efivars.c

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/*
 * EFI Variables - efivars.c
 *
 * Copyright (C) 2001,2003,2004 Dell <[email protected]>
 * Copyright (C) 2004 Intel Corporation <[email protected]>
 *
 * 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 <[email protected]>
 *   remove check for efi_enabled in exit
 *   add MODULE_VERSION
 *
 *  26 Apr 2004 - Matt Domsch <[email protected]>
 *   minor bug fixes
 *
 *  21 Apr 2004 - Matt Tolentino <[email protected])
 *   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 <[email protected]>
 *   fix locking per Peter Chubb's findings
 *
 *  25 Mar 2002 - Matt Domsch <[email protected]>
 *   move uuid_unparse() to include/asm-ia64/efi.h:efi_guid_unparse()
 *
 *  12 Feb 2002 - Matt Domsch <[email protected]>
 *   use list_for_each_safe when deleting vars.
 *   remove ifdef CONFIG_SMP around include <linux/smp.h>
 *   v0.04 release to [email protected]
 *
 *  20 April 2001 - Matt Domsch <[email protected]>
 *   Moved vars from /proc/efi to /proc/efi/vars, and made
 *   efi.c own the /proc/efi directory.
 *   v0.03 release to [email protected]
 *
 *  26 March 2001 - Matt Domsch <[email protected]>
 *   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 <[email protected]>
 *   Feedback received from Stephane Eranian incorporated.
 *   efivar_write() checks copy_from_user() return value.
 *   efivar_read/write() returns proper errno.
 *   v0.02 release to [email protected]
 *
 *  26 February 2001 - Matt Domsch <[email protected]>
 *   v0.01 release to [email protected]
 */

#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 <asm/uaccess.h>

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

MODULE_AUTHOR("Matt Domsch <[email protected]>");
MODULE_DESCRIPTION("sysfs interface to EFI Variables");
MODULE_LICENSE("GPL");
MODULE_VERSION(EFIVARS_VERSION);

#define DUMP_NAME_LEN 52

/*
 * 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);
};

#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);

/* 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;

    spin_lock(&efivars->lock);
    status = get_var_data_locked(efivars, var);
    spin_unlock(&efivars->lock);

    if (status != EFI_SUCCESS) {
        printk(KERN_WARNING "efivars: get_variable() failed 0x%lx!\n",
            status);
    }
    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(&efivars->lock);
    status = efivars->ops->set_variable(new_var->VariableName,
                        &new_var->VendorGuid,
                        new_var->Attributes,
                        new_var->DataSize,
                        new_var->Data);

    spin_unlock(&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 struct pstore_info efi_pstore_info;

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

#ifdef CONFIG_PSTORE

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

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

static ssize_t efi_pstore_read(u64 *id, enum pstore_type_id *type,
                   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;
    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-%lu", type, &part, &time) == 3) {
                *id = part;
                timespec->tv_sec = time;
                timespec->tv_nsec = 0;
                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, size_t size, struct pstore_info *psi)
{
    char name[DUMP_NAME_LEN];
    char stub_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;
    struct efivar_entry *entry, *found = NULL;
    int i, ret = 0;

    sprintf(stub_name, "dump-type%u-%u-", type, part);
    sprintf(name, "%s%lu", stub_name, get_seconds());

    spin_lock(&efivars->lock);

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

    /*
     * Clean up any entries 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)))
            continue;
        /* Needs to be a prefix */
        if (entry->var.VariableName[utf16_strlen(efi_name)] == 0)
            continue;

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

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

    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(&efivars->lock);

    if (found)
        efivar_unregister(found);

    if (size)
        ret = efivar_create_sysfs_entry(efivars,
                      utf16_strsize(efi_name,
                            DUMP_NAME_LEN * 2),
                      efi_name, &vendor);

    *id = part;
    return ret;
};

static int efi_pstore_erase(enum pstore_type_id type, u64 id,
                struct pstore_info *psi)
{
    efi_pstore_write(type, 0, &id, (unsigned int)id, 0, psi);

    return 0;
}
#else
static int efi_pstore_open(struct pstore_info *psi)
{
    return 0;
}

static int efi_pstore_close(struct pstore_info *psi)
{
    return 0;
}

static ssize_t efi_pstore_read(u64 *id, enum pstore_type_id *type,
                   struct timespec *timespec,
                   char **buf, struct pstore_info *psi)
{
    return -1;
}

static int efi_pstore_write(enum pstore_type_id type,
        enum kmsg_dump_reason reason, u64 *id,
        unsigned int part, size_t size, struct pstore_info *psi)
{
    return 0;
}

static int efi_pstore_erase(enum pstore_type_id type, u64 id,
                struct pstore_info *psi)
{
    return 0;
}
#endif

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

    /* 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(&efivars->lock);
        return -EIO;
    }
    spin_unlock(&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(&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(&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(&efivars->lock);
        return -EIO;
    }
    list_del(&search_efivar->list);
    /* We need to release this lock before unregistering. */
    spin_unlock(&efivars->lock);
    efivar_unregister(search_efivar);

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

/*
 * 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 = variable_name_size / sizeof(efi_char16_t) + 38;
    char *short_name;
    struct efivar_entry *new_efivar;

    short_name = kzalloc(short_name_size + 1, 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(&efivars->lock);
    list_add(&new_efivar->list, &efivars->list);
    spin_unlock(&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(&efivars->lock);
        list_del(&entry->list);
        spin_unlock(&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);
    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;
    }

    /*
     * 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);

    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);
    }

out:
    kfree(variable_name);

    return error;
}
EXPORT_SYMBOL_GPL(register_efivars);

static struct efivars __efivars;
static struct efivar_operations ops;

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

module_init(efivars_init);
module_exit(efivars_exit);