/*
 * 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/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/slab.h>
#include <linux/printk.h>
#include <linux/mount.h>
#include <linux/init.h>
#include <linux/idr.h>
#include <linux/namei.h>
#include <linux/bitops.h>
#include <linux/spinlock.h>
#include <linux/completion.h>
#include <asm/uaccess.h>

#include "internal.h"

static DEFINE_SPINLOCK(proc_subdir_lock);

static int proc_match(unsigned int len, const char *name, struct proc_dir_entry *de)
{
        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 = container_of(node,
                                                         struct proc_dir_entry,
                                                         subdir_node);
                int result = proc_match(len, name, de);

                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 =
                        container_of(*new, struct proc_dir_entry, subdir_node);
                int result = proc_match(de->namelen, de->name, this);

                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 dentry *dentry, struct iattr *iattr)
{
        struct inode *inode = dentry->d_inode;
        struct proc_dir_entry *de = PDE(inode);
        int error;

        error = inode_change_ok(inode, iattr);
        if (error)
                return error;

        setattr_copy(inode, iattr);
        mark_inode_dirty(inode);

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

static int proc_getattr(struct vfsmount *mnt, struct dentry *dentry,
                        struct kstat *stat)
{
        struct inode *inode = dentry->d_inode;
        struct proc_dir_entry *de = PROC_I(inode)->pde;
        if (de && de->nlink)
                set_nlink(inode, de->nlink);

        generic_fillattr(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;
        unsigned int            len;

        de = *ret;
        if (!de)
                de = &proc_root;

        while (1) {
                next = strchr(cp, '/');
                if (!next)
                        break;

                len = next - cp;
                de = pde_subdir_find(de, cp, len);
                if (!de) {
                        WARN(1, "name '%s'\n", name);
                        return -ENOENT;
                }
                cp += len + 1;
        }
        *residual = cp;
        *ret = de;
        return 0;
}

static int xlate_proc_name(const char *name, struct proc_dir_entry **ret,
                           const char **residual)
{
        int rv;

        spin_lock(&proc_subdir_lock);
        rv = __xlate_proc_name(name, ret, residual);
        spin_unlock(&proc_subdir_lock);
        return rv;
}

static DEFINE_IDA(proc_inum_ida);
static DEFINE_SPINLOCK(proc_inum_lock); /* protects the above */

#define PROC_DYNAMIC_FIRST 0xF0000000U

/*
 * Return an inode number between PROC_DYNAMIC_FIRST and
 * 0xffffffff, or zero on failure.
 */
int proc_alloc_inum(unsigned int *inum)
{
        unsigned int i;
        int error;

retry:
        if (!ida_pre_get(&proc_inum_ida, GFP_KERNEL))
                return -ENOMEM;

        spin_lock_irq(&proc_inum_lock);
        error = ida_get_new(&proc_inum_ida, &i);
        spin_unlock_irq(&proc_inum_lock);
        if (error == -EAGAIN)
                goto retry;
        else if (error)
                return error;

        if (i > UINT_MAX - PROC_DYNAMIC_FIRST) {
                spin_lock_irq(&proc_inum_lock);
                ida_remove(&proc_inum_ida, i);
                spin_unlock_irq(&proc_inum_lock);
                return -ENOSPC;
        }
        *inum = PROC_DYNAMIC_FIRST + i;
        return 0;
}

void proc_free_inum(unsigned int inum)
{
        unsigned long flags;
        spin_lock_irqsave(&proc_inum_lock, flags);
        ida_remove(&proc_inum_ida, inum - PROC_DYNAMIC_FIRST);
        spin_unlock_irqrestore(&proc_inum_lock, flags);
}

static void *proc_follow_link(struct dentry *dentry, struct nameidata *nd)
{
        nd_set_link(nd, __PDE_DATA(dentry->d_inode));
        return NULL;
}

static const struct inode_operations proc_link_inode_operations = {
        .readlink       = generic_readlink,
        .follow_link    = proc_follow_link,
};

