/*
 * Implement fast CRC32C with PCLMULQDQ instructions. (x86_64)
 *
 * The white papers on CRC32C calculations with PCLMULQDQ instruction can be
 * downloaded from:
 * http://www.intel.com/content/dam/www/public/us/en/documents/white-papers/crc-iscsi-polynomial-crc32-instruction-paper.pdf
 * http://www.intel.com/content/dam/www/public/us/en/documents/white-papers/fast-crc-computation-paper.pdf
 *
 * Copyright (C) 2012 Intel Corporation.
 *
 * Authors:
 *	Wajdi Feghali <wajdi.k.feghali@intel.com>
 *	James Guilford <james.guilford@intel.com>
 *	David Cote <david.m.cote@intel.com>
 *	Tim Chen <tim.c.chen@linux.intel.com>
 *
 * This software is available to you under a choice of one of two
 * licenses.  You may choose to be licensed under the terms of the GNU
 * General Public License (GPL) Version 2, available from the file
 * COPYING in the main directory of this source tree, or the
 * OpenIB.org BSD license below:
 *
 *     Redistribution and use in source and binary forms, with or
 *     without modification, are permitted provided that the following
 *     conditions are met:
 *
 *      - Redistributions of source code must retain the above
 *        copyright notice, this list of conditions and the following
 *        disclaimer.
 *
 *      - Redistributions in binary form must reproduce the above
 *        copyright notice, this list of conditions and the following
 *        disclaimer in the documentation and/or other materials
 *        provided with the distribution.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
 * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
 * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
 * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
 * BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
 * ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
 * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
 * SOFTWARE.
 */

#include <linux/linkage.h>
#include <asm/nospec-branch.h>

## ISCSI CRC 32 Implementation with crc32 and pclmulqdq Instruction

.macro LABEL prefix n
\prefix\n\():
.endm

.macro JMPTBL_ENTRY i
.quad crc_\i
.endm

.macro JNC_LESS_THAN j
	jnc less_than_\j
.endm

# Define threshold where buffers are considered "small" and routed to more
# efficient "by-1" code. This "by-1" code only handles up to 255 bytes, so
# SMALL_SIZE can be no larger than 255.

#define SMALL_SIZE 200

.if (SMALL_SIZE > 255)
.error "SMALL_ SIZE must be < 256"
.endif

# unsigned int crc_pcl(u8 *buffer, int len, unsigned int crc_init);

.text
SYM_FUNC_START(crc_pcl)
#define    bufp		rdi
#define    bufp_dw	%edi
#define    bufp_w	%di
#define    bufp_b	%dil
#define    bufptmp	%rcx
#define    block_0	%rcx
#define    block_1	%rdx
#define    block_2	%r11
#define    len		%rsi
#define    len_dw	%esi
#define    len_w	%si
#define    len_b	%sil
#define    crc_init_arg %rdx
#define    tmp		%rbx
#define    crc_init	%r8
#define    crc_init_dw	%r8d
#define    crc1		%r9
#define    crc2		%r10

	pushq   %rbx
	pushq   %rdi
	pushq   %rsi

	## Move crc_init for Linux to a different
	mov     crc_init_arg, crc_init

	################################################################
	## 1) ALIGN:
	################################################################

	mov     %bufp, bufptmp		# rdi = *buf
	neg     %bufp
	and     $7, %bufp		# calculate the unalignment amount of
					# the address
	je      proc_block		# Skip if aligned

	## If len is less than 8 and we're unaligned, we need to jump
	## to special code to avoid reading beyond the end of the buffer
	cmp     $8, len
	jae     do_align
	# less_than_8 expects length in upper 3 bits of len_dw
	# less_than_8_post_shl1 expects length = carryflag * 8 + len_dw[31:30]
	shl     $32-3+1, len_dw
	jmp     less_than_8_post_shl1

do_align:
	#### Calculate CRC of unaligned bytes of the buffer (if any)
	movq    (bufptmp), tmp		# load a quadward from the buffer
	add     %bufp, bufptmp		# align buffer pointer for quadword
					# processing
	sub     %bufp, len		# update buffer length
align_loop:
	crc32b  %bl, crc_init_dw 	# compute crc32 of 1-byte
	shr     $8, tmp			# get next byte
	dec     %bufp
	jne     align_loop

proc_block:

	################################################################
	## 2) PROCESS  BLOCKS:
	################################################################

