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 <linux/bug.h>
  14#include <linux/sha256.h>
  15#include <asm/purgatory.h>
  16
  17#include "../boot/string.h"
  18
  19unsigned long purgatory_backup_dest __section(.kexec-purgatory);
  20unsigned long purgatory_backup_src __section(.kexec-purgatory);
  21unsigned long purgatory_backup_sz __section(.kexec-purgatory);
  22
  23u8 purgatory_sha256_digest[SHA256_DIGEST_SIZE] __section(.kexec-purgatory);
  24
  25struct kexec_sha_region purgatory_sha_regions[KEXEC_SEGMENT_MAX] __section(.kexec-purgatory);
  26
  27/*
  28 * On x86, second kernel requries first 640K of memory to boot. Copy
  29 * first 640K to a backup region in reserved memory range so that second
  30 * kernel can use first 640K.
  31 */
  32static int copy_backup_region(void)
  33{
  34        if (purgatory_backup_dest) {
  35                memcpy((void *)purgatory_backup_dest,
  36                       (void *)purgatory_backup_src, purgatory_backup_sz);
  37        }
  38        return 0;
  39}
  40
  41static int verify_sha256_digest(void)
  42{
  43        struct kexec_sha_region *ptr, *end;
  44        u8 digest[SHA256_DIGEST_SIZE];
  45        struct sha256_state sctx;
  46
  47        sha256_init(&sctx);
  48        end = purgatory_sha_regions + ARRAY_SIZE(purgatory_sha_regions);
  49
  50        for (ptr = purgatory_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, purgatory_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