// SPDX-License-Identifier: GPL-2.0
/*
 *  linux/fs/proc/root.c
 *
 *  Copyright (C) 1991, 1992 Linus Torvalds
 *
 *  proc root directory handling functions
 */

#include <linux/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/sched/stat.h>
#include <linux/module.h>
#include <linux/bitops.h>
#include <linux/user_namespace.h>
#include <linux/mount.h>
#include <linux/pid_namespace.h>
#include <linux/parser.h>
#include <linux/cred.h>

#include "internal.h"

enum {
        Opt_gid, Opt_hidepid, Opt_err,
};

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

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 < HIDEPID_OFF ||
                            option > HIDEPID_INVISIBLE) {
                                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;

        sync_filesystem(sb);
        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)
{
        struct pid_namespace *ns;

        if (flags & SB_KERNMOUNT) {
                ns = data;
                data = NULL;
        } else {
                ns = task_active_pid_ns(current);
        }

        return mount_ns(fs_type, flags, data, ns, ns->user_ns, proc_fill_super);
}

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

        ns = (struct pid_namespace *)sb->s_fs_info;
        if (ns->proc_self)
                dput(ns->proc_self);
        if (ns->proc_thread_self)
                dput(ns->proc_thread_self);
        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,
        .fs_flags       = FS_USERNS_MOUNT,
};

void __init proc_root_init(void)
{
        proc_init_kmemcache();
        set_proc_pid_nlink();
        proc_self_init();
        proc_thread_self_init();
        proc_symlink("mounts", NULL, "self/mounts");

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

        register_filesystem(&proc_fs_type);
}

static int proc_root_getattr(const struct path *path, struct kstat *stat,
                             u32 request_mask, unsigned int query_flags)
{
        generic_fillattr(d_inode(path->dentry), 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_pid_lookup(dir, dentry, flags))
                return NULL;
        
        return proc_lookup(dir, dentry, flags);
}

static int proc_root_readdir(struct file *file, struct dir_context *ctx)
{
        if (ctx->pos < FIRST_PROCESS_ENTRY) {
                int error = proc_readdir(file, ctx);
                if (unlikely(error <= 0))
                        return error;
                ctx->pos = FIRST_PROCESS_ENTRY;
        }

        return proc_pid_readdir(file, ctx);
}

/*
 * 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,
        .iterate_shared  = proc_root_readdir,
        .llseek         = generic_file_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, 
        .refcnt         = REFCOUNT_INIT(1),
        .proc_iops      = &proc_root_inode_operations, 
        .proc_fops      = &proc_root_operations,
        .parent         = &proc_root,
        .subdir         = RB_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);
}