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 #include <linux/ucs2_string.h>
  14
  15 #define MAX_DATA_LEN    512
  16
  17 static int efibc_set_variable(efi_char16_t *name, efi_char16_t *value,
  18                               unsigned long len)
  19 {
  20         efi_status_t status;
  21
  22         status = efi.set_variable(name, &LINUX_EFI_LOADER_ENTRY_GUID,
  23                                   EFI_VARIABLE_NON_VOLATILE
  24                                   | EFI_VARIABLE_BOOTSERVICE_ACCESS
  25                                   | EFI_VARIABLE_RUNTIME_ACCESS,
  26                                   len * sizeof(efi_char16_t), value);
  27
  28         if (status != EFI_SUCCESS) {
  29                 pr_err("failed to set EFI variable: 0x%lx\n", status);
  30                 return -EIO;
  31         }
  32         return 0;
  33 }
  34
  35 static int efibc_reboot_notifier_call(struct notifier_block *notifier,
  36                                       unsigned long event, void *data)
  37 {
  38         efi_char16_t *reason = event == SYS_RESTART ? L"reboot"
  39                                                     : L"shutdown";
  40         const u8 *str = data;
  41         efi_char16_t *wdata;
  42         unsigned long l;
  43         int ret;
  44
  45         ret = efibc_set_variable(L"LoaderEntryRebootReason", reason,
  46                                  ucs2_strlen(reason));
  47         if (ret || !data)
  48                 return NOTIFY_DONE;
  49
  50         wdata = kmalloc(MAX_DATA_LEN * sizeof(efi_char16_t), GFP_KERNEL);
  51         if (!wdata)
  52                 return NOTIFY_DONE;
  53
  54         for (l = 0; l < MAX_DATA_LEN - 1 && str[l] != '\0'; l++)
  55                 wdata[l] = str[l];
  56         wdata[l] = L'\0';
  57
  58         efibc_set_variable(L"LoaderEntryOneShot", wdata, l);
  59
  60         kfree(wdata);
  61         return NOTIFY_DONE;
  62 }
  63
  64 static struct notifier_block efibc_reboot_notifier = {
  65         .notifier_call = efibc_reboot_notifier_call,
  66 };
  67
  68 static int __init efibc_init(void)
  69 {
  70         int ret;
  71
  72         if (!efi_rt_services_supported(EFI_RT_SUPPORTED_SET_VARIABLE))
  73                 return -ENODEV;
  74
  75         ret = register_reboot_notifier(&efibc_reboot_notifier);
  76         if (ret)
  77                 pr_err("unable to register reboot notifier\n");
  78
  79         return ret;
  80 }
  81 module_init(efibc_init);
  82
  83 static void __exit efibc_exit(void)
  84 {
  85         unregister_reboot_notifier(&efibc_reboot_notifier);
  86 }
  87 module_exit(efibc_exit);
  88
  89 MODULE_AUTHOR("Jeremy Compostella <jeremy.compostella@intel.com>");
  90 MODULE_AUTHOR("Matt Gumbel <matthew.k.gumbel@intel.com");
  91 MODULE_DESCRIPTION("EFI Bootloader Control");
  92 MODULE_LICENSE("GPL v2");