src/security/vboot/vbnv_cmos.c

   1 /* SPDX-License-Identifier: GPL-2.0-only */
   2
   3 #include <bootstate.h>
   4 #include <boot/coreboot_tables.h>
   5 #include <console/console.h>
   6 #include <types.h>
   7 #include <pc80/mc146818rtc.h>
   8 #include <security/vboot/vbnv.h>
   9 #include <security/vboot/vbnv_layout.h>
  10
  11 static void clear_vbnv_battery_cutoff_flag(uint8_t *vbnv_copy)
  12 {
  13         /*
  14          * Currently battery cutoff is done in payload stage, which does not
  15          * update backup VBNV. And doing battery cutoff will invalidate CMOS.
  16          * This means for every reboot after cutoff, read_vbnv_cmos will reload
  17          * backup VBNV and try to cutoff again, causing endless reboot loop.
  18          * So we should always clear battery cutoff flag from loaded backup.
  19          */
  20         if (vbnv_copy[MISC_FLAGS_OFFSET] & MISC_FLAGS_BATTERY_CUTOFF_MASK) {
  21                 printk(BIOS_INFO, "VBNV: Remove battery cut-off request.\n");
  22                 vbnv_copy[MISC_FLAGS_OFFSET] &= ~MISC_FLAGS_BATTERY_CUTOFF_MASK;
  23                 regen_vbnv_crc(vbnv_copy);
  24         }
  25 }
  26
  27 /* Return non-zero if backup was used. */
  28 static int restore_from_backup(uint8_t *vbnv_copy)
  29 {
  30         if (!CONFIG(VBOOT_VBNV_CMOS_BACKUP_TO_FLASH))
  31                 return 0;
  32
  33         printk(BIOS_INFO, "VBNV: CMOS invalid, restoring from flash\n");
  34         read_vbnv_flash(vbnv_copy);
  35
  36         if (verify_vbnv(vbnv_copy)) {
  37                 clear_vbnv_battery_cutoff_flag(vbnv_copy);
  38                 save_vbnv_cmos(vbnv_copy);
  39                 printk(BIOS_INFO, "VBNV: Flash backup restored\n");
  40                 return 1;
  41         }
  42
  43         printk(BIOS_INFO, "VBNV: Restore from flash failed\n");
  44
  45         return 0;
  46 }
  47
  48 void read_vbnv_cmos(uint8_t *vbnv_copy)
  49 {
  50         int i;
  51
  52         for (i = 0; i < VBOOT_VBNV_BLOCK_SIZE; i++)
  53                 vbnv_copy[i] = cmos_read(CONFIG_VBOOT_VBNV_OFFSET + 14 + i);
  54
  55         /* Verify contents before attempting a restore from backup storage. */
  56         if (verify_vbnv(vbnv_copy))
  57                 return;
  58
  59         restore_from_backup(vbnv_copy);
  60 }
  61
  62 void save_vbnv_cmos(const uint8_t *vbnv_copy)
  63 {
  64         int i;
  65
  66         for (i = 0; i < VBOOT_VBNV_BLOCK_SIZE; i++)
  67                 cmos_write(vbnv_copy[i], CONFIG_VBOOT_VBNV_OFFSET + 14 + i);
  68 }
  69
  70 void vbnv_init_cmos(uint8_t *vbnv_copy)
  71 {
  72         /* If no CMOS failure just defer to the normal read path for checking
  73            vbnv contents' integrity. */
  74         if (!vbnv_cmos_failed())
  75                 return;
  76
  77         /* In the case of CMOS failure force the backup. If backup wasn't used
  78            force the vbnv CMOS to be reset. */
  79         if (!restore_from_backup(vbnv_copy)) {
  80                 vbnv_reset(vbnv_copy);
  81                 /* This parallels the vboot_reference implementation. */
  82                 vbnv_copy[HEADER_OFFSET] = HEADER_SIGNATURE |
  83                         HEADER_FIRMWARE_SETTINGS_RESET |
  84                         HEADER_KERNEL_SETTINGS_RESET;
  85                 regen_vbnv_crc(vbnv_copy);
  86                 save_vbnv_cmos(vbnv_copy);
  87         }
  88 }
  89
  90 void lb_table_add_vbnv_cmos(struct lb_header *header)
  91 {
  92         struct lb_range *vbnv;
  93
  94         vbnv = (struct lb_range *)lb_new_record(header);
  95         vbnv->tag = LB_TAG_VBNV;
  96         vbnv->size = sizeof(*vbnv);
  97         vbnv->range_start = CONFIG_VBOOT_VBNV_OFFSET + 14;
  98         vbnv->range_size = VBOOT_VBNV_BLOCK_SIZE;
  99 }
 100
 101 #if CONFIG(VBOOT_VBNV_CMOS_BACKUP_TO_FLASH)
 102 static void back_up_vbnv_cmos(void *unused)
 103 {
 104         uint8_t vbnv_cmos[VBOOT_VBNV_BLOCK_SIZE];
 105
 106         /* Read current VBNV from CMOS. */
 107         read_vbnv_cmos(vbnv_cmos);
 108
 109         /* Save to flash, will only be saved if different. */
 110         save_vbnv_flash(vbnv_cmos);
 111 }
 112 BOOT_STATE_INIT_ENTRY(BS_POST_DEVICE, BS_ON_EXIT, back_up_vbnv_cmos, NULL);
 113 #endif