efivars: Add module parameter to disable use as a pstore backend

[deliverable/linux.git] / drivers / firmware / efivars.c

/*
 * EFI Variables - efivars.c
 *
 * Copyright (C) 2001,2003,2004 Dell <Matt_Domsch@dell.com>
 * Copyright (C) 2004 Intel Corporation <matthew.e.tolentino@intel.com>
 *
 * This code takes all variables accessible from EFI runtime and
 *  exports them via sysfs
 *
 *  This program is free software; you can redistribute it and/or modify
 *  it under the terms of the GNU General Public License as published by
 *  the Free Software Foundation; either version 2 of the License, or
 *  (at your option) any later version.
 *
 *  This program is distributed in the hope that it will be useful,
 *  but WITHOUT ANY WARRANTY; without even the implied warranty of
 *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *  GNU General Public License for more details.
 *
 *  You should have received a copy of the GNU General Public License
 *  along with this program; if not, write to the Free Software
 *  Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 *
 * Changelog:
 *
 *  17 May 2004 - Matt Domsch <Matt_Domsch@dell.com>
 *   remove check for efi_enabled in exit
 *   add MODULE_VERSION
 *
 *  26 Apr 2004 - Matt Domsch <Matt_Domsch@dell.com>
 *   minor bug fixes
 *
 *  21 Apr 2004 - Matt Tolentino <matthew.e.tolentino@intel.com)
 *   converted driver to export variable information via sysfs
 *   and moved to drivers/firmware directory
 *   bumped revision number to v0.07 to reflect conversion & move
 *
 *  10 Dec 2002 - Matt Domsch <Matt_Domsch@dell.com>
 *   fix locking per Peter Chubb's findings
 *
 *  25 Mar 2002 - Matt Domsch <Matt_Domsch@dell.com>
 *   move uuid_unparse() to include/asm-ia64/efi.h:efi_guid_unparse()
 *
 *  12 Feb 2002 - Matt Domsch <Matt_Domsch@dell.com>
 *   use list_for_each_safe when deleting vars.
 *   remove ifdef CONFIG_SMP around include <linux/smp.h>
 *   v0.04 release to linux-ia64@linuxia64.org
 *
 *  20 April 2001 - Matt Domsch <Matt_Domsch@dell.com>
 *   Moved vars from /proc/efi to /proc/efi/vars, and made
 *   efi.c own the /proc/efi directory.
 *   v0.03 release to linux-ia64@linuxia64.org
 *
 *  26 March 2001 - Matt Domsch <Matt_Domsch@dell.com>
 *   At the request of Stephane, moved ownership of /proc/efi
 *   to efi.c, and now efivars lives under /proc/efi/vars.
 *
 *  12 March 2001 - Matt Domsch <Matt_Domsch@dell.com>
 *   Feedback received from Stephane Eranian incorporated.
 *   efivar_write() checks copy_from_user() return value.
 *   efivar_read/write() returns proper errno.
 *   v0.02 release to linux-ia64@linuxia64.org
 *
 *  26 February 2001 - Matt Domsch <Matt_Domsch@dell.com>
 *   v0.01 release to linux-ia64@linuxia64.org
 */

#include <linux/capability.h>
#include <linux/types.h>
#include <linux/errno.h>
#include <linux/init.h>
#include <linux/mm.h>
#include <linux/module.h>
#include <linux/string.h>
#include <linux/smp.h>
#include <linux/efi.h>
#include <linux/sysfs.h>
#include <linux/kobject.h>
#include <linux/device.h>
#include <linux/slab.h>
#include <linux/pstore.h>
#include <linux/ctype.h>

#include <linux/fs.h>
#include <linux/ramfs.h>
#include <linux/pagemap.h>

#include <asm/uaccess.h>

#define EFIVARS_VERSION "0.08"
#define EFIVARS_DATE "2004-May-17"

MODULE_AUTHOR("Matt Domsch <Matt_Domsch@Dell.com>");
MODULE_DESCRIPTION("sysfs interface to EFI Variables");
MODULE_LICENSE("GPL");
MODULE_VERSION(EFIVARS_VERSION);

#define DUMP_NAME_LEN 52

/*
 * Length of a GUID string (strlen("aaaaaaaa-bbbb-cccc-dddd-eeeeeeeeeeee"))
 * not including trailing NUL
 */
#define GUID_LEN 36

static bool efivars_pstore_disable =
        IS_ENABLED(EFI_VARS_PSTORE_DEFAULT_DISABLE);

module_param_named(pstore_disable, efivars_pstore_disable, bool, 0644);

/*
 * The maximum size of VariableName + Data = 1024
 * Therefore, it's reasonable to save that much
 * space in each part of the structure,
 * and we use a page for reading/writing.
 */

struct efi_variable {
        efi_char16_t  VariableName[1024/sizeof(efi_char16_t)];
        efi_guid_t    VendorGuid;
        unsigned long DataSize;
        __u8          Data[1024];
        efi_status_t  Status;
        __u32         Attributes;
} __attribute__((packed));

struct efivar_entry {
        struct efivars *efivars;
        struct efi_variable var;
        struct list_head list;
        struct kobject kobj;
};

struct efivar_attribute {
        struct attribute attr;
        ssize_t (*show) (struct efivar_entry *entry, char *buf);
        ssize_t (*store)(struct efivar_entry *entry, const char *buf, size_t count);
};

static struct efivars __efivars;
static struct efivar_operations ops;

#define PSTORE_EFI_ATTRIBUTES \
        (EFI_VARIABLE_NON_VOLATILE | \
         EFI_VARIABLE_BOOTSERVICE_ACCESS | \
         EFI_VARIABLE_RUNTIME_ACCESS)

#define EFIVAR_ATTR(_name, _mode, _show, _store) \
struct efivar_attribute efivar_attr_##_name = { \
        .attr = {.name = __stringify(_name), .mode = _mode}, \
        .show = _show, \
        .store = _store, \
};

#define to_efivar_attr(_attr) container_of(_attr, struct efivar_attribute, attr)
#define to_efivar_entry(obj)  container_of(obj, struct efivar_entry, kobj)

/*
 * Prototype for sysfs creation function
 */
static int
efivar_create_sysfs_entry(struct efivars *efivars,
                          unsigned long variable_name_size,
                          efi_char16_t *variable_name,
                          efi_guid_t *vendor_guid);

/*
 * Prototype for workqueue functions updating sysfs entry
 */

static void efivar_update_sysfs_entries(struct work_struct *);
static DECLARE_WORK(efivar_work, efivar_update_sysfs_entries);

/* Return the number of unicode characters in data */
static unsigned long
utf16_strnlen(efi_char16_t *s, size_t maxlength)
{
        unsigned long length = 0;

        while (*s++ != 0 && length < maxlength)
                length++;
        return length;
}

static inline unsigned long
utf16_strlen(efi_char16_t *s)
{
        return utf16_strnlen(s, ~0UL);
}

