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
  49struct vfsmount *proc_mnt;
  50
  51static struct kmem_cache * proc_inode_cachep;
  52
  53static struct inode *proc_alloc_inode(struct super_block *sb)
  54{
  55        struct proc_inode *ei;
  56        struct inode *inode;
  57
  58        ei = (struct proc_inode *)kmem_cache_alloc(proc_inode_cachep, GFP_KERNEL);
  59        if (!ei)
  60                return NULL;
  61        ei->pid = NULL;
  62        ei->fd = 0;
  63        ei->op.proc_get_link = NULL;
  64        ei->pde = NULL;
  65        ei->sysctl = NULL;
  66        ei->sysctl_entry = NULL;
  67        inode = &ei->vfs_inode;
  68        inode->i_mtime = inode->i_atime = inode->i_ctime = CURRENT_TIME;
  69        return inode;
  70}
  71
  72static void proc_i_callback(struct rcu_head *head)
  73{
  74        struct inode *inode = container_of(head, struct inode, i_rcu);
  75        INIT_LIST_HEAD(&inode->i_dentry);
  76        kmem_cache_free(proc_inode_cachep, PROC_I(inode));
  77}
  78
  79static void proc_destroy_inode(struct inode *inode)
  80{
  81        call_rcu(&inode->i_rcu, proc_i_callback);
  82}
  83
  84static void init_once(void *foo)
  85{
  86        struct proc_inode *ei = (struct proc_inode *) foo;
  87
  88        inode_init_once(&ei->vfs_inode);
  89}
  90
  91void __init proc_init_inodecache(void)
  92{
  93        proc_inode_cachep = kmem_cache_create("proc_inode_cache",
  94                                             sizeof(struct proc_inode),
  95                                             0, (SLAB_RECLAIM_ACCOUNT|
  96                                                SLAB_MEM_SPREAD|SLAB_PANIC),
  97                                             init_once);
  98}
  99
 100static const struct super_operations proc_sops = {
 101        .alloc_inode    = proc_alloc_inode,
 102        .destroy_inode  = proc_destroy_inode,
 103        .drop_inode     = generic_delete_inode,
 104        .evict_inode    = proc_evict_inode,
 105        .statfs         = simple_statfs,
 106};
 107
 108static void __pde_users_dec(struct proc_dir_entry *pde)
 109{
 110        pde->pde_users--;
 111        if (pde->pde_unload_completion && pde->pde_users == 0)
 112                complete(pde->pde_unload_completion);
 113}
 114
 115void pde_users_dec(struct proc_dir_entry *pde)
 116{
 117        spin_lock(&pde->pde_unload_lock);
 118        __pde_users_dec(pde);
 119        spin_unlock(&pde->pde_unload_lock);
 120}
 121
 122static loff_t proc_reg_llseek(struct file *file, loff_t offset, int whence)
 123{
 124        struct proc_dir_entry *pde = PDE(file->f_path.dentry->d_inode);
 125        loff_t rv = -EINVAL;
 126        loff_t (*llseek)(struct file *, loff_t, int);
 127
 128        spin_lock(&pde->pde_unload_lock);
 129        /*
 130         * remove_proc_entry() is going to delete PDE (as part of module
 131         * cleanup sequence). No new callers into module allowed.
 132         */
 133        if (!pde->proc_fops) {
 134                spin_unlock(&pde->pde_unload_lock);
 135                return rv;
 136        }
 137        /*
 138         * Bump refcount so that remove_proc_entry will wail for ->llseek to
 139         * complete.
 140         */
 141        pde->pde_users++;
 142        /*
 143         * Save function pointer under lock, to protect against ->proc_fops
 144         * NULL'ifying right after ->pde_unload_lock is dropped.
