diff options
Diffstat (limited to 'fs/sysfs/file.c')
-rw-r--r-- | fs/sysfs/file.c | 725 |
1 files changed, 725 insertions, 0 deletions
diff --git a/fs/sysfs/file.c b/fs/sysfs/file.c new file mode 100644 index 0000000..1f4a3f8 --- /dev/null +++ b/fs/sysfs/file.c @@ -0,0 +1,725 @@ +/* + * fs/sysfs/file.c - sysfs regular (text) file implementation + * + * Copyright (c) 2001-3 Patrick Mochel + * Copyright (c) 2007 SUSE Linux Products GmbH + * Copyright (c) 2007 Tejun Heo <teheo@suse.de> + * + * This file is released under the GPLv2. + * + * Please see Documentation/filesystems/sysfs.txt for more information. + */ + +#include <linux/module.h> +#include <linux/kobject.h> +#include <linux/kallsyms.h> +#include <linux/slab.h> +#include <linux/fsnotify.h> +#include <linux/namei.h> +#include <linux/poll.h> +#include <linux/list.h> +#include <linux/mutex.h> +#include <linux/limits.h> +#include <asm/uaccess.h> + +#include "sysfs.h" + +/* used in crash dumps to help with debugging */ +static char last_sysfs_file[PATH_MAX]; +void sysfs_printk_last_file(void) +{ + printk(KERN_EMERG "last sysfs file: %s\n", last_sysfs_file); +} + +/* + * There's one sysfs_buffer for each open file and one + * sysfs_open_dirent for each sysfs_dirent with one or more open + * files. + * + * filp->private_data points to sysfs_buffer and + * sysfs_dirent->s_attr.open points to sysfs_open_dirent. s_attr.open + * is protected by sysfs_open_dirent_lock. + */ +static DEFINE_SPINLOCK(sysfs_open_dirent_lock); + +struct sysfs_open_dirent { + atomic_t refcnt; + atomic_t event; + wait_queue_head_t poll; + struct list_head buffers; /* goes through sysfs_buffer.list */ +}; + +struct sysfs_buffer { + size_t count; + loff_t pos; + char * page; + struct sysfs_ops * ops; + struct mutex mutex; + int needs_read_fill; + int event; + struct list_head list; +}; + +/** + * fill_read_buffer - allocate and fill buffer from object. + * @dentry: dentry pointer. + * @buffer: data buffer for file. + * + * Allocate @buffer->page, if it hasn't been already, then call the + * kobject's show() method to fill the buffer with this attribute's + * data. + * This is called only once, on the file's first read unless an error + * is returned. + */ +static int fill_read_buffer(struct dentry * dentry, struct sysfs_buffer * buffer) +{ + struct sysfs_dirent *attr_sd = dentry->d_fsdata; + struct kobject *kobj = attr_sd->s_parent->s_dir.kobj; + struct sysfs_ops * ops = buffer->ops; + int ret = 0; + ssize_t count; + + if (!buffer->page) + buffer->page = (char *) get_zeroed_page(GFP_KERNEL); + if (!buffer->page) + return -ENOMEM; + + /* need attr_sd for attr and ops, its parent for kobj */ + if (!sysfs_get_active_two(attr_sd)) + return -ENODEV; + + buffer->event = atomic_read(&attr_sd->s_attr.open->event); + count = ops->show(kobj, attr_sd->s_attr.attr, buffer->page); + + sysfs_put_active_two(attr_sd); + + /* + * The code works fine with PAGE_SIZE return but it's likely to + * indicate truncated result or overflow in normal use cases. + */ + if (count >= (ssize_t)PAGE_SIZE) { + print_symbol("fill_read_buffer: %s returned bad count\n", + (unsigned long)ops->show); + /* Try to struggle along */ + count = PAGE_SIZE - 1; + } + if (count >= 0) { + buffer->needs_read_fill = 0; + buffer->count = count; + } else { + ret = count; + } + return ret; +} + +/** + * sysfs_read_file - read an attribute. + * @file: file pointer. + * @buf: buffer to fill. + * @count: number of bytes to read. + * @ppos: starting offset in file. + * + * Userspace wants to read an attribute file. The attribute descriptor + * is in the file's ->d_fsdata. The target object is in the directory's + * ->d_fsdata. + * + * We call fill_read_buffer() to allocate and fill the buffer from the + * object's