/*
 * Return the number of bytes is the length of this string
 * Note: this is NOT the same as the number of unicode characters
 */
static inline unsigned long
utf16_strsize(efi_char16_t *data, unsigned long maxlength)
{
        return utf16_strnlen(data, maxlength/sizeof(efi_char16_t)) * sizeof(efi_char16_t);
}

static inline int
utf16_strncmp(const efi_char16_t *a, const efi_char16_t *b, size_t len)
{
        while (1) {
                if (len == 0)
                        return 0;
                if (*a < *b)
                        return -1;
                if (*a > *b)
                        return 1;
                if (*a == 0) /* implies *b == 0 */
                        return 0;
                a++;
                b++;
                len--;
        }
}

static bool
validate_device_path(struct efi_variable *var, int match, u8 *buffer,
                     unsigned long len)
{
        struct efi_generic_dev_path *node;
        int offset = 0;

        node = (struct efi_generic_dev_path *)buffer;

        if (len < sizeof(*node))
                return false;

        while (offset <= len - sizeof(*node) &&
               node->length >= sizeof(*node) &&
                node->length <= len - offset) {
                offset += node->length;

                if ((node->type == EFI_DEV_END_PATH ||
                     node->type == EFI_DEV_END_PATH2) &&
                    node->sub_type == EFI_DEV_END_ENTIRE)
                        return true;

                node = (struct efi_generic_dev_path *)(buffer + offset);
        }

        /*
         * If we're here then either node->length pointed past the end
         * of the buffer or we reached the end of the buffer without
         * finding a device path end node.
         */
        return false;
}

static bool
validate_boot_order(struct efi_variable *var, int match, u8 *buffer,
                    unsigned long len)
{
        /* An array of 16-bit integers */
        if ((len % 2) != 0)
                return false;

        return true;
}

static bool
validate_load_option(struct efi_variable *var, int match, u8 *buffer,
                     unsigned long len)
{
        u16 filepathlength;
        int i, desclength = 0, namelen;

        namelen = utf16_strnlen(var->VariableName, sizeof(var->VariableName));

        /* Either "Boot" or "Driver" followed by four digits of hex */
        for (i = match; i < match+4; i++) {
                if (var->VariableName[i] > 127 ||
                    hex_to_bin(var->VariableName[i] & 0xff) < 0)
                        return true;
        }

        /* Reject it if there's 4 digits of hex and then further content */
        if (namelen > match + 4)
                return false;

        /* A valid entry must be at least 8 bytes */
        if (len < 8)
                return false;

        filepathlength = buffer[4] | buffer[5] << 8;

        /*
         * There's no stored length for the description, so it has to be
         * found by hand
         */
        desclength = utf16_strsize((efi_char16_t *)(buffer + 6), len - 6) + 2;

        /* Each boot entry must have a descriptor */
        if (!desclength)
                return false;

        /*
         * If the sum of the length of the description, the claimed filepath
         * length and the original header are greater than the length of the
         * variable, it's malformed
         */
        if ((desclength + filepathlength + 6) > len)
                return false;

        /*
         * And, finally, check the filepath
         */
        return validate_device_path(var, match, buffer + desclength + 6,
                                    filepathlength);
}

static bool
validate_uint16(struct efi_variable *var, int match, u8 *buffer,
                unsigned long len)
{
        /* A single 16-bit integer */
        if (len != 2)
                return false;

        return true;
}

static bool
validate_ascii_string(struct efi_variable *var, int match, u8 *buffer,
                      unsigned long len)
{
        int i;

        for (i = 0; i < len; i++) {
                if (buffer[i] > 127)
                        return false;

                if (buffer[i] == 0)
                        return true;
        }

        return false;
}

struct variable_validate {
        char *name;
        bool (*validate)(struct efi_variable *var, int match, u8 *data,
                         unsigned long len);
};

static const struct variable_validate variable_validate[] = {
        { "BootNext", validate_uint16 },
        { "BootOrder", validate_boot_order },
        { "DriverOrder", validate_boot_order },
        { "Boot*", validate_load_option },
        { "Driver*", validate_load_option },
        { "ConIn", validate_device_path },
        { "ConInDev", validate_device_path },
        { "ConOut", validate_device_path },
        { "ConOutDev", validate_device_path },
        { "ErrOut", validate_device_path },
        { "ErrOutDev", validate_device_path },
        { "Timeout", validate_uint16 },
        { "Lang", validate_ascii_string },
        { "PlatformLang", validate_ascii_string },
        { "", NULL },
};

static bool
validate_var(struct efi_variable *var, u8 *data, unsigned long len)
{
        int i;
        u16 *unicode_name = var->VariableName;

        for (i = 0; variable_validate[i].validate != NULL; i++) {
                const char *name = variable_validate[i].name;
                int match;

                for (match = 0; ; match++) {
                        char c = name[match];
                        u16 u = unicode_name[match];

                        /* All special variables are plain ascii */
                        if (u > 127)
                                return true;

                        /* Wildcard in the matching name means we've matched */
                        if (c == '*')
                                return variable_validate[i].validate(var,
                                                             match, data, len);

                        /* Case sensitive match */
                        if (c != u)
                                break;

                        /* Reached the end of the string while matching */
                        if (!c)
                                return variable_validate[i].validate(var,
                                                             match, data, len);
                }
        }

        return true;
}

static efi_status_t
get_var_data_locked(struct efivars *efivars, struct efi_variable *var)
{
        efi_status_t status;

        var->DataSize = 1024;
        status = efivars->ops->get_variable(var->VariableName,
                                            &var->VendorGuid,
                                            &var->Attributes,
                                            &var->DataSize,
                                            var->Data);
        return status;
}

static efi_status_t
get_var_data(struct efivars *efivars, struct efi_variable *var)
{
        efi_status_t status;
        unsigned long flags;

        spin_lock_irqsave(&efivars->lock, flags);
        status = get_var_data_locked(efivars, var);
        spin_unlock_irqrestore(&efivars->lock, flags);

        if (status != EFI_SUCCESS) {
                printk(KERN_WARNING "efivars: get_variable() failed 0x%lx!\n",
                        status);
        }
        return status;
}

static efi_status_t
check_var_size_locked(struct efivars *efivars, u32 attributes,
                        unsigned long size)
{
        u64 storage_size, remaining_size, max_size;
        efi_status_t status;
        const struct efivar_operations *fops = efivars->ops;

        if (!efivars->ops->query_variable_info)
                return EFI_UNSUPPORTED;

        status = fops->query_variable_info(attributes, &storage_size,
                                           &remaining_size, &max_size);

        if (status != EFI_SUCCESS)
                return status;

        if (!storage_size || size > remaining_size || size > max_size ||
            (remaining_size - size) < (storage_size / 2))
                return EFI_OUT_OF_RESOURCES;

        return status;
}


static efi_status_t
check_var_size(struct efivars *efivars, u32 attributes, unsigned long size)
{
        efi_status_t status;
        unsigned long flags;

        spin_lock_irqsave(&efivars->lock, flags);
        status = check_var_size_locked(efivars, attributes, size);
        spin_unlock_irqrestore(&efivars->lock, flags);

        return status;
}

static ssize_t
efivar_guid_read(struct efivar_entry *entry, char *buf)
{
        struct efi_variable *var = &entry->var;
        char *str = buf;

        if (!entry || !buf)
                return 0;

        efi_guid_unparse(&var->VendorGuid, str);
        str += strlen(str);
        str += sprintf(str, "\n");

        return str - buf;
}

static ssize_t
efivar_attr_read(struct efivar_entry *entry, char *buf)
{
        struct efi_variable *var = &entry->var;
        char *str = buf;
        efi_status_t status;

        if (!entry || !buf)
                return -EINVAL;

        status = get_var_data(entry->efivars, var);
        if (status != EFI_SUCCESS)
                return -EIO;

