// SPDX-License-Identifier: GPL-1.0+
/*
 *    Hypervisor filesystem for Linux on s390.
 *
 *    Copyright IBM Corp. 2006, 2008
 *    Author(s): Michael Holzheu <holzheu@de.ibm.com>
 */

#define pr_fmt(fmt) "hypfs: " fmt

#include <linux/types.h>
#include <linux/errno.h>
#include <linux/fs.h>
#include <linux/fs_context.h>
#include <linux/fs_parser.h>
#include <linux/namei.h>
#include <linux/vfs.h>
#include <linux/slab.h>
#include <linux/pagemap.h>
#include <linux/time.h>
#include <linux/sysfs.h>
#include <linux/init.h>
#include <linux/kobject.h>
#include <linux/seq_file.h>
#include <linux/uio.h>
#include <asm/machine.h>
#include <asm/ebcdic.h>
#include "hypfs.h"

#define HYPFS_MAGIC 0x687970    /* ASCII 'hyp' */
#define TMP_SIZE 64             /* size of temporary buffers */

static struct dentry *hypfs_create_update_file(struct dentry *dir);

struct hypfs_sb_info {
        kuid_t uid;                     /* uid used for files and dirs */
        kgid_t gid;                     /* gid used for files and dirs */
        struct dentry *update_file;     /* file to trigger update */
        time64_t last_update;           /* last update, CLOCK_MONOTONIC time */
        struct mutex lock;              /* lock to protect update process */
};

static const struct file_operations hypfs_file_ops;
static struct file_system_type hypfs_type;
static const struct super_operations hypfs_s_ops;

/* start of list of all dentries, which have to be deleted on update */
static struct dentry *hypfs_last_dentry;

static void hypfs_update_update(struct super_block *sb)
{
        struct hypfs_sb_info *sb_info = sb->s_fs_info;
        struct inode *inode = d_inode(sb_info->update_file);

        sb_info->last_update = ktime_get_seconds();
        simple_inode_init_ts(inode);
}

/* directory tree removal functions */

static void hypfs_add_dentry(struct dentry *dentry)
{
        if (IS_ROOT(dentry->d_parent)) {
                dentry->d_fsdata = hypfs_last_dentry;
                hypfs_last_dentry = dentry;
        }
}

static void hypfs_delete_tree(void)
{
        while (hypfs_last_dentry) {
                struct dentry *next_dentry = hypfs_last_dentry->d_fsdata;
                simple_recursive_removal(hypfs_last_dentry, NULL);
                hypfs_last_dentry = next_dentry;
        }
}

static struct inode *hypfs_make_inode(struct super_block *sb, umode_t mode)
{
        struct inode *ret = new_inode(sb);

        if (ret) {
                struct hypfs_sb_info *hypfs_info = sb->s_fs_info;
                ret->i_ino = get_next_ino();
                ret->i_mode = mode;
                ret->i_uid = hypfs_info->uid;
                ret->i_gid = hypfs_info->gid;
                simple_inode_init_ts(ret);
                if (S_ISDIR(mode))
                        set_nlink(ret, 2);
        }
        return ret;
}

static void hypfs_evict_inode(struct inode *inode)
{
        clear_inode(inode);
        kfree(inode->i_private);
}

static int hypfs_open(struct inode *inode, struct file *filp)
{
        char *data = file_inode(filp)->i_private;
        struct hypfs_sb_info *fs_info;

        if (filp->f_mode & FMODE_WRITE) {
                if (!(inode->i_mode & S_IWUGO))
                        return -EACCES;
        }
        if (filp->f_mode & FMODE_READ) {
                if (!(inode->i_mode & S_IRUGO))
                        return -EACCES;
        }

        fs_info = inode->i_sb->s_fs_info;
        if(data) {
                mutex_lock(&fs_info->lock);
                filp->private_data = kstrdup(data, GFP_KERNEL);
                if (!filp->private_data) {
                        mutex_unlock(&fs_info->lock);
                        return -ENOMEM;
                }
                mutex_unlock(&fs_info->lock);
        }
        return nonseekable_open(inode, filp);
}

static ssize_t hypfs_read_iter(struct kiocb *iocb, struct iov_iter *to)
{
        struct file *file = iocb->ki_filp;
        char *data = file->private_data;
        size_t available = strlen(data);
        loff_t pos = iocb->ki_pos;
        size_t count;

        if (pos < 0)
                return -EINVAL;
        if (pos >= available || !iov_iter_count(to))
                return 0;
        count = copy_to_iter(data + pos, available - pos, to);
        if (!count)
                return -EFAULT;
        iocb->ki_pos = pos + count;
        file_accessed(file);
        return count;
}

static ssize_t hypfs_write_iter(struct kiocb *iocb, struct iov_iter *from)
{
        int rc;
        struct super_block *sb = file_inode(iocb->ki_filp)->i_sb;
        struct hypfs_sb_info *fs_info = sb->s_fs_info;
        size_t count = iov_iter_count(from);

