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 boot_params->acpi_rsdp_addr = 0; 40 memset(&boot_params->ext_ramdisk_image, 0, 41 (char *)&boot_params->efi_info - 42 (char *)&boot_params->ext_ramdisk_image); 43 memset(&boot_params->kbd_status, 0, 44 (char *)&boot_params->hdr - 45 (char *)&boot_params->kbd_status); 46 memset(&boot_params->_pad7[0], 0, 47 (char *)&boot_params->edd_mbr_sig_buffer[0] - 48 (char *)&boot_params->_pad7[0]); 49 memset(&boot_params->_pad8[0], 0, 50 (char *)&boot_params->eddbuf[0] - 51 (char *)&boot_params->_pad8[0]); 52 memset(&boot_params->_pad9[0], 0, sizeof(boot_params->_pad9)); 53 } 54 } 55 56 #endif /* _ASM_X86_BOOTPARAM_UTILS_H */ 57