drivers/firmware/efi/efibc.c

   1 /*
   2  * efibc: control EFI bootloaders which obey LoaderEntryOneShot var
   3  * Copyright (c) 2013-2016, Intel Corporation.
   4  *
   5  * This program is free software; you can redistribute it and/or modify it
   6  * under the terms and conditions of the GNU General Public License,
   7  * version 2, as published by the Free Software Foundation.
   8  *
   9  * This program is distributed in the hope it will be useful, but WITHOUT
  10  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  11  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
  12  * more details.
  13  */
  14
  15 #define pr_fmt(fmt) "efibc: " fmt
  16
  17 #include <linux/efi.h>
  18 #include <linux/module.h>
  19 #include <linux/reboot.h>
  20 #include <linux/slab.h>
  21
  22 static void efibc_str_to_str16(const char *str, efi_char16_t *str16)
  23 {
  24         size_t i;
  25
  26         for (i = 0; i < strlen(str); i++)
  27                 str16[i] = str[i];
  28
  29         str16[i] = '\0';
  30 }
  31
  32 static int efibc_set_variable(const char *name, const char *value)
  33 {
  34         int ret;
  35         efi_guid_t guid = LINUX_EFI_LOADER_ENTRY_GUID;
  36         struct efivar_entry *entry;
  37         size_t size = (strlen(value) + 1) * sizeof(efi_char16_t);
  38
  39         if (size > sizeof(entry->var.Data)) {
  40                 pr_err("value is too large (%zu bytes) for '%s' EFI variable\n", size, name);
  41                 return -EINVAL;
  42         }
  43
  44         entry = kmalloc(sizeof(*entry), GFP_KERNEL);
  45         if (!entry) {
  46                 pr_err("failed to allocate efivar entry for '%s' EFI variable\n", name);
  47                 return -ENOMEM;
  48         }
  49
  50         efibc_str_to_str16(name, entry->var.VariableName);
  51         efibc_str_to_str16(value, (efi_char16_t *)entry->var.Data);
  52         memcpy(&entry->var.VendorGuid, &guid, sizeof(guid));
  53
  54         ret = efivar_entry_set(entry,
  55                                EFI_VARIABLE_NON_VOLATILE
  56                                | EFI_VARIABLE_BOOTSERVICE_ACCESS
  57                                | EFI_VARIABLE_RUNTIME_ACCESS,
  58                                size, entry->var.Data, NULL);
  59         if (ret)
  60                 pr_err("failed to set %s EFI variable: 0x%x\n",
  61                        name, ret);
  62
  63         kfree(entry);
  64         return ret;
  65 }
  66
  67 static int efibc_reboot_notifier_call(struct notifier_block *notifier,
  68                                       unsigned long event, void *data)
  69 {
  70         const char *reason = "shutdown";
  71         int ret;
  72
  73         if (event == SYS_RESTART)
  74                 reason = "reboot";
  75
  76         ret = efibc_set_variable("LoaderEntryRebootReason", reason);
  77         if (ret || !data)
  78                 return NOTIFY_DONE;
  79
  80         efibc_set_variable("LoaderEntryOneShot", (char *)data);
  81
  82         return NOTIFY_DONE;
  83 }
  84
  85 static struct notifier_block efibc_reboot_notifier = {
  86         .notifier_call = efibc_reboot_notifier_call,
  87 };
  88
  89 static int __init efibc_init(void)
  90 {
  91         int ret;
  92
  93         if (!efi_enabled(EFI_RUNTIME_SERVICES))
  94                 return -ENODEV;
  95
  96         ret = register_reboot_notifier(&efibc_reboot_notifier);
  97         if (ret)
  98                 pr_err("unable to register reboot notifier\n");
  99
 100         return ret;
 101 }
 102 module_init(efibc_init);
 103
 104 static void __exit efibc_exit(void)
 105 {
 106         unregister_reboot_notifier(&efibc_reboot_notifier);
 107 }
 108 module_exit(efibc_exit);
 109
 110 MODULE_AUTHOR("Jeremy Compostella <jeremy.compostella@intel.com>");
 111 MODULE_AUTHOR("Matt Gumbel <matthew.k.gumbel@intel.com");
 112 MODULE_DESCRIPTION("EFI Bootloader Control");
 113 MODULE_LICENSE("GPL v2");