kernel/arch/x86/include/asm/bootparam_utils.h

   1 #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  *
  17  * Note: efi_info is commonly left uninitialized, but that field has a
  18  * private magic, so it is better to leave it unchanged.
  19  */
  20 static void sanitize_boot_params(struct boot_params *boot_params)
  21 {
  22         /*
  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          */
  36         if (boot_params->sentinel) {
  37                 /* fields in boot_params are left uninitialized, clear them */
  38                 memset(&boot_params->ext_ramdisk_image, 0,
  39                        (char *)&boot_params->efi_info -
  40                         (char *)&boot_params->ext_ramdisk_image);
  41                 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 */