Linux 4.14.215

[linux/fpc-iii.git] / fs / sysfs / file.c

/*
 * 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/list.h>
#include <linux/mutex.h>
#include <linux/seq_file.h>

#include "sysfs.h"
#include "../kernfs/kernfs-internal.h"

/*
 * Determine ktype->sysfs_ops for the given kernfs_node.  This function
 * must be called while holding an active reference.
 */
static const struct sysfs_ops *sysfs_file_ops(struct kernfs_node *kn)
{
        struct kobject *kobj = kn->parent->priv;

        if (kn->flags & KERNFS_LOCKDEP)
                lockdep_assert_held(kn);
        return kobj->ktype ? kobj->ktype->sysfs_ops : NULL;
}

/*
 * Reads on sysfs are handled through seq_file, which takes care of hairy
 * details like buffering and seeking.  The following function pipes
 * sysfs_ops->show() result through seq_file.
 */
static int sysfs_kf_seq_show(struct seq_file *sf, void *v)
{
        struct kernfs_open_file *of = sf->private;
        struct kobject *kobj = of->kn->parent->priv;
        const struct sysfs_ops *ops = sysfs_file_ops(of->kn);
        ssize_t count;
        char *buf;

        /* acquire buffer and ensure that it's >= PAGE_SIZE and clear */
        count = seq_get_buf(sf, &buf);
        if (count < PAGE_SIZE) {
                seq_commit(sf, -1);
                return 0;
        }
        memset(buf, 0, PAGE_SIZE);

        /*
         * Invoke show().  Control may reach here via seq file lseek even
         * if @ops->show() isn't implemented.
         */
        if (ops->show) {
                count = ops->show(kobj, of->kn->priv, buf);
                if (count < 0)
                        return count;
        }

        /*
         * 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;
        }
        seq_commit(sf, count);
        return 0;
}

static ssize_t sysfs_kf_bin_read(struct kernfs_open_file *of, char *buf,
                                 size_t count, loff_t pos)
{
        struct bin_attribute *battr = of->kn->priv;
        struct kobject *kobj = of->kn->parent->priv;
        loff_t size = file_inode(of->file)->i_size;

        if (!count)
                return 0;

        if (size) {
                if (pos >= size)
                        return 0;
                if (pos + count > size)
                        count = size - pos;
        }

        if (!battr->read)
                return -EIO;

        return battr->read(of->file, kobj, battr, buf, pos, count);
}

/* kernfs read callback for regular sysfs files with pre-alloc */
static ssize_t sysfs_kf_read(struct kernfs_open_file *of, char *buf,
                             size_t count, loff_t pos)
{
        const struct sysfs_ops *ops = sysfs_file_ops(of->kn);
        struct kobject *kobj = of->kn->parent->priv;
        ssize_t len;

        /*
         * If buf != of->prealloc_buf, we don't know how
         * large it is, so cannot safely pass it to ->show
         */
        if (WARN_ON_ONCE(buf != of->prealloc_buf))
                return 0;
        len = ops->show(kobj, of->kn->priv, buf);
        if (len < 0)
                return len;
        if (pos) {
                if (len <= pos)
                        return 0;
                len -= pos;
                memmove(buf, buf + pos, len);
        }
        return min_t(ssize_t, count, len);
}

/* kernfs write callback for regular sysfs files */
static ssize_t sysfs_kf_write(struct kernfs_open_file *of, char *buf,
                              size_t count, loff_t pos)
{
        const struct sysfs_ops *ops = sysfs_file_ops(of->kn);
        struct kobject *kobj = of->kn->parent->priv;

        if (!count)
                return 0;

        return ops->store(kobj, of->kn->priv, buf, count);
}

/* kernfs write callback for bin sysfs files */
static ssize_t sysfs_kf_bin_write(struct kernfs_open_file *of, char *buf,
                                  size_t count, loff_t pos)
{
        struct bin_attribute *battr = of->kn->priv;
        struct kobject *kobj = of->kn->parent->priv;
        loff_t size = file_inode(of->file)->i_size;

