mirror of https://gitee.com/openkylin/linux.git
480 lines
11 KiB
C
480 lines
11 KiB
C
/*
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* /proc/sys support
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*/
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#include <linux/sysctl.h>
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#include <linux/proc_fs.h>
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#include <linux/security.h>
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#include "internal.h"
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static struct dentry_operations proc_sys_dentry_operations;
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static const struct file_operations proc_sys_file_operations;
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static struct inode_operations proc_sys_inode_operations;
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static void proc_sys_refresh_inode(struct inode *inode, struct ctl_table *table)
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{
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/* Refresh the cached information bits in the inode */
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if (table) {
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inode->i_uid = 0;
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inode->i_gid = 0;
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inode->i_mode = table->mode;
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if (table->proc_handler) {
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inode->i_mode |= S_IFREG;
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inode->i_nlink = 1;
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} else {
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inode->i_mode |= S_IFDIR;
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inode->i_nlink = 0; /* It is too hard to figure out */
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}
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}
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}
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static struct inode *proc_sys_make_inode(struct inode *dir, struct ctl_table *table)
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{
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struct inode *inode;
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struct proc_inode *dir_ei, *ei;
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int depth;
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inode = new_inode(dir->i_sb);
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if (!inode)
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goto out;
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/* A directory is always one deeper than it's parent */
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dir_ei = PROC_I(dir);
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depth = dir_ei->fd + 1;
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ei = PROC_I(inode);
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ei->fd = depth;
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inode->i_mtime = inode->i_atime = inode->i_ctime = CURRENT_TIME;
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inode->i_op = &proc_sys_inode_operations;
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inode->i_fop = &proc_sys_file_operations;
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inode->i_flags |= S_PRIVATE; /* tell selinux to ignore this inode */
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proc_sys_refresh_inode(inode, table);
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out:
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return inode;
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}
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static struct dentry *proc_sys_ancestor(struct dentry *dentry, int depth)
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{
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for (;;) {
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struct proc_inode *ei;
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ei = PROC_I(dentry->d_inode);
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if (ei->fd == depth)
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break; /* found */
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dentry = dentry->d_parent;
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}
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return dentry;
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}
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static struct ctl_table *proc_sys_lookup_table_one(struct ctl_table *table,
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struct qstr *name)
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{
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int len;
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for ( ; table->ctl_name || table->procname; table++) {
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if (!table->procname)
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continue;
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len = strlen(table->procname);
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if (len != name->len)
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continue;
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if (memcmp(table->procname, name->name, len) != 0)
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continue;
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/* I have a match */
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return table;
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}
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return NULL;
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}
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static struct ctl_table *proc_sys_lookup_table(struct dentry *dentry,
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struct ctl_table *table)
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{
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struct dentry *ancestor;
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struct proc_inode *ei;
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int depth, i;
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ei = PROC_I(dentry->d_inode);
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depth = ei->fd;
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if (depth == 0)
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return table;
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for (i = 1; table && (i <= depth); i++) {
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ancestor = proc_sys_ancestor(dentry, i);
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table = proc_sys_lookup_table_one(table, &ancestor->d_name);
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if (table)
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table = table->child;
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}
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return table;
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}
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static struct ctl_table *proc_sys_lookup_entry(struct dentry *dparent,
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struct qstr *name,
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struct ctl_table *table)
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{
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table = proc_sys_lookup_table(dparent, table);
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if (table)
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table = proc_sys_lookup_table_one(table, name);
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return table;
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}
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static struct ctl_table *do_proc_sys_lookup(struct dentry *parent,
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struct qstr *name,
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struct ctl_table_header **ptr)
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{
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struct ctl_table_header *head;
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struct ctl_table *table = NULL;
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for (head = sysctl_head_next(NULL); head;
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head = sysctl_head_next(head)) {
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table = proc_sys_lookup_entry(parent, name, head->ctl_table);
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if (table)
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break;
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}
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*ptr = head;
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return table;
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}
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static struct dentry *proc_sys_lookup(struct inode *dir, struct dentry *dentry,
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struct nameidata *nd)
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{
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struct ctl_table_header *head;
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struct inode *inode;
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struct dentry *err;
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struct ctl_table *table;
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err = ERR_PTR(-ENOENT);
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table = do_proc_sys_lookup(dentry->d_parent, &dentry->d_name, &head);
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if (!table)
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goto out;
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err = ERR_PTR(-ENOMEM);
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inode = proc_sys_make_inode(dir, table);
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if (!inode)
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goto out;
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err = NULL;
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dentry->d_op = &proc_sys_dentry_operations;
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d_add(dentry, inode);
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out:
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sysctl_head_finish(head);
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return err;
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}
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static ssize_t proc_sys_read(struct file *filp, char __user *buf,
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size_t count, loff_t *ppos)
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{
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struct dentry *dentry = filp->f_dentry;
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struct ctl_table_header *head;
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struct ctl_table *table;
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ssize_t error, res;
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table = do_proc_sys_lookup(dentry->d_parent, &dentry->d_name, &head);
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/* Has the sysctl entry disappeared on us? */
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error = -ENOENT;
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if (!table)
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goto out;
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/* Has the sysctl entry been replaced by a directory? */
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error = -EISDIR;
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if (!table->proc_handler)
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goto out;
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/*
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* At this point we know that the sysctl was not unregistered
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* and won't be until we finish.
