Line data    Source code

       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           1 : 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           1 :         if (boot_params->sentinel) {
      52           0 :                 static struct boot_params scratch;
      53           0 :                 char *bp_base = (char *)boot_params;
      54           0 :                 char *save_base = (char *)&scratch;
      55           0 :                 int i;
      56             : 
      57           0 :                 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           0 :                 memset(&scratch, 0, sizeof(scratch));
      80             : 
      81           0 :                 for (i = 0; i < ARRAY_SIZE(to_save); i++) {
      82           0 :                         memcpy(save_base + to_save[i].start,
      83             :                                bp_base + to_save[i].start, to_save[i].len);
      84             :                 }
      85             : 
      86           0 :                 memcpy(boot_params, save_base, sizeof(*boot_params));
      87             :         }
      88           1 : }
      89             : 
      90             : #endif /* _ASM_X86_BOOTPARAM_UTILS_H */