        /*
         * Currently we only allow one update per second for two reasons:
         * 1. diag 204 is VERY expensive
         * 2. If several processes do updates in parallel and then read the
         *    hypfs data, the likelihood of collisions is reduced, if we restrict
         *    the minimum update interval. A collision occurs, if during the
         *    data gathering of one process another process triggers an update
         *    If the first process wants to ensure consistent data, it has
         *    to restart data collection in this case.
         */
        mutex_lock(&fs_info->lock);
        if (fs_info->last_update == ktime_get_seconds()) {
                rc = -EBUSY;
                goto out;
        }
        hypfs_delete_tree();
        if (machine_is_vm())
                rc = hypfs_vm_create_files(sb->s_root);
        else
                rc = hypfs_diag_create_files(sb->s_root);
        if (rc) {
                pr_err("Updating the hypfs tree failed\n");
                hypfs_delete_tree();
                goto out;
        }
        hypfs_update_update(sb);
        rc = count;
        iov_iter_advance(from, count);
out:
        mutex_unlock(&fs_info->lock);
        return rc;
}

static int hypfs_release(struct inode *inode, struct file *filp)
{
        kfree(filp->private_data);
        return 0;
}

enum { Opt_uid, Opt_gid, };

static const struct fs_parameter_spec hypfs_fs_parameters[] = {
        fsparam_u32("gid", Opt_gid),
        fsparam_u32("uid", Opt_uid),
        {}
};

static int hypfs_parse_param(struct fs_context *fc, struct fs_parameter *param)
{
        struct hypfs_sb_info *hypfs_info = fc->s_fs_info;
        struct fs_parse_result result;
        kuid_t uid;
        kgid_t gid;
        int opt;

        opt = fs_parse(fc, hypfs_fs_parameters, param, &result);
        if (opt < 0)
                return opt;

        switch (opt) {
        case Opt_uid:
                uid = make_kuid(current_user_ns(), result.uint_32);
                if (!uid_valid(uid))
                        return invalf(fc, "Unknown uid");
                hypfs_info->uid = uid;
                break;
        case Opt_gid:
                gid = make_kgid(current_user_ns(), result.uint_32);
                if (!gid_valid(gid))
                        return invalf(fc, "Unknown gid");
                hypfs_info->gid = gid;
                break;
        }
        return 0;
}

static int hypfs_show_options(struct seq_file *s, struct dentry *root)
{
        struct hypfs_sb_info *hypfs_info = root->d_sb->s_fs_info;

        seq_printf(s, ",uid=%u", from_kuid_munged(&init_user_ns, hypfs_info->uid));
        seq_printf(s, ",gid=%u", from_kgid_munged(&init_user_ns, hypfs_info->gid));
        return 0;
}

static int hypfs_fill_super(struct super_block *sb, struct fs_context *fc)
{
        struct hypfs_sb_info *sbi = sb->s_fs_info;
        struct inode *root_inode;
        struct dentry *root_dentry, *update_file;
        int rc;

        sb->s_blocksize = PAGE_SIZE;
        sb->s_blocksize_bits = PAGE_SHIFT;
        sb->s_magic = HYPFS_MAGIC;
        sb->s_op = &hypfs_s_ops;

        root_inode = hypfs_make_inode(sb, S_IFDIR | 0755);
        if (!root_inode)
                return -ENOMEM;
        root_inode->i_op = &simple_dir_inode_operations;
        root_inode->i_fop = &simple_dir_operations;
        sb->s_root = root_dentry = d_make_root(root_inode);
        if (!root_dentry)
                return -ENOMEM;
        if (machine_is_vm())
                rc = hypfs_vm_create_files(root_dentry);
        else
                rc = hypfs_diag_create_files(root_dentry);
        if (rc)
                return rc;
        update_file = hypfs_create_update_file(root_dentry);
        if (IS_ERR(update_file))
                return PTR_ERR(update_file);
        sbi->update_file = update_file;
        hypfs_update_update(sb);
        pr_info("Hypervisor filesystem mounted\n");
        return 0;
}

static int hypfs_get_tree(struct fs_context *fc)
{
        return get_tree_single(fc, hypfs_fill_super);
}

static void hypfs_free_fc(struct fs_context *fc)
{
        kfree(fc->s_fs_info);
}

static const struct fs_context_operations hypfs_context_ops = {
        .free           = hypfs_free_fc,
        .parse_param    = hypfs_parse_param,
        .get_tree       = hypfs_get_tree,
};