        if (size) {
                if (size <= pos)
                        return -EFBIG;
                count = min_t(ssize_t, count, size - pos);
        }
        if (!count)
                return 0;

        if (!battr->write)
                return -EIO;

        return battr->write(of->file, kobj, battr, buf, pos, count);
}

static int sysfs_kf_bin_mmap(struct kernfs_open_file *of,
                             struct vm_area_struct *vma)
{
        struct bin_attribute *battr = of->kn->priv;
        struct kobject *kobj = of->kn->parent->priv;

        return battr->mmap(of->file, kobj, battr, vma);
}

void sysfs_notify(struct kobject *kobj, const char *dir, const char *attr)
{
        struct kernfs_node *kn = kobj->sd, *tmp;

        if (kn && dir)
                kn = kernfs_find_and_get(kn, dir);
        else
                kernfs_get(kn);

        if (kn && attr) {
                tmp = kernfs_find_and_get(kn, attr);
                kernfs_put(kn);
                kn = tmp;
        }

        if (kn) {
                kernfs_notify(kn);
                kernfs_put(kn);
        }
}
EXPORT_SYMBOL_GPL(sysfs_notify);

static const struct kernfs_ops sysfs_file_kfops_empty = {
};

static const struct kernfs_ops sysfs_file_kfops_ro = {
        .seq_show       = sysfs_kf_seq_show,
};

static const struct kernfs_ops sysfs_file_kfops_wo = {
        .write          = sysfs_kf_write,
};

static const struct kernfs_ops sysfs_file_kfops_rw = {
        .seq_show       = sysfs_kf_seq_show,
        .write          = sysfs_kf_write,
};

static const struct kernfs_ops sysfs_prealloc_kfops_ro = {
        .read           = sysfs_kf_read,
        .prealloc       = true,
};

static const struct kernfs_ops sysfs_prealloc_kfops_wo = {
        .write          = sysfs_kf_write,
        .prealloc       = true,
};

static const struct kernfs_ops sysfs_prealloc_kfops_rw = {
        .read           = sysfs_kf_read,
        .write          = sysfs_kf_write,
        .prealloc       = true,
};

static const struct kernfs_ops sysfs_bin_kfops_ro = {
        .read           = sysfs_kf_bin_read,
};

static const struct kernfs_ops sysfs_bin_kfops_wo = {
        .write          = sysfs_kf_bin_write,
};

static const struct kernfs_ops sysfs_bin_kfops_rw = {
        .read           = sysfs_kf_bin_read,
        .write          = sysfs_kf_bin_write,
};

static const struct kernfs_ops sysfs_bin_kfops_mmap = {
        .read           = sysfs_kf_bin_read,
        .write          = sysfs_kf_bin_write,
        .mmap           = sysfs_kf_bin_mmap,
};

int sysfs_add_file_mode_ns(struct kernfs_node *parent,
                           const struct attribute *attr, bool is_bin,
                           umode_t mode, const void *ns)
{
        struct lock_class_key *key = NULL;
        const struct kernfs_ops *ops;
        struct kernfs_node *kn;
        loff_t size;

        if (!is_bin) {
                struct kobject *kobj = parent->priv;
                const struct sysfs_ops *sysfs_ops = kobj->ktype->sysfs_ops;

                /* every kobject with an attribute needs a ktype assigned */
                if (WARN(!sysfs_ops, KERN_ERR
                         "missing sysfs attribute operations for kobject: %s\n",
                         kobject_name(kobj)))
                        return -EINVAL;

                if (sysfs_ops->show && sysfs_ops->store) {
                        if (mode & SYSFS_PREALLOC)
                                ops = &sysfs_prealloc_kfops_rw;
                        else
                                ops = &sysfs_file_kfops_rw;
                } else if (sysfs_ops->show) {
                        if (mode & SYSFS_PREALLOC)
                                ops = &sysfs_prealloc_kfops_ro;
                        else
                                ops = &sysfs_file_kfops_ro;
                } else if (sysfs_ops->store) {
                        if (mode & SYSFS_PREALLOC)
                                ops = &sysfs_prealloc_kfops_wo;
                        else
                                ops = &sysfs_file_kfops_wo;
                } else
                        ops = &sysfs_file_kfops_empty;

