generic.c

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/*
 * 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/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"

DEFINE_SPINLOCK(proc_subdir_lock);

static int proc_match(unsigned int len, const char *name, struct proc_dir_entry *de)
{
    if (de->namelen != len)
        return 0;
    return !memcmp(name, de->name, len);
}

/* buffer size is one page but our output routines use some slack for overruns */
#define PROC_BLOCK_SIZE (PAGE_SIZE - 1024)

static ssize_t
__proc_file_read(struct file *file, char __user *buf, size_t nbytes,
           loff_t *ppos)
{
    struct inode * inode = file->f_path.dentry->d_inode;
    char    *page;
    ssize_t retval=0;
    int eof=0;
    ssize_t n, count;
    char    *start;
    struct proc_dir_entry * dp;
    unsigned long long pos;

    /*
     * Gaah, please just use "seq_file" instead. The legacy /proc
     * interfaces cut loff_t down to off_t for reads, and ignore
     * the offset entirely for writes..
     */
    pos = *ppos;
    if (pos > MAX_NON_LFS)
        return 0;
    if (nbytes > MAX_NON_LFS - pos)
        nbytes = MAX_NON_LFS - pos;

    dp = PDE(inode);
    if (!(page = (char*) __get_free_page(GFP_TEMPORARY)))
        return -ENOMEM;

    while ((nbytes > 0) && !eof) {
        count = min_t(size_t, PROC_BLOCK_SIZE, nbytes);

        start = NULL;
        if (dp->read_proc) {
            /*
             * How to be a proc read function
             * ------------------------------
             * Prototype:
             *    int f(char *buffer, char **start, off_t offset,
             *          int count, int *peof, void *dat)
             *
             * Assume that the buffer is "count" bytes in size.
             *
             * If you know you have supplied all the data you
             * have, set *peof.
             *
             * You have three ways to return data:
             * 0) Leave *start = NULL.  (This is the default.)
             *    Put the data of the requested offset at that
             *    offset within the buffer.  Return the number (n)
             *    of bytes there are from the beginning of the
             *    buffer up to the last byte of data.  If the
             *    number of supplied bytes (= n - offset) is 
             *    greater than zero and you didn't signal eof
             *    and the reader is prepared to take more data
             *    you will be called again with the requested
             *    offset advanced by the number of bytes 
             *    absorbed.  This interface is useful for files
             *    no larger than the buffer.
             * 1) Set *start = an unsigned long value less than
             *    the buffer address but greater than zero.
             *    Put the data of the requested offset at the
             *    beginning of the buffer.  Return the number of
             *    bytes of data placed there.  If this number is
             *    greater than zero and you didn't signal eof
             *    and the reader is prepared to take more data
             *    you will be called again with the requested
             *    offset advanced by *start.  This interface is
             *    useful when you have a large file consisting
             *    of a series of blocks which you want to count
             *    and return as wholes.
             *    (Hack by [email protected])
             * 2) Set *start = an address within the buffer.
             *    Put the data of the requested offset at *start.
             *    Return the number of bytes of data placed there.
             *    If this number is greater than zero and you
             *    didn't signal eof and the reader is prepared to
             *    take more data you will be called again with the
             *    requested offset advanced by the number of bytes
             *    absorbed.
             */
            n = dp->read_proc(page, &start, *ppos,
                      count, &eof, dp->data);
        } else
            break;

        if (n == 0)   /* end of file */
            break;
        if (n < 0) {  /* error */
            if (retval == 0)
                retval = n;
            break;
        }

        if (start == NULL) {
            if (n > PAGE_SIZE) {
                printk(KERN_ERR
                       "proc_file_read: Apparent buffer overflow!\n");
                n = PAGE_SIZE;
            }
            n -= *ppos;
            if (n <= 0)
                break;
            if (n > count)
                n = count;
            start = page + *ppos;
        } else if (start < page) {
            if (n > PAGE_SIZE) {
                printk(KERN_ERR
                       "proc_file_read: Apparent buffer overflow!\n");
                n = PAGE_SIZE;
            }
            if (n > count) {
                /*
                 * Don't reduce n because doing so might
                 * cut off part of a data block.
                 */
                printk(KERN_WARNING
                       "proc_file_read: Read count exceeded\n");
            }
        } else /* start >= page */ {
            unsigned long startoff = (unsigned long)(start - page);
            if (n > (PAGE_SIZE - startoff)) {
                printk(KERN_ERR
                       "proc_file_read: Apparent buffer overflow!\n");
                n = PAGE_SIZE - startoff;
            }
            if (n > count)
                n = count;
        }
        
        n -= copy_to_user(buf, start < page ? page : start, n);
        if (n == 0) {
            if (retval == 0)
                retval = -EFAULT;
            break;
        }