        if (var->Attributes & EFI_VARIABLE_NON_VOLATILE)
                str += sprintf(str, "EFI_VARIABLE_NON_VOLATILE\n");
        if (var->Attributes & EFI_VARIABLE_BOOTSERVICE_ACCESS)
                str += sprintf(str, "EFI_VARIABLE_BOOTSERVICE_ACCESS\n");
        if (var->Attributes & EFI_VARIABLE_RUNTIME_ACCESS)
                str += sprintf(str, "EFI_VARIABLE_RUNTIME_ACCESS\n");
        if (var->Attributes & EFI_VARIABLE_HARDWARE_ERROR_RECORD)
                str += sprintf(str, "EFI_VARIABLE_HARDWARE_ERROR_RECORD\n");
        if (var->Attributes & EFI_VARIABLE_AUTHENTICATED_WRITE_ACCESS)
                str += sprintf(str,
                        "EFI_VARIABLE_AUTHENTICATED_WRITE_ACCESS\n");
        if (var->Attributes &
                        EFI_VARIABLE_TIME_BASED_AUTHENTICATED_WRITE_ACCESS)
                str += sprintf(str,
                        "EFI_VARIABLE_TIME_BASED_AUTHENTICATED_WRITE_ACCESS\n");
        if (var->Attributes & EFI_VARIABLE_APPEND_WRITE)
                str += sprintf(str, "EFI_VARIABLE_APPEND_WRITE\n");
        return str - buf;
}

static ssize_t
efivar_size_read(struct efivar_entry *entry, char *buf)
{
        struct efi_variable *var = &entry->var;
        char *str = buf;
        efi_status_t status;

        if (!entry || !buf)
                return -EINVAL;

        status = get_var_data(entry->efivars, var);
        if (status != EFI_SUCCESS)
                return -EIO;

        str += sprintf(str, "0x%lx\n", var->DataSize);
        return str - buf;
}

static ssize_t
efivar_data_read(struct efivar_entry *entry, char *buf)
{
        struct efi_variable *var = &entry->var;
        efi_status_t status;

        if (!entry || !buf)
                return -EINVAL;

        status = get_var_data(entry->efivars, var);
        if (status != EFI_SUCCESS)
                return -EIO;

        memcpy(buf, var->Data, var->DataSize);
        return var->DataSize;
}
/*
 * We allow each variable to be edited via rewriting the
 * entire efi variable structure.
 */
static ssize_t
efivar_store_raw(struct efivar_entry *entry, const char *buf, size_t count)
{
        struct efi_variable *new_var, *var = &entry->var;
        struct efivars *efivars = entry->efivars;
        efi_status_t status = EFI_NOT_FOUND;

        if (count != sizeof(struct efi_variable))
                return -EINVAL;

        new_var = (struct efi_variable *)buf;
        /*
         * If only updating the variable data, then the name
         * and guid should remain the same
         */
        if (memcmp(new_var->VariableName, var->VariableName, sizeof(var->VariableName)) ||
                efi_guidcmp(new_var->VendorGuid, var->VendorGuid)) {
                printk(KERN_ERR "efivars: Cannot edit the wrong variable!\n");
                return -EINVAL;
        }

        if ((new_var->DataSize <= 0) || (new_var->Attributes == 0)){
                printk(KERN_ERR "efivars: DataSize & Attributes must be valid!\n");
                return -EINVAL;
        }

        if ((new_var->Attributes & ~EFI_VARIABLE_MASK) != 0 ||
            validate_var(new_var, new_var->Data, new_var->DataSize) == false) {
                printk(KERN_ERR "efivars: Malformed variable content\n");
                return -EINVAL;
        }

        spin_lock_irq(&efivars->lock);

        status = check_var_size_locked(efivars, new_var->Attributes,
               new_var->DataSize + utf16_strsize(new_var->VariableName, 1024));

        if (status == EFI_SUCCESS || status == EFI_UNSUPPORTED)
                status = efivars->ops->set_variable(new_var->VariableName,
                                                    &new_var->VendorGuid,
                                                    new_var->Attributes,
                                                    new_var->DataSize,
                                                    new_var->Data);

        spin_unlock_irq(&efivars->lock);

        if (status != EFI_SUCCESS) {
                printk(KERN_WARNING "efivars: set_variable() failed: status=%lx\n",
                        status);
                return -EIO;
        }

        memcpy(&entry->var, new_var, count);
        return count;
}

static ssize_t
efivar_show_raw(struct efivar_entry *entry, char *buf)
{
        struct efi_variable *var = &entry->var;
        efi_status_t status;

        if (!entry || !buf)
                return 0;

        status = get_var_data(entry->efivars, var);
        if (status != EFI_SUCCESS)
                return -EIO;

        memcpy(buf, var, sizeof(*var));
        return sizeof(*var);
}

/*
 * Generic read/write functions that call the specific functions of
 * the attributes...
 */
static ssize_t efivar_attr_show(struct kobject *kobj, struct attribute *attr,
                                char *buf)
{
        struct efivar_entry *var = to_efivar_entry(kobj);
        struct efivar_attribute *efivar_attr = to_efivar_attr(attr);
        ssize_t ret = -EIO;

        if (!capable(CAP_SYS_ADMIN))
                return -EACCES;

        if (efivar_attr->show) {
                ret = efivar_attr->show(var, buf);
        }
        return ret;
}

static ssize_t efivar_attr_store(struct kobject *kobj, struct attribute *attr,
                                const char *buf, size_t count)
{
        struct efivar_entry *var = to_efivar_entry(kobj);
        struct efivar_attribute *efivar_attr = to_efivar_attr(attr);
        ssize_t ret = -EIO;

        if (!capable(CAP_SYS_ADMIN))
                return -EACCES;

        if (efivar_attr->store)
                ret = efivar_attr->store(var, buf, count);

        return ret;
}

static const struct sysfs_ops efivar_attr_ops = {
        .show = efivar_attr_show,
        .store = efivar_attr_store,
};

static void efivar_release(struct kobject *kobj)
{
        struct efivar_entry *var = container_of(kobj, struct efivar_entry, kobj);
        kfree(var);
}

static EFIVAR_ATTR(guid, 0400, efivar_guid_read, NULL);
static EFIVAR_ATTR(attributes, 0400, efivar_attr_read, NULL);
static EFIVAR_ATTR(size, 0400, efivar_size_read, NULL);
static EFIVAR_ATTR(data, 0400, efivar_data_read, NULL);
static EFIVAR_ATTR(raw_var, 0600, efivar_show_raw, efivar_store_raw);

static struct attribute *def_attrs[] = {
        &efivar_attr_guid.attr,
        &efivar_attr_size.attr,
        &efivar_attr_attributes.attr,
        &efivar_attr_data.attr,
        &efivar_attr_raw_var.attr,
        NULL,
};

static struct kobj_type efivar_ktype = {
        .release = efivar_release,
        .sysfs_ops = &efivar_attr_ops,
        .default_attrs = def_attrs,
};

static inline void
efivar_unregister(struct efivar_entry *var)
{
        kobject_put(&var->kobj);
}

static int efivarfs_file_open(struct inode *inode, struct file *file)
{
        file->private_data = inode->i_private;
        return 0;
}

static int efi_status_to_err(efi_status_t status)
{
        int err;

        switch (status) {
        case EFI_INVALID_PARAMETER:
                err = -EINVAL;
                break;
        case EFI_OUT_OF_RESOURCES:
                err = -ENOSPC;
                break;
        case EFI_DEVICE_ERROR:
                err = -EIO;
                break;
        case EFI_WRITE_PROTECTED:
                err = -EROFS;
                break;
        case EFI_SECURITY_VIOLATION:
                err = -EACCES;
                break;
        case EFI_NOT_FOUND:
                err = -EIO;
                break;
        default:
                err = -EINVAL;
        }

        return err;
}

static ssize_t efivarfs_file_write(struct file *file,
                const char __user *userbuf, size_t count, loff_t *ppos)
{
        struct efivar_entry *var = file->private_data;
        struct efivars *efivars;
        efi_status_t status;
        void *data;
        u32 attributes;
        struct inode *inode = file->f_mapping->host;
        unsigned long datasize = count - sizeof(attributes);
        unsigned long newdatasize, varsize;
        ssize_t bytes = 0;

        if (count < sizeof(attributes))
                return -EINVAL;

        if (copy_from_user(&attributes, userbuf, sizeof(attributes)))
                return -EFAULT;

        if (attributes & ~(EFI_VARIABLE_MASK))
                return -EINVAL;

        efivars = var->efivars;