                size = PAGE_SIZE;
        } else {
                struct bin_attribute *battr = (void *)attr;

                if (battr->mmap)
                        ops = &sysfs_bin_kfops_mmap;
                else if (battr->read && battr->write)
                        ops = &sysfs_bin_kfops_rw;
                else if (battr->read)
                        ops = &sysfs_bin_kfops_ro;
                else if (battr->write)
                        ops = &sysfs_bin_kfops_wo;
                else
                        ops = &sysfs_file_kfops_empty;

                size = battr->size;
        }

#ifdef CONFIG_DEBUG_LOCK_ALLOC
        if (!attr->ignore_lockdep)
                key = attr->key ?: (struct lock_class_key *)&attr->skey;
#endif
        kn = __kernfs_create_file(parent, attr->name, mode & 0777, size, ops,
                                  (void *)attr, ns, key);
        if (IS_ERR(kn)) {
                if (PTR_ERR(kn) == -EEXIST)
                        sysfs_warn_dup(parent, attr->name);
                return PTR_ERR(kn);
        }
        return 0;
}

int sysfs_add_file(struct kernfs_node *parent, const struct attribute *attr,
                   bool is_bin)
{
        return sysfs_add_file_mode_ns(parent, attr, is_bin, attr->mode, NULL);
}

/**
 * sysfs_create_file_ns - create an attribute file for an object with custom ns
 * @kobj: object we're creating for
 * @attr: attribute descriptor
 * @ns: namespace the new file should belong to
 */
int sysfs_create_file_ns(struct kobject *kobj, const struct attribute *attr,
                         const void *ns)
{
        BUG_ON(!kobj || !kobj->sd || !attr);

        return sysfs_add_file_mode_ns(kobj->sd, attr, false, attr->mode, ns);

}
EXPORT_SYMBOL_GPL(sysfs_create_file_ns);

int sysfs_create_files(struct kobject *kobj, const struct attribute **ptr)
{
        int err = 0;
        int i;

        for (i = 0; ptr[i] && !err; i++)
                err = sysfs_create_file(kobj, ptr[i]);
        if (err)
                while (--i >= 0)
                        sysfs_remove_file(kobj, ptr[i]);
        return err;
}
EXPORT_SYMBOL_GPL(sysfs_create_files);

/**
 * 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 kernfs_node *parent;
        int error;

        if (group) {
                parent = kernfs_find_and_get(kobj->sd, group);
        } else {
                parent = kobj->sd;
                kernfs_get(parent);
        }

        if (!parent)
                return -ENOENT;

        error = sysfs_add_file(parent, attr, false);
        kernfs_put(parent);

        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, const struct attribute *attr,
                     umode_t mode)
{
        struct kernfs_node *kn;
        struct iattr newattrs;
        int rc;

        kn = kernfs_find_and_get(kobj->sd, attr->name);
        if (!kn)
                return -ENOENT;

        newattrs.ia_mode = (mode & S_IALLUGO) | (kn->mode & ~S_IALLUGO);
        newattrs.ia_valid = ATTR_MODE;

        rc = kernfs_setattr(kn, &newattrs);

        kernfs_put(kn);
        return rc;
}
EXPORT_SYMBOL_GPL(sysfs_chmod_file);

/**
 * sysfs_break_active_protection - break "active" protection
 * @kobj: The kernel object @attr is associated with.
 * @attr: The attribute to break the "active" protection for.
 *
 * With sysfs, just like kernfs, deletion of an attribute is postponed until
 * all active .show() and .store() callbacks have finished unless this function
 * is called. Hence this function is useful in methods that implement self
 * deletion.
 */
struct kernfs_node *sysfs_break_active_protection(struct kobject *kobj,
                                                  const struct attribute *attr)
{
        struct kernfs_node *kn;

        kobject_get(kobj);
        kn = kernfs_find_and_get(kobj->sd, attr->name);
        if (kn)
                kernfs_break_active_protection(kn);
        return kn;
}
EXPORT_SYMBOL_GPL(sysfs_break_active_protection);