/*
 * Don't create negative dentries here, return -ENOENT by hand
 * instead.
 */
struct dentry *proc_lookup_de(struct proc_dir_entry *de, struct inode *dir,
                struct dentry *dentry)
{
        struct inode *inode;

        spin_lock(&proc_subdir_lock);
        de = pde_subdir_find(de, dentry->d_name.name, dentry->d_name.len);
        if (de) {
                pde_get(de);
                spin_unlock(&proc_subdir_lock);
                inode = proc_get_inode(dir->i_sb, de);
                if (!inode)
                        return ERR_PTR(-ENOMEM);
                d_set_d_op(dentry, &simple_dentry_operations);
                d_add(dentry, inode);
                return NULL;
        }
        spin_unlock(&proc_subdir_lock);
        return ERR_PTR(-ENOENT);
}

struct dentry *proc_lookup(struct inode *dir, struct dentry *dentry,
                unsigned int flags)
{
        return proc_lookup_de(PDE(dir), dir, dentry);
}

/*
 * This returns non-zero if at EOF, so that the /proc
 * root directory can use this and check if it should
 * continue with the <pid> entries..
 *
 * Note that the VFS-layer doesn't care about the return
 * value of the readdir() call, as long as it's non-negative
 * for success..
 */
int proc_readdir_de(struct proc_dir_entry *de, struct file *file,
                    struct dir_context *ctx)
{
        int i;

        if (!dir_emit_dots(file, ctx))
                return 0;

        spin_lock(&proc_subdir_lock);
        de = pde_subdir_first(de);
        i = ctx->pos - 2;
        for (;;) {
                if (!de) {
                        spin_unlock(&proc_subdir_lock);
                        return 0;
                }
                if (!i)
                        break;
                de = pde_subdir_next(de);
                i--;
        }

        do {
                struct proc_dir_entry *next;
                pde_get(de);
                spin_unlock(&proc_subdir_lock);
                if (!dir_emit(ctx, de->name, de->namelen,
                            de->low_ino, de->mode >> 12)) {
                        pde_put(de);
                        return 0;
                }
                spin_lock(&proc_subdir_lock);
                ctx->pos++;
                next = pde_subdir_next(de);
                pde_put(de);
                de = next;
        } while (de);
        spin_unlock(&proc_subdir_lock);
        return 1;
}

int proc_readdir(struct file *file, struct dir_context *ctx)
{
        struct inode *inode = file_inode(file);

        return proc_readdir_de(PDE(inode), file, ctx);
}

/*
 * These are the generic /proc directory operations. They
 * use the in-memory "struct proc_dir_entry" tree to parse
 * the /proc directory.
 */
static const struct file_operations proc_dir_operations = {
        .llseek                 = generic_file_llseek,
        .read                   = generic_read_dir,
        .iterate                = proc_readdir,
};

/*
 * proc directories can do almost nothing..
 */
static const struct inode_operations proc_dir_inode_operations = {
        .lookup         = proc_lookup,
        .getattr        = proc_getattr,
        .setattr        = proc_notify_change,
};

static int proc_register(struct proc_dir_entry * dir, struct proc_dir_entry * dp)
{
        int ret;

        ret = proc_alloc_inum(&dp->low_ino);
        if (ret)
                return ret;

        if (S_ISDIR(dp->mode)) {
                dp->proc_fops = &proc_dir_operations;
                dp->proc_iops = &proc_dir_inode_operations;
                dir->nlink++;
        } else if (S_ISLNK(dp->mode)) {
                dp->proc_iops = &proc_link_inode_operations;
        } else if (S_ISREG(dp->mode)) {
                BUG_ON(dp->proc_fops == NULL);
                dp->proc_iops = &proc_file_inode_operations;
        } else {
                WARN_ON(1);
                proc_free_inum(dp->low_ino);
                return -EINVAL;
        }

