path: root/fs/proc/generic.c

// SPDX-License-Identifier: GPL-2.0-only
/*
 * proc/fs/generic.c --- generic routines for the proc-fs
 *
 * This file contains generic proc-fs routines for handling
 * directories and files.
 * 
 * Copyright (C) 1991, 1992 Linus Torvalds.
 * Copyright (C) 1997 Theodore Ts'o
 */

#include <linux/cache.h>
#include <linux/errno.h>
#include <linux/time.h>
#include <linux/proc_fs.h>
#include <linux/stat.h>
#include <linux/mm.h>
#include <linux/module.h>
#include <linux/namei.h>
#include <linux/slab.h>
#include <linux/printk.h>
#include <linux/mount.h>
#include <linux/init.h>
#include <linux/idr.h>
#include <linux/bitops.h>
#include <linux/spinlock.h>
#include <linux/completion.h>
#include <linux/uaccess.h>
#include <linux/seq_file.h>

#include "internal.h"

static DEFINE_RWLOCK(proc_subdir_lock);

struct kmem_cache *proc_dir_entry_cache __ro_after_init;

void pde_free(struct proc_dir_entry *pde)
{
	if (S_ISLNK(pde->mode))
		kfree(pde->data);
	if (pde->name != pde->inline_name)
		kfree(pde->name);
	kmem_cache_free(proc_dir_entry_cache, pde);
}

static int proc_match(const char *name, struct proc_dir_entry *de, unsigned int len)
{
	if (len < de->namelen)
		return -1;
	if (len > de->namelen)
		return 1;

	return memcmp(name, de->name, len);
}

static struct proc_dir_entry *pde_subdir_first(struct proc_dir_entry *dir)
{
	return rb_entry_safe(rb_first(&dir->subdir), struct proc_dir_entry,
			     subdir_node);
}

static struct proc_dir_entry *pde_subdir_next(struct proc_dir_entry *dir)
{
	return rb_entry_safe(rb_next(&dir->subdir_node), struct proc_dir_entry,
			     subdir_node);
}

static struct proc_dir_entry *pde_subdir_find(struct proc_dir_entry *dir,
					      const char *name,
					      unsigned int len)
{
	struct rb_node *node = dir->subdir.rb_node;

	while (node) {
		struct proc_dir_entry *de = rb_entry(node,
						     struct proc_dir_entry,
						     subdir_node);
		int result = proc_match(name, de, len);

		if (result < 0)
			node = node->rb_left;
		else if (result > 0)
			node = node->rb_right;
		else
			return de;
	}
	return NULL;
}

static bool pde_subdir_insert(struct proc_dir_entry *dir,
			      struct proc_dir_entry *de)
{
	struct rb_root *root = &dir->subdir;
	struct rb_node **new = &root->rb_node, *parent = NULL;

	/* Figure out where to put new node */
	while (*new) {
		struct proc_dir_entry *this = rb_entry(*new,
						       struct proc_dir_entry,
						       subdir_node);
		int result = proc_match(de->name, this, de->namelen);

		parent = *new;
		if (result < 0)
			new = &(*new)->rb_left;
		else if (result > 0)
			new = &(*new)->rb_right;
		else
			return false;
	}

	/* Add new node and rebalance tree. */
	rb_link_node(&de->subdir_node, parent, new);
	rb_insert_color(&de->subdir_node, root);
	return true;
}

static int proc_notify_change(struct mnt_idmap *idmap,
			      struct dentry *dentry, struct iattr *iattr)
{
	struct inode *inode = d_inode(dentry);
	struct proc_dir_entry *de = PDE(inode);
	int error;

	error = setattr_prepare(&nop_mnt_idmap, dentry, iattr);
	if (error)
		return error;

	setattr_copy(&nop_mnt_idmap, inode, iattr);

	proc_set_user(de, inode->i_uid, inode->i_gid);
	de->mode = inode->i_mode;
	return 0;
}

static int proc_getattr(struct mnt_idmap *idmap,
			const struct path *path, struct kstat *stat,
			u32 request_mask, unsigned int query_flags)
{
	struct inode *inode = d_inode(path->dentry);
	struct proc_dir_entry *de = PDE(inode);
	if (de) {
		nlink_t nlink = READ_ONCE(de->nlink);
		if (nlink > 0) {
			set_nlink(inode, nlink);
		}
	}

	generic_fillattr(&nop_mnt_idmap, request_mask, inode, stat);
	return 0;
}

static const struct inode_operations proc_file_inode_operations = {
	.setattr	= proc_notify_change,
};

/*
 * This function parses a name such as "tty/driver/serial", and
 * returns the struct proc_dir_entry for "/proc/tty/driver", and
 * returns "serial" in residual.
 */
static int __xlate_proc_name(const char *name, struct proc_dir_entry **ret,
			     const char **residual)
{
	const char     		*cp = name, *next;
	struct proc_dir_entry	*de;

	de = *ret ?: &proc_root;
	while ((next = strchr