        /*
         * Ensure that the user can't allocate arbitrarily large
         * amounts of memory. Pick a default size of 64K if
         * QueryVariableInfo() isn't supported by the firmware.
         */

        varsize = datasize + utf16_strsize(var->var.VariableName, 1024);
        status = check_var_size(efivars, attributes, varsize);

        if (status != EFI_SUCCESS) {
                if (status != EFI_UNSUPPORTED)
                        return efi_status_to_err(status);

                if (datasize > 65536)
                        return -ENOSPC;
        }

        data = kmalloc(datasize, GFP_KERNEL);
        if (!data)
                return -ENOMEM;

        if (copy_from_user(data, userbuf + sizeof(attributes), datasize)) {
                bytes = -EFAULT;
                goto out;
        }

        if (validate_var(&var->var, data, datasize) == false) {
                bytes = -EINVAL;
                goto out;
        }

        /*
         * The lock here protects the get_variable call, the conditional
         * set_variable call, and removal of the variable from the efivars
         * list (in the case of an authenticated delete).
         */
        spin_lock_irq(&efivars->lock);

        /*
         * Ensure that the available space hasn't shrunk below the safe level
         */

        status = check_var_size_locked(efivars, attributes, varsize);

        if (status != EFI_SUCCESS && status != EFI_UNSUPPORTED) {
                spin_unlock_irq(&efivars->lock);
                kfree(data);

                return efi_status_to_err(status);
        }

        status = efivars->ops->set_variable(var->var.VariableName,
                                            &var->var.VendorGuid,
                                            attributes, datasize,
                                            data);

        if (status != EFI_SUCCESS) {
                spin_unlock_irq(&efivars->lock);
                kfree(data);

                return efi_status_to_err(status);
        }

        bytes = count;

        /*
         * Writing to the variable may have caused a change in size (which
         * could either be an append or an overwrite), or the variable to be
         * deleted. Perform a GetVariable() so we can tell what actually
         * happened.
         */
        newdatasize = 0;
        status = efivars->ops->get_variable(var->var.VariableName,
                                            &var->var.VendorGuid,
                                            NULL, &newdatasize,
                                            NULL);

        if (status == EFI_BUFFER_TOO_SMALL) {
                spin_unlock_irq(&efivars->lock);
                mutex_lock(&inode->i_mutex);
                i_size_write(inode, newdatasize + sizeof(attributes));
                mutex_unlock(&inode->i_mutex);

        } else if (status == EFI_NOT_FOUND) {
                list_del(&var->list);
                spin_unlock_irq(&efivars->lock);
                efivar_unregister(var);
                drop_nlink(inode);
                d_delete(file->f_dentry);
                dput(file->f_dentry);

        } else {
                spin_unlock_irq(&efivars->lock);
                pr_warn("efivarfs: inconsistent EFI variable implementation? "
                                "status = %lx\n", status);
        }

out:
        kfree(data);

        return bytes;
}

static ssize_t efivarfs_file_read(struct file *file, char __user *userbuf,
                size_t count, loff_t *ppos)
{
        struct efivar_entry *var = file->private_data;
        struct efivars *efivars = var->efivars;
        efi_status_t status;
        unsigned long datasize = 0;
        u32 attributes;
        void *data;
        ssize_t size = 0;

        spin_lock_irq(&efivars->lock);
        status = efivars->ops->get_variable(var->var.VariableName,
                                            &var->var.VendorGuid,
                                            &attributes, &datasize, NULL);
        spin_unlock_irq(&efivars->lock);

        if (status != EFI_BUFFER_TOO_SMALL)
                return efi_status_to_err(status);

        data = kmalloc(datasize + sizeof(attributes), GFP_KERNEL);

        if (!data)
                return -ENOMEM;

        spin_lock_irq(&efivars->lock);
        status = efivars->ops->get_variable(var->var.VariableName,
                                            &var->var.VendorGuid,
                                            &attributes, &datasize,
                                            (data + sizeof(attributes)));
        spin_unlock_irq(&efivars->lock);

        if (status != EFI_SUCCESS) {
                size = efi_status_to_err(status);
                goto out_free;
        }

        memcpy(data, &attributes, sizeof(attributes));
        size = simple_read_from_buffer(userbuf, count, ppos,
                                       data, datasize + sizeof(attributes));
out_free:
        kfree(data);

        return size;
}

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;

static const struct inode_operations efivarfs_dir_inode_operations;

static const struct file_operations efivarfs_file_operations = {
        .open   = efivarfs_file_open,
        .read   = efivarfs_file_read,
        .write  = efivarfs_file_write,
        .llseek = no_llseek,
};

static struct inode *efivarfs_get_inode(struct super_block *sb,
                                const struct inode *dir, int mode, dev_t dev)
{
        struct inode *inode = new_inode(sb);

        if (inode) {
                inode->i_ino = get_next_ino();
                inode->i_mode = mode;
                inode->i_atime = inode->i_mtime = inode->i_ctime = CURRENT_TIME;
                switch (mode & S_IFMT) {
                case S_IFREG:
                        inode->i_fop = &efivarfs_file_operations;
                        break;
                case S_IFDIR:
                        inode->i_op = &efivarfs_dir_inode_operations;
                        inode->i_fop = &simple_dir_operations;
                        inc_nlink(inode);
                        break;
                }
        }
        return inode;
}

/*
 * Return true if 'str' is a valid efivarfs filename of the form,
 *
 *      VariableName-12345678-1234-1234-1234-1234567891bc
 */
static bool efivarfs_valid_name(const char *str, int len)
{
        static const char dashes[GUID_LEN] = {
                [8] = 1, [13] = 1, [18] = 1, [23] = 1
        };
        const char *s = str + len - GUID_LEN;
        int i;

        /*
         * We need a GUID, plus at least one letter for the variable name,
         * plus the '-' separator
         */
        if (len < GUID_LEN + 2)
                return false;

        /* GUID must be preceded by a '-' */
        if (*(s - 1) != '-')
                return false;