show() method exactly once (if the read is happening from + * the beginning of the file). That should fill the entire buffer with + * all the data the object has to offer for that attribute. + * We then call flush_read_buffer() to copy the buffer to userspace + * in the increments specified. + */ + +static ssize_t +sysfs_read_file(struct file *file, char __user *buf, size_t count, loff_t *ppos) +{ + struct sysfs_buffer * buffer = file->private_data; + ssize_t retval = 0; + + mutex_lock(&buffer->mutex); + if (buffer->needs_read_fill || *ppos == 0) { + retval = fill_read_buffer(file->f_path.dentry,buffer); + if (retval) + goto out; + } + pr_debug("%s: count = %zd, ppos = %lld, buf = %s\n", + __func__, count, *ppos, buffer->page); + retval = simple_read_from_buffer(buf, count, ppos, buffer->page, + buffer->count); +out: + mutex_unlock(&buffer->mutex); + return retval; +} + +/** + * fill_write_buffer - copy buffer from userspace. + * @buffer: data buffer for file. + * @buf: data from user. + * @count: number of bytes in @userbuf. + * + * Allocate @buffer->page if it hasn't been already, then + * copy the user-supplied buffer into it. + */ + +static int +fill_write_buffer(struct sysfs_buffer * buffer, const char __user * buf, size_t count) +{ + int error; + + if (!buffer->page) + buffer->page = (char *)get_zeroed_page(GFP_KERNEL); + if (!buffer->page) + return -ENOMEM; + + if (count >= PAGE_SIZE) + count = PAGE_SIZE - 1; + error = copy_from_user(buffer->page,buf,count); + buffer->needs_read_fill = 1; + /* if buf is assumed to contain a string, terminate it by \0, + so e.g. sscanf() can scan the string easily */ + buffer->page[count] = 0; + return error ? -EFAULT : count; +} + + +/** + * flush_write_buffer - push buffer to kobject. + * @dentry: dentry to the attribute + * @buffer: data buffer for file. + * @count: number of bytes + * + * Get the correct pointers for the kobject and the attribute we're + * dealing with, then call the store() method for the attribute, + * passing the buffer that we acquired in fill_write_buffer(). + */ + +static int +flush_write_buffer(struct dentry * dentry, struct sysfs_buffer * buffer, size_t count) +{ + struct sysfs_dirent *attr_sd = dentry->d_fsdata; + struct kobject *kobj = attr_sd->s_parent->s_dir.kobj; + struct sysfs_ops * ops = buffer->ops; + int rc; + + /* need attr_sd for attr and ops, its parent for kobj */ + if (!sysfs_get_active_two(attr_sd)) + return -ENODEV; + + rc = ops->store(kobj, attr_sd->s_attr.attr, buffer->page, count); + + sysfs_put_active_two(attr_sd); + + return rc; +} + + +/** + * sysfs_write_file - write an attribute. + * @file: file pointer + * @buf: data to write + * @count: number of bytes + * @ppos: starting offset + * + * Similar to sysfs_read_file(), though working in the opposite direction. + * We allocate and fill the data from the user in fill_write_buffer(), + * then push it to the kobject in flush_write_buffer(). + * There is no easy way for us to know if userspace is only doing a partial + * write, so we don't support them. We expect the entire buffer to come + * on the first write. + * Hint: if you're writing a value, first read the file, modify only the + * the value you're changing, then write entire buffer back. + */ + +static ssize_t +sysfs_write_file(struct file *file, const char __user *buf, size_t count, loff_t *ppos) +{ + struct sysfs_buffer * buffer = file->private_data; + ssize_t len; + + mutex_lock(&buffer->mutex); + len = fill_write_buffer(buffer, buf, count); + if (len > 0) + len = flush_write_buffer(file->f_path.dentry, buffer, len); + if (len > 0) + *ppos += len; + mutex_unlock(&buffer->mutex); + return len; +} + +/** + * sysfs_get_open_dirent - get or create sysfs_open_dirent + * @sd: target sysfs_dirent + * @buffer: