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
efibc_str_to_str16(const char * str,efi_char16_t * str16)14 static 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
efibc_set_variable(const char * name,const char * value)24 static 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
efibc_reboot_notifier_call(struct notifier_block * notifier,unsigned long event,void * data)61 static 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
79 static struct notifier_block efibc_reboot_notifier = {
80 .notifier_call = efibc_reboot_notifier_call,
81 };
82
efibc_init(void)83 static 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 }
96 module_init(efibc_init);
97
efibc_exit(void)98 static void __exit efibc_exit(void)
99 {
100 unregister_reboot_notifier(&efibc_reboot_notifier);
101 }
102 module_exit(efibc_exit);
103
104 MODULE_AUTHOR("Jeremy Compostella <jeremy.compostella@intel.com>");
105 MODULE_AUTHOR("Matt Gumbel <matthew.k.gumbel@intel.com");
106 MODULE_DESCRIPTION("EFI Bootloader Control");
107 MODULE_LICENSE("GPL v2");
108