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H. Peter Anvin5dcd14e2013-01-29 01:05:24 -08001#ifndef _ASM_X86_BOOTPARAM_UTILS_H
2#define _ASM_X86_BOOTPARAM_UTILS_H
3
4#include <asm/bootparam.h>
5
6/*
7 * This file is included from multiple environments. Do not
8 * add completing #includes to make it standalone.
9 */
10
11/*
12 * Deal with bootloaders which fail to initialize unknown fields in
13 * boot_params to zero. The list fields in this list are taken from
14 * analysis of kexec-tools; if other broken bootloaders initialize a
15 * different set of fields we will need to figure out how to disambiguate.
16 *
Josh Boyer2e604c02013-03-06 20:23:30 -080017 * Note: efi_info is commonly left uninitialized, but that field has a
18 * private magic, so it is better to leave it unchanged.
H. Peter Anvin5dcd14e2013-01-29 01:05:24 -080019 */
20static void sanitize_boot_params(struct boot_params *boot_params)
21{
Peter Jones3c4aff62013-03-06 13:00:23 -050022 /*
23 * IMPORTANT NOTE TO BOOTLOADER AUTHORS: do not simply clear
24 * this field. The purpose of this field is to guarantee
25 * compliance with the x86 boot spec located in
26 * Documentation/x86/boot.txt . That spec says that the
27 * *whole* structure should be cleared, after which only the
28 * portion defined by struct setup_header (boot_params->hdr)
29 * should be copied in.
30 *
31 * If you're having an issue because the sentinel is set, you
32 * need to change the whole structure to be cleared, not this
33 * (or any other) individual field, or you will soon have
34 * problems again.
35 */
H. Peter Anvin5dcd14e2013-01-29 01:05:24 -080036 if (boot_params->sentinel) {
Peter Jones3c4aff62013-03-06 13:00:23 -050037 /* fields in boot_params are left uninitialized, clear them */
Daniel Draked55e37b2013-08-09 18:14:20 -040038 memset(&boot_params->ext_ramdisk_image, 0,
Josh Boyer2e604c02013-03-06 20:23:30 -080039 (char *)&boot_params->efi_info -
Daniel Draked55e37b2013-08-09 18:14:20 -040040 (char *)&boot_params->ext_ramdisk_image);
H. Peter Anvin5dcd14e2013-01-29 01:05:24 -080041 memset(&boot_params->kbd_status, 0,
42 (char *)&boot_params->hdr -
43 (char *)&boot_params->kbd_status);
44 memset(&boot_params->_pad7[0], 0,
45 (char *)&boot_params->edd_mbr_sig_buffer[0] -
46 (char *)&boot_params->_pad7[0]);
47 memset(&boot_params->_pad8[0], 0,
48 (char *)&boot_params->eddbuf[0] -
49 (char *)&boot_params->_pad8[0]);
50 memset(&boot_params->_pad9[0], 0, sizeof(boot_params->_pad9));
51 }
52}
53
54#endif /* _ASM_X86_BOOTPARAM_UTILS_H */