        spin_lock(&proc_subdir_lock);
        dp->parent = dir;
        if (pde_subdir_insert(dir, dp) == false) {
                WARN(1, "proc_dir_entry '%s/%s' already registered\n",
                     dir->name, dp->name);
                spin_unlock(&proc_subdir_lock);
                if (S_ISDIR(dp->mode))
                        dir->nlink--;
                proc_free_inum(dp->low_ino);
                return -EEXIST;
        }
        spin_unlock(&proc_subdir_lock);

        return 0;
}

static struct proc_dir_entry *__proc_create(struct proc_dir_entry **parent,
                                          const char *name,
                                          umode_t mode,
                                          nlink_t nlink)
{
        struct proc_dir_entry *ent = NULL;
        const char *fn;
        struct qstr qstr;

        if (xlate_proc_name(name, parent, &fn) != 0)
                goto out;
        qstr.name = fn;
        qstr.len = strlen(fn);
        if (qstr.len == 0 || qstr.len >= 256) {
                WARN(1, "name len %u\n", qstr.len);
                return NULL;
        }
        if (*parent == &proc_root && name_to_int(&qstr) != ~0U) {
                WARN(1, "create '/proc/%s' by hand\n", qstr.name);
                return NULL;
        }

        ent = kzalloc(sizeof(struct proc_dir_entry) + qstr.len + 1, GFP_KERNEL);
        if (!ent)
                goto out;

        memcpy(ent->name, fn, qstr.len + 1);
        ent->namelen = qstr.len;
        ent->mode = mode;
        ent->nlink = nlink;
        ent->subdir = RB_ROOT;
        atomic_set(&ent->count, 1);
        spin_lock_init(&ent->pde_unload_lock);
        INIT_LIST_HEAD(&ent->pde_openers);
out:
        return ent;
}

struct proc_dir_entry *proc_symlink(const char *name,
                struct proc_dir_entry *parent, const char *dest)
{
        struct proc_dir_entry *ent;

        ent = __proc_create(&parent, name,
                          (S_IFLNK | S_IRUGO | S_IWUGO | S_IXUGO),1);

        if (ent) {
                ent->data = kmalloc((ent->size=strlen(dest))+1, GFP_KERNEL);
                if (ent->data) {
                        strcpy((char*)ent->data,dest);
                        if (proc_register(parent, ent) < 0) {
                                kfree(ent->data);
                                kfree(ent);
                                ent = NULL;
                        }
                } else {
                        kfree(ent);
                        ent = NULL;
                }
        }
        return ent;
}
EXPORT_SYMBOL(proc_symlink);

struct proc_dir_entry *proc_mkdir_data(const char *name, umode_t mode,
                struct proc_dir_entry *parent, void *data)
{
        struct proc_dir_entry *ent;

        if (mode == 0)
                mode = S_IRUGO | S_IXUGO;

        ent = __proc_create(&parent, name, S_IFDIR | mode, 2);
        if (ent) {
                ent->data = data;
                if (proc_register(parent, ent) < 0) {
                        kfree(ent);
                        ent = NULL;
                }
        }
        return ent;
}
EXPORT_SYMBOL_GPL(proc_mkdir_data);

struct proc_dir_entry *proc_mkdir_mode(const char *name, umode_t mode,
                                       struct proc_dir_entry *parent)
{
        return proc_mkdir_data(name, mode, parent, NULL);
}
EXPORT_SYMBOL(proc_mkdir_mode);

struct proc_dir_entry *proc_mkdir(const char *name,
                struct proc_dir_entry *parent)
{
        return proc_mkdir_data(name, 0, parent, NULL);
}
EXPORT_SYMBOL(proc_mkdir);

struct proc_dir_entry *proc_create_data(const char *name, umode_t mode,
                                        struct proc_dir_entry *parent,
                                        const struct file_operations *proc_fops,
                                        void *data)
{
        struct proc_dir_entry *pde;
        if ((mode & S_IFMT) == 0)
                mode |= S_IFREG;

        if (!S_ISREG(mode)) {
                WARN_ON(1);     /* use proc_mkdir() */
                return NULL;
        }

