1/* SPDX-License-Identifier: GPL-2.0 */
2#ifndef _ASM_X86_BOOTPARAM_UTILS_H
3#define _ASM_X86_BOOTPARAM_UTILS_H
4
5#include <asm/bootparam.h>
6
7/*
8 * This file is included from multiple environments. Do not
9 * add completing #includes to make it standalone.
10 */
11
12/*
13 * Deal with bootloaders which fail to initialize unknown fields in
14 * boot_params to zero. The list fields in this list are taken from
15 * analysis of kexec-tools; if other broken bootloaders initialize a
16 * different set of fields we will need to figure out how to disambiguate.
17 *
18 * Note: efi_info is commonly left uninitialized, but that field has a
19 * private magic, so it is better to leave it unchanged.
20 */
21static void sanitize_boot_params(struct boot_params *boot_params)
22{
23 /*
24 * IMPORTANT NOTE TO BOOTLOADER AUTHORS: do not simply clear
25 * this field. The purpose of this field is to guarantee
26 * compliance with the x86 boot spec located in
27 * Documentation/x86/boot.txt . That spec says that the
28 * *whole* structure should be cleared, after which only the
29 * portion defined by struct setup_header (boot_params->hdr)
30 * should be copied in.
31 *
32 * If you're having an issue because the sentinel is set, you
33 * need to change the whole structure to be cleared, not this
34 * (or any other) individual field, or you will soon have
35 * problems again.
36 */
37 if (boot_params->sentinel) {
38 /* fields in boot_params are left uninitialized, clear them */
39 boot_params->acpi_rsdp_addr = 0;
40 memset(&boot_params->ext_ramdisk_image, 0,
41 (char *)&boot_params->efi_info -
42 (char *)&boot_params->ext_ramdisk_image);
43 memset(&boot_params->kbd_status, 0,
44 (char *)&boot_params->hdr -
45 (char *)&boot_params->kbd_status);
46 memset(&boot_params->_pad7[0], 0,
47 (char *)&boot_params->edd_mbr_sig_buffer[0] -
48 (char *)&boot_params->_pad7[0]);
49 memset(&boot_params->_pad8[0], 0,
50 (char *)&boot_params->eddbuf[0] -
51 (char *)&boot_params->_pad8[0]);
52 memset(&boot_params->_pad9[0], 0, sizeof(boot_params->_pad9));
53 }
54}
55
56#endif /* _ASM_X86_BOOTPARAM_UTILS_H */
57