        *ppos += start < page ? (unsigned long)start : n;
        nbytes -= n;
        buf += n;
        retval += n;
    }
    free_page((unsigned long) page);
    return retval;
}

static ssize_t
proc_file_read(struct file *file, char __user *buf, size_t nbytes,
           loff_t *ppos)
{
    struct proc_dir_entry *pde = PDE(file->f_path.dentry->d_inode);
    ssize_t rv = -EIO;

    spin_lock(&pde->pde_unload_lock);
    if (!pde->proc_fops) {
        spin_unlock(&pde->pde_unload_lock);
        return rv;
    }
    pde->pde_users++;
    spin_unlock(&pde->pde_unload_lock);

    rv = __proc_file_read(file, buf, nbytes, ppos);

    pde_users_dec(pde);
    return rv;
}

static ssize_t
proc_file_write(struct file *file, const char __user *buffer,
        size_t count, loff_t *ppos)
{
    struct proc_dir_entry *pde = PDE(file->f_path.dentry->d_inode);
    ssize_t rv = -EIO;

    if (pde->write_proc) {
        spin_lock(&pde->pde_unload_lock);
        if (!pde->proc_fops) {
            spin_unlock(&pde->pde_unload_lock);
            return rv;
        }
        pde->pde_users++;
        spin_unlock(&pde->pde_unload_lock);

        /* FIXME: does this routine need ppos?  probably... */
        rv = pde->write_proc(file, buffer, count, pde->data);
        pde_users_dec(pde);
    }
    return rv;
}


static loff_t
proc_file_lseek(struct file *file, loff_t offset, int orig)
{
    loff_t retval = -EINVAL;
    switch (orig) {
    case 1:
        offset += file->f_pos;
    /* fallthrough */
    case 0:
        if (offset < 0 || offset > MAX_NON_LFS)
            break;
        file->f_pos = retval = offset;
    }
    return retval;
}

static const struct file_operations proc_file_operations = {
    .llseek     = proc_file_lseek,
    .read       = proc_file_read,
    .write      = proc_file_write,
};

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;

    if ((iattr->ia_valid & ATTR_SIZE) &&
        iattr->ia_size != i_size_read(inode)) {
        error = vmtruncate(inode, iattr->ia_size);
        if (error)
            return error;
    }

    setattr_copy(inode, iattr);
    mark_inode_dirty(inode);
    
    de->uid = inode->i_uid;
    de->gid = 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;
        for (de = de->subdir; de ; de = de->next) {
            if (proc_match(len, cp, de))
                break;
        }
        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.
 */
static unsigned int get_inode_number(void)
{
    unsigned int i;
    int error;

retry:
    if (ida_pre_get(&proc_inum_ida, GFP_KERNEL) == 0)
        return 0;

    spin_lock(&proc_inum_lock);
    error = ida_get_new(&proc_inum_ida, &i);
    spin_unlock(&proc_inum_lock);
    if (error == -EAGAIN)
        goto retry;
    else if (error)
        return 0;

    if (i > UINT_MAX - PROC_DYNAMIC_FIRST) {
        spin_lock(&proc_inum_lock);
        ida_remove(&proc_inum_ida, i);
        spin_unlock(&proc_inum_lock);
        return 0;
    }
    return PROC_DYNAMIC_FIRST + i;
}

static void release_inode_number(unsigned int inum)
{
    spin_lock(&proc_inum_lock);
    ida_remove(&proc_inum_ida, inum - PROC_DYNAMIC_FIRST);
    spin_unlock(&proc_inum_lock);
}