sysfs_buffer for this instance of open + * + * If @sd->s_attr.open exists, increment its reference count; + * otherwise, create one. @buffer is chained to the buffers + * list. + * + * LOCKING: + * Kernel thread context (may sleep). + * + * RETURNS: + * 0 on success, -errno on failure. + */ +static int sysfs_get_open_dirent(struct sysfs_dirent *sd, + struct sysfs_buffer *buffer) +{ + struct sysfs_open_dirent *od, *new_od = NULL; + + retry: + spin_lock(&sysfs_open_dirent_lock); + + if (!sd->s_attr.open && new_od) { + sd->s_attr.open = new_od; + new_od = NULL; + } + + od = sd->s_attr.open; + if (od) { + atomic_inc(&od->refcnt); + list_add_tail(&buffer->list, &od->buffers); + } + + spin_unlock(&sysfs_open_dirent_lock); + + if (od) { + kfree(new_od); + return 0; + } + + /* not there, initialize a new one and retry */ + new_od = kmalloc(sizeof(*new_od), GFP_KERNEL); + if (!new_od) + return -ENOMEM; + + atomic_set(&new_od->refcnt, 0); + atomic_set(&new_od->event, 1); + init_waitqueue_head(&new_od->poll); + INIT_LIST_HEAD(&new_od->buffers); + goto retry; +} + +/** + * sysfs_put_open_dirent - put sysfs_open_dirent + * @sd: target sysfs_dirent + * @buffer: associated sysfs_buffer + * + * Put @sd->s_attr.open and unlink @buffer from the buffers list. + * If reference count reaches zero, disassociate and free it. + * + * LOCKING: + * None. + */ +static void sysfs_put_open_dirent(struct sysfs_dirent *sd, + struct sysfs_buffer *buffer) +{ + struct sysfs_open_dirent *od = sd->s_attr.open; + + spin_lock(&sysfs_open_dirent_lock); + + list_del(&buffer->list); + if (atomic_dec_and_test(&od->refcnt)) + sd->s_attr.open = NULL; + else + od = NULL; + + spin_unlock(&sysfs_open_dirent_lock); + + kfree(od); +} + +static int sysfs_open_file(struct inode *inode, struct file *file) +{ + struct sysfs_dirent *attr_sd = file->f_path.dentry->d_fsdata; + struct kobject *kobj = attr_sd->s_parent->s_dir.kobj; + struct sysfs_buffer *buffer; + struct sysfs_ops *ops; + int error = -EACCES; + char *p; + + p = d_path(&file->f_path, last_sysfs_file, sizeof(last_sysfs_file)); + if (p) + memmove(last_sysfs_file, p, strlen(p) + 1); + + /* need attr_sd for attr and ops, its parent for kobj */ + if (!sysfs_get_active_two(attr_sd)) + return -ENODEV; + + /* every kobject with an attribute needs a ktype assigned */ + if (kobj->ktype && kobj->ktype->sysfs_ops) + ops = kobj->ktype->sysfs_ops; + else { + WARN(1, KERN_ERR "missing sysfs attribute operations for " + "kobject: %s\n", kobject_name(kobj)); + goto err_out; + } + + /* File needs write support. + * The inode's perms must say it's ok, + * and we must have a store method. + */ + if (file->f_mode & FMODE_WRITE) { + if (!(inode->i_mode & S_IWUGO) || !ops->store) + goto err_out; + } + + /* File needs read support. + * The inode's perms must say it's ok, and we there + * must be a show method for it. + */ + if (file->f_mode & FMODE_READ) { + if (!(inode->i_mode & S_IRUGO) || !ops->show) + goto err_out; + } + + /* No error? Great, allocate a buffer for the file, and store it + * it in file->private_data for easy access. + */ + error = -ENOMEM; + buffer = kzalloc(sizeof(struct sysfs_buffer), GFP_KERNEL); + if (!buffer) + goto err_out; + + mutex_init(&buffer->mutex); + buffer->needs_read_fill = 1; + buffer->ops = ops; + file->private_data = buffer; + + /* make sure we have open dirent struct */ + error = sysfs_get_open_dirent(attr_sd, buffer); + if (error) + goto err_free; + + /* open succeeded, put active references */ + sysfs_put_active_two(attr_sd); + return 0; + + err_free: + kfree(buffer); + err_out: + sysfs_put_active_two(attr_sd); + return error; +} + +static int sysfs_release(struct inode *inode, struct file *filp) +{ + struct sysfs_dirent *sd = filp->f_path.dentry->d_fsdata; + struct