/*
   * SHA1 routine optimized to do word accesses rather than byte accesses,
   * and to avoid unnecessary copies into the context array.
   *
   * This was based on the git SHA1 implementation.
   */
  
  #include <linux/kernel.h>
  #include <linux/export.h>
  #include <linux/bitops.h>
  #include <linux/cryptohash.h>
  #include <asm/unaligned.h>
  
  /*
   * If you have 32 registers or more, the compiler can (and should)
   * try to change the array[] accesses into registers. However, on
   * machines with less than ~25 registers, that won't really work,
   * and at least gcc will make an unholy mess of it.
   *
   * So to avoid that mess which just slows things down, we force
   * the stores to memory to actually happen (we might be better off
   * with a 'W(t)=(val);asm("":"+m" (W(t))' there instead, as
   * suggested by Artur Skawina - that will also make gcc unable to
   * try to do the silly "optimize away loads" part because it won't
   * see what the value will be).
   *
   * Ben Herrenschmidt reports that on PPC, the C version comes close
   * to the optimized asm with this (ie on PPC you don't want that
   * 'volatile', since there are lots of registers).
   *
   * On ARM we get the best code generation by forcing a full memory barrier
   * between each SHA_ROUND, otherwise gcc happily get wild with spilling and
   * the stack frame size simply explode and performance goes down the drain.
   */
  
  #ifdef CONFIG_X86
    #define setW(x, val) (*(volatile __u32 *)&W(x) = (val))
  #elif defined(CONFIG_ARM)
    #define setW(x, val) do { W(x) = (val); __asm__("":::"memory"); } while (0)
  #else
    #define setW(x, val) (W(x) = (val))
  #endif
  
  /* This "rolls" over the 512-bit array */
  #define W(x) (array[(x)&15])
  
  /*
   * Where do we get the source from? The first 16 iterations get it from
   * the input data, the next mix it from the 512-bit array.
   */
  #define SHA_SRC(t) get_unaligned_be32((__u32 *)data + t)
  #define SHA_MIX(t) rol32(W(t+13) ^ W(t+8) ^ W(t+2) ^ W(t), 1)
  
  #define SHA_ROUND(t, input, fn, constant, A, B, C, D, E) do { \
  	__u32 TEMP = input(t); setW(t, TEMP); \
  	E += TEMP + rol32(A,5) + (fn) + (constant); \
  	B = ror32(B, 2); } while (0)
  
  #define T_0_15(t, A, B, C, D, E)  SHA_ROUND(t, SHA_SRC, (((C^D)&B)^D) , 0x5a827999, A, B, C, D, E )
  #define T_16_19(t, A, B, C, D, E) SHA_ROUND(t, SHA_MIX, (((C^D)&B)^D) , 0x5a827999, A, B, C, D, E )
  #define T_20_39(t, A, B, C, D, E) SHA_ROUND(t, SHA_MIX, (B^C^D) , 0x6ed9eba1, A, B, C, D, E )
  #define T_40_59(t, A, B, C, D, E) SHA_ROUND(t, SHA_MIX, ((B&C)+(D&(B^C))) , 0x8f1bbcdc, A, B, C, D, E )
  #define T_60_79(t, A, B, C, D, E) SHA_ROUND(t, SHA_MIX, (B^C^D) ,  0xca62c1d6, A, B, C, D, E )
  
  /**
   * sha_transform - single block SHA1 transform
   *
   * @digest: 160 bit digest to update
   * @data:   512 bits of data to hash
   * @array:  16 words of workspace (see note)
   *
   * This function generates a SHA1 digest for a single 512-bit block.
   * Be warned, it does not handle padding and message digest, do not
   * confuse it with the full FIPS 180-1 digest algorithm for variable
   * length messages.
   *
   * Note: If the hash is security sensitive, the caller should be sure
   * to clear the workspace. This is left to the caller to avoid
   * unnecessary clears between chained hashing operations.
   */
  void sha_transform(__u32 *digest, const char *data, __u32 *array)
  {
  	__u32 A, B, C, D, E;
  
  	A = digest[0];
  	B = digest[1];
  	C = digest[2];
  	D = digest[3];
  	E = digest[4];
  