        /*
         * Validate that 's' is of the correct format, e.g.
         *
         *      12345678-1234-1234-1234-123456789abc
         */
        for (i = 0; i < GUID_LEN; i++) {
                if (dashes[i]) {
                        if (*s++ != '-')
                                return false;
                } else {
                        if (!isxdigit(*s++))
                                return false;
                }
        }

        return true;
}

static void efivarfs_hex_to_guid(const char *str, efi_guid_t *guid)
{
        guid->b[0] = hex_to_bin(str[6]) << 4 | hex_to_bin(str[7]);
        guid->b[1] = hex_to_bin(str[4]) << 4 | hex_to_bin(str[5]);
        guid->b[2] = hex_to_bin(str[2]) << 4 | hex_to_bin(str[3]);
        guid->b[3] = hex_to_bin(str[0]) << 4 | hex_to_bin(str[1]);
        guid->b[4] = hex_to_bin(str[11]) << 4 | hex_to_bin(str[12]);
        guid->b[5] = hex_to_bin(str[9]) << 4 | hex_to_bin(str[10]);
        guid->b[6] = hex_to_bin(str[16]) << 4 | hex_to_bin(str[17]);
        guid->b[7] = hex_to_bin(str[14]) << 4 | hex_to_bin(str[15]);
        guid->b[8] = hex_to_bin(str[19]) << 4 | hex_to_bin(str[20]);
        guid->b[9] = hex_to_bin(str[21]) << 4 | hex_to_bin(str[22]);
        guid->b[10] = hex_to_bin(str[24]) << 4 | hex_to_bin(str[25]);
        guid->b[11] = hex_to_bin(str[26]) << 4 | hex_to_bin(str[27]);
        guid->b[12] = hex_to_bin(str[28]) << 4 | hex_to_bin(str[29]);
        guid->b[13] = hex_to_bin(str[30]) << 4 | hex_to_bin(str[31]);
        guid->b[14] = hex_to_bin(str[32]) << 4 | hex_to_bin(str[33]);
        guid->b[15] = hex_to_bin(str[34]) << 4 | hex_to_bin(str[35]);
}

static int efivarfs_create(struct inode *dir, struct dentry *dentry,
                          umode_t mode, bool excl)
{
        struct inode *inode;
        struct efivars *efivars = &__efivars;
        struct efivar_entry *var;
        int namelen, i = 0, err = 0;

        if (!efivarfs_valid_name(dentry->d_name.name, dentry->d_name.len))
                return -EINVAL;

        inode = efivarfs_get_inode(dir->i_sb, dir, mode, 0);
        if (!inode)
                return -ENOMEM;

        var = kzalloc(sizeof(struct efivar_entry), GFP_KERNEL);
        if (!var) {
                err = -ENOMEM;
                goto out;
        }

        /* length of the variable name itself: remove GUID and separator */
        namelen = dentry->d_name.len - GUID_LEN - 1;

        efivarfs_hex_to_guid(dentry->d_name.name + namelen + 1,
                        &var->var.VendorGuid);

        for (i = 0; i < namelen; i++)
                var->var.VariableName[i] = dentry->d_name.name[i];

        var->var.VariableName[i] = '\0';

        inode->i_private = var;
        var->efivars = efivars;
        var->kobj.kset = efivars->kset;

        err = kobject_init_and_add(&var->kobj, &efivar_ktype, NULL, "%s",
                             dentry->d_name.name);
        if (err)
                goto out;

        kobject_uevent(&var->kobj, KOBJ_ADD);
        spin_lock_irq(&efivars->lock);
        list_add(&var->list, &efivars->list);
        spin_unlock_irq(&efivars->lock);
        d_instantiate(dentry, inode);
        dget(dentry);
out:
        if (err) {
                kfree(var);
                iput(inode);
        }
        return err;
}

static int efivarfs_unlink(struct inode *dir, struct dentry *dentry)
{
        struct efivar_entry *var = dentry->d_inode->i_private;
        struct efivars *efivars = var->efivars;
        efi_status_t status;

        spin_lock_irq(&efivars->lock);

        status = efivars->ops->set_variable(var->var.VariableName,
                                            &var->var.VendorGuid,
                                            0, 0, NULL);

        if (status == EFI_SUCCESS || status == EFI_NOT_FOUND) {
                list_del(&var->list);
                spin_unlock_irq(&efivars->lock);
                efivar_unregister(var);
                drop_nlink(dentry->d_inode);
                dput(dentry);
                return 0;
        }

        spin_unlock_irq(&efivars->lock);
        return -EINVAL;
};

/*
 * 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 - 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, 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-- > 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_fill_super(struct super_block *sb, void *data, int silent)
{
        struct inode *inode = NULL;
        struct dentry *root;
        struct efivar_entry *entry, *n;
        struct efivars *efivars = &__efivars;
        char *name;
        int err = -ENOMEM;

        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;

        list_for_each_entry_safe(entry, n, &efivars->list, list) {
                struct dentry *dentry, *root = efivarfs_sb->s_root;
                unsigned long size = 0;
                int len, i;

                inode = NULL;

                len = utf16_strlen(entry->var.VariableName);

                /* name, plus '-', plus GUID, plus NUL*/
                name = kmalloc(len + 1 + GUID_LEN + 1, GFP_ATOMIC);
                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+GUID_LEN+1] = '\0';

                inode = efivarfs_get_inode(efivarfs_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);

                spin_lock_irq(&efivars->lock);
                efivars->ops->get_variable(entry->var.VariableName,
                                           &entry->var.VendorGuid,
                                           &entry->var.Attributes,
                                           &size,
                                           NULL);
                spin_unlock_irq(&efivars->lock);

                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:
        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;
}

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

/*
 * Handle negative dentry.
 */
static struct dentry *efivarfs_lookup(struct inode *dir, struct dentry *dentry,
                                      unsigned int flags)
{
        if (dentry->d_name.len > NAME_MAX)
                return ERR_PTR(-ENAMETOOLONG);
        d_add(dentry, NULL);
        return NULL;
}

static const struct inode_operations efivarfs_dir_inode_operations = {
        .lookup = efivarfs_lookup,
        .unlink = efivarfs_unlink,
        .create = efivarfs_create,
};

#ifdef CONFIG_EFI_VARS_PSTORE

static int efi_pstore_open(struct pstore_info *psi)
{
        struct efivars *efivars = psi->data;

        spin_lock_irq(&efivars->lock);
        efivars->walk_entry = list_first_entry(&efivars->list,
                                               struct efivar_entry, list);
        return 0;
}

static int efi_pstore_close(struct pstore_info *psi)
{
        struct efivars *efivars = psi->data;

        spin_unlock_irq(&efivars->lock);
        return 0;
}

static ssize_t efi_pstore_read(u64 *id, enum pstore_type_id *type,
                               int *count, struct timespec *timespec,
                               char **buf, struct pstore_info *psi)
{
        efi_guid_t vendor = LINUX_EFI_CRASH_GUID;
        struct efivars *efivars = psi->data;
        char name[DUMP_NAME_LEN];
        int i;
        int cnt;
        unsigned int part, size;
        unsigned long time;

        while (&efivars->walk_entry->list != &efivars->list) {
                if (!efi_guidcmp(efivars->walk_entry->var.VendorGuid,
                                 vendor)) {
                        for (i = 0; i < DUMP_NAME_LEN; i++) {
                                name[i] = efivars->walk_entry->var.VariableName[i];
                        }
                        if (sscanf(name, "dump-type%u-%u-%d-%lu",
                                   type, &part, &cnt, &time) == 4) {
                                *id = part;
                                *count = cnt;
                                timespec->tv_sec = time;
                                timespec->tv_nsec = 0;
                        } else if (sscanf(name, "dump-type%u-%u-%lu",
                                   type, &part, &time) == 3) {
                                /*
                                 * Check if an old format,
                                 * which doesn't support holding
                                 * multiple logs, remains.
                                 */
                                *id = part;
                                *count = 0;
                                timespec->tv_sec = time;
                                timespec->tv_nsec = 0;
                        } else {
                                efivars->walk_entry = list_entry(
                                                efivars->walk_entry->list.next,
                                                struct efivar_entry, list);
                                continue;
                        }