sysfs_buffer *buffer = filp->private_data; + + sysfs_put_open_dirent(sd, buffer); + + if (buffer->page) + free_page((unsigned long)buffer->page); + kfree(buffer); + + return 0; +} + +/* Sysfs 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 POLLERR|POLLPRI, 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 unsigned int sysfs_poll(struct file *filp, poll_table *wait) +{ + struct sysfs_buffer * buffer = filp->private_data; + struct sysfs_dirent *attr_sd = filp->f_path.dentry->d_fsdata; + struct sysfs_open_dirent *od = attr_sd->s_attr.open; + + /* need parent for the kobj, grab both */ + if (!sysfs_get_active_two(attr_sd)) + goto trigger; + + poll_wait(filp, &od->poll, wait); + + sysfs_put_active_two(attr_sd); + + if (buffer->event != atomic_read(&od->event)) + goto trigger; + + return 0; + + trigger: + buffer->needs_read_fill = 1; + return POLLERR|POLLPRI; +} + +void sysfs_notify_dirent(struct sysfs_dirent *sd) +{ + struct sysfs_open_dirent *od; + + spin_lock(&sysfs_open_dirent_lock); + + od = sd->s_attr.open; + if (od) { + atomic_inc(&od->event); + wake_up_interruptible(&od->poll); + } + + spin_unlock(&sysfs_open_dirent_lock); +} +EXPORT_SYMBOL_GPL(sysfs_notify_dirent); + +void sysfs_notify(struct kobject *k, const char *dir, const char *attr) +{ + struct sysfs_dirent *sd = k->sd; + + mutex_lock(&sysfs_mutex); + + if (sd && dir) + sd = sysfs_find_dirent(sd, dir); + if (sd && attr) + sd = sysfs_find_dirent(sd, attr); + if (sd) + sysfs_notify_dirent(sd); + + mutex_unlock(&sysfs_mutex); +} +EXPORT_SYMBOL_GPL(sysfs_notify); + +const struct file_operations sysfs_file_operations = { + .read = sysfs_read_file, + .write = sysfs_write_file, + .llseek = generic_file_llseek, + .open = sysfs_open_file, + .release = sysfs_release, + .poll = sysfs_poll, +}; + +int sysfs_add_file_mode(struct sysfs_dirent *dir_sd, + const struct attribute *attr, int type, mode_t amode) +{ + umode_t mode = (amode & S_IALLUGO) | S_IFREG; + struct sysfs_addrm_cxt acxt; + struct sysfs_dirent *sd; + int rc; + + sd = sysfs_new_dirent(attr->name, mode, type); + if (!sd) + return -ENOMEM; + sd->s_attr.attr = (void *)attr; + + sysfs_addrm_start(&acxt, dir_sd); + rc = sysfs_add_one(&acxt, sd); + sysfs_addrm_finish(&acxt); + + if (rc) + sysfs_put(sd); + + return rc; +} + + +int sysfs_add_file(struct sysfs_dirent *dir_sd, const struct attribute *attr, + int type) +{ + return sysfs_add_file_mode(dir_sd, attr, type, attr->mode); +} + + +/** + * sysfs_create_file - create an attribute file for an object. + * @kobj: object we're creating for. + * @attr: attribute descriptor. + */ + +int sysfs_create_file(struct kobject * kobj, const struct attribute * attr) +{ + BUG_ON(!kobj || !kobj->sd || !attr); + + return sysfs_add_file(kobj->sd, attr, SYSFS_KOBJ_ATTR); + +} + + +/** + * sysfs_add_file_to_group - add an attribute file to a pre-existing group. + * @kobj: object we're acting for. + * @attr: attribute descriptor. + * @group: group name. + */ +int sysfs_add_file_to_group(struct kobject *kobj, + const struct attribute *attr, const char *group) +{ + struct sysfs_dirent *dir_sd; + int error; + + if (group) + dir_sd = sysfs_get_dirent(kobj->sd, group); + else + dir_sd = sysfs_get(kobj->sd); + + if (!dir_sd) + return -ENOENT; + + error = sysfs_add_file(dir_sd, attr, SYSFS_KOBJ_ATTR); + sysfs_put(dir_sd); + + return error; +} +EXPORT_SYMBOL_GPL(sysfs_add_file_to_group); + +/** + * sysfs_chmod_file - update the modified mode value on an object attribute. + * @kobj: object we're acting for. + * @attr: attribute descriptor. + * @mode: file permissions. + * + */ +int sysfs_chmod_file(struct kobject *kobj, struct attribute *attr, mode_t mode) +{ + struct sysfs_dirent *victim_sd = NULL; + struct dentry *victim = NULL; + struct