LXR linux/drivers/firmware/efi/efibc.c

   1// SPDX-License-Identifier: GPL-2.0
   2/*
   3 * efibc: control EFI bootloaders which obey LoaderEntryOneShot var
   4 * Copyright (c) 2013-2016, Intel Corporation.
   5 */
   6
   7#define pr_fmt(fmt) "efibc: " fmt
   8
   9#include <linux/efi.h>
  10#include <linux/module.h>
  11#include <linux/reboot.h>
  12#include <linux/slab.h>
  13
  14static void efibc_str_to_str16(const char *str, efi_char16_t *str16)
  15{
  16        size_t i;
  17
  18        for (i = 0; i < strlen(str); i++)
  19                str16[i] = str[i];
  20
  21        str16[i] = '\0';
  22}
  23
  24static int efibc_set_variable(const char *name, const char *value)
  25{
  26        int ret;
  27        efi_guid_t guid = LINUX_EFI_LOADER_ENTRY_GUID;
  28        struct efivar_entry *entry;
  29        size_t size = (strlen(value) + 1) * sizeof(efi_char16_t);
  30
  31        if (size > sizeof(entry->var.Data)) {
  32                pr_err("value is too large (%zu bytes) for '%s' EFI variable\n", size, name);
  33                return -EINVAL;
  34        }
  35
  36        entry = kmalloc(sizeof(*entry), GFP_KERNEL);
  37        if (!entry) {
  38                pr_err("failed to allocate efivar entry for '%s' EFI variable\n", name);
  39                return -ENOMEM;
  40        }
  41
  42        efibc_str_to_str16(name, entry->var.VariableName);
  43        efibc_str_to_str16(value, (efi_char16_t *)entry->var.Data);
  44        memcpy(&entry->var.VendorGuid, &guid, sizeof(guid));
  45
  46        ret = efivar_entry_set_safe(entry->var.VariableName,
  47                                    entry->var.VendorGuid,
  48                                    EFI_VARIABLE_NON_VOLATILE
  49                                    | EFI_VARIABLE_BOOTSERVICE_ACCESS
  50                                    | EFI_VARIABLE_RUNTIME_ACCESS,
  51                                    false, size, entry->var.Data);
  52
  53        if (ret)
  54                pr_err("failed to set %s EFI variable: 0x%x\n",
  55                       name, ret);
  56
  57        kfree(entry);
  58        return ret;
  59}
  60
  61static int efibc_reboot_notifier_call(struct notifier_block *notifier,
  62                                      unsigned long event, void *data)
  63{
  64        const char *reason = "shutdown";
  65        int ret;
  66
  67        if (event == SYS_RESTART)
  68                reason = "reboot";
  69
  70        ret = efibc_set_variable("LoaderEntryRebootReason", reason);
  71        if (ret || !data)
  72                return NOTIFY_DONE;
  73
  74        efibc_set_variable("LoaderEntryOneShot", (char *)data);
  75
  76        return NOTIFY_DONE;
  77}
  78
  79static struct notifier_block efibc_reboot_notifier = {
  80        .notifier_call = efibc_reboot_notifier_call,
  81};
  82
  83static int __init efibc_init(void)
  84{
  85        int ret;
  86
  87        if (!efivars_kobject() || !efivar_supports_writes())
  88                return -ENODEV;
  89
  90        ret = register_reboot_notifier(&efibc_reboot_notifier);
  91        if (ret)
  92                pr_err("unable to register reboot notifier\n");
  93
  94        return ret;
  95}
  96module_init(efibc_init);
  97
  98static void __exit efibc_exit(void)
  99{
 100        unregister_reboot_notifier(&efibc_reboot_notifier);
 101}
 102module_exit(efibc_exit);
 103
 104MODULE_AUTHOR("Jeremy Compostella <jeremy.compostella@intel.com>");
 105MODULE_AUTHOR("Matt Gumbel <matthew.k.gumbel@intel.com");
 106MODULE_DESCRIPTION("EFI Bootloader Control");
 107MODULE_LICENSE("GPL v2");
 108