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

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

/*
 * As some entries in /proc are volatile, we want to 
 * get rid of unused dentries.  This could be made 
 * smarter: we could keep a "volatile" flag in the 
 * inode to indicate which ones to keep.
 */
static int proc_delete_dentry(const struct dentry * dentry)
{
    return 1;
}

static const struct dentry_operations proc_dentry_operations =
{
    .d_delete   = proc_delete_dentry,
};

/*
 * 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 = NULL;
    int error = -ENOENT;

    spin_lock(&proc_subdir_lock);
    for (de = de->subdir; de ; de = de->next) {
        if (de->namelen != dentry->d_name.len)
            continue;
        if (!memcmp(dentry->d_name.name, de->name, de->namelen)) {
            pde_get(de);
            spin_unlock(&proc_subdir_lock);
            error = -ENOMEM;
            inode = proc_get_inode(dir->i_sb, de);
            goto out_unlock;
        }
    }
    spin_unlock(&proc_subdir_lock);
out_unlock:

    if (inode) {
        d_set_d_op(dentry, &proc_dentry_operations);
        d_add(dentry, inode);
        return NULL;
    }
    if (de)
        pde_put(de);
    return ERR_PTR(error);
}

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 *filp, void *dirent,
        filldir_t filldir)
{
    unsigned int ino;
    int i;
    struct inode *inode = filp->f_path.dentry->d_inode;
    int ret = 0;

    ino = inode->i_ino;
    i = filp->f_pos;
    switch (i) {
        case 0:
            if (filldir(dirent, ".", 1, i, ino, DT_DIR) < 0)
                goto out;
            i++;
            filp->f_pos++;
            /* fall through */
        case 1:
            if (filldir(dirent, "..", 2, i,
                    parent_ino(filp->f_path.dentry),
                    DT_DIR) < 0)
                goto out;
            i++;
            filp->f_pos++;
            /* fall through */
        default:
            spin_lock(&proc_subdir_lock);
            de = de->subdir;
            i -= 2;
            for (;;) {
                if (!de) {
                    ret = 1;
                    spin_unlock(&proc_subdir_lock);
                    goto out;
                }
                if (!i)
                    break;
                de = de->next;
                i--;
            }

            do {
                struct proc_dir_entry *next;

                /* filldir passes info to user space */
                pde_get(de);
                spin_unlock(&proc_subdir_lock);
                if (filldir(dirent, de->name, de->namelen, filp->f_pos,
                        de->low_ino, de->mode >> 12) < 0) {
                    pde_put(de);
                    goto out;
                }
                spin_lock(&proc_subdir_lock);
                filp->f_pos++;
                next = de->next;
                pde_put(de);
                de = next;
            } while (de);
            spin_unlock(&proc_subdir_lock);
    }
    ret = 1;
out:
    return ret; 
}

int proc_readdir(struct file *filp, void *dirent, filldir_t filldir)
{
    struct inode *inode = filp->f_path.dentry->d_inode;

    return proc_readdir_de(PDE(inode), filp, dirent, filldir);
}

/*
 * 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,
    .readdir        = 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)
{
    unsigned int i;
    struct proc_dir_entry *tmp;
    
    i = get_inode_number();
    if (i == 0)
        return -EAGAIN;
    dp->low_ino = i;

    if (S_ISDIR(dp->mode)) {
        if (dp->proc_iops == NULL) {
            dp->proc_fops = &proc_dir_operations;
            dp->proc_iops = &proc_dir_inode_operations;
        }
        dir->nlink++;
    } else if (S_ISLNK(dp->mode)) {
        if (dp->proc_iops == NULL)
            dp->proc_iops = &proc_link_inode_operations;
    } else if (S_ISREG(dp->mode)) {
        if (dp->proc_fops == NULL)
            dp->proc_fops = &proc_file_operations;
        if (dp->proc_iops == NULL)
            dp->proc_iops = &proc_file_inode_operations;
    }

    spin_lock(&proc_subdir_lock);

    for (tmp = dir->subdir; tmp; tmp = tmp->next)
        if (strcmp(tmp->name, dp->name) == 0) {
            WARN(1, KERN_WARNING "proc_dir_entry '%s/%s' already registered\n",
                dir->name, dp->name);
            break;
        }

    dp->next = dir->subdir;
    dp->parent = dir;
    dir->subdir = dp;
    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 = name;
    unsigned int len;

