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"); 114