path: root/fs/proc/proc_sysctl.c

/*
 * /proc/sys support
 */
#include <linux/init.h>
#include <linux/sysctl.h>
#include <linux/poll.h>
#include <linux/proc_fs.h>
#include <linux/printk.h>
#include <linux/security.h>
#include <linux/sched.h>
#include <linux/namei.h>
#include <linux/mm.h>
#include <linux/module.h>
#include "internal.h"

static const struct dentry_operations proc_sys_dentry_operations;
static const struct file_operations proc_sys_file_operations;
static const struct inode_operations proc_sys_inode_operations;
static const struct file_operations proc_sys_dir_file_operations;
static const struct inode_operations proc_sys_dir_operations;

/* Support for permanently empty directories */

struct ctl_table sysctl_mount_point[] = {
	{ }
};

static bool is_empty_dir(struct ctl_table_header *head)
{
	return head->ctl_table[0].child == sysctl_mount_point;
}

static void set_empty_dir(struct ctl_dir *dir)
{
	dir->header.ctl_table[0].child = sysctl_mount_point;
}

static void clear_empty_dir(struct ctl_dir *dir)

{
	dir->header.ctl_table[0].child = NULL;
}

void proc_sys_poll_notify(struct ctl_table_poll *poll)
{
	if (!poll)
		return;

	atomic_inc(&poll->event);
	wake_up_interruptible(&poll->wait);
}

static struct ctl_table root_table[] = {
	{
		.procname = "",
		.mode = S_IFDIR|S_IRUGO|S_IXUGO,
	},
	{ }
};
static struct ctl_table_root sysctl_table_root = {
	.default_set.dir.header = {
		{{.count = 1,
		  .nreg = 1,
		  .ctl_table = root_table }},
		.ctl_table_arg = root_table,
		.root = &sysctl_table_root,
		.set = &sysctl_table_root.default_set,
	},
};

static DEFINE_SPINLOCK(sysctl_lock);

static void drop_sysctl_table(struct ctl_table_header *header);
static int sysctl_follow_link(struct ctl_table_header **phead,
	struct ctl_table **pentry);
static int insert_links(struct ctl_table_header *head);
static void put_links(struct ctl_table_header *header);

static void sysctl_print_dir(struct ctl_dir *dir)
{
	if (dir->header.parent)
		sysctl_print_dir(dir->header.parent);
	pr_cont("%s/", dir->header.ctl_table[0].procname);
}

static int namecmp(const char *name1, int len1, const char *name2, int len2)
{
	int minlen;
	int cmp;

	minlen = len1;
	if (minlen > len2)
		minlen = len2;

	cmp = memcmp(name1, name2, minlen);
	if (cmp == 0)
		cmp = len1 - len2;
	return cmp;
}

/* Called under sysctl_lock */
static struct ctl_table *find_entry(struct ctl_table_header **phead,
	struct ctl_dir *dir, const char *name, int namelen)
{
	struct ctl_table_header *head;
	struct ctl_table *entry;
	struct rb_node *node = dir->root.rb_node;

	while (node)
	{
		struct ctl_node *ctl_node;
		const char *procname;
		int cmp;

		ctl_node = rb_entry(node, struct ctl_node, node);
		head = ctl_node->header;
		entry = &head->ctl_table[ctl_node - head->node];
		procname = entry->procname;

		cmp = namecmp(name, namelen, procname, strlen(procname));
		if (cmp < 0)
			node = node->rb_left;
		else if (cmp > 0)
			node = node->rb_right;
		else {
			*phead = head;
			return entry;
		}
	}
	return NULL;
}

static int insert_entry(struct ctl_table_header *head, struct ctl_table *entry)
{
	struct rb_node *node = &head->node[entry - head->ctl_table].node;
	struct rb_node **p = &head->parent->root.rb_node;
	struct rb_node *parent = NULL;
	const char *name = entry->procname;
	int namelen = strlen(name);

	while (*p) {
		struct ctl_table_header *parent_head;
		struct ctl_table *parent_entry;
		struct ctl_node *parent_node;
		const char *parent_name;
		int cmp;

		parent = *p;
		parent_node = rb_entry(parent, struct ctl_node, node);
		parent_head = parent_node->header;
		parent_entry = &parent_head->ctl_table[parent_node - parent_head->node];
		parent_name = parent_entry->procname;

		cmp = namecmp(name, namelen, parent_name, strlen(parent_name));
		if (cmp < 0)
			p = &(*p)->rb_left;
		else if (cmp > 0)
			p = &(*p)->rb_right;
		else {
			pr_err("sysctl duplicate entry: ");
			sysctl_print_dir(head->parent);
			pr_cont("/%s\n", entry->procname);