linux/fs/proc/inode.c
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   1/*
   2 *  linux/fs/proc/inode.c
   3 *
   4 *  Copyright (C) 1991, 1992  Linus Torvalds
   5 */
   6
   7#include <linux/time.h>
   8#include <linux/proc_fs.h>
   9#include <linux/kernel.h>
  10#include <linux/mm.h>
  11#include <linux/string.h>
  12#include <linux/stat.h>
  13#include <linux/completion.h>
  14#include <linux/poll.h>
  15#include <linux/file.h>
  16#include <linux/limits.h>
  17#include <linux/init.h>
  18#include <linux/module.h>
  19#include <linux/sysctl.h>
  20#include <linux/slab.h>
  21
  22#include <asm/system.h>
  23#include <asm/uaccess.h>
  24
  25#include "internal.h"
  26
  27static void proc_evict_inode(struct inode *inode)
  28{
  29        struct proc_dir_entry *de;
  30        struct ctl_table_header *head;
  31
  32        truncate_inode_pages(&inode->i_data, 0);
  33        end_writeback(inode);
  34
  35        /* Stop tracking associated processes */
  36        put_pid(PROC_I(inode)->pid);
  37
  38        /* Let go of any associated proc directory entry */
  39        de = PROC_I(inode)->pde;
  40        if (de)
  41                pde_put(de);
  42        head = PROC_I(inode)->sysctl;
  43        if (head) {
  44                rcu_assign_pointer(PROC_I(inode)->sysctl, NULL);
  45                sysctl_head_put(head);
  46        }
  47}
  48
  49static struct kmem_cache * proc_inode_cachep;
  50
  51static struct inode *proc_alloc_inode(struct super_block *sb)
  52{
  53        struct proc_inode *ei;
  54        struct inode *inode;
  55
  56        ei = (struct proc_inode *)kmem_cache_alloc(proc_inode_cachep, GFP_KERNEL);
  57        if (!ei)
  58                return NULL;
  59        ei->pid = NULL;
  60        ei->fd = 0;
  61        ei->op.proc_get_link = NULL;
  62        ei->pde = NULL;
  63        ei->sysctl = NULL;
  64        ei->sysctl_entry = NULL;
  65        inode = &ei->vfs_inode;
  66        inode->i_mtime = inode->i_atime = inode->i_ctime = CURRENT_TIME;
  67        return inode;
  68}
  69
  70static void proc_i_callback(struct rcu_head *head)
  71{
  72        struct inode *inode = container_of(head, struct inode, i_rcu);
  73        INIT_LIST_HEAD(&inode->i_dentry);
  74        kmem_cache_free(proc_inode_cachep, PROC_I(inode));
  75}
  76
  77static void proc_destroy_inode(struct inode *inode)
  78{
  79        call_rcu(&inode->i_rcu, proc_i_callback);
  80}
  81
  82static void init_once(void *foo)
  83{
  84        struct proc_inode *ei = (struct proc_inode *) foo;
  85
  86        inode_init_once(&ei->vfs_inode);
  87}
  88
  89void __init proc_init_inodecache(void)
  90{
  91        proc_inode_cachep = kmem_cache_create("proc_inode_cache",
  92                                             sizeof(struct proc_inode),
  93                                             0, (SLAB_RECLAIM_ACCOUNT|
  94                                                SLAB_MEM_SPREAD|SLAB_PANIC),
  95                                             init_once);
  96}
  97
  98static const struct super_operations proc_sops = {
  99        .alloc_inode    = proc_alloc_inode,
 100        .destroy_inode  = proc_destroy_inode,
 101        .drop_inode     = generic_delete_inode,
 102        .evict_inode    = proc_evict_inode,
 103        .statfs         = simple_statfs,
 104};
 105
 106static void __pde_users_dec(struct proc_dir_entry *pde)
 107{
 108        pde->pde_users--;
 109        if (pde->pde_unload_completion && pde->pde_users == 0)
 110                complete(pde->pde_unload_completion);
 111}
 112
 113void pde_users_dec(struct proc_dir_entry *pde)
 114{
 115        spin_lock(&pde->pde_unload_lock);
 116        __pde_users_dec(pde);
 117        spin_unlock(&pde->pde_unload_lock);
 118}
 119
 120static loff_t proc_reg_llseek(struct file *file, loff_t offset, int whence)
 121{
 122        struct proc_dir_entry *pde = PDE(file->f_path.dentry->d_inode);
 123        loff_t rv = -EINVAL;
 124        loff_t (*llseek)(struct file *, loff_t, int);
 125
 126        spin_lock(&pde->pde_unload_lock);
 127        /*
 128         * remove_proc_entry() is going to delete PDE (as part of module
 129         * cleanup sequence). No new callers into module allowed.
