text: // SPDX-License-Identifier: GPL-2.0
  /*
   * Purgatory code running between two kernels.
   *
   * Copyright IBM Corp. 2018
   *
   * Author(s): Philipp Rudo <prudo@linux.vnet.ibm.com>
   */
  
  #include <linux/kexec.h>
  #include <linux/sha256.h>
  #include <linux/string.h>
  #include <asm/purgatory.h>
  
  int verify_sha256_digest(void)
  {
  	struct kexec_sha_region *ptr, *end;
  	u8 digest[SHA256_DIGEST_SIZE];
  	struct sha256_state sctx;
  
  	sha256_init(&sctx);
  	end = purgatory_sha_regions + ARRAY_SIZE(purgatory_sha_regions);
  
  	for (ptr = purgatory_sha_regions; ptr < end; ptr++)
  		sha256_update(&sctx, (uint8_t *)(ptr->start), ptr->len);
  
  	sha256_final(&sctx, digest);
  
  	if (memcmp(digest, purgatory_sha256_digest, sizeof(digest)))
  		return 1;
  
  	return 0;
  }
  