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       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                 :         21 : 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         [ -  + ]:         21 :         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                 :         21 : }
      89                 :            : 
      90                 :            : #endif /* _ASM_X86_BOOTPARAM_UTILS_H */