inode * inode; + struct iattr newattrs; + int rc; + + rc = -ENOENT; + victim_sd = sysfs_get_dirent(kobj->sd, attr->name); + if (!victim_sd) + goto out; + + mutex_lock(&sysfs_rename_mutex); + victim = sysfs_get_dentry(victim_sd); + mutex_unlock(&sysfs_rename_mutex); + if (IS_ERR(victim)) { + rc = PTR_ERR(victim); + victim = NULL; + goto out; + } + + inode = victim->d_inode; + + mutex_lock(&inode->i_mutex); + + newattrs.ia_mode = (mode & S_IALLUGO) | (inode->i_mode & ~S_IALLUGO); + newattrs.ia_valid = ATTR_MODE | ATTR_CTIME; + newattrs.ia_ctime = current_fs_time(inode->i_sb); + rc = sysfs_setattr(victim, &newattrs); + + if (rc == 0) { + fsnotify_change(victim, newattrs.ia_valid); + mutex_lock(&sysfs_mutex); + victim_sd->s_mode = newattrs.ia_mode; + mutex_unlock(&sysfs_mutex); + } + + mutex_unlock(&inode->i_mutex); + out: + dput(victim); + sysfs_put(victim_sd); + return rc; +} +EXPORT_SYMBOL_GPL(sysfs_chmod_file); + + +/** + * sysfs_remove_file - remove an object attribute. + * @kobj: object we're acting for. + * @attr: attribute descriptor. + * + * Hash the attribute name and kill the victim. + */ + +void sysfs_remove_file(struct kobject * kobj, const struct attribute * attr) +{ + sysfs_hash_and_remove(kobj->sd, attr->name); +} + + +/** + * sysfs_remove_file_from_group - remove an attribute file from a group. + * @kobj: object we're acting for. + * @attr: attribute descriptor. + * @group: group name. + */ +void sysfs_remove_file_from_group(struct kobject *kobj, + const struct attribute *attr, const char *group) +{ + struct sysfs_dirent *dir_sd; + + if (group) + dir_sd = sysfs_get_dirent(kobj->sd, group); + else + dir_sd = sysfs_get(kobj->sd); + if (dir_sd) { + sysfs_hash_and_remove(dir_sd, attr->name); + sysfs_put(dir_sd); + } +} +EXPORT_SYMBOL_GPL(sysfs_remove_file_from_group); + +struct sysfs_schedule_callback_struct { + struct kobject *kobj; + void (*func)(void *); + void *data; + struct module *owner; + struct work_struct work; +}; + +static void sysfs_schedule_callback_work(struct work_struct *work) +{ + struct sysfs_schedule_callback_struct *ss = container_of(work, + struct sysfs_schedule_callback_struct, work); + + (ss->func)(ss->data); + kobject_put(ss->kobj); + module_put(ss->owner); + kfree(ss); +} + +/** + * sysfs_schedule_callback - helper to schedule a callback for a kobject + * @kobj: object we're acting for. + * @func: callback function to invoke later. + * @data: argument to pass to @func. + * @owner: module owning the callback code + * + * sysfs attribute methods must not unregister themselves or their parent + * kobject (which would amount to the same thing). Attempts to do so will + * deadlock, since unregistration is mutually exclusive with driver + * callbacks. + * + * Instead methods can call this routine, which will attempt to allocate + * and schedule a workqueue request to call back @func with @data as its + * argument in the workqueue's process context. @kobj will be pinned + * until @func returns. + * + * Returns 0 if the request was submitted, -ENOMEM if storage could not + * be allocated, -ENODEV if a reference to @owner isn't available. + */ +int sysfs_schedule_callback(struct kobject *kobj, void (*func)(void *), + void *data, struct module *owner) +{ + struct sysfs_schedule_callback_struct *ss; + + if (!try_module_get(owner)) + return -ENODEV; + ss = kmalloc(sizeof(*ss), GFP_KERNEL); + if (!ss) { + module_put(owner); + return -ENOMEM; + } + kobject_get(kobj); + ss->kobj = kobj; + ss->func = func; + ss->data = data; + ss->owner = owner; + INIT_WORK(&ss->work, sysfs_schedule_callback_work); + schedule_work(&ss->work); + return 0; +} +EXPORT_SYMBOL_GPL(sysfs_schedule_callback); + + +EXPORT_SYMBOL_GPL(sysfs_create_file); +EXPORT_SYMBOL_GPL(sysfs_remove_file); |