text: /*
   * CDDL HEADER START
   *
   * The contents of this file are subject to the terms of the
   * Common Development and Distribution License (the "License").
   * You may not use this file except in compliance with the License.
   *
   * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
   * or http://www.opensolaris.org/os/licensing.
   * See the License for the specific language governing permissions
   * and limitations under the License.
   *
   * When distributing Covered Code, include this CDDL HEADER in each
   * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
   * If applicable, add the following below this CDDL HEADER, with the
   * fields enclosed by brackets "[]" replaced with your own identifying
   * information: Portions Copyright [yyyy] [name of copyright owner]
   *
   * CDDL HEADER END
   */
  
  /*
   * Copyright (C) 2016 Gvozden Nešković. All rights reserved.
   */
  
  #include <sys/vdev_raidz_impl.h>
  
  /*
   * Provide native CPU scalar routines.
   * Support 32bit and 64bit CPUs.
   */
  #if ((~(0x0ULL)) >> 24) == 0xffULL
  #define	ELEM_SIZE	4
  typedef uint32_t iv_t;
  #elif ((~(0x0ULL)) >> 56) == 0xffULL
  #define	ELEM_SIZE	8
  typedef uint64_t iv_t;
  #endif
  
  /*
   * Vector type used in scalar implementation
   *
   * The union is expected to be of native CPU register size. Since addition
   * uses XOR operation, it can be performed an all byte elements at once.
   * Multiplication requires per byte access.
   */
  typedef union {
  	iv_t e;
  	uint8_t b[ELEM_SIZE];
  } v_t;
  
  /*
   * Precomputed lookup tables for multiplication by a constant
   *
   * Reconstruction path requires multiplication by a constant factors. Instead of
   * performing two step lookup (log & exp tables), a direct lookup can be used
   * instead. Multiplication of element 'a' by a constant 'c' is obtained as:
   *
   * 	r = vdev_raidz_mul_lt[c_log][a];
   *
   * where c_log = vdev_raidz_log2[c]. Log of coefficient factors is used because
   * they are faster to obtain while solving the syndrome equations.
   *
   * PERFORMANCE NOTE:
   * Even though the complete lookup table uses 64kiB, only relatively small
   * portion of it is used at the same time. Following shows number of accessed
   * bytes for different cases:
   * 	- 1 failed disk: 256B (1 mul. coefficient)
   * 	- 2 failed disks: 512B (2 mul. coefficients)
   * 	- 3 failed disks: 1536B (6 mul. coefficients)
   *
   * Size of actually accessed lookup table regions is only larger for
   * reconstruction of 3 failed disks, when compared to traditional log/exp
   * method. But since the result is obtained in one lookup step performance is
   * doubled.
   */
  static uint8_t vdev_raidz_mul_lt[256][256] __attribute__((aligned(256)));
  
  static void
  raidz_init_scalar(void)
  {
  	int c, i;
  	for (c = 0; c < 256; c++)
  		for (i = 0; i < 256; i++)
  			vdev_raidz_mul_lt[c][i] = gf_mul(c, i);
  
  }
  
  #define	PREFETCHNTA(ptr, offset)	{}
  #define	PREFETCH(ptr, offset) 		{}
  
  #define	XOR_ACC(src, acc)	acc.e ^= ((v_t *)src)[0].e
  #define	XOR(src, acc)		acc.e ^= src.e
  #define	ZERO(acc)		acc.e = 0
  #define	COPY(src, dst)		dst = src
  #define	LOAD(src, val) 		val = ((v_t *)src)[0]
  #define	STORE(dst, val)		((v_t *)dst)[0] = val
  
  /*
   * Constants used for optimized multiplication by 2.
   */
  static const struct {
  	iv_t mod;
  	iv_t mask;
  	iv_t msb;
  } scalar_mul2_consts = {
  #if ELEM_SIZE == 8
  	.mod	= 0x1d1d1d1d1d1d1d1dULL,
  	.mask	= 0xfefefefefefefefeULL,
  	.msb	= 0x8080808080808080ULL,
  #else
  	.mod	= 0x1d1d1d1dULL,
  	.mask	= 0xfefefefeULL,
  	.msb	= 0x80808080ULL,
  #endif
  };
  