                        get_var_data_locked(efivars, &efivars->walk_entry->var);
                        size = efivars->walk_entry->var.DataSize;
                        *buf = kmalloc(size, GFP_KERNEL);
                        if (*buf == NULL)
                                return -ENOMEM;
                        memcpy(*buf, efivars->walk_entry->var.Data,
                               size);
                        efivars->walk_entry = list_entry(
                                        efivars->walk_entry->list.next,
                                        struct efivar_entry, list);
                        return size;
                }
                efivars->walk_entry = list_entry(efivars->walk_entry->list.next,
                                                 struct efivar_entry, list);
        }
        return 0;
}

static int efi_pstore_write(enum pstore_type_id type,
                enum kmsg_dump_reason reason, u64 *id,
                unsigned int part, int count, size_t size,
                struct pstore_info *psi)
{
        char name[DUMP_NAME_LEN];
        efi_char16_t efi_name[DUMP_NAME_LEN];
        efi_guid_t vendor = LINUX_EFI_CRASH_GUID;
        struct efivars *efivars = psi->data;
        int i, ret = 0;
        efi_status_t status = EFI_NOT_FOUND;
        unsigned long flags;

        if (pstore_cannot_block_path(reason)) {
                /*
                 * If the lock is taken by another cpu in non-blocking path,
                 * this driver returns without entering firmware to avoid
                 * hanging up.
                 */
                if (!spin_trylock_irqsave(&efivars->lock, flags))
                        return -EBUSY;
        } else
                spin_lock_irqsave(&efivars->lock, flags);

        /*
         * Check if there is a space enough to log.
         * size: a size of logging data
         * DUMP_NAME_LEN * 2: a maximum size of variable name
         */

        status = check_var_size_locked(efivars, PSTORE_EFI_ATTRIBUTES,
                                         size + DUMP_NAME_LEN * 2);

        if (status) {
                spin_unlock_irqrestore(&efivars->lock, flags);
                *id = part;
                return -ENOSPC;
        }

        sprintf(name, "dump-type%u-%u-%d-%lu", type, part, count,
                get_seconds());

        for (i = 0; i < DUMP_NAME_LEN; i++)
                efi_name[i] = name[i];

        efivars->ops->set_variable(efi_name, &vendor, PSTORE_EFI_ATTRIBUTES,
                                   size, psi->buf);

        spin_unlock_irqrestore(&efivars->lock, flags);

        if (reason == KMSG_DUMP_OOPS)
                schedule_work(&efivar_work);

        *id = part;
        return ret;
};

static int efi_pstore_erase(enum pstore_type_id type, u64 id, int count,
                            struct timespec time, struct pstore_info *psi)
{
        char name[DUMP_NAME_LEN];
        efi_char16_t efi_name[DUMP_NAME_LEN];
        char name_old[DUMP_NAME_LEN];
        efi_char16_t efi_name_old[DUMP_NAME_LEN];
        efi_guid_t vendor = LINUX_EFI_CRASH_GUID;
        struct efivars *efivars = psi->data;
        struct efivar_entry *entry, *found = NULL;
        int i;

        sprintf(name, "dump-type%u-%u-%d-%lu", type, (unsigned int)id, count,
                time.tv_sec);

        spin_lock_irq(&efivars->lock);

        for (i = 0; i < DUMP_NAME_LEN; i++)
                efi_name[i] = name[i];

        /*
         * Clean up an entry with the same name
         */

        list_for_each_entry(entry, &efivars->list, list) {
                get_var_data_locked(efivars, &entry->var);

                if (efi_guidcmp(entry->var.VendorGuid, vendor))
                        continue;
                if (utf16_strncmp(entry->var.VariableName, efi_name,
                                  utf16_strlen(efi_name))) {
                        /*
                         * Check if an old format,
                         * which doesn't support holding
                         * multiple logs, remains.
                         */
                        sprintf(name_old, "dump-type%u-%u-%lu", type,
                                (unsigned int)id, time.tv_sec);

                        for (i = 0; i < DUMP_NAME_LEN; i++)
                                efi_name_old[i] = name_old[i];

                        if (utf16_strncmp(entry->var.VariableName, efi_name_old,
                                          utf16_strlen(efi_name_old)))
                                continue;
                }

                /* found */
                found = entry;
                efivars->ops->set_variable(entry->var.VariableName,
                                           &entry->var.VendorGuid,
                                           PSTORE_EFI_ATTRIBUTES,
                                           0, NULL);
                break;
        }

        if (found)
                list_del(&found->list);

        spin_unlock_irq(&efivars->lock);

        if (found)
                efivar_unregister(found);

        return 0;
}

static struct pstore_info efi_pstore_info = {
        .owner          = THIS_MODULE,
        .name           = "efi",
        .open           = efi_pstore_open,
        .close          = efi_pstore_close,
        .read           = efi_pstore_read,
        .write          = efi_pstore_write,
        .erase          = efi_pstore_erase,
};

static void efivar_pstore_register(struct efivars *efivars)
{
        efivars->efi_pstore_info = efi_pstore_info;
        efivars->efi_pstore_info.buf = kmalloc(4096, GFP_KERNEL);
        if (efivars->efi_pstore_info.buf) {
                efivars->efi_pstore_info.bufsize = 1024;
                efivars->efi_pstore_info.data = efivars;
                spin_lock_init(&efivars->efi_pstore_info.buf_lock);
                pstore_register(&efivars->efi_pstore_info);
        }
}
#else
static void efivar_pstore_register(struct efivars *efivars)
{
        return;
}
#endif

static ssize_t efivar_create(struct file *filp, struct kobject *kobj,
                             struct bin_attribute *bin_attr,
                             char *buf, loff_t pos, size_t count)
{
        struct efi_variable *new_var = (struct efi_variable *)buf;
        struct efivars *efivars = bin_attr->private;
        struct efivar_entry *search_efivar, *n;
        unsigned long strsize1, strsize2;
        efi_status_t status = EFI_NOT_FOUND;
        int found = 0;

        if (!capable(CAP_SYS_ADMIN))
                return -EACCES;

        if ((new_var->Attributes & ~EFI_VARIABLE_MASK) != 0 ||
            validate_var(new_var, new_var->Data, new_var->DataSize) == false) {
                printk(KERN_ERR "efivars: Malformed variable content\n");
                return -EINVAL;
        }

        spin_lock_irq(&efivars->lock);

        /*
         * Does this variable already exist?
         */
        list_for_each_entry_safe(search_efivar, n, &efivars->list, list) {
                strsize1 = utf16_strsize(search_efivar->var.VariableName, 1024);
                strsize2 = utf16_strsize(new_var->VariableName, 1024);
                if (strsize1 == strsize2 &&
                        !memcmp(&(search_efivar->var.VariableName),
                                new_var->VariableName, strsize1) &&
                        !efi_guidcmp(search_efivar->var.VendorGuid,
                                new_var->VendorGuid)) {
                        found = 1;
                        break;
                }
        }
        if (found) {
                spin_unlock_irq(&efivars->lock);
                return -EINVAL;
        }

        status = check_var_size_locked(efivars, new_var->Attributes,
               new_var->DataSize + utf16_strsize(new_var->VariableName, 1024));

        if (status && status != EFI_UNSUPPORTED) {
                spin_unlock_irq(&efivars->lock);
                return efi_status_to_err(status);
        }

        /* now *really* create the variable via EFI */
        status = efivars->ops->set_variable(new_var->VariableName,
                                            &new_var->VendorGuid,
                                            new_var->Attributes,
                                            new_var->DataSize,
                                            new_var->Data);

        if (status != EFI_SUCCESS) {
                printk(KERN_WARNING "efivars: set_variable() failed: status=%lx\n",
                        status);
                spin_unlock_irq(&efivars->lock);
                return -EIO;
        }
        spin_unlock_irq(&efivars->lock);