 145         */
 146        llseek = pde->proc_fops->llseek;
 147        spin_unlock(&pde->pde_unload_lock);
 148
 149        if (!llseek)
 150                llseek = default_llseek;
 151        rv = llseek(file, offset, whence);
 152
 153        pde_users_dec(pde);
 154        return rv;
 155}
 156
 157static ssize_t proc_reg_read(struct file *file, char __user *buf, size_t count, loff_t *ppos)
 158{
 159        struct proc_dir_entry *pde = PDE(file->f_path.dentry->d_inode);
 160        ssize_t rv = -EIO;
 161        ssize_t (*read)(struct file *, char __user *, size_t, loff_t *);
 162
 163        spin_lock(&pde->pde_unload_lock);
 164        if (!pde->proc_fops) {
 165                spin_unlock(&pde->pde_unload_lock);
 166                return rv;
 167        }
 168        pde->pde_users++;
 169        read = pde->proc_fops->read;
 170        spin_unlock(&pde->pde_unload_lock);
 171
 172        if (read)
 173                rv = read(file, buf, count, ppos);
 174
 175        pde_users_dec(pde);
 176        return rv;
 177}
 178
 179static ssize_t proc_reg_write(struct file *file, const char __user *buf, size_t count, loff_t *ppos)
 180{
 181        struct proc_dir_entry *pde = PDE(file->f_path.dentry->d_inode);
 182        ssize_t rv = -EIO;
 183        ssize_t (*write)(struct file *, const char __user *, size_t, loff_t *);
 184
 185        spin_lock(&pde->pde_unload_lock);
 186        if (!pde->proc_fops) {
 187                spin_unlock(&pde->pde_unload_lock);
 188                return rv;
 189        }
 190        pde->pde_users++;
 191        write = pde->proc_fops->write;
 192        spin_unlock(&pde->pde_unload_lock);
 193
 194        if (write)
 195                rv = write(file, buf, count, ppos);
 196
 197        pde_users_dec(pde);
 198        return rv;
 199}
 200
 201static unsigned int proc_reg_poll(struct file *file, struct poll_table_struct *pts)
 202{
 203        struct proc_dir_entry *pde = PDE(file->f_path.dentry->d_inode);
 204        unsigned int rv = DEFAULT_POLLMASK;
 205        unsigned int (*poll)(struct file *, struct poll_table_struct *);
 206
 207        spin_lock(&pde->pde_unload_lock);
 208        if (!pde->proc_fops) {
 209                spin_unlock(&pde->pde_unload_lock);
 210                return rv;
 211        }
 212        pde->pde_users++;
 213        poll = pde->proc_fops->poll;
 214        spin_unlock(&pde->pde_unload_lock);
 215
 216        if (poll)
 217                rv = poll(file, pts);
 218
 219        pde_users_dec(pde);
 220        return rv;
 221}
 222
 223static long proc_reg_unlocked_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
 224{
 225        struct proc_dir_entry *pde = PDE(file->f_path.dentry->d_inode);
 226        long rv = -ENOTTY;
 227        long (*ioctl)(struct file *, unsigned int, unsigned long);
 228
 229        spin_lock(&pde->pde_unload_lock);
 230        if (!pde->proc_fops) {
 231                spin_unlock(&pde->pde_unload_lock);
 232                return rv;
 233        }
 234        pde->pde_users++;
 235        ioctl = pde->proc_fops->unlocked_ioctl;
 236        spin_unlock(&pde->pde_unload_lock);
 237
 238        if (ioctl)
 239                rv = ioctl(file, cmd, arg);
 240
 241        pde_users_dec(pde);
 242        return rv;
 243}
 244
 245#ifdef CONFIG_COMPAT
 246static long proc_reg_compat_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
 247{
 248        struct proc_dir_entry *pde = PDE(file->f_path.dentry->d_inode);
 249        long rv = -ENOTTY;
 250        long (*compat_ioctl)(struct file *, unsigned int, unsigned long);
 251
 252        spin_lock(&pde->pde_unload_lock);
 253        if (!pde->proc_fops) {
 254                spin_unlock(&pde->pde_unload_lock);
 255                return rv;
 256        }
 257        pde->pde_users++;
 258        compat_ioctl = pde->proc_fops->compat_ioctl;
 259        spin_unlock(&pde->pde_unload_lock);
 260
 261        if (compat_ioctl)
 262                rv = compat_ioctl(file, cmd, arg);
 263
 264        pde_users_dec(pde);
 265        return rv;
 266}
 267#endif
 268
 269static int proc_reg_mmap(struct file *file, struct vm_area_struct *vma)
 270{
 271        struct proc_dir_entry *pde = PDE(file->f_path.dentry->d_inode);
 272        int rv = -EIO;
 273        int (*mmap)(struct file *, struct vm_area_struct *);
 274
 275        spin_lock(&pde->pde_unload_lock);
 276        if (!pde->proc_fops) {
 277                spin_unlock(&pde->pde_unload_lock);
 278                return rv;
 279        }
 280        pde->pde_users++;
 281        mmap = pde->proc_fops->mmap;
 282        spin_unlock(&pde->pde_unload_lock);
 283
 284        if (mmap)
 285                rv = mmap(file, vma);
 286
 287        pde_users_dec(pde);
 288        return rv;
 289}
 290
 291static int proc_reg_open(struct inode *inode, struct file *file)
 292{
 293        struct proc_dir_entry *pde = PDE(inode);
 294        int rv = 0;
 295        int (*open)(struct inode *, struct file *);
 296        int (*release)(struct inode *, struct file *);
 297        struct pde_opener *pdeo;
 298
 299        /*
 300         * What for, you ask? Well, we can have open, rmmod, remove_proc_entry
 301         * sequence. ->release won't be called because ->proc_fops will be
 302         * cleared. Depending on complexity of ->release, consequences vary.