  #define	MUL2_SETUP() {}
  
  #define	MUL2(a)								\
  {									\
  	iv_t _mask;							\
  									\
  	_mask = (a).e & scalar_mul2_consts.msb;				\
  	_mask = (_mask << 1) - (_mask >> 7);				\
  	(a).e = ((a).e << 1) & scalar_mul2_consts.mask;			\
  	(a).e = (a).e ^ (_mask & scalar_mul2_consts.mod);		\
  }
  
  #define	MUL4(a) 							\
  {									\
  	MUL2(a);							\
  	MUL2(a);							\
  }
  
  #define	MUL(c, a)							\
  {									\
  	const uint8_t *mul_lt = vdev_raidz_mul_lt[c];			\
  	switch (ELEM_SIZE) {						\
  	case 8:								\
  		a.b[7] = mul_lt[a.b[7]];				\
  		a.b[6] = mul_lt[a.b[6]];				\
  		a.b[5] = mul_lt[a.b[5]];				\
  		a.b[4] = mul_lt[a.b[4]];				\
  		/* falls through */					\
  	case 4:								\
  		a.b[3] = mul_lt[a.b[3]];				\
  		a.b[2] = mul_lt[a.b[2]];				\
  		a.b[1] = mul_lt[a.b[1]];				\
  		a.b[0] = mul_lt[a.b[0]];				\
  		break;							\
  	}								\
  }
  
  #define	raidz_math_begin()	{}
  #define	raidz_math_end()	{}
  
  #define	SYN_STRIDE		1
  
  #define	ZERO_DEFINE()		v_t d0
  #define	ZERO_STRIDE		1
  #define	ZERO_D			d0
  
  #define	COPY_DEFINE()		v_t d0
  #define	COPY_STRIDE		1
  #define	COPY_D			d0
  
  #define	ADD_DEFINE()		v_t d0
  #define	ADD_STRIDE		1
  #define	ADD_D			d0
  
  #define	MUL_DEFINE()		v_t d0
  #define	MUL_STRIDE		1
  #define	MUL_D			d0
  
  #define	GEN_P_STRIDE		1
  #define	GEN_P_DEFINE()		v_t p0
  #define	GEN_P_P			p0
  
  #define	GEN_PQ_STRIDE		1
  #define	GEN_PQ_DEFINE()		v_t d0, c0
  #define	GEN_PQ_D		d0
  #define	GEN_PQ_C		c0
  
  #define	GEN_PQR_STRIDE		1
  #define	GEN_PQR_DEFINE()	v_t d0, c0
  #define	GEN_PQR_D		d0
  #define	GEN_PQR_C		c0
  
  #define	SYN_Q_DEFINE()		v_t d0, x0
  #define	SYN_Q_D			d0
  #define	SYN_Q_X			x0
  
  
  #define	SYN_R_DEFINE()		v_t d0, x0
  #define	SYN_R_D			d0
  #define	SYN_R_X			x0
  
  
  #define	SYN_PQ_DEFINE()		v_t d0, x0
  #define	SYN_PQ_D		d0
  #define	SYN_PQ_X		x0
  
  
  #define	REC_PQ_STRIDE		1
  #define	REC_PQ_DEFINE()		v_t x0, y0, t0
  #define	REC_PQ_X		x0
  #define	REC_PQ_Y		y0
  #define	REC_PQ_T		t0
  
  
  #define	SYN_PR_DEFINE()		v_t d0, x0
  #define	SYN_PR_D		d0
  #define	SYN_PR_X		x0
  
  #define	REC_PR_STRIDE		1
  #define	REC_PR_DEFINE()		v_t x0, y0, t0
  #define	REC_PR_X		x0
  #define	REC_PR_Y		y0
  #define	REC_PR_T		t0
  
  
  #define	SYN_QR_DEFINE()		v_t d0, x0
  #define	SYN_QR_D		d0
  #define	SYN_QR_X		x0
  
  
  #define	REC_QR_STRIDE		1
  #define	REC_QR_DEFINE()		v_t x0, y0, t0
  #define	REC_QR_X		x0
  #define	REC_QR_Y		y0
  #define	REC_QR_T		t0
  
  
  #define	SYN_PQR_DEFINE()	v_t d0, x0
  #define	SYN_PQR_D		d0
  #define	SYN_PQR_X		x0
  
