text: /*
   * sha256_base.h - core logic for SHA-256 implementations
   *
   * Copyright (C) 2015 Linaro Ltd <ard.biesheuvel@linaro.org>
   *
   * This program is free software; you can redistribute it and/or modify
   * it under the terms of the GNU General Public License version 2 as
   * published by the Free Software Foundation.
   */
  
  #include <crypto/internal/hash.h>
  #include <crypto/sha.h>
  #include <linux/crypto.h>
  #include <linux/module.h>
  
  #include <asm/unaligned.h>
  
  typedef void (sha256_block_fn)(struct sha256_state *sst, u8 const *src,
  			       int blocks);
  
  static inline int sha224_base_init(struct shash_desc *desc)
  {
  	struct sha256_state *sctx = shash_desc_ctx(desc);
  
  	sctx->state[0] = SHA224_H0;
  	sctx->state[1] = SHA224_H1;
  	sctx->state[2] = SHA224_H2;
  	sctx->state[3] = SHA224_H3;
  	sctx->state[4] = SHA224_H4;
  	sctx->state[5] = SHA224_H5;
  	sctx->state[6] = SHA224_H6;
  	sctx->state[7] = SHA224_H7;
  	sctx->count = 0;
  
  	return 0;
  }
  
  static inline int sha256_base_init(struct shash_desc *desc)
  {
  	struct sha256_state *sctx = shash_desc_ctx(desc);
  
  	sctx->state[0] = SHA256_H0;
  	sctx->state[1] = SHA256_H1;
  	sctx->state[2] = SHA256_H2;
  	sctx->state[3] = SHA256_H3;
  	sctx->state[4] = SHA256_H4;
  	sctx->state[5] = SHA256_H5;
  	sctx->state[6] = SHA256_H6;
  	sctx->state[7] = SHA256_H7;
  	sctx->count = 0;
  
  	return 0;
  }
  
  static inline int sha256_base_do_update(struct shash_desc *desc,
  					const u8 *data,
  					unsigned int len,
  					sha256_block_fn *block_fn)
  {
  	struct sha256_state *sctx = shash_desc_ctx(desc);
  	unsigned int partial = sctx->count % SHA256_BLOCK_SIZE;
  
  	sctx->count += len;
  
  	if (unlikely((partial + len) >= SHA256_BLOCK_SIZE)) {
  		int blocks;
  
  		if (partial) {
  			int p = SHA256_BLOCK_SIZE - partial;
  
  			memcpy(sctx->buf + partial, data, p);
  			data += p;
  			len -= p;
  
  			block_fn(sctx, sctx->buf, 1);
  		}
  
  		blocks = len / SHA256_BLOCK_SIZE;
  		len %= SHA256_BLOCK_SIZE;
  
  		if (blocks) {
  			block_fn(sctx, data, blocks);
  			data += blocks * SHA256_BLOCK_SIZE;
  		}
  		partial = 0;
  	}
  	if (len)
  		memcpy(sctx->buf + partial, data, len);
  
  	return 0;
  }
  
  static inline int sha256_base_do_finalize(struct shash_desc *desc,
  					  sha256_block_fn *block_fn)
  {
  	const int bit_offset = SHA256_BLOCK_SIZE - sizeof(__be64);
  	struct sha256_state *sctx = shash_desc_ctx(desc);
  	__be64 *bits = (__be64 *)(sctx->buf + bit_offset);
  	unsigned int partial = sctx->count % SHA256_BLOCK_SIZE;
  
  	sctx->buf[partial++] = 0x80;
  	if (partial > bit_offset) {
  		memset(sctx->buf + partial, 0x0, SHA256_BLOCK_SIZE - partial);
  		partial = 0;
  
  		block_fn(sctx, sctx->buf, 1);
  	}
  
  	memset(sctx->buf + partial, 0x0, bit_offset - partial);
  	*bits = cpu_to_be64(sctx->count << 3);
  	block_fn(sctx, sctx->buf, 1);
  
  	return 0;
  }
  
  static inline int sha256_base_finish(struct shash_desc *desc, u8 *out)
  {
  	unsigned int digest_size = crypto_shash_digestsize(desc->tfm);
  	struct sha256_state *sctx = shash_desc_ctx(desc);
  	__be32 *digest = (__be32 *)out;
  	int i;
  
  	for (i = 0; digest_size > 0; i++, digest_size -= sizeof(__be32))
  		put_unaligned_be32(sctx->state[i], digest++);
  
  	*sctx = (struct sha256_state){};
  	return 0;
  }
  