    /* make sure name is valid */
    if (!name || !strlen(name))
        goto out;

    if (xlate_proc_name(name, parent, &fn) != 0)
        goto out;

    /* At this point there must not be any '/' characters beyond *fn */
    if (strchr(fn, '/'))
        goto out;

    len = strlen(fn);

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

    memcpy(ent->name, fn, len + 1);
    ent->namelen = len;
    ent->mode = mode;
    ent->nlink = nlink;
    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_mode(const char *name, umode_t mode,
        struct proc_dir_entry *parent)
{
    struct proc_dir_entry *ent;

    ent = __proc_create(&parent, name, S_IFDIR | mode, 2);
    if (ent) {
        if (proc_register(parent, ent) < 0) {
            kfree(ent);
            ent = NULL;
        }
    }
    return ent;
}
EXPORT_SYMBOL(proc_mkdir_mode);

struct proc_dir_entry *proc_net_mkdir(struct net *net, const char *name,
        struct proc_dir_entry *parent)
{
    struct proc_dir_entry *ent;

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

struct proc_dir_entry *proc_mkdir(const char *name,
        struct proc_dir_entry *parent)
{
    return proc_mkdir_mode(name, S_IRUGO | S_IXUGO, parent);
}
EXPORT_SYMBOL(proc_mkdir);

struct proc_dir_entry *create_proc_entry(const char *name, umode_t mode,
                     struct proc_dir_entry *parent)
{
    struct proc_dir_entry *ent;
    nlink_t nlink;

    if (S_ISDIR(mode)) {
        if ((mode & S_IALLUGO) == 0)
            mode |= S_IRUGO | S_IXUGO;
        nlink = 2;
    } else {
        if ((mode & S_IFMT) == 0)
            mode |= S_IFREG;
        if ((mode & S_IALLUGO) == 0)
            mode |= S_IRUGO;
        nlink = 1;
    }

    ent = __proc_create(&parent, name, mode, nlink);
    if (ent) {
        if (proc_register(parent, ent) < 0) {
            kfree(ent);
            ent = NULL;
        }
    }
    return ent;
}
EXPORT_SYMBOL(create_proc_entry);

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;
    nlink_t nlink;

    if (S_ISDIR(mode)) {
        if ((mode & S_IALLUGO) == 0)
            mode |= S_IRUGO | S_IXUGO;
        nlink = 2;
    } else {
        if ((mode & S_IFMT) == 0)
            mode |= S_IFREG;
        if ((mode & S_IALLUGO) == 0)
            mode |= S_IRUGO;
        nlink = 1;
    }

    pde = __proc_create(&parent, name, mode, nlink);
    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);

static void free_proc_entry(struct proc_dir_entry *de)
{
    release_inode_number(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 **p;
    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);

    for (p = &parent->subdir; *p; p=&(*p)->next ) {
        if (proc_match(len, fn, *p)) {
            de = *p;
            *p = de->next;
            de->next = NULL;
            break;
        }
    }
    spin_unlock(&proc_subdir_lock);
    if (!de) {
        WARN(1, "name '%s'\n", name);
        return;
    }

    spin_lock(&de->pde_unload_lock);
    /*
     * Stop accepting new callers into module. If you're
     * dynamically allocating ->proc_fops, save a pointer somewhere.
     */
    de->proc_fops = NULL;
    /* Wait until all existing callers into module are done. */
    if (de->pde_users > 0) {
        DECLARE_COMPLETION_ONSTACK(c);

        if (!de->pde_unload_completion)
            de->pde_unload_completion = &c;

        spin_unlock(&de->pde_unload_lock);

        wait_for_completion(de->pde_unload_completion);

        spin_lock(&de->pde_unload_lock);
    }

    while (!list_empty(&de->pde_openers)) {
        struct pde_opener *pdeo;

        pdeo = list_first_entry(&de->pde_openers, struct pde_opener, lh);
        list_del(&pdeo->lh);
        spin_unlock(&de->pde_unload_lock);
        pdeo->release(pdeo->inode, pdeo->file);
        kfree(pdeo);
        spin_lock(&de->pde_unload_lock);
    }
    spin_unlock(&de->pde_unload_lock);

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