  #define	REC_PQR_STRIDE		1
  #define	REC_PQR_DEFINE()	v_t x0, y0, z0, xs0, ys0
  #define	REC_PQR_X		x0
  #define	REC_PQR_Y		y0
  #define	REC_PQR_Z		z0
  #define	REC_PQR_XS		xs0
  #define	REC_PQR_YS		ys0
  
  #include "vdev_raidz_math_impl.h"
  
  DEFINE_GEN_METHODS(scalar);
  DEFINE_REC_METHODS(scalar);
  
  boolean_t
  raidz_will_scalar_work(void)
  {
  	return (B_TRUE); /* always */
  }
  
  const raidz_impl_ops_t vdev_raidz_scalar_impl = {
  	.init = raidz_init_scalar,
  	.fini = NULL,
  	.gen = RAIDZ_GEN_METHODS(scalar),
  	.rec = RAIDZ_REC_METHODS(scalar),
  	.is_supported = &raidz_will_scalar_work,
  	.name = "scalar"
  };
  
  /* Powers of 2 in the RAID-Z Galois field. */
  const uint8_t vdev_raidz_pow2[256] __attribute__((aligned(256))) = {
  	0x01, 0x02, 0x04, 0x08, 0x10, 0x20, 0x40, 0x80,
  	0x1d, 0x3a, 0x74, 0xe8, 0xcd, 0x87, 0x13, 0x26,
  	0x4c, 0x98, 0x2d, 0x5a, 0xb4, 0x75, 0xea, 0xc9,
  	0x8f, 0x03, 0x06, 0x0c, 0x18, 0x30, 0x60, 0xc0,
  	0x9d, 0x27, 0x4e, 0x9c, 0x25, 0x4a, 0x94, 0x35,
  	0x6a, 0xd4, 0xb5, 0x77, 0xee, 0xc1, 0x9f, 0x23,
  	0x46, 0x8c, 0x05, 0x0a, 0x14, 0x28, 0x50, 0xa0,
  	0x5d, 0xba, 0x69, 0xd2, 0xb9, 0x6f, 0xde, 0xa1,
  	0x5f, 0xbe, 0x61, 0xc2, 0x99, 0x2f, 0x5e, 0xbc,
  	0x65, 0xca, 0x89, 0x0f, 0x1e, 0x3c, 0x78, 0xf0,
  	0xfd, 0xe7, 0xd3, 0xbb, 0x6b, 0xd6, 0xb1, 0x7f,
  	0xfe, 0xe1, 0xdf, 0xa3, 0x5b, 0xb6, 0x71, 0xe2,
  	0xd9, 0xaf, 0x43, 0x86, 0x11, 0x22, 0x44, 0x88,
  	0x0d, 0x1a, 0x34, 0x68, 0xd0, 0xbd, 0x67, 0xce,
  	0x81, 0x1f, 0x3e, 0x7c, 0xf8, 0xed, 0xc7, 0x93,
  	0x3b, 0x76, 0xec, 0xc5, 0x97, 0x33, 0x66, 0xcc,
  	0x85, 0x17, 0x2e, 0x5c, 0xb8, 0x6d, 0xda, 0xa9,
  	0x4f, 0x9e, 0x21, 0x42, 0x84, 0x15, 0x2a, 0x54,
  	0xa8, 0x4d, 0x9a, 0x29, 0x52, 0xa4, 0x55, 0xaa,
  	0x49, 0x92, 0x39, 0x72, 0xe4, 0xd5, 0xb7, 0x73,
  	0xe6, 0xd1, 0xbf, 0x63, 0xc6, 0x91, 0x3f, 0x7e,
  	0xfc, 0xe5, 0xd7, 0xb3, 0x7b, 0xf6, 0xf1, 0xff,
  	0xe3, 0xdb, 0xab, 0x4b, 0x96, 0x31, 0x62, 0xc4,
  	0x95, 0x37, 0x6e, 0xdc, 0xa5, 0x57, 0xae, 0x41,
  	0x82, 0x19, 0x32, 0x64, 0xc8, 0x8d, 0x07, 0x0e,
  	0x1c, 0x38, 0x70, 0xe0, 0xdd, 0xa7, 0x53, 0xa6,
  	0x51, 0xa2, 0x59, 0xb2, 0x79, 0xf2, 0xf9, 0xef,
  	0xc3, 0x9b, 0x2b, 0x56, 0xac, 0x45, 0x8a, 0x09,
  	0x12, 0x24, 0x48, 0x90, 0x3d, 0x7a, 0xf4, 0xf5,
  	0xf7, 0xf3, 0xfb, 0xeb, 0xcb, 0x8b, 0x0b, 0x16,
  	0x2c, 0x58, 0xb0, 0x7d, 0xfa, 0xe9, 0xcf, 0x83,
  	0x1b, 0x36, 0x6c, 0xd8, 0xad, 0x47, 0x8e, 0x01
  };
  
