root.c

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/*
 *  linux/fs/proc/root.c
 *
 *  Copyright (C) 1991, 1992 Linus Torvalds
 *
 *  proc root directory handling functions
 */

#include <asm/uaccess.h>

#include <linux/errno.h>
#include <linux/time.h>
#include <linux/proc_fs.h>
#include <linux/stat.h>
#include <linux/init.h>
#include <linux/sched.h>
#include <linux/module.h>
#include <linux/bitops.h>
#include <linux/mount.h>
#include <linux/pid_namespace.h>
#include <linux/parser.h>

#include "internal.h"

static int proc_test_super(struct super_block *sb, void *data)
{
    return sb->s_fs_info == data;
}

static int proc_set_super(struct super_block *sb, void *data)
{
    int err = set_anon_super(sb, NULL);
    if (!err) {
        struct pid_namespace *ns = (struct pid_namespace *)data;
        sb->s_fs_info = get_pid_ns(ns);
    }
    return err;
}

enum {
    Opt_gid, Opt_hidepid, Opt_err,
};

static const match_table_t tokens = {
    {Opt_hidepid, "hidepid=%u"},
    {Opt_gid, "gid=%u"},
    {Opt_err, NULL},
};

static int proc_parse_options(char *options, struct pid_namespace *pid)
{
    char *p;
    substring_t args[MAX_OPT_ARGS];
    int option;

    if (!options)
        return 1;

    while ((p = strsep(&options, ",")) != NULL) {
        int token;
        if (!*p)
            continue;

        args[0].to = args[0].from = NULL;
        token = match_token(p, tokens, args);
        switch (token) {
        case Opt_gid:
            if (match_int(&args[0], &option))
                return 0;
            pid->pid_gid = make_kgid(current_user_ns(), option);
            break;
        case Opt_hidepid:
            if (match_int(&args[0], &option))
                return 0;
            if (option < 0 || option > 2) {
                pr_err("proc: hidepid value must be between 0 and 2.\n");
                return 0;
            }
            pid->hide_pid = option;
            break;
        default:
            pr_err("proc: unrecognized mount option \"%s\" "
                   "or missing value\n", p);
            return 0;
        }
    }

    return 1;
}

int proc_remount(struct super_block *sb, int *flags, char *data)
{
    struct pid_namespace *pid = sb->s_fs_info;
    return !proc_parse_options(data, pid);
}

static struct dentry *proc_mount(struct file_system_type *fs_type,
    int flags, const char *dev_name, void *data)
{
    int err;
    struct super_block *sb;
    struct pid_namespace *ns;
    struct proc_inode *ei;
    char *options;

    if (flags & MS_KERNMOUNT) {
        ns = (struct pid_namespace *)data;
        options = NULL;
    } else {
        ns = current->nsproxy->pid_ns;
        options = data;
    }

    sb = sget(fs_type, proc_test_super, proc_set_super, flags, ns);
    if (IS_ERR(sb))
        return ERR_CAST(sb);

    if (!proc_parse_options(options, ns)) {
        deactivate_locked_super(sb);
        return ERR_PTR(-EINVAL);
    }

    if (!sb->s_root) {
        err = proc_fill_super(sb);
        if (err) {
            deactivate_locked_super(sb);
            return ERR_PTR(err);
        }

        sb->s_flags |= MS_ACTIVE;
    }

    ei = PROC_I(sb->s_root->d_inode);
    if (!ei->pid) {
        rcu_read_lock();
        ei->pid = get_pid(find_pid_ns(1, ns));
        rcu_read_unlock();
    }

    return dget(sb->s_root);
}

static void proc_kill_sb(struct super_block *sb)
{
    struct pid_namespace *ns;

    ns = (struct pid_namespace *)sb->s_fs_info;
    kill_anon_super(sb);
    put_pid_ns(ns);
}

static struct file_system_type proc_fs_type = {
    .name       = "proc",
    .mount      = proc_mount,
    .kill_sb    = proc_kill_sb,
};

void __init proc_root_init(void)
{
    int err;

    proc_init_inodecache();
    err = register_filesystem(&proc_fs_type);
    if (err)
        return;
    err = pid_ns_prepare_proc(&init_pid_ns);
    if (err) {
        unregister_filesystem(&proc_fs_type);
        return;
    }

    proc_symlink("mounts", NULL, "self/mounts");

    proc_net_init();

#ifdef CONFIG_SYSVIPC
    proc_mkdir("sysvipc", NULL);
#endif
    proc_mkdir("fs", NULL);
    proc_mkdir("driver", NULL);
    proc_mkdir("fs/nfsd", NULL); /* somewhere for the nfsd filesystem to be mounted */
#if defined(CONFIG_SUN_OPENPROMFS) || defined(CONFIG_SUN_OPENPROMFS_MODULE)
    /* just give it a mountpoint */
    proc_mkdir("openprom", NULL);
#endif
    proc_tty_init();
#ifdef CONFIG_PROC_DEVICETREE
    proc_device_tree_init();
#endif
    proc_mkdir("bus", NULL);
    proc_sys_init();
}

static int proc_root_getattr(struct vfsmount *mnt, struct dentry *dentry, struct kstat *stat
)
{
    generic_fillattr(dentry->d_inode, stat);
    stat->nlink = proc_root.nlink + nr_processes();
    return 0;
}

static struct dentry *proc_root_lookup(struct inode * dir, struct dentry * dentry, unsigned int flags)
{
    if (!proc_lookup(dir, dentry, flags))
        return NULL;
    
    return proc_pid_lookup(dir, dentry, flags);
}

static int proc_root_readdir(struct file * filp,
    void * dirent, filldir_t filldir)
{
    unsigned int nr = filp->f_pos;
    int ret;

    if (nr < FIRST_PROCESS_ENTRY) {
        int error = proc_readdir(filp, dirent, filldir);
        if (error <= 0)
            return error;
        filp->f_pos = FIRST_PROCESS_ENTRY;
    }

    ret = proc_pid_readdir(filp, dirent, filldir);
    return ret;
}

/*
 * The root /proc directory is special, as it has the
 * <pid> directories. Thus we don't use the generic
 * directory handling functions for that..
 */
static const struct file_operations proc_root_operations = {
    .read        = generic_read_dir,
    .readdir     = proc_root_readdir,
    .llseek     = default_llseek,
};

/*
 * proc root can do almost nothing..
 */
static const struct inode_operations proc_root_inode_operations = {
    .lookup     = proc_root_lookup,
    .getattr    = proc_root_getattr,
};

/*
 * This is the root "inode" in the /proc tree..
 */
struct proc_dir_entry proc_root = {
    .low_ino    = PROC_ROOT_INO, 
    .namelen    = 5, 
    .mode       = S_IFDIR | S_IRUGO | S_IXUGO, 
    .nlink      = 2, 
    .count      = ATOMIC_INIT(1),
    .proc_iops  = &proc_root_inode_operations, 
    .proc_fops  = &proc_root_operations,
    .parent     = &proc_root,
    .name       = "/proc",
};

int pid_ns_prepare_proc(struct pid_namespace *ns)
{
    struct vfsmount *mnt;

    mnt = kern_mount_data(&proc_fs_type, ns);
    if (IS_ERR(mnt))
        return PTR_ERR(mnt);

    ns->proc_mnt = mnt;
    return 0;
}

void pid_ns_release_proc(struct pid_namespace *ns)
{
    kern_unmount(ns->proc_mnt);
}