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/arch/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 | BOOT_PARAM_PRESERVE(cc_blob_address), |
78 | }; |
79 | |
80 | memset(&scratch, 0, sizeof(scratch)); |
81 | |
82 | for (i = 0; i < ARRAY_SIZE(to_save); i++) { |
83 | memcpy(save_base + to_save[i].start, |
84 | bp_base + to_save[i].start, to_save[i].len); |
85 | } |
86 | |
87 | memcpy(boot_params, save_base, sizeof(*boot_params)); |
88 | } |
89 | } |
90 | |
91 | #endif /* _ASM_X86_BOOTPARAM_UTILS_H */ |
92 | |