| 1 |
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| 2 | #ifndef _ASM_X86_BOOTPARAM_UTILS_H
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| 3 | #define _ASM_X86_BOOTPARAM_UTILS_H
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| 4 |
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| 5 | #include <asm/bootparam.h>
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| 6 |
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| 7 | |
| 8 | * This file is included from multiple environments. Do not
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| 9 | * add completing #includes to make it standalone.
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| 10 |
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| 11 |
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| 12 | |
| 13 | * Deal with bootloaders which fail to initialize unknown fields in
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| 14 | * boot_params to zero. The list fields in this list are taken from
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| 15 | * analysis of kexec-tools; if other broken bootloaders initialize a
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| 16 | * different set of fields we will need to figure out how to disambiguate.
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| 17 | *
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| 18 | * Note: efi_info is commonly left uninitialized, but that field has a
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| 19 | * private magic, so it is better to leave it unchanged.
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| 20 |
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| 21 |
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| 22 | #define sizeof_mbr(type, member) ({ sizeof(((type *)0)->member); })
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| 23 |
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| 24 | #define BOOT_PARAM_PRESERVE(struct_member) \
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| 25 | { \
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| 26 | .start = offsetof(struct boot_params, struct_member), \
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| 27 | .len = sizeof_mbr(struct boot_params, struct_member), \
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| 28 | }
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| 29 |
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| 30 | struct boot_params_to_save {
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| 31 | unsigned int start;
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| 32 | unsigned int len;
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| 33 | };
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| 34 |
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| 35 | static void sanitize_boot_params(struct boot_params *boot_params)
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| 36 | {
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| 37 | |
| 38 | * IMPORTANT NOTE TO BOOTLOADER AUTHORS: do not simply clear
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| 39 | * this field. The purpose of this field is to guarantee
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| 40 | * compliance with the x86 boot spec located in
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| 41 | * Documentation/arch/x86/boot.rst . That spec says that the
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| 42 | * *whole* structure should be cleared, after which only the
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| 43 | * portion defined by struct setup_header (boot_params->hdr)
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| 44 | * should be copied in.
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| 45 | *
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| 46 | * If you're having an issue because the sentinel is set, you
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| 47 | * need to change the whole structure to be cleared, not this
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| 48 | * (or any other) individual field, or you will soon have
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| 49 | * problems again.
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| 50 |
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| 51 | if (boot_params->sentinel) {
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| 52 | static struct boot_params scratch;
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| 53 | char *bp_base = (char *)boot_params;
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| 54 | char *save_base = (char *)&scratch;
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| 55 | int i;
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| 56 |
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| 57 | const struct boot_params_to_save to_save[] = {
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| 58 | BOOT_PARAM_PRESERVE(screen_info),
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| 59 | BOOT_PARAM_PRESERVE(apm_bios_info),
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| 60 | BOOT_PARAM_PRESERVE(tboot_addr),
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| 61 | BOOT_PARAM_PRESERVE(ist_info),
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| 62 | BOOT_PARAM_PRESERVE(hd0_info),
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| 63 | BOOT_PARAM_PRESERVE(hd1_info),
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| 64 | BOOT_PARAM_PRESERVE(sys_desc_table),
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| 65 | BOOT_PARAM_PRESERVE(olpc_ofw_header),
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| 66 | BOOT_PARAM_PRESERVE(efi_info),
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| 67 | BOOT_PARAM_PRESERVE(alt_mem_k),
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| 68 | BOOT_PARAM_PRESERVE(scratch),
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| 69 | BOOT_PARAM_PRESERVE(e820_entries),
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| 70 | BOOT_PARAM_PRESERVE(eddbuf_entries),
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| 71 | BOOT_PARAM_PRESERVE(edd_mbr_sig_buf_entries),
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| 72 | BOOT_PARAM_PRESERVE(edd_mbr_sig_buffer),
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| 73 | BOOT_PARAM_PRESERVE(secure_boot),
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| 74 | BOOT_PARAM_PRESERVE(hdr),
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| 75 | BOOT_PARAM_PRESERVE(e820_table),
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| 76 | BOOT_PARAM_PRESERVE(eddbuf),
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| 77 | BOOT_PARAM_PRESERVE(cc_blob_address),
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| 78 | };
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| 79 |
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| 80 | memset(&scratch, 0, sizeof(scratch));
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| 81 |
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| 82 | for (i = 0; i < ARRAY_SIZE(to_save); i++) {
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| 83 | memcpy(save_base + to_save[i].start,
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| 84 | bp_base + to_save[i].start, to_save[i].len);
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| 85 | }
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| 86 |
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| 87 | memcpy(boot_params, save_base, sizeof(*boot_params));
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| 88 | }
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| 89 | }
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| 90 |
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| 91 | #endif
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