 303         *
 304         * We can't wait for mercy when close will be done for real, it's
 305         * deadlockable: rmmod foo </proc/foo . So, we're going to do ->release
 306         * by hand in remove_proc_entry(). For this, save opener's credentials
 307         * for later.
 308         */
 309        pdeo = kmalloc(sizeof(struct pde_opener), GFP_KERNEL);
 310        if (!pdeo)
 311                return -ENOMEM;
 312
 313        spin_lock(&pde->pde_unload_lock);
 314        if (!pde->proc_fops) {
 315                spin_unlock(&pde->pde_unload_lock);
 316                kfree(pdeo);
 317                return -EINVAL;
 318        }
 319        pde->pde_users++;
 320        open = pde->proc_fops->open;
 321        release = pde->proc_fops->release;
 322        spin_unlock(&pde->pde_unload_lock);
 323
 324        if (open)
 325                rv = open(inode, file);
 326
 327        spin_lock(&pde->pde_unload_lock);
 328        if (rv == 0 && release) {
 329                /* To know what to release. */
 330                pdeo->inode = inode;
 331                pdeo->file = file;
 332                /* Strictly for "too late" ->release in proc_reg_release(). */
 333                pdeo->release = release;
 334                list_add(&pdeo->lh, &pde->pde_openers);
 335        } else
 336                kfree(pdeo);
 337        __pde_users_dec(pde);
 338        spin_unlock(&pde->pde_unload_lock);
 339        return rv;
 340}
 341
 342static struct pde_opener *find_pde_opener(struct proc_dir_entry *pde,
 343                                        struct inode *inode, struct file *file)
 344{
 345        struct pde_opener *pdeo;
 346
 347        list_for_each_entry(pdeo, &pde->pde_openers, lh) {
 348                if (pdeo->inode == inode && pdeo->file == file)
 349                        return pdeo;
 350        }
 351        return NULL;
 352}
 353
 354static int proc_reg_release(struct inode *inode, struct file *file)
 355{
 356        struct proc_dir_entry *pde = PDE(inode);
 357        int rv = 0;
 358        int (*release)(struct inode *, struct file *);
 359        struct pde_opener *pdeo;
 360
 361        spin_lock(&pde->pde_unload_lock);
 362        pdeo = find_pde_opener(pde, inode, file);
 363        if (!pde->proc_fops) {
 364                /*
 365                 * Can't simply exit, __fput() will think that everything is OK,
 366                 * and move on to freeing struct file. remove_proc_entry() will
 367                 * find slacker in opener's list and will try to do non-trivial
 368                 * things with struct file. Therefore, remove opener from list.
 369                 *
 370                 * But if opener is removed from list, who will ->release it?
