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