cachepc-linux

Fork of AMDESE/linux with modifications for CachePC side-channel attack
git clone https://git.sinitax.com/sinitax/cachepc-linux
Log | Files | Refs | README | LICENSE | sfeed.txt

efibc.c (2589B)

      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");