| b.liu | e958203 | 2025-04-17 19:18:16 +0800 | [diff] [blame^] | 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 */ |