  	/* Round 1 - iterations 0-16 take their input from 'data' */
  	T_0_15( 0, A, B, C, D, E);
  	T_0_15( 1, E, A, B, C, D);
  	T_0_15( 2, D, E, A, B, C);
  	T_0_15( 3, C, D, E, A, B);
  	T_0_15( 4, B, C, D, E, A);
  	T_0_15( 5, A, B, C, D, E);
  	T_0_15( 6, E, A, B, C, D);
  	T_0_15( 7, D, E, A, B, C);
  	T_0_15( 8, C, D, E, A, B);
  	T_0_15( 9, B, C, D, E, A);
  	T_0_15(10, A, B, C, D, E);
  	T_0_15(11, E, A, B, C, D);
  	T_0_15(12, D, E, A, B, C);
  	T_0_15(13, C, D, E, A, B);
  	T_0_15(14, B, C, D, E, A);
  	T_0_15(15, A, B, C, D, E);
  
  	/* Round 1 - tail. Input from 512-bit mixing array */
  	T_16_19(16, E, A, B, C, D);
  	T_16_19(17, D, E, A, B, C);
  	T_16_19(18, C, D, E, A, B);
  	T_16_19(19, B, C, D, E, A);
  
  	/* Round 2 */
  	T_20_39(20, A, B, C, D, E);
  	T_20_39(21, E, A, B, C, D);
  	T_20_39(22, D, E, A, B, C);
  	T_20_39(23, C, D, E, A, B);
  	T_20_39(24, B, C, D, E, A);
  	T_20_39(25, A, B, C, D, E);
  	T_20_39(26, E, A, B, C, D);
  	T_20_39(27, D, E, A, B, C);
  	T_20_39(28, C, D, E, A, B);
  	T_20_39(29, B, C, D, E, A);
  	T_20_39(30, A, B, C, D, E);
  	T_20_39(31, E, A, B, C, D);
  	T_20_39(32, D, E, A, B, C);
  	T_20_39(33, C, D, E, A, B);
  	T_20_39(34, B, C, D, E, A);
  	T_20_39(35, A, B, C, D, E);
  	T_20_39(36, E, A, B, C, D);
  	T_20_39(37, D, E, A, B, C);
  	T_20_39(38, C, D, E, A, B);
  	T_20_39(39, B, C, D, E, A);
  
  	/* Round 3 */
  	T_40_59(40, A, B, C, D, E);
  	T_40_59(41, E, A, B, C, D);
  	T_40_59(42, D, E, A, B, C);
  	T_40_59(43, C, D, E, A, B);
  	T_40_59(44, B, C, D, E, A);
  	T_40_59(45, A, B, C, D, E);
  	T_40_59(46, E, A, B, C, D);
  	T_40_59(47, D, E, A, B, C);
  	T_40_59(48, C, D, E, A, B);
  	T_40_59(49, B, C, D, E, A);
  	T_40_59(50, A, B, C, D, E);
  	T_40_59(51, E, A, B, C, D);
  	T_40_59(52, D, E, A, B, C);
  	T_40_59(53, C, D, E, A, B);
  	T_40_59(54, B, C, D, E, A);
  	T_40_59(55, A, B, C, D, E);
  	T_40_59(56, E, A, B, C, D);
  	T_40_59(57, D, E, A, B, C);
  	T_40_59(58, C, D, E, A, B);
  	T_40_59(59, B, C, D, E, A);
  
  	/* Round 4 */
  	T_60_79(60, A, B, C, D, E);
  	T_60_79(61, E, A, B, C, D);
  	T_60_79(62, D, E, A, B, C);
  	T_60_79(63, C, D, E, A, B);
  	T_60_79(64, B, C, D, E, A);
  	T_60_79(65, A, B, C, D, E);
  	T_60_79(66, E, A, B, C, D);
  	T_60_79(67, D, E, A, B, C);
  	T_60_79(68, C, D, E, A, B);
  	T_60_79(69, B, C, D, E, A);
  	T_60_79(70, A, B, C, D, E);
  	T_60_79(71, E, A, B, C, D);
  	T_60_79(72, D, E, A, B, C);
  	T_60_79(73, C, D, E, A, B);
  	T_60_79(74, B, C, D, E, A);
  	T_60_79(75, A, B, C, D, E);
  	T_60_79(76, E, A, B, C, D);
  	T_60_79(77, D, E, A, B, C);
  	T_60_79(78, C, D, E, A, B);
  	T_60_79(79, B, C, D, E, A);
  
  	digest[0] += A;
  	digest[1] += B;
  	digest[2] += C;
  	digest[3] += D;
  	digest[4] += E;
  }
  EXPORT_SYMBOL(sha_transform);
  
  /**
   * sha_init - initialize the vectors for a SHA1 digest
   * @buf: vector to initialize
   */
  void sha_init(__u32 *buf)
  {
  	buf[0] = 0x67452301;
  	buf[1] = 0xefcdab89;
  	buf[2] = 0x98badcfe;
  	buf[3] = 0x10325476;
  	buf[4] = 0xc3d2e1f0;
  }