  /* Logs of 2 in the RAID-Z Galois field. */
  const uint8_t vdev_raidz_log2[256] __attribute__((aligned(256))) = {
  	0x00, 0x00, 0x01, 0x19, 0x02, 0x32, 0x1a, 0xc6,
  	0x03, 0xdf, 0x33, 0xee, 0x1b, 0x68, 0xc7, 0x4b,
  	0x04, 0x64, 0xe0, 0x0e, 0x34, 0x8d, 0xef, 0x81,
  	0x1c, 0xc1, 0x69, 0xf8, 0xc8, 0x08, 0x4c, 0x71,
  	0x05, 0x8a, 0x65, 0x2f, 0xe1, 0x24, 0x0f, 0x21,
  	0x35, 0x93, 0x8e, 0xda, 0xf0, 0x12, 0x82, 0x45,
  	0x1d, 0xb5, 0xc2, 0x7d, 0x6a, 0x27, 0xf9, 0xb9,
  	0xc9, 0x9a, 0x09, 0x78, 0x4d, 0xe4, 0x72, 0xa6,
  	0x06, 0xbf, 0x8b, 0x62, 0x66, 0xdd, 0x30, 0xfd,
  	0xe2, 0x98, 0x25, 0xb3, 0x10, 0x91, 0x22, 0x88,
  	0x36, 0xd0, 0x94, 0xce, 0x8f, 0x96, 0xdb, 0xbd,
  	0xf1, 0xd2, 0x13, 0x5c, 0x83, 0x38, 0x46, 0x40,
  	0x1e, 0x42, 0xb6, 0xa3, 0xc3, 0x48, 0x7e, 0x6e,
  	0x6b, 0x3a, 0x28, 0x54, 0xfa, 0x85, 0xba, 0x3d,
  	0xca, 0x5e, 0x9b, 0x9f, 0x0a, 0x15, 0x79, 0x2b,
  	0x4e, 0xd4, 0xe5, 0xac, 0x73, 0xf3, 0xa7, 0x57,
  	0x07, 0x70, 0xc0, 0xf7, 0x8c, 0x80, 0x63, 0x0d,
  	0x67, 0x4a, 0xde, 0xed, 0x31, 0xc5, 0xfe, 0x18,
  	0xe3, 0xa5, 0x99, 0x77, 0x26, 0xb8, 0xb4, 0x7c,
  	0x11, 0x44, 0x92, 0xd9, 0x23, 0x20, 0x89, 0x2e,
  	0x37, 0x3f, 0xd1, 0x5b, 0x95, 0xbc, 0xcf, 0xcd,
  	0x90, 0x87, 0x97, 0xb2, 0xdc, 0xfc, 0xbe, 0x61,
  	0xf2, 0x56, 0xd3, 0xab, 0x14, 0x2a, 0x5d, 0x9e,
  	0x84, 0x3c, 0x39, 0x53, 0x47, 0x6d, 0x41, 0xa2,
  	0x1f, 0x2d, 0x43, 0xd8, 0xb7, 0x7b, 0xa4, 0x76,
  	0xc4, 0x17, 0x49, 0xec, 0x7f, 0x0c, 0x6f, 0xf6,
  	0x6c, 0xa1, 0x3b, 0x52, 0x29, 0x9d, 0x55, 0xaa,
  	0xfb, 0x60, 0x86, 0xb1, 0xbb, 0xcc, 0x3e, 0x5a,
  	0xcb, 0x59, 0x5f, 0xb0, 0x9c, 0xa9, 0xa0, 0x51,
  	0x0b, 0xf5, 0x16, 0xeb, 0x7a, 0x75, 0x2c, 0xd7,
  	0x4f, 0xae, 0xd5, 0xe9, 0xe6, 0xe7, 0xad, 0xe8,
  	0x74, 0xd6, 0xf4, 0xea, 0xa8, 0x50, 0x58, 0xaf,
  };
  