        /* Create the entry in sysfs.  Locking is not required here */
        status = efivar_create_sysfs_entry(efivars,
                                           utf16_strsize(new_var->VariableName,
                                                         1024),
                                           new_var->VariableName,
                                           &new_var->VendorGuid);
        if (status) {
                printk(KERN_WARNING "efivars: variable created, but sysfs entry wasn't.\n");
        }
        return count;
}

static ssize_t efivar_delete(struct file *filp, struct kobject *kobj,
                             struct bin_attribute *bin_attr,
                             char *buf, loff_t pos, size_t count)
{
        struct efi_variable *del_var = (struct efi_variable *)buf;
        struct efivars *efivars = bin_attr->private;
        struct efivar_entry *search_efivar, *n;
        unsigned long strsize1, strsize2;
        efi_status_t status = EFI_NOT_FOUND;
        int found = 0;

        if (!capable(CAP_SYS_ADMIN))
                return -EACCES;

        spin_lock_irq(&efivars->lock);

        /*
         * Does this variable already exist?
         */
        list_for_each_entry_safe(search_efivar, n, &efivars->list, list) {
                strsize1 = utf16_strsize(search_efivar->var.VariableName, 1024);
                strsize2 = utf16_strsize(del_var->VariableName, 1024);
                if (strsize1 == strsize2 &&
                        !memcmp(&(search_efivar->var.VariableName),
                                del_var->VariableName, strsize1) &&
                        !efi_guidcmp(search_efivar->var.VendorGuid,
                                del_var->VendorGuid)) {
                        found = 1;
                        break;
                }
        }
        if (!found) {
                spin_unlock_irq(&efivars->lock);
                return -EINVAL;
        }
        /* force the Attributes/DataSize to 0 to ensure deletion */
        del_var->Attributes = 0;
        del_var->DataSize = 0;

        status = efivars->ops->set_variable(del_var->VariableName,
                                            &del_var->VendorGuid,
                                            del_var->Attributes,
                                            del_var->DataSize,
                                            del_var->Data);

        if (status != EFI_SUCCESS) {
                printk(KERN_WARNING "efivars: set_variable() failed: status=%lx\n",
                        status);
                spin_unlock_irq(&efivars->lock);
                return -EIO;
        }
        list_del(&search_efivar->list);
        /* We need to release this lock before unregistering. */
        spin_unlock_irq(&efivars->lock);
        efivar_unregister(search_efivar);

        /* It's dead Jim.... */
        return count;
}

static bool variable_is_present(efi_char16_t *variable_name, efi_guid_t *vendor)
{
        struct efivar_entry *entry, *n;
        struct efivars *efivars = &__efivars;
        unsigned long strsize1, strsize2;
        bool found = false;

        strsize1 = utf16_strsize(variable_name, 1024);
        list_for_each_entry_safe(entry, n, &efivars->list, list) {
                strsize2 = utf16_strsize(entry->var.VariableName, 1024);
                if (strsize1 == strsize2 &&
                        !memcmp(variable_name, &(entry->var.VariableName),
                                strsize2) &&
                        !efi_guidcmp(entry->var.VendorGuid,
                                *vendor)) {
                        found = true;
                        break;
                }
        }
        return found;
}

static void efivar_update_sysfs_entries(struct work_struct *work)
{
        struct efivars *efivars = &__efivars;
        efi_guid_t vendor;
        efi_char16_t *variable_name;
        unsigned long variable_name_size = 1024;
        efi_status_t status = EFI_NOT_FOUND;
        bool found;

        /* Add new sysfs entries */
        while (1) {
                variable_name = kzalloc(variable_name_size, GFP_KERNEL);
                if (!variable_name) {
                        pr_err("efivars: Memory allocation failed.\n");
                        return;
                }

                spin_lock_irq(&efivars->lock);
                found = false;
                while (1) {
                        variable_name_size = 1024;
                        status = efivars->ops->get_next_variable(
                                                        &variable_name_size,
                                                        variable_name,
                                                        &vendor);
                        if (status != EFI_SUCCESS) {
                                break;
                        } else {
                                if (!variable_is_present(variable_name,
                                    &vendor)) {
                                        found = true;
                                        break;
                                }
                        }
                }
                spin_unlock_irq(&efivars->lock);

                if (!found) {
                        kfree(variable_name);
                        break;
                } else
                        efivar_create_sysfs_entry(efivars,
                                                  variable_name_size,
                                                  variable_name, &vendor);
        }
}

/*
 * Let's not leave out systab information that snuck into
 * the efivars driver
 */
static ssize_t systab_show(struct kobject *kobj,
                           struct kobj_attribute *attr, char *buf)
{
        char *str = buf;

        if (!kobj || !buf)
                return -EINVAL;

        if (efi.mps != EFI_INVALID_TABLE_ADDR)
                str += sprintf(str, "MPS=0x%lx\n", efi.mps);
        if (efi.acpi20 != EFI_INVALID_TABLE_ADDR)
                str += sprintf(str, "ACPI20=0x%lx\n", efi.acpi20);
        if (efi.acpi != EFI_INVALID_TABLE_ADDR)
                str += sprintf(str, "ACPI=0x%lx\n", efi.acpi);
        if (efi.smbios != EFI_INVALID_TABLE_ADDR)
                str += sprintf(str, "SMBIOS=0x%lx\n", efi.smbios);
        if (efi.hcdp != EFI_INVALID_TABLE_ADDR)
                str += sprintf(str, "HCDP=0x%lx\n", efi.hcdp);
        if (efi.boot_info != EFI_INVALID_TABLE_ADDR)
                str += sprintf(str, "BOOTINFO=0x%lx\n", efi.boot_info);
        if (efi.uga != EFI_INVALID_TABLE_ADDR)
                str += sprintf(str, "UGA=0x%lx\n", efi.uga);

        return str - buf;
}

static struct kobj_attribute efi_attr_systab =
                        __ATTR(systab, 0400, systab_show, NULL);

static struct attribute *efi_subsys_attrs[] = {
        &efi_attr_systab.attr,
        NULL,   /* maybe more in the future? */
};

static struct attribute_group efi_subsys_attr_group = {
        .attrs = efi_subsys_attrs,
};

static struct kobject *efi_kobj;

/*
 * efivar_create_sysfs_entry()
 * Requires:
 *    variable_name_size = number of bytes required to hold
 *                         variable_name (not counting the NULL
 *                         character at the end.
 *    efivars->lock is not held on entry or exit.
 * Returns 1 on failure, 0 on success
 */
static int
efivar_create_sysfs_entry(struct efivars *efivars,
                          unsigned long variable_name_size,
                          efi_char16_t *variable_name,
                          efi_guid_t *vendor_guid)
{
        int i, short_name_size;
        char *short_name;
        struct efivar_entry *new_efivar;

        /*
         * Length of the variable bytes in ASCII, plus the '-' separator,
         * plus the GUID, plus trailing NUL
         */
        short_name_size = variable_name_size / sizeof(efi_char16_t)
                                + 1 + GUID_LEN + 1;

        short_name = kzalloc(short_name_size, GFP_KERNEL);
        new_efivar = kzalloc(sizeof(struct efivar_entry), GFP_KERNEL);

        if (!short_name || !new_efivar)  {
                kfree(short_name);
                kfree(new_efivar);
                return 1;
        }

        new_efivar->efivars = efivars;
        memcpy(new_efivar->var.VariableName, variable_name,
                variable_name_size);
        memcpy(&(new_efivar->var.VendorGuid), vendor_guid, sizeof(efi_guid_t));