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*/
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error = -EPERM;
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if (sysctl_perm(table, MAY_READ))
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goto out;
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/* careful: calling conventions are nasty here */
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res = count;
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error = table->proc_handler(table, 0, filp, buf, &res, ppos);
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if (!error)
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error = res;
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out:
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sysctl_head_finish(head);
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return error;
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}
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static ssize_t proc_sys_write(struct file *filp, const char __user *buf,
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size_t count, loff_t *ppos)
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{
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struct dentry *dentry = filp->f_dentry;
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struct ctl_table_header *head;
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struct ctl_table *table;
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ssize_t error, res;
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table = do_proc_sys_lookup(dentry->d_parent, &dentry->d_name, &head);
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/* Has the sysctl entry disappeared on us? */
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error = -ENOENT;
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if (!table)
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goto out;
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/* Has the sysctl entry been replaced by a directory? */
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error = -EISDIR;
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if (!table->proc_handler)
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goto out;
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/*
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* At this point we know that the sysctl was not unregistered
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* and won't be until we finish.
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*/
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error = -EPERM;
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if (sysctl_perm(table, MAY_WRITE))
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goto out;
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/* careful: calling conventions are nasty here */
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res = count;
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error = table->proc_handler(table, 1, filp, (char __user *)buf,
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&res, ppos);
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if (!error)
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error = res;
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out:
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sysctl_head_finish(head);
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return error;
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}
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static int proc_sys_fill_cache(struct file *filp, void *dirent,
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filldir_t filldir, struct ctl_table *table)
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{
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struct ctl_table_header *head;
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struct ctl_table *child_table = NULL;
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struct dentry *child, *dir = filp->f_path.dentry;
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struct inode *inode;
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struct qstr qname;
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ino_t ino = 0;
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unsigned type = DT_UNKNOWN;
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int ret;
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qname.name = table->procname;
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qname.len = strlen(table->procname);
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qname.hash = full_name_hash(qname.name, qname.len);
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/* Suppress duplicates.
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* Only fill a directory entry if it is the value that
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* an ordinary lookup of that name returns. Hide all
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* others.
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*
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* If we ever cache this translation in the dcache
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* I should do a dcache lookup first. But for now
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* it is just simpler not to.
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*/
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ret = 0;
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child_table = do_proc_sys_lookup(dir, &qname, &head);
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sysctl_head_finish(head);
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if (child_table != table)
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return 0;
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child = d_lookup(dir, &qname);
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if (!child) {
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struct dentry *new;
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new = d_alloc(dir, &qname);
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if (new) {
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inode = proc_sys_make_inode(dir->d_inode, table);
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if (!inode)
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child = ERR_PTR(-ENOMEM);
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else {
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new->d_op = &proc_sys_dentry_operations;
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d_add(new, inode);
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}
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if (child)
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dput(new);
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else
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child = new;
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}
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}
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if (!child || IS_ERR(child) || !child->d_inode)
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goto end_instantiate;
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inode = child->d_inode;
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if (inode) {
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ino = inode->i_ino;
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type = inode->i_mode >> 12;
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}
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dput(child);
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end_instantiate:
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if (!ino)
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ino= find_inode_number(dir, &qname);
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if (!ino)
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ino = 1;
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return filldir(dirent, qname.name, qname.len, filp->f_pos, ino, type);
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}
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static int proc_sys_readdir(struct file *filp, void *dirent, filldir_t filldir)
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{
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struct dentry *dentry = filp->f_dentry;
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struct inode *inode = dentry->d_inode;
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struct ctl_table_header *head = NULL;
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struct ctl_table *table;
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unsigned long pos;
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int ret;
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ret = -ENOTDIR;
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if (!S_ISDIR(inode->i_mode))
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goto out;
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ret = 0;
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/* Avoid a switch here: arm builds fail with missing __cmpdi2 */
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if (filp->f_pos == 0) {
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if (filldir(dirent, ".", 1, filp->f_pos,
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inode->i_ino, DT_DIR) < 0)
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goto out;
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filp->f_pos++;
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}
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if (filp->f_pos == 1) {
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if (filldir(dirent, "..", 2, filp->f_pos,
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parent_ino(dentry), DT_DIR) < 0)
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goto out;
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filp->f_pos++;
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}
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pos = 2;
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/* - Find each instance of the directory
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* - Read all entries in each instance
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* - Before returning an entry to user space lookup the entry
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* by name and if I find a different entry don't return
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* this one because it means it is a buried dup.