/**
 * sysfs_unbreak_active_protection - restore "active" protection
 * @kn: Pointer returned by sysfs_break_active_protection().
 *
 * Undo the effects of sysfs_break_active_protection(). Since this function
 * calls kernfs_put() on the kernfs node that corresponds to the 'attr'
 * argument passed to sysfs_break_active_protection() that attribute may have
 * been removed between the sysfs_break_active_protection() and
 * sysfs_unbreak_active_protection() calls, it is not safe to access @kn after
 * this function has returned.
 */
void sysfs_unbreak_active_protection(struct kernfs_node *kn)
{
        struct kobject *kobj = kn->parent->priv;

        kernfs_unbreak_active_protection(kn);
        kernfs_put(kn);
        kobject_put(kobj);
}
EXPORT_SYMBOL_GPL(sysfs_unbreak_active_protection);

/**
 * sysfs_remove_file_ns - remove an object attribute with a custom ns tag
 * @kobj: object we're acting for
 * @attr: attribute descriptor
 * @ns: namespace tag of the file to remove
 *
 * Hash the attribute name and namespace tag and kill the victim.
 */
void sysfs_remove_file_ns(struct kobject *kobj, const struct attribute *attr,
                          const void *ns)
{
        struct kernfs_node *parent = kobj->sd;

        kernfs_remove_by_name_ns(parent, attr->name, ns);
}
EXPORT_SYMBOL_GPL(sysfs_remove_file_ns);

/**
 * sysfs_remove_file_self - remove an object attribute from its own method
 * @kobj: object we're acting for
 * @attr: attribute descriptor
 *
 * See kernfs_remove_self() for details.
 */
bool sysfs_remove_file_self(struct kobject *kobj, const struct attribute *attr)
{
        struct kernfs_node *parent = kobj->sd;
        struct kernfs_node *kn;
        bool ret;

        kn = kernfs_find_and_get(parent, attr->name);
        if (WARN_ON_ONCE(!kn))
                return false;

        ret = kernfs_remove_self(kn);

        kernfs_put(kn);
        return ret;
}

void sysfs_remove_files(struct kobject *kobj, const struct attribute **ptr)
{
        int i;
        for (i = 0; ptr[i]; i++)
                sysfs_remove_file(kobj, ptr[i]);
}
EXPORT_SYMBOL_GPL(sysfs_remove_files);

/**
 * 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 kernfs_node *parent;

        if (group) {
                parent = kernfs_find_and_get(kobj->sd, group);
        } else {
                parent = kobj->sd;
                kernfs_get(parent);
        }

        if (parent) {
                kernfs_remove_by_name(parent, attr->name);
                kernfs_put(parent);
        }
}
EXPORT_SYMBOL_GPL(sysfs_remove_file_from_group);

/**
 *      sysfs_create_bin_file - create binary file for object.
 *      @kobj:  object.
 *      @attr:  attribute descriptor.
 */
int sysfs_create_bin_file(struct kobject *kobj,
                          const struct bin_attribute *attr)
{
        BUG_ON(!kobj || !kobj->sd || !attr);

        return sysfs_add_file(kobj->sd, &attr->attr, true);
}
EXPORT_SYMBOL_GPL(sysfs_create_bin_file);

/**
 *      sysfs_remove_bin_file - remove binary file for object.
 *      @kobj:  object.
 *      @attr:  attribute descriptor.
 */
void sysfs_remove_bin_file(struct kobject *kobj,
                           const struct bin_attribute *attr)
{
        kernfs_remove_by_name(kobj->sd, attr->attr.name);
}
EXPORT_SYMBOL_GPL(sysfs_remove_bin_file);