static int hypfs_init_fs_context(struct fs_context *fc)
{
        struct hypfs_sb_info *sbi;

        sbi = kzalloc_obj(struct hypfs_sb_info);
        if (!sbi)
                return -ENOMEM;

        mutex_init(&sbi->lock);
        sbi->uid = current_uid();
        sbi->gid = current_gid();

        fc->s_fs_info = sbi;
        fc->ops = &hypfs_context_ops;
        return 0;
}

static void hypfs_kill_super(struct super_block *sb)
{
        struct hypfs_sb_info *sb_info = sb->s_fs_info;

        hypfs_last_dentry = NULL;
        kill_anon_super(sb);
        kfree(sb_info);
}

static struct dentry *hypfs_create_file(struct dentry *parent, const char *name,
                                        char *data, umode_t mode)
{
        struct dentry *dentry;
        struct inode *inode;

        dentry = simple_start_creating(parent, name);
        if (IS_ERR(dentry))
                return ERR_PTR(-ENOMEM);
        inode = hypfs_make_inode(parent->d_sb, mode);
        if (!inode) {
                simple_done_creating(dentry);
                return ERR_PTR(-ENOMEM);
        }
        if (S_ISREG(mode)) {
                inode->i_fop = &hypfs_file_ops;
                if (data)
                        inode->i_size = strlen(data);
                else
                        inode->i_size = 0;
        } else if (S_ISDIR(mode)) {
                inode->i_op = &simple_dir_inode_operations;
                inode->i_fop = &simple_dir_operations;
                inc_nlink(d_inode(parent));
        } else
                BUG();
        inode->i_private = data;
        d_make_persistent(dentry, inode);
        simple_done_creating(dentry);
        return dentry;   // borrowed
}

struct dentry *hypfs_mkdir(struct dentry *parent, const char *name)
{
        struct dentry *dentry;

        dentry = hypfs_create_file(parent, name, NULL, S_IFDIR | DIR_MODE);
        if (IS_ERR(dentry))
                return dentry;
        hypfs_add_dentry(dentry);
        return dentry;
}

static struct dentry *hypfs_create_update_file(struct dentry *dir)
{
        struct dentry *dentry;

        dentry = hypfs_create_file(dir, "update", NULL,
                                   S_IFREG | UPDATE_FILE_MODE);
        /*
         * We do not put the update file on the 'delete' list with
         * hypfs_add_dentry(), since it should not be removed when the tree
         * is updated.
         */
        return dentry;
}

int hypfs_create_u64(struct dentry *dir, const char *name, __u64 value)
{
        char *buffer;
        char tmp[TMP_SIZE];
        struct dentry *dentry;

        snprintf(tmp, TMP_SIZE, "%llu\n", (unsigned long long int)value);
        buffer = kstrdup(tmp, GFP_KERNEL);
        if (!buffer)
                return -ENOMEM;
        dentry =
            hypfs_create_file(dir, name, buffer, S_IFREG | REG_FILE_MODE);
        if (IS_ERR(dentry)) {
                kfree(buffer);
                return -ENOMEM;
        }
        hypfs_add_dentry(dentry);
        return 0;
}

int hypfs_create_str(struct dentry *dir, const char *name, char *string)
{
        char *buffer;
        struct dentry *dentry;

        buffer = kmalloc(strlen(string) + 2, GFP_KERNEL);
        if (!buffer)
                return -ENOMEM;
        sprintf(buffer, "%s\n", string);
        dentry =
            hypfs_create_file(dir, name, buffer, S_IFREG | REG_FILE_MODE);
        if (IS_ERR(dentry)) {
                kfree(buffer);
                return -ENOMEM;
        }
        hypfs_add_dentry(dentry);
        return 0;
}

static const struct file_operations hypfs_file_ops = {
        .open           = hypfs_open,
        .release        = hypfs_release,
        .read_iter      = hypfs_read_iter,
        .write_iter     = hypfs_write_iter,
};

static struct file_system_type hypfs_type = {
        .owner          = THIS_MODULE,
        .name           = "s390_hypfs",
        .init_fs_context = hypfs_init_fs_context,
        .parameters     = hypfs_fs_parameters,
        .kill_sb        = hypfs_kill_super
};

static const struct super_operations hypfs_s_ops = {
        .statfs         = simple_statfs,
        .evict_inode    = hypfs_evict_inode,
        .show_options   = hypfs_show_options,
};

int __init __hypfs_fs_init(void)
{
        int rc;

        rc = sysfs_create_mount_point(hypervisor_kobj, "s390");
        if (rc)
                return rc;
        rc = register_filesystem(&hypfs_type);
        if (rc)
                goto fail;
        return 0;
fail:
        sysfs_remove_mount_point(hypervisor_kobj, "s390");
        return rc;
}