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 30 struct boot_params_to_save { 31 unsigned int start; 32 unsigned int len; 33 }; 34 35 static 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