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