/*
 * Copyright (C) 2012 Red Hat, Inc.
 * Copyright (C) 2012 Jeremy Kerr <jeremy.kerr@canonical.com>
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 */

#include <linux/ctype.h>
#include <linux/efi.h>
#include <linux/fs.h>
#include <linux/module.h>
#include <linux/pagemap.h>
#include <linux/ucs2_string.h>
#include <linux/slab.h>
#include <linux/magic.h>

#include "internal.h"

LIST_HEAD(efivarfs_list);

static void efivarfs_evict_inode(struct inode *inode)
{
        clear_inode(inode);
}

static const struct super_operations efivarfs_ops = {
        .statfs = simple_statfs,
        .drop_inode = generic_delete_inode,
        .evict_inode = efivarfs_evict_inode,
        .show_options = generic_show_options,
};

static struct super_block *efivarfs_sb;

/*
 * Compare two efivarfs file names.
 *
 * An efivarfs filename is composed of two parts,
 *
 *      1. A case-sensitive variable name
 *      2. A case-insensitive GUID
 *
 * So we need to perform a case-sensitive match on part 1 and a
 * case-insensitive match on part 2.
 */
static int efivarfs_d_compare(const struct dentry *parent, const struct inode *pinode,
                              const struct dentry *dentry, const struct inode *inode,
                              unsigned int len, const char *str,
                              const struct qstr *name)
{
        int guid = len - EFI_VARIABLE_GUID_LEN;

        if (name->len != len)
                return 1;

        /* Case-sensitive compare for the variable name */
        if (memcmp(str, name->name, guid))
                return 1;

        /* Case-insensitive compare for the GUID */
        return strncasecmp(name->name + guid, str + guid, EFI_VARIABLE_GUID_LEN);
}

static int efivarfs_d_hash(const struct dentry *dentry,
                           const struct inode *inode, struct qstr *qstr)
{
        unsigned long hash = init_name_hash();
        const unsigned char *s = qstr->name;
        unsigned int len = qstr->len;

        if (!efivarfs_valid_name(s, len))
                return -EINVAL;

        while (len-- > EFI_VARIABLE_GUID_LEN)
                hash = partial_name_hash(*s++, hash);

        /* GUID is case-insensitive. */
        while (len--)
                hash = partial_name_hash(tolower(*s++), hash);

        qstr->hash = end_name_hash(hash);
        return 0;
}

/*
 * Retaining negative dentries for an in-memory filesystem just wastes
 * memory and lookup time: arrange for them to be deleted immediately.
 */
static int efivarfs_delete_dentry(const struct dentry *dentry)
{
        return 1;
}

static struct dentry_operations efivarfs_d_ops = {
        .d_compare = efivarfs_d_compare,
        .d_hash = efivarfs_d_hash,
        .d_delete = efivarfs_delete_dentry,
};

static struct dentry *efivarfs_alloc_dentry(struct dentry *parent, char *name)
{
        struct dentry *d;
        struct qstr q;
        int err;

        q.name = name;
        q.len = strlen(name);

        err = efivarfs_d_hash(NULL, NULL, &q);
        if (err)
                return ERR_PTR(err);

        d = d_alloc(parent, &q);
        if (d)
                return d;

        return ERR_PTR(-ENOMEM);
}

static int efivarfs_callback(efi_char16_t *name16, efi_guid_t vendor,
                             unsigned long name_size, void *data)
{
        struct super_block *sb = (struct super_block *)data;
        struct efivar_entry *entry;
        struct inode *inode = NULL;
        struct dentry *dentry, *root = sb->s_root;
        unsigned long size = 0;
        char *name;
        int len, i;
        int err = -ENOMEM;

        entry = kmalloc(sizeof(*entry), GFP_KERNEL);
        if (!entry)
                return err;

        memcpy(entry->var.VariableName, name16, name_size);
        memcpy(&(entry->var.VendorGuid), &vendor, sizeof(efi_guid_t));

        len = ucs2_strlen(entry->var.VariableName);