        if ((mode & S_IALLUGO) == 0)
                mode |= S_IRUGO;
        pde = __proc_create(&parent, name, mode, 1);
        if (!pde)
                goto out;
        pde->proc_fops = proc_fops;
        pde->data = data;
        if (proc_register(parent, pde) < 0)
                goto out_free;
        return pde;
out_free:
        kfree(pde);
out:
        return NULL;
}
EXPORT_SYMBOL(proc_create_data);
 
void proc_set_size(struct proc_dir_entry *de, loff_t size)
{
        de->size = size;
}
EXPORT_SYMBOL(proc_set_size);

void proc_set_user(struct proc_dir_entry *de, kuid_t uid, kgid_t gid)
{
        de->uid = uid;
        de->gid = gid;
}
EXPORT_SYMBOL(proc_set_user);

static void free_proc_entry(struct proc_dir_entry *de)
{
        proc_free_inum(de->low_ino);

        if (S_ISLNK(de->mode))
                kfree(de->data);
        kfree(de);
}

void pde_put(struct proc_dir_entry *pde)
{
        if (atomic_dec_and_test(&pde->count))
                free_proc_entry(pde);
}

/*
 * Remove a /proc entry and free it if it's not currently in use.
 */
void remove_proc_entry(const char *name, struct proc_dir_entry *parent)
{
        struct proc_dir_entry *de = NULL;
        const char *fn = name;
        unsigned int len;

        spin_lock(&proc_subdir_lock);
        if (__xlate_proc_name(name, &parent, &fn) != 0) {
                spin_unlock(&proc_subdir_lock);
                return;
        }
        len = strlen(fn);

        de = pde_subdir_find(parent, fn, len);
        if (de)
                rb_erase(&de->subdir_node, &parent->subdir);
        spin_unlock(&proc_subdir_lock);
        if (!de) {
                WARN(1, "name '%s'\n", name);
                return;
        }

        proc_entry_rundown(de);

        if (S_ISDIR(de->mode))
                parent->nlink--;
        de->nlink = 0;
        WARN(pde_subdir_first(de),
             "%s: removing non-empty directory '%s/%s', leaking at least '%s'\n",
             __func__, de->parent->name, de->name, pde_subdir_first(de)->name);
        pde_put(de);
}
EXPORT_SYMBOL(remove_proc_entry);

int remove_proc_subtree(const char *name, struct proc_dir_entry *parent)
{
        struct proc_dir_entry *root = NULL, *de, *next;
        const char *fn = name;
        unsigned int len;

        spin_lock(&proc_subdir_lock);
        if (__xlate_proc_name(name, &parent, &fn) != 0) {
                spin_unlock(&proc_subdir_lock);
                return -ENOENT;
        }
        len = strlen(fn);

        root = pde_subdir_find(parent, fn, len);
        if (!root) {
                spin_unlock(&proc_subdir_lock);
                return -ENOENT;
        }
        rb_erase(&root->subdir_node, &parent->subdir);

        de = root;
        while (1) {
                next = pde_subdir_first(de);
                if (next) {
                        rb_erase(&next->subdir_node, &de->subdir);
                        de = next;
                        continue;
                }
                spin_unlock(&proc_subdir_lock);

                proc_entry_rundown(de);
                next = de->parent;
                if (S_ISDIR(de->mode))
                        next->nlink--;
                de->nlink = 0;
                if (de == root)
                        break;
                pde_put(de);

                spin_lock(&proc_subdir_lock);
                de = next;
        }
        pde_put(root);
        return 0;
}
EXPORT_SYMBOL(remove_proc_subtree);

void *proc_get_parent_data(const struct inode *inode)
{
        struct proc_dir_entry *de = PDE(inode);
        return de->parent->data;
}
EXPORT_SYMBOL_GPL(proc_get_parent_data);

void proc_remove(struct proc_dir_entry *de)
{
        if (de)
                remove_proc_subtree(de->name, de->parent);
}
EXPORT_SYMBOL(proc_remove);

void *PDE_DATA(const struct inode *inode)
{
        return __PDE_DATA(inode);
}
EXPORT_SYMBOL(PDE_DATA);