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* For sysctl this should only happen for directory entries.
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*/
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for (head = sysctl_head_next(NULL); head; head = sysctl_head_next(head)) {
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table = proc_sys_lookup_table(dentry, head->ctl_table);
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if (!table)
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continue;
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for (; table->ctl_name || table->procname; table++, pos++) {
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/* Can't do anything without a proc name */
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if (!table->procname)
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continue;
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if (pos < filp->f_pos)
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continue;
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if (proc_sys_fill_cache(filp, dirent, filldir, table) < 0)
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goto out;
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filp->f_pos = pos + 1;
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}
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}
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ret = 1;
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out:
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sysctl_head_finish(head);
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return ret;
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}
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static int proc_sys_permission(struct inode *inode, int mask, struct nameidata *nd)
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{
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/*
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* sysctl entries that are not writeable,
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* are _NOT_ writeable, capabilities or not.
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*/
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struct ctl_table_header *head;
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struct ctl_table *table;
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struct dentry *dentry;
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int mode;
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int depth;
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int error;
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head = NULL;
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depth = PROC_I(inode)->fd;
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/* First check the cached permissions, in case we don't have
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* enough information to lookup the sysctl table entry.
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*/
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error = -EACCES;
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mode = inode->i_mode;
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if (current->euid == 0)
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mode >>= 6;
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else if (in_group_p(0))
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mode >>= 3;
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if ((mode & mask & (MAY_READ|MAY_WRITE|MAY_EXEC)) == mask)
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error = 0;
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/* If we can't get a sysctl table entry the permission
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* checks on the cached mode will have to be enough.
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*/
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if (!nd || !depth)
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goto out;
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dentry = nd->dentry;
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table = do_proc_sys_lookup(dentry->d_parent, &dentry->d_name, &head);
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/* If the entry does not exist deny permission */
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error = -EACCES;
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if (!table)
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goto out;
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/* Use the permissions on the sysctl table entry */
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error = sysctl_perm(table, mask);
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out:
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sysctl_head_finish(head);
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return error;
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}
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static int proc_sys_setattr(struct dentry *dentry, struct iattr *attr)
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{
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struct inode *inode = dentry->d_inode;
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int error;
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if (attr->ia_valid & (ATTR_MODE | ATTR_UID | ATTR_GID))
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return -EPERM;
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error = inode_change_ok(inode, attr);
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if (!error) {
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error = security_inode_setattr(dentry, attr);
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if (!error)
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error = inode_setattr(inode, attr);
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}
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return error;
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}
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/* I'm lazy and don't distinguish between files and directories,
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* until access time.
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*/
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static const struct file_operations proc_sys_file_operations = {
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.read = proc_sys_read,
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.write = proc_sys_write,
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.readdir = proc_sys_readdir,
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};
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static struct inode_operations proc_sys_inode_operations = {
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.lookup = proc_sys_lookup,
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.permission = proc_sys_permission,
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.setattr = proc_sys_setattr,
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};
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static int proc_sys_revalidate(struct dentry *dentry, struct nameidata *nd)
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{
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struct ctl_table_header *head;
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struct ctl_table *table;
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table = do_proc_sys_lookup(dentry->d_parent, &dentry->d_name, &head);
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proc_sys_refresh_inode(dentry->d_inode, table);
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sysctl_head_finish(head);
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return !!table;
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}
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static struct dentry_operations proc_sys_dentry_operations = {
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.d_revalidate = proc_sys_revalidate,
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};
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static struct proc_dir_entry *proc_sys_root;
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int proc_sys_init(void)
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{
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proc_sys_root = proc_mkdir("sys", NULL);
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proc_sys_root->proc_iops = &proc_sys_inode_operations;
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proc_sys_root->proc_fops = &proc_sys_file_operations;
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proc_sys_root->nlink = 0;
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return 0;
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}
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