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/* SPDX-License-Identifier: GPL-2.0 */
#ifndef _ASM_X86_BOOTPARAM_UTILS_H
#define _ASM_X86_BOOTPARAM_UTILS_H
#include <asm/bootparam.h>
/*
* This file is included from multiple environments. Do not
* add completing #includes to make it standalone.
*/
/*
* Deal with bootloaders which fail to initialize unknown fields in
* boot_params to zero. The list fields in this list are taken from
* analysis of kexec-tools; if other broken bootloaders initialize a
* different set of fields we will need to figure out how to disambiguate.
*
* Note: efi_info is commonly left uninitialized, but that field has a
* private magic, so it is better to leave it unchanged.
*/
#define sizeof_mbr(type, member) ({ sizeof(((type *)0)->member); })
#define BOOT_PARAM_PRESERVE(struct_member) \
{ \
.start = offsetof(struct boot_params, struct_member), \
.len = sizeof_mbr(struct boot_params, struct_member), \
}
struct boot_params_to_save {
unsigned int start;
unsigned int len;
};
static void sanitize_boot_params(struct boot_params *boot_params)
{
/*
* IMPORTANT NOTE TO BOOTLOADER AUTHORS: do not simply clear
* this field. The purpose of this field is to guarantee
* compliance with the x86 boot spec located in
* Documentation/x86/boot.rst . That spec says that the
* *whole* structure should be cleared, after which only the
* portion defined by struct setup_header (boot_params->hdr)
* should be copied in.
*
* If you're having an issue because the sentinel is set, you
* need to change the whole structure to be cleared, not this
* (or any other) individual field, or you will soon have
* problems again.
*/
if (boot_params->sentinel) {
static struct boot_params scratch;
char *bp_base = (char *)boot_params;
char *save_base = (char *)&scratch;
int i;
const struct boot_params_to_save to_save[] = {
BOOT_PARAM_PRESERVE(screen_info),
BOOT_PARAM_PRESERVE(apm_bios_info),
BOOT_PARAM_PRESERVE(tboot_addr),
BOOT_PARAM_PRESERVE(ist_info),
BOOT_PARAM_PRESERVE(hd0_info),
BOOT_PARAM_PRESERVE(hd1_info),
BOOT_PARAM_PRESERVE(sys_desc_table),
BOOT_PARAM_PRESERVE(olpc_ofw_header),
BOOT_PARAM_PRESERVE(efi_info),
BOOT_PARAM_PRESERVE(alt_mem_k),
BOOT_PARAM_PRESERVE(scratch),
BOOT_PARAM_PRESERVE(e820_entries),
BOOT_PARAM_PRESERVE(eddbuf_entries),
BOOT_PARAM_PRESERVE(edd_mbr_sig_buf_entries),
BOOT_PARAM_PRESERVE(edd_mbr_sig_buffer),
BOOT_PARAM_PRESERVE(secure_boot),
BOOT_PARAM_PRESERVE(hdr),
BOOT_PARAM_PRESERVE(e820_table),
BOOT_PARAM_PRESERVE(eddbuf),
};
memset(&scratch, 0, sizeof(scratch));
for (i = 0; i < ARRAY_SIZE(to_save); i++) {
memcpy(save_base + to_save[i].start,
bp_base + to_save[i].start, to_save[i].len);
}
memcpy(boot_params, save_base, sizeof(*boot_params));
}
}
#endif /* _ASM_X86_BOOTPARAM_UTILS_H */
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