        /* Convert Unicode to normal chars (assume top bits are 0),
           ala UTF-8 */
        for (i=0; i < (int)(variable_name_size / sizeof(efi_char16_t)); i++) {
                short_name[i] = variable_name[i] & 0xFF;
        }
        /* This is ugly, but necessary to separate one vendor's
           private variables from another's.         */

        *(short_name + strlen(short_name)) = '-';
        efi_guid_unparse(vendor_guid, short_name + strlen(short_name));

        new_efivar->kobj.kset = efivars->kset;
        i = kobject_init_and_add(&new_efivar->kobj, &efivar_ktype, NULL,
                                 "%s", short_name);
        if (i) {
                kfree(short_name);
                kfree(new_efivar);
                return 1;
        }

        kobject_uevent(&new_efivar->kobj, KOBJ_ADD);
        kfree(short_name);
        short_name = NULL;

        spin_lock_irq(&efivars->lock);
        list_add(&new_efivar->list, &efivars->list);
        spin_unlock_irq(&efivars->lock);

        return 0;
}

static int
create_efivars_bin_attributes(struct efivars *efivars)
{
        struct bin_attribute *attr;
        int error;

        /* new_var */
        attr = kzalloc(sizeof(*attr), GFP_KERNEL);
        if (!attr)
                return -ENOMEM;

        attr->attr.name = "new_var";
        attr->attr.mode = 0200;
        attr->write = efivar_create;
        attr->private = efivars;
        efivars->new_var = attr;

        /* del_var */
        attr = kzalloc(sizeof(*attr), GFP_KERNEL);
        if (!attr) {
                error = -ENOMEM;
                goto out_free;
        }
        attr->attr.name = "del_var";
        attr->attr.mode = 0200;
        attr->write = efivar_delete;
        attr->private = efivars;
        efivars->del_var = attr;

        sysfs_bin_attr_init(efivars->new_var);
        sysfs_bin_attr_init(efivars->del_var);

        /* Register */
        error = sysfs_create_bin_file(&efivars->kset->kobj,
                                      efivars->new_var);
        if (error) {
                printk(KERN_ERR "efivars: unable to create new_var sysfs file"
                        " due to error %d\n", error);
                goto out_free;
        }
        error = sysfs_create_bin_file(&efivars->kset->kobj,
                                      efivars->del_var);
        if (error) {
                printk(KERN_ERR "efivars: unable to create del_var sysfs file"
                        " due to error %d\n", error);
                sysfs_remove_bin_file(&efivars->kset->kobj,
                                      efivars->new_var);
                goto out_free;
        }

        return 0;
out_free:
        kfree(efivars->del_var);
        efivars->del_var = NULL;
        kfree(efivars->new_var);
        efivars->new_var = NULL;
        return error;
}

void unregister_efivars(struct efivars *efivars)
{
        struct efivar_entry *entry, *n;

        list_for_each_entry_safe(entry, n, &efivars->list, list) {
                spin_lock_irq(&efivars->lock);
                list_del(&entry->list);
                spin_unlock_irq(&efivars->lock);
                efivar_unregister(entry);
        }
        if (efivars->new_var)
                sysfs_remove_bin_file(&efivars->kset->kobj, efivars->new_var);
        if (efivars->del_var)
                sysfs_remove_bin_file(&efivars->kset->kobj, efivars->del_var);
        kfree(efivars->new_var);
        kfree(efivars->del_var);
        kobject_put(efivars->kobject);
        kset_unregister(efivars->kset);
}
EXPORT_SYMBOL_GPL(unregister_efivars);

int register_efivars(struct efivars *efivars,
                     const struct efivar_operations *ops,
                     struct kobject *parent_kobj)
{
        efi_status_t status = EFI_NOT_FOUND;
        efi_guid_t vendor_guid;
        efi_char16_t *variable_name;
        unsigned long variable_name_size = 1024;
        int error = 0;

        variable_name = kzalloc(variable_name_size, GFP_KERNEL);
        if (!variable_name) {
                printk(KERN_ERR "efivars: Memory allocation failed.\n");
                return -ENOMEM;
        }

        spin_lock_init(&efivars->lock);
        INIT_LIST_HEAD(&efivars->list);
        efivars->ops = ops;

        efivars->kset = kset_create_and_add("vars", NULL, parent_kobj);
        if (!efivars->kset) {
                printk(KERN_ERR "efivars: Subsystem registration failed.\n");
                error = -ENOMEM;
                goto out;
        }

        efivars->kobject = kobject_create_and_add("efivars", parent_kobj);
        if (!efivars->kobject) {
                pr_err("efivars: Subsystem registration failed.\n");
                error = -ENOMEM;
                kset_unregister(efivars->kset);
                goto out;
        }

        /*
         * Per EFI spec, the maximum storage allocated for both
         * the variable name and variable data is 1024 bytes.
         */

        do {
                variable_name_size = 1024;

                status = ops->get_next_variable(&variable_name_size,
                                                variable_name,
                                                &vendor_guid);
                switch (status) {
                case EFI_SUCCESS:
                        efivar_create_sysfs_entry(efivars,
                                                  variable_name_size,
                                                  variable_name,
                                                  &vendor_guid);
                        break;
                case EFI_NOT_FOUND:
                        break;
                default:
                        printk(KERN_WARNING "efivars: get_next_variable: status=%lx\n",
                                status);
                        status = EFI_NOT_FOUND;
                        break;
                }
        } while (status != EFI_NOT_FOUND);

        error = create_efivars_bin_attributes(efivars);
        if (error)
                unregister_efivars(efivars);

        if (!efivars_pstore_disable)
                efivar_pstore_register(efivars);

        register_filesystem(&efivarfs_type);

out:
        kfree(variable_name);

        return error;
}
EXPORT_SYMBOL_GPL(register_efivars);

/*
 * For now we register the efi subsystem with the firmware subsystem
 * and the vars subsystem with the efi subsystem.  In the future, it
 * might make sense to split off the efi subsystem into its own
 * driver, but for now only efivars will register with it, so just
 * include it here.
 */

static int __init
efivars_init(void)
{
        int error = 0;

        printk(KERN_INFO "EFI Variables Facility v%s %s\n", EFIVARS_VERSION,
               EFIVARS_DATE);

        if (!efi_enabled(EFI_RUNTIME_SERVICES))
                return 0;

        /* For now we'll register the efi directory at /sys/firmware/efi */
        efi_kobj = kobject_create_and_add("efi", firmware_kobj);
        if (!efi_kobj) {
                printk(KERN_ERR "efivars: Firmware registration failed.\n");
                return -ENOMEM;
        }

        ops.get_variable = efi.get_variable;
        ops.set_variable = efi.set_variable;
        ops.get_next_variable = efi.get_next_variable;
        ops.query_variable_info = efi.query_variable_info;

        error = register_efivars(&__efivars, &ops, efi_kobj);
        if (error)
                goto err_put;

        /* Don't forget the systab entry */
        error = sysfs_create_group(efi_kobj, &efi_subsys_attr_group);
        if (error) {
                printk(KERN_ERR
                       "efivars: Sysfs attribute export failed with error %d.\n",
                       error);
                goto err_unregister;
        }

        return 0;

err_unregister:
        unregister_efivars(&__efivars);
err_put:
        kobject_put(efi_kobj);
        return error;
}

static void __exit
efivars_exit(void)
{
        cancel_work_sync(&efivar_work);

        if (efi_enabled(EFI_RUNTIME_SERVICES)) {
                unregister_efivars(&__efivars);
                kobject_put(efi_kobj);
        }
}

module_init(efivars_init);
module_exit(efivars_exit);