 130         */
 131        if (!pde->proc_fops) {
 132                spin_unlock(&pde->pde_unload_lock);
 133                return rv;
 134        }
 135        /*
 136         * Bump refcount so that remove_proc_entry will wail for ->llseek to
 137         * complete.
 138         */
 139        pde->pde_users++;
 140        /*
 141         * Save function pointer under lock, to protect against ->proc_fops
 142         * NULL'ifying right after ->pde_unload_lock is dropped.
 143         */
 144        llseek = pde->proc_fops->llseek;
 145        spin_unlock(&pde->pde_unload_lock);
 146
 147        if (!llseek)
 148                llseek = default_llseek;
 149        rv = llseek(file, offset, whence);
 150
 151        pde_users_dec(pde);
 152        return rv;
 153}
 154
 155static ssize_t proc_reg_read(struct file *file, char __user *buf, size_t count, loff_t *ppos)
 156{
 157        struct proc_dir_entry *pde = PDE(file->f_path.dentry->d_inode);
 158        ssize_t rv = -EIO;
 159        ssize_t (*read)(struct file *, char __user *, size_t, loff_t *);
 160
 161        spin_lock(&pde->pde_unload_lock);
 162        if (!pde->proc_fops) {
 163                spin_unlock(&pde->pde_unload_lock);
 164                return rv;
 165        }
 166        pde->pde_users++;
 167        read = pde->proc_fops->read;
 168        spin_unlock(&pde->pde_unload_lock);
 169
 170        if (read)
 171                rv = read(file, buf, count, ppos);
 172
 173        pde_users_dec(pde);
 174        return rv;
 175}
 176
 177static ssize_t proc_reg_write(struct file *file, const char __user *buf, size_t count, loff_t *ppos)
 178{
 179        struct proc_dir_entry *pde = PDE(file->f_path.dentry->d_inode);
 180        ssize_t rv = -EIO;
 181        ssize_t (*write)(struct file *, const char __user *, size_t, loff_t *);
 182
 183        spin_lock(&pde->pde_unload_lock);
 184        if (!pde->proc_fops) {
 185                spin_unlock(&pde->pde_unload_lock);
 186                return rv;
 187        }
 188        pde->pde_users++;
 189        write = pde->proc_fops->write;
 190        spin_unlock(&pde->pde_unload_lock);
 191
 192        if (write)
 193                rv = write(file, buf, count, ppos);
 194
 195        pde_users_dec(pde);
 196        return rv;
 197}
 198
 199static unsigned int proc_reg_poll(struct file *file, struct poll_table_struct *pts)
 200{
 201        struct proc_dir_entry *pde = PDE(file->f_path.dentry->d_inode);
 202        unsigned int rv = DEFAULT_POLLMASK;
 203        unsigned int (*poll)(struct file *, struct poll_table_struct *);
 204
 205        spin_lock(&pde->pde_unload_lock);
 206        if (!pde->proc_fops) {
 207                spin_unlock(&pde->pde_unload_lock);
 208                return rv;
 209        }
 210        pde->pde_users++;
 211        poll = pde->proc_fops->poll;
 212        spin_unlock(&pde->pde_unload_lock);
 213
 214        if (poll)
 215                rv = poll(file, pts);
 216
 217        pde_users_dec(pde);
 218        return rv;
 219}
 220
 221static long proc_reg_unlocked_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
 222{
 223        struct proc_dir_entry *pde = PDE(file->f_path.dentry->d_inode);
 224        long rv = -ENOTTY;
 225        long (*ioctl)(struct file *, unsigned int, unsigned long);
 226
 227        spin_lock(&pde->pde_unload_lock);
 228        if (!pde->proc_fops) {
 229                spin_unlock(&pde->pde_unload_lock);
 230                return rv;
 231        }
 232        pde->pde_users++;
 233        ioctl = pde->proc_fops->unlocked_ioctl;
 234        spin_unlock(&pde->pde_unload_lock);
 235
 236        if (ioctl)
 237                rv = ioctl(file, cmd, arg);
 238
 239        pde_users_dec(pde);
 240        return rv;
 241}
 242
 243#ifdef CONFIG_COMPAT
 244static long proc_reg_compat_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
 245{
 246        struct proc_dir_entry *pde = PDE(file->f_path.dentry->d_inode);
 247        long rv = -ENOTTY;
 248        long (*compat_ioctl)(struct file *, unsigned int, unsigned long);
 249
 250        spin_lock(&pde->pde_unload_lock);
 251        if (!pde->proc_fops) {
 252                spin_unlock(&pde->pde_unload_lock);
 253                return rv;
