LXR linux/arch/x86/include/asm/bootparam

   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 */
  21
  22#define sizeof_mbr(type, member) ({ sizeof(((type *)0)->member); })
  23
  24#define BOOT_PARAM_PRESERVE(struct_member)                              \
  25        {                                                               \
  26                .start = offsetof(struct boot_params, struct_member),   \
  27                .len   = sizeof_mbr(struct boot_params, struct_member), \
  28        }
  29
  30struct boot_params_to_save {
  31        unsigned int start;
  32        unsigned int len;
  33};
  34
  35static void sanitize_boot_params(struct boot_params *boot_params)
  36{
  37        /* 
  38         * IMPORTANT NOTE TO BOOTLOADER AUTHORS: do not simply clear
  39         * this field.  The purpose of this field is to guarantee
  40         * compliance with the x86 boot spec located in
  41         * Documentation/x86/boot.rst .  That spec says that the
  42         * *whole* structure should be cleared, after which only the
  43         * portion defined by struct setup_header (boot_params->hdr)
  44         * should be copied in.
  45         *
  46         * If you're having an issue because the sentinel is set, you
  47         * need to change the whole structure to be cleared, not this
  48         * (or any other) individual field, or you will soon have
  49         * problems again.
  50         */
  51        if (boot_params->sentinel) {
  52                static struct boot_params scratch;
  53                char *bp_base = (char *)boot_params;
  54                char *save_base = (char *)&scratch;
  55                int i;
  56
  57                const struct boot_params_to_save to_save[] = {
  58                        BOOT_PARAM_PRESERVE(screen_info),
  59                        BOOT_PARAM_PRESERVE(apm_bios_info),
  60                        BOOT_PARAM_PRESERVE(tboot_addr),
  61                        BOOT_PARAM_PRESERVE(ist_info),
  62                        BOOT_PARAM_PRESERVE(hd0_info),
  63                        BOOT_PARAM_PRESERVE(hd1_info),
  64                        BOOT_PARAM_PRESERVE(sys_desc_table),
  65                        BOOT_PARAM_PRESERVE(olpc_ofw_header),
  66                        BOOT_PARAM_PRESERVE(efi_info),
  67                        BOOT_PARAM_PRESERVE(alt_mem_k),
  68                        BOOT_PARAM_PRESERVE(scratch),
  69                        BOOT_PARAM_PRESERVE(e820_entries),
  70                        BOOT_PARAM_PRESERVE(eddbuf_entries),
  71                        BOOT_PARAM_PRESERVE(edd_mbr_sig_buf_entries),
  72                        BOOT_PARAM_PRESERVE(edd_mbr_sig_buffer),
  73                        BOOT_PARAM_PRESERVE(secure_boot),
  74                        BOOT_PARAM_PRESERVE(hdr),
  75                        BOOT_PARAM_PRESERVE(e820_table),
  76                        BOOT_PARAM_PRESERVE(eddbuf),
  77                };
  78
  79                memset(&scratch, 0, sizeof(scratch));
  80
  81                for (i = 0; i < ARRAY_SIZE(to_save); i++) {
  82                        memcpy(save_base + to_save[i].start,
  83                               bp_base + to_save[i].start, to_save[i].len);
  84                }
  85
  86                memcpy(boot_params, save_base, sizeof(*boot_params));
  87        }
  88}
  89
  90#endif /* _ASM_X86_BOOTPARAM_UTILS_H */
  91