 371                 */
 372                if (pdeo) {
 373                        list_del(&pdeo->lh);
 374                        spin_unlock(&pde->pde_unload_lock);
 375                        rv = pdeo->release(inode, file);
 376                        kfree(pdeo);
 377                } else
 378                        spin_unlock(&pde->pde_unload_lock);
 379                return rv;
 380        }
 381        pde->pde_users++;
 382        release = pde->proc_fops->release;
 383        if (pdeo) {
 384                list_del(&pdeo->lh);
 385                kfree(pdeo);
 386        }
 387        spin_unlock(&pde->pde_unload_lock);
 388
 389        if (release)
 390                rv = release(inode, file);
 391
 392        pde_users_dec(pde);
 393        return rv;
 394}
 395
 396static const struct file_operations proc_reg_file_ops = {
 397        .llseek         = proc_reg_llseek,
 398        .read           = proc_reg_read,
 399        .write          = proc_reg_write,
 400        .poll           = proc_reg_poll,
 401        .unlocked_ioctl = proc_reg_unlocked_ioctl,
 402#ifdef CONFIG_COMPAT
 403        .compat_ioctl   = proc_reg_compat_ioctl,
 404#endif
 405        .mmap           = proc_reg_mmap,
 406        .open           = proc_reg_open,
 407        .release        = proc_reg_release,
 408};
 409
 410#ifdef CONFIG_COMPAT
 411static const struct file_operations proc_reg_file_ops_no_compat = {
 412        .llseek         = proc_reg_llseek,
 413        .read           = proc_reg_read,
 414        .write          = proc_reg_write,
 415        .poll           = proc_reg_poll,
 416        .unlocked_ioctl = proc_reg_unlocked_ioctl,
 417        .mmap           = proc_reg_mmap,
 418        .open           = proc_reg_open,
 419        .release        = proc_reg_release,
 420};
 421#endif
 422
 423struct inode *proc_get_inode(struct super_block *sb, struct proc_dir_entry *de)
 424{
 425        struct inode * inode;
 426
 427        inode = iget_locked(sb, de->low_ino);
 428        if (!inode)
 429                return NULL;
 430        if (inode->i_state & I_NEW) {
 431                inode->i_mtime = inode->i_atime = inode->i_ctime = CURRENT_TIME;
 432                PROC_I(inode)->fd = 0;
 433                PROC_I(inode)->pde = de;
 434
 435                if (de->mode) {
 436                        inode->i_mode = de->mode;
 437                        inode->i_uid = de->uid;
 438                        inode->i_gid = de->gid;
 439                }
 440                if (de->size)
 441                        inode->i_size = de->size;
 442                if (de->nlink)
 443                        inode->i_nlink = de->nlink;
 444                if (de->proc_iops)
 445                        inode->i_op = de->proc_iops;
 446                if (de->proc_fops) {
 447                        if (S_ISREG(inode->i_mode)) {
 448#ifdef CONFIG_COMPAT
 449                                if (!de->proc_fops->compat_ioctl)
 450                                        inode->i_fop =
 451                                                &proc_reg_file_ops_no_compat;
 452                                else
 453#endif
 454                                        inode->i_fop = &proc_reg_file_ops;
 455                        } else {
 456                                inode->i_fop = de->proc_fops;
 457                        }
 458                }
 459                unlock_new_inode(inode);
 460        } else
 461               pde_put(de);
 462        return inode;
 463}                       
 464
 465int proc_fill_super(struct super_block *s)
 466{
 467        struct inode * root_inode;
 468
 469        s->s_flags |= MS_NODIRATIME | MS_NOSUID | MS_NOEXEC;
 470        s->s_blocksize = 1024;
 471        s->s_blocksize_bits = 10;
 472        s->s_magic = PROC_SUPER_MAGIC;
 473        s->s_op = &proc_sops;
 474        s->s_time_gran = 1;
 475        
 476        pde_get(&proc_root);
 477        root_inode = proc_get_inode(s, &proc_root);
 478        if (!root_inode)
 479                goto out_no_root;
 480        root_inode->i_uid = 0;
 481        root_inode->i_gid = 0;
 482        s->s_root = d_alloc_root(root_inode);
 483        if (!s->s_root)
 484                goto out_no_root;
 485        return 0;
 486
 487out_no_root:
 488        printk("proc_read_super: get root inode failed\n");
 489        iput(root_inode);
 490        pde_put(&proc_root);
 491        return -ENOMEM;
 492}
 493