 254        }
 255        pde->pde_users++;
 256        compat_ioctl = pde->proc_fops->compat_ioctl;
 257        spin_unlock(&pde->pde_unload_lock);
 258
 259        if (compat_ioctl)
 260                rv = compat_ioctl(file, cmd, arg);
 261
 262        pde_users_dec(pde);
 263        return rv;
 264}
 265#endif
 266
 267static int proc_reg_mmap(struct file *file, struct vm_area_struct *vma)
 268{
 269        struct proc_dir_entry *pde = PDE(file->f_path.dentry->d_inode);
 270        int rv = -EIO;
 271        int (*mmap)(struct file *, struct vm_area_struct *);
 272
 273        spin_lock(&pde->pde_unload_lock);
 274        if (!pde->proc_fops) {
 275                spin_unlock(&pde->pde_unload_lock);
 276                return rv;
 277        }
 278        pde->pde_users++;
 279        mmap = pde->proc_fops->mmap;
 280        spin_unlock(&pde->pde_unload_lock);
 281
 282        if (mmap)
 283                rv = mmap(file, vma);
 284
 285        pde_users_dec(pde);
 286        return rv;
 287}
 288
 289static int proc_reg_open(struct inode *inode, struct file *file)
 290{
 291        struct proc_dir_entry *pde = PDE(inode);
 292        int rv = 0;
 293        int (*open)(struct inode *, struct file *);
 294        int (*release)(struct inode *, struct file *);
 295        struct pde_opener *pdeo;
 296
 297        /*
 298         * What for, you ask? Well, we can have open, rmmod, remove_proc_entry
 299         * sequence. ->release won't be called because ->proc_fops will be
 300         * cleared. Depending on complexity of ->release, consequences vary.
 301         *
 302         * We can't wait for mercy when close will be done for real, it's
 303         * deadlockable: rmmod foo </proc/foo . So, we're going to do ->release
 304         * by hand in remove_proc_entry(). For this, save opener's credentials
 305         * for later.
 306         */
 307        pdeo = kmalloc(sizeof(struct pde_opener), GFP_KERNEL);
 308        if (!pdeo)
 309                return -ENOMEM;
 310
 311        spin_lock(&pde->pde_unload_lock);
 312        if (!pde->proc_fops) {
 313                spin_unlock(&pde->pde_unload_lock);
 314                kfree(pdeo);
 315                return -EINVAL;
 316        }
 317        pde->pde_users++;
 318        open = pde->proc_fops->open;
 319        release = pde->proc_fops->release;
 320        spin_unlock(&pde->pde_unload_lock);
 321
 322        if (open)
 323                rv = open(inode, file);
 324
 325        spin_lock(&pde->pde_unload_lock);
 326        if (rv == 0 && release) {
 327                /* To know what to release. */
 328                pdeo->inode = inode;
 329                pdeo->file = file;
 330                /* Strictly for "too late" ->release in proc_reg_release(). */
 331                pdeo->release = release;
 332                list_add(&pdeo->lh, &pde->pde_openers);
 333        } else
 334                kfree(pdeo);
 335        __pde_users_dec(pde);
 336        spin_unlock(&pde->pde_unload_lock);
 337        return rv;
 338}
 339
 340static struct pde_opener *find_pde_opener(struct proc_dir_entry *pde,
 341                                        struct inode *inode, struct file *file)
 342{
 343        struct pde_opener *pdeo;
 344
 345        list_for_each_entry(pdeo, &pde->pde_openers, lh) {
 346                if (pdeo->inode == inode && pdeo->file == file)
 347                        return pdeo;
 348        }
 349        return NULL;
 350}
 351
 352static int proc_reg_release(struct inode *inode, struct file *file)
 353{
 354        struct proc_dir_entry *pde = PDE(inode);
 355        int rv = 0;
 356        int (*release)(struct inode *, struct file *);
 357        struct pde_opener *pdeo;
 358
 359        spin_lock(&pde->pde_unload_lock);
 360        pdeo = find_pde_opener(pde, inode, file);
 361        if (!pde->proc_fops) {
 362                /*
 363                 * Can't simply exit, __fput() will think that everything is OK,
 364                 * and move on to freeing struct file. remove_proc_entry() will
 365                 * find slacker in opener's list and will try to do non-trivial
 366                 * things with struct file. Therefore, remove opener from list.
