
|
}
|
|
|
|
mutex_unlock(&kernfs_open_file_mutex);
|
|
|
|
kernfs_put_open_node(kn, NULL);
|
|
}
|
|
|
|
/*
|
|
* Kernfs attribute files are pollable. The idea is that you read
|
|
* the content and then you use 'poll' or 'select' to wait for
|
|
* the content to change. When the content changes (assuming the
|
|
* manager for the kobject supports notification), poll will
|
|
* return EPOLLERR|EPOLLPRI, and select will return the fd whether
|
|
* it is waiting for read, write, or exceptions.
|
|
* Once poll/select indicates that the value has changed, you
|
|
* need to close and re-open the file, or seek to 0 and read again.
|
|
* Reminder: this only works for attributes which actively support
|
|
* it, and it is not possible to test an attribute from userspace
|
|
* to see if it supports poll (Neither 'poll' nor 'select' return
|
|
* an appropriate error code). When in doubt, set a suitable timeout value.
|
|
*/
|
|
static __poll_t kernfs_fop_poll(struct file *filp, poll_table *wait)
|
|
{
|
|
struct kernfs_open_file *of = kernfs_of(filp);
|
|
struct kernfs_node *kn = kernfs_dentry_node(filp->f_path.dentry);
|
|
struct kernfs_open_node *on = kn->attr.open;
|
|
|
|
if (!kernfs_get_active(kn))
|
|
goto trigger;
|
|
|
|
poll_wait(filp, &on->poll, wait);
|
|
|
|
kernfs_put_active(kn);
|
|
|
|
if (of->event != atomic_read(&on->event))
|
|
goto trigger;
|
|
|
|
return DEFAULT_POLLMASK;
|
|
|
|
trigger:
|
|
return DEFAULT_POLLMASK|EPOLLERR|EPOLLPRI;
|
|
}
|
|
|
|
static void kernfs_notify_workfn(struct work_struct *work)
|
|
{
|
|
struct kernfs_node *kn;
|
|
struct kernfs_open_node *on;
|
|
struct kernfs_super_info *info;
|
|
repeat:
|
|
/* pop one off the notify_list */
|
|
spin_lock_irq(&kernfs_notify_lock);
|
|
kn = kernfs_notify_list;
|
|
if (kn == KERNFS_NOTIFY_EOL) {
|
|
spin_unlock_irq(&kernfs_notify_lock);
|
|
return;
|
|
}
|
|
kernfs_notify_list = kn->attr.notify_next;
|
|
kn->attr.notify_next = NULL;
|
|
spin_unlock_irq(&kernfs_notify_lock);
|
|
|
|
/* kick poll */
|
|
spin_lock_irq(&kernfs_open_node_lock);
|
|
|
|
on = kn->attr.open;
|
|
if (on) {
|
|
atomic_inc(&on->event);
|
|
wake_up_interruptible(&on->poll);
|
|
}
|
|
|
|
spin_unlock_irq(&kernfs_open_node_lock);
|
|
|
|
/* kick fsnotify */
|
|
mutex_lock(&kernfs_mutex);
|
|
|
|
list_for_each_entry(info, &kernfs_root(kn)->supers, node) {
|
|
struct kernfs_node *parent;
|
|
struct inode *inode;
|
|
|
|
/*
|
|
* We want fsnotify_modify() on @kn but as the
|
|
* modifications aren't originating from userland don't
|
|
* have the matching @file available. Look up the inodes
|
|
* and generate the events manually.
|
|
*/
|
|
inode = ilookup(info->sb, kn->id.ino);
|
|
if (!inode)
|
|
continue;
|
|
|
|
parent = kernfs_get_parent(kn);
|
|
if (parent) {
|
|
struct inode *p_inode;
|
|
|
|
p_inode = ilookup(info->sb, parent->id.ino);
|
|
if (p_inode) {
|
|
fsnotify(p_inode, FS_MODIFY | FS_EVENT_ON_CHILD,
|
|
inode, FSNOTIFY_EVENT_INODE, kn->name, 0);
|
|
iput(p_inode);
|
|
}
|
|
|
|
kernfs_put(parent);
|
|
}
|
|
|
|
fsnotify(inode, FS_MODIFY, inode, FSNOTIFY_EVENT_INODE,
|
|
kn->name, 0);
|
|
iput(inode);
|
|
}
|
|
|
|
mutex_unlock(&kernfs_mutex);
|
|
kernfs_put(kn);
|
|
goto repeat;
|
|
}
|
|
|
|
/**
|
|
* kernfs_notify - notify a kernfs file
|
|
* @kn: file to notify
|
|
*
|
|
* Notify @kn such that poll(2) on @kn wakes up. Maybe be called from any
|
|
* context.
