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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 <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);

/*
 * efivars_lock protects two things:
 * 1) efivar_list - adds, removals, reads, writes
 * 2) efi.[gs]et_variable() calls.
 * It must not be held when creating sysfs entries or calling kmalloc.
 * efi.get_next_variable() is only called from efivars_init(),
 * which is protected by the BKL, so that path is safe.
 */
static DEFINE_SPINLOCK(efivars_lock);
static LIST_HEAD(efivar_list);

/*
 * 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 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 EFI_ATTR(_name, _mode, _show, _store) \
struct subsys_attribute efi_attr_##_name = { \
      .attr = {.name = __stringify(_name), .mode = _mode}, \
      .show = _show, \
      .store = _store, \
};

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

#define VAR_SUBSYS_ATTR(_name, _mode, _show, _store) \
struct subsys_attribute var_subsys_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(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
utf8_strlen(efi_char16_t *data, unsigned long maxlength)
{
      unsigned long length = 0;

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

/*
 * 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
utf8_strsize(efi_char16_t *data, unsigned long maxlength)
{
      return utf8_strlen(data, maxlength/sizeof(efi_char16_t)) * sizeof(efi_char16_t);
}

static efi_status_t
get_var_data(struct efi_variable *var)
{
      efi_status_t status;

      spin_lock(&efivars_lock);
      var->DataSize = 1024;
      status = efi.get_variable(var->VariableName,
                        &var->VendorGuid,
                        &var->Attributes,
                        &var->DataSize,
                        var->Data);
      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(var);
      if (status != EFI_SUCCESS)
            return -EIO;

      if (var->Attributes & 0x1)
            str += sprintf(str, "EFI_VARIABLE_NON_VOLATILE\n");
      if (var->Attributes & 0x2)
            str += sprintf(str, "EFI_VARIABLE_BOOTSERVICE_ACCESS\n");
      if (var->Attributes & 0x4)
            str += sprintf(str, "EFI_VARIABLE_RUNTIME_ACCESS\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(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(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;
      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;
      }

      spin_lock(&efivars_lock);
      status = efi.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(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 atttributes...
 */
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 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 ssize_t
dummy(struct kset *kset, char *buf)
{
      return -ENODEV;
}

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


static ssize_t
efivar_create(struct kset *kset, const char *buf, size_t count)
{
      struct efi_variable *new_var = (struct efi_variable *)buf;
      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, &efivar_list, list) {
            strsize1 = utf8_strsize(search_efivar->var.VariableName, 1024);
            strsize2 = utf8_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 = efi.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(utf8_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 kset *kset, const char *buf, size_t count)
{
      struct efi_variable *del_var = (struct efi_variable *)buf;
      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, &efivar_list, list) {
            strsize1 = utf8_strsize(search_efivar->var.VariableName, 1024);
            strsize2 = utf8_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 = efi.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;
}

static VAR_SUBSYS_ATTR(new_var, 0200, dummy, efivar_create);
static VAR_SUBSYS_ATTR(del_var, 0200, dummy, efivar_delete);

static struct subsys_attribute *var_subsys_attrs[] = {
      &var_subsys_attr_new_var,
      &var_subsys_attr_del_var,
      NULL,
};

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

      if (!kset || !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 EFI_ATTR(systab, 0400, systab_read, NULL);

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

static decl_subsys(vars, &efivar_ktype, NULL);
static decl_subsys(efi, NULL, NULL);

/*
 * 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(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;
      }

      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));

      kobject_set_name(&new_efivar->kobj, "%s", short_name);
      kobj_set_kset_s(new_efivar, vars_subsys);
      i = kobject_register(&new_efivar->kobj);
      if (i) {
            kfree(short_name);
            kfree(new_efivar);
            return 1;
      }

      kfree(short_name);
      short_name = NULL;

      spin_lock(&efivars_lock);
      list_add(&new_efivar->list, &efivar_list);
      spin_unlock(&efivars_lock);

      return 0;
}
/*
 * 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)
{
      efi_status_t status = EFI_NOT_FOUND;
      efi_guid_t vendor_guid;
      efi_char16_t *variable_name;
      struct subsys_attribute *attr;
      unsigned long variable_name_size = 1024;
      int i, error = 0;

      if (!efi_enabled)
            return -ENODEV;

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

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

      /*
       * For now we'll register the efi subsys within this driver
       */

      error = firmware_register(&efi_subsys);

      if (error) {
            printk(KERN_ERR "efivars: Firmware registration failed with error %d.\n", error);
            goto out_free;
      }

      kobj_set_kset_s(&vars_subsys, efi_subsys);

      error = subsystem_register(&vars_subsys);

      if (error) {
            printk(KERN_ERR "efivars: Subsystem registration failed with error %d.\n", error);
            goto out_firmware_unregister;
      }

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

      do {
            variable_name_size = 1024;

            status = efi.get_next_variable(&variable_name_size,
                                    variable_name,
                                    &vendor_guid);
            switch (status) {
            case EFI_SUCCESS:
                  efivar_create_sysfs_entry(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);

      /*
       * Now add attributes to allow creation of new vars
       * and deletion of existing ones...
       */

      for (i = 0; (attr = var_subsys_attrs[i]) && !error; i++) {
            if (attr->show && attr->store)
                  error = subsys_create_file(&vars_subsys, attr);
      }

      /* Don't forget the systab entry */

      for (i = 0; (attr = efi_subsys_attrs[i]) && !error; i++) {
            if (attr->show)
                  error = subsys_create_file(&efi_subsys, attr);
      }

      if (error)
            printk(KERN_ERR "efivars: Sysfs attribute export failed with error %d.\n", error);
      else
            goto out_free;

      subsystem_unregister(&vars_subsys);

out_firmware_unregister:
      firmware_unregister(&efi_subsys);

out_free:
      kfree(variable_name);

      return error;
}

static void __exit
efivars_exit(void)
{
      struct efivar_entry *entry, *n;

      list_for_each_entry_safe(entry, n, &efivar_list, list) {
            spin_lock(&efivars_lock);
            list_del(&entry->list);
            spin_unlock(&efivars_lock);
            efivar_unregister(entry);
      }

      subsystem_unregister(&vars_subsys);
      firmware_unregister(&efi_subsys);
}

module_init(efivars_init);
module_exit(efivars_exit);


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