 367                 *
 368                 * But if opener is removed from list, who will ->release it?
 369                 */
 370                if (pdeo) {
 371                        list_del(&pdeo->lh);
 372                        spin_unlock(&pde->pde_unload_lock);
 373                        rv = pdeo->release(inode, file);
 374                        kfree(pdeo);
 375                } else
 376                        spin_unlock(&pde->pde_unload_lock);
 377                return rv;
 378        }
 379        pde->pde_users++;
 380        release = pde->proc_fops->release;
 381        if (pdeo) {
 382                list_del(&pdeo->lh);
 383                kfree(pdeo);
 384        }
 385        spin_unlock(&pde->pde_unload_lock);
 386
 387        if (release)
 388                rv = release(inode, file);
 389
 390        pde_users_dec(pde);
 391        return rv;
 392}
 393
 394static const struct file_operations proc_reg_file_ops = {
 395        .llseek         = proc_reg_llseek,
 396        .read           = proc_reg_read,
 397        .write          = proc_reg_write,
 398        .poll           = proc_reg_poll,
 399        .unlocked_ioctl = proc_reg_unlocked_ioctl,
 400#ifdef CONFIG_COMPAT
 401        .compat_ioctl   = proc_reg_compat_ioctl,
 402#endif
 403        .mmap           = proc_reg_mmap,
 404        .open           = proc_reg_open,
 405        .release        = proc_reg_release,
 406};
 407
 408#ifdef CONFIG_COMPAT
 409static const struct file_operations proc_reg_file_ops_no_compat = {
 410        .llseek         = proc_reg_llseek,
 411        .read           = proc_reg_read,
 412        .write          = proc_reg_write,
 413        .poll           = proc_reg_poll,
 414        .unlocked_ioctl = proc_reg_unlocked_ioctl,
 415        .mmap           = proc_reg_mmap,
 416        .open           = proc_reg_open,
 417        .release        = proc_reg_release,
 418};
 419#endif
 420
 421struct inode *proc_get_inode(struct super_block *sb, struct proc_dir_entry *de)
 422{
 423        struct inode * inode;
 424
 425        inode = iget_locked(sb, de->low_ino);
 426        if (!inode)
 427                return NULL;
 428        if (inode->i_state & I_NEW) {
 429                inode->i_mtime = inode->i_atime = inode->i_ctime = CURRENT_TIME;
 430                PROC_I(inode)->fd = 0;
 431                PROC_I(inode)->pde = de;
 432
 433                if (de->mode) {
 434                        inode->i_mode = de->mode;
 435                        inode->i_uid = de->uid;
 436                        inode->i_gid = de->gid;
 437                }
 438                if (de->size)
 439                        inode->i_size = de->size;
 440                if (de->nlink)
 441                        inode->i_nlink = de->nlink;
 442                if (de->proc_iops)
 443                        inode->i_op = de->proc_iops;
 444                if (de->proc_fops) {
 445                        if (S_ISREG(inode->i_mode)) {
 446#ifdef CONFIG_COMPAT
 447                                if (!de->proc_fops->compat_ioctl)
 448                                        inode->i_fop =
 449                                                &proc_reg_file_ops_no_compat;
 450                                else
 451#endif
 452                                        inode->i_fop = &proc_reg_file_ops;
 453                        } else {
 454                                inode->i_fop = de->proc_fops;
 455                        }
 456                }
 457                unlock_new_inode(inode);
 458        } else
 459               pde_put(de);
 460        return inode;
 461}                       
 462
 463int proc_fill_super(struct super_block *s)
 464{
 465        struct inode * root_inode;
 466
 467        s->s_flags |= MS_NODIRATIME | MS_NOSUID | MS_NOEXEC;
 468        s->s_blocksize = 1024;
 469        s->s_blocksize_bits = 10;
 470        s->s_magic = PROC_SUPER_MAGIC;
 471        s->s_op = &proc_sops;
 472        s->s_time_gran = 1;
 473        
 474        pde_get(&proc_root);
 475        root_inode = proc_get_inode(s, &proc_root);
 476        if (!root_inode)
 477                goto out_no_root;
 478        root_inode->i_uid = 0;
 479        root_inode->i_gid = 0;
 480        s->s_root = d_alloc_root(root_inode);
 481        if (!s->s_root)
 482                goto out_no_root;
 483        return 0;
 484
 485out_no_root:
 486        printk("proc_read_super: get root inode failed\n");
 487        iput(root_inode);
 488        pde_put(&proc_root);
 489        return -ENOMEM;
 490}
 491