arch/x86/include/asm/bootparam_utils.h

   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 static 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                 memset(&boot_params->ext_ramdisk_image, 0,
  40                        (char *)&boot_params->efi_info -
  41                         (char *)&boot_params->ext_ramdisk_image);
  42                 memset(&boot_params->kbd_status, 0,
  43                        (char *)&boot_params->hdr -
  44                        (char *)&boot_params->kbd_status);
  45                 memset(&boot_params->_pad7[0], 0,
  46                        (char *)&boot_params->edd_mbr_sig_buffer[0] -
  47                         (char *)&boot_params->_pad7[0]);
  48                 memset(&boot_params->_pad8[0], 0,
  49                        (char *)&boot_params->eddbuf[0] -
  50                         (char *)&boot_params->_pad8[0]);
  51                 memset(&boot_params->_pad9[0], 0, sizeof(boot_params->_pad9));
  52         }
  53 }
  54
  55 #endif /* _ASM_X86_BOOTPARAM_UTILS_H */