|
|
*/
|
|
void kernfs_notify(struct kernfs_node *kn)
|
|
{
|
|
static DECLARE_WORK(kernfs_notify_work, kernfs_notify_workfn);
|
|
unsigned long flags;
|
|
|
|
if (WARN_ON(kernfs_type(kn) != KERNFS_FILE))
|
|
return;
|
|
|
|
spin_lock_irqsave(&kernfs_notify_lock, flags);
|
|
if (!kn->attr.notify_next) {
|
|
kernfs_get(kn);
|
|
kn->attr.notify_next = kernfs_notify_list;
|
|
kernfs_notify_list = kn;
|
|
schedule_work(&kernfs_notify_work);
|
|
}
|
|
spin_unlock_irqrestore(&kernfs_notify_lock, flags);
|
|
}
|
|
EXPORT_SYMBOL_GPL(kernfs_notify);
|
|
|
|
const struct file_operations kernfs_file_fops = {
|
|
.read = kernfs_fop_read,
|
|
.write = kernfs_fop_write,
|
|
.llseek = generic_file_llseek,
|
|
.mmap = kernfs_fop_mmap,
|
|
.open = kernfs_fop_open,
|
|
.release = kernfs_fop_release,
|
|
.poll = kernfs_fop_poll,
|
|
.fsync = noop_fsync,
|
|
};
|
|
|
|
/**
|
|
* __kernfs_create_file - kernfs internal function to create a file
|
|
* @parent: directory to create the file in
|
|
* @name: name of the file
|
|
* @mode: mode of the file
|
|
* @uid: uid of the file
|
|
* @gid: gid of the file
|
|
* @size: size of the file
|
|
* @ops: kernfs operations for the file
|
|
* @priv: private data for the file
|
|
* @ns: optional namespace tag of the file
|
|
* @key: lockdep key for the file's active_ref, %NULL to disable lockdep
|
|
*
|
|
* Returns the created node on success, ERR_PTR() value on error.
|
|
*/
|
|
struct kernfs_node *__kernfs_create_file(struct kernfs_node *parent,
|
|
const char *name,
|
|
umode_t mode, kuid_t uid, kgid_t gid,
|
|
loff_t size,
|
|
const struct kernfs_ops *ops,
|
|
void *priv, const void *ns,
|
|
struct lock_class_key *key)
|
|
{
|
|
struct kernfs_node *kn;
|
|
unsigned flags;
|
|
int rc;
|
|
|
|
flags = KERNFS_FILE;
|
|
|
|
kn = kernfs_new_node(parent, name, (mode & S_IALLUGO) | S_IFREG,
|
|
uid, gid, flags);
|
|
if (!kn)
|
|
return ERR_PTR(-ENOMEM);
|
|
|
|
kn->attr.ops = ops;
|
|
kn->attr.size = size;
|
|
kn->ns = ns;
|
|
kn->priv = priv;
|
|
|
|
#ifdef CONFIG_DEBUG_LOCK_ALLOC
|
|
if (key) {
|
|
lockdep_init_map(&kn->dep_map, "kn->count", key, 0);
|
|
kn->flags |= KERNFS_LOCKDEP;
|
|
}
|
|
#endif
|
|
|
|
/*
|
|
* kn->attr.ops is accesible only while holding active ref. We
|
|
* need to know whether some ops are implemented outside active
|
|
* ref. Cache their existence in flags.
|
|
*/
|
|
if (ops->seq_show)
|
|
kn->flags |= KERNFS_HAS_SEQ_SHOW;
|
|
if (ops->mmap)
|
|
kn->flags |= KERNFS_HAS_MMAP;
|
|
if (ops->release)
|
|
kn->flags |= KERNFS_HAS_RELEASE;
|
|
|
|
rc = kernfs_add_one(kn);
|
|
if (rc) {
|
|
kernfs_put(kn);
|
|
return ERR_PTR(rc);
|
|
}
|
|
return kn;
|
|
}
|