LXR linux/arch/x86/purgatory/purgatory.c

   1/*
   2 * purgatory: Runs between two kernels
   3 *
   4 * Copyright (C) 2014 Red Hat Inc.
   5 *
   6 * Author:
   7 *       Vivek Goyal <vgoyal@redhat.com>
   8 *
   9 * This source code is licensed under the GNU General Public License,
  10 * Version 2.  See the file COPYING for more details.
  11 */
  12
  13#include "sha256.h"
  14#include "../boot/string.h"
  15
  16struct sha_region {
  17        unsigned long start;
  18        unsigned long len;
  19};
  20
  21unsigned long backup_dest = 0;
  22unsigned long backup_src = 0;
  23unsigned long backup_sz = 0;
  24
  25u8 sha256_digest[SHA256_DIGEST_SIZE] = { 0 };
  26
  27struct sha_region sha_regions[16] = {};
  28
  29/*
  30 * On x86, second kernel requries first 640K of memory to boot. Copy
  31 * first 640K to a backup region in reserved memory range so that second
  32 * kernel can use first 640K.
  33 */
  34static int copy_backup_region(void)
  35{
  36        if (backup_dest)
  37                memcpy((void *)backup_dest, (void *)backup_src, backup_sz);
  38
  39        return 0;
  40}
  41
  42int verify_sha256_digest(void)
  43{
  44        struct sha_region *ptr, *end;
  45        u8 digest[SHA256_DIGEST_SIZE];
  46        struct sha256_state sctx;
  47
  48        sha256_init(&sctx);
  49        end = &sha_regions[sizeof(sha_regions)/sizeof(sha_regions[0])];
  50        for (ptr = sha_regions; ptr < end; ptr++)
  51                sha256_update(&sctx, (uint8_t *)(ptr->start), ptr->len);
  52
  53        sha256_final(&sctx, digest);
  54
  55        if (memcmp(digest, sha256_digest, sizeof(digest)))
  56                return 1;
  57
  58        return 0;
  59}
  60
  61void purgatory(void)
  62{
  63        int ret;
  64
  65        ret = verify_sha256_digest();
  66        if (ret) {
  67                /* loop forever */
  68                for (;;)
  69                        ;
  70        }
  71        copy_backup_region();
  72}
  73