        /* name, plus '-', plus GUID, plus NUL*/
        name = kmalloc(len + 1 + EFI_VARIABLE_GUID_LEN + 1, GFP_KERNEL);
        if (!name)
                goto fail;

        for (i = 0; i < len; i++)
                name[i] = entry->var.VariableName[i] & 0xFF;

        name[len] = '-';

        efi_guid_unparse(&entry->var.VendorGuid, name + len + 1);

        name[len + EFI_VARIABLE_GUID_LEN+1] = '\0';

        inode = efivarfs_get_inode(sb, root->d_inode, S_IFREG | 0644, 0);
        if (!inode)
                goto fail_name;

        dentry = efivarfs_alloc_dentry(root, name);
        if (IS_ERR(dentry)) {
                err = PTR_ERR(dentry);
                goto fail_inode;
        }

        /* copied by the above to local storage in the dentry. */
        kfree(name);

        efivar_entry_size(entry, &size);
        efivar_entry_add(entry, &efivarfs_list);

        mutex_lock(&inode->i_mutex);
        inode->i_private = entry;
        i_size_write(inode, size + sizeof(entry->var.Attributes));
        mutex_unlock(&inode->i_mutex);
        d_add(dentry, inode);

        return 0;

fail_inode:
        iput(inode);
fail_name:
        kfree(name);
fail:
        kfree(entry);
        return err;
}

static int efivarfs_destroy(struct efivar_entry *entry, void *data)
{
        efivar_entry_remove(entry);
        kfree(entry);
        return 0;
}

static int efivarfs_fill_super(struct super_block *sb, void *data, int silent)
{
        struct inode *inode = NULL;
        struct dentry *root;
        int err;

        efivarfs_sb = sb;

        sb->s_maxbytes          = MAX_LFS_FILESIZE;
        sb->s_blocksize         = PAGE_CACHE_SIZE;
        sb->s_blocksize_bits    = PAGE_CACHE_SHIFT;
        sb->s_magic             = EFIVARFS_MAGIC;
        sb->s_op                = &efivarfs_ops;
        sb->s_d_op              = &efivarfs_d_ops;
        sb->s_time_gran         = 1;

        inode = efivarfs_get_inode(sb, NULL, S_IFDIR | 0755, 0);
        if (!inode)
                return -ENOMEM;
        inode->i_op = &efivarfs_dir_inode_operations;

        root = d_make_root(inode);
        sb->s_root = root;
        if (!root)
                return -ENOMEM;

        INIT_LIST_HEAD(&efivarfs_list);

        err = efivar_init(efivarfs_callback, (void *)sb, false,
                          true, &efivarfs_list);
        if (err)
                __efivar_entry_iter(efivarfs_destroy, &efivarfs_list, NULL, NULL);

        return err;
}

static struct dentry *efivarfs_mount(struct file_system_type *fs_type,
                                    int flags, const char *dev_name, void *data)
{
        return mount_single(fs_type, flags, data, efivarfs_fill_super);
}

static void efivarfs_kill_sb(struct super_block *sb)
{
        kill_litter_super(sb);
        efivarfs_sb = NULL;

        /* Remove all entries and destroy */
        __efivar_entry_iter(efivarfs_destroy, &efivarfs_list, NULL, NULL);
}

static struct file_system_type efivarfs_type = {
        .name    = "efivarfs",
        .mount   = efivarfs_mount,
        .kill_sb = efivarfs_kill_sb,
};

static __init int efivarfs_init(void)
{
        if (!efi_enabled(EFI_RUNTIME_SERVICES))
                return 0;

        if (!efivars_kobject())
                return 0;

        return register_filesystem(&efivarfs_type);
}

MODULE_AUTHOR("Matthew Garrett, Jeremy Kerr");
MODULE_DESCRIPTION("EFI Variable Filesystem");
MODULE_LICENSE("GPL");
MODULE_ALIAS_FS("efivarfs");

module_init(efivarfs_init);