	## compute num of bytes to be processed
	movq    len, tmp		# save num bytes in tmp

	cmpq    $128*24, len
	jae     full_block

continue_block:
	cmpq    $SMALL_SIZE, len
	jb      small

	## len < 128*24
	movq    $2731, %rax		# 2731 = ceil(2^16 / 24)
	mul     len_dw
	shrq    $16, %rax

	## eax contains floor(bytes / 24) = num 24-byte chunks to do

	## process rax 24-byte chunks (128 >= rax >= 0)

	## compute end address of each block
	## block 0 (base addr + RAX * 8)
	## block 1 (base addr + RAX * 16)
	## block 2 (base addr + RAX * 24)
	lea     (bufptmp, %rax, 8), block_0
	lea     (block_0, %rax, 8), block_1
	lea     (block_1, %rax, 8), block_2

	xor     crc1, crc1
	xor     crc2, crc2

	## branch into array
	mov	jump_table(,%rax,8), %bufp
	JMP_NOSPEC bufp

	################################################################
	## 2a) PROCESS FULL BLOCKS:
	################################################################
full_block:
	movl    $128,%eax
	lea     128*8*2(block_0), block_1
	lea     128*8*3(block_0), block_2
	add     $128*8*1, block_0

	xor     crc1,crc1
	xor     crc2,crc2

	# Fall thruogh into top of crc array (crc_128)

	################################################################
	## 3) CRC Array:
	################################################################

crc_array:
	i=128
.rept 128-1
.altmacro
LABEL crc_ %i
.noaltmacro
	crc32q   -i*8(block_0), crc_init
	crc32q   -i*8(block_1), crc1
	crc32q   -i*8(block_2), crc2
	i=(i-1)
.endr

.altmacro
LABEL crc_ %i
.noaltmacro
	crc32q   -i*8(block_0), crc_init
	crc32q   -i*8(block_1), crc1
# SKIP  crc32  -i*8(block_2), crc2 ; Don't do this one yet

	mov     block_2, block_0

	################################################################
	## 4) Combine three results:
	################################################################

	lea	(K_table-8)(%rip), %bufp		# first entry is for idx 1
	shlq    $3, %rax			# rax *= 8
	pmovzxdq (%bufp,%rax), %xmm0		# 2 consts: K1:K2
	leal	(%eax,%eax,2), %eax		# rax *= 3 (total *24)
	subq    %rax, tmp			# tmp -= rax*24

	movq    crc_init, %xmm1			# CRC for block 1
	pclmulqdq $0x00, %xmm0, %xmm1		# Multiply by K2

	movq    crc1, %xmm2			# CRC for block 2
	pclmulqdq $0x10, %xmm0, %xmm2		# Multiply by K1

	pxor    %xmm2,%xmm1
	movq    %xmm1, %rax
	xor     -i*8(block_2), %rax
	mov     crc2, crc_init
	crc32   %rax, crc_init

	################################################################
	## 5) Check for end:
	################################################################

LABEL crc_ 0
	mov     tmp, len
	cmp     $128*24, tmp
	jae     full_block
	cmp     $24, tmp
	jae     continue_block

less_than_24:
	shl     $32-4, len_dw			# less_than_16 expects length
						# in upper 4 bits of len_dw
	jnc     less_than_16
	crc32q  (bufptmp), crc_init
	crc32q  8(bufptmp), crc_init
	jz      do_return
	add     $16, bufptmp
	# len is less than 8 if we got here
	# less_than_8 expects length in upper 3 bits of len_dw
	# less_than_8_post_shl1 expects length = carryflag * 8 + len_dw[31:30]
	shl     $2, len_dw
	jmp     less_than_8_post_shl1

	#######################################################################
	## 6) LESS THAN 256-bytes REMAIN AT THIS POINT (8-bits of len are full)
	#######################################################################
small:
	shl $32-8, len_dw		# Prepare len_dw for less_than_256
	j=256
.rept 5					# j = {256, 128, 64, 32, 16}
.altmacro
LABEL less_than_ %j			# less_than_j: Length should be in
					# upper lg(j) bits of len_dw
	j=(j/2)
	shl     $1, len_dw		# Get next MSB
	JNC_LESS_THAN %j
.noaltmacro
	i=0
.rept (j/8)
	crc32q  i(bufptmp), crc_init	# Compute crc32 of 8-byte data
	i=i+8
.endr
	jz      do_return		# Return if remaining length is zero
	add     $j, bufptmp		# Advance buf
.endr

less_than_8:				# Length should be stored in
					# upper 3 bits of len_dw
	shl     $1, len_dw
less_than_8_post_shl1:
	jnc     less_than_4
	crc32l  (bufptmp), crc_init_dw	# CRC of 4 bytes
	jz      do_return		# return if remaining data is zero
	add     $4, bufptmp
less_than_4:				# Length should be stored in
					# upper 2 bits of len_dw
	shl     $1, len_dw
	jnc     less_than_2
	crc32w  (bufptmp), crc_init_dw	# CRC of 2 bytes
	jz      do_return		# return if remaining data is zero
	add     $2, bufptmp
less_than_2:				# Length should be stored in the MSB
					# of len_dw
	shl     $1, len_dw
	jnc     less_than_1
	crc32b  (bufptmp), crc_init_dw	# CRC of 1 byte
less_than_1:				# Length should be zero
do_return:
	movq    crc_init, %rax
	popq    %rsi
	popq    %rdi
	popq    %rbx
        ret
SYM_FUNC_END(crc_pcl)

.section	.rodata, "a", @progbits
        ################################################################
        ## jump table        Table is 129 entries x 2 bytes each
        ################################################################
.align 4
jump_table:
	i=0
.rept 129
.altmacro
JMPTBL_ENTRY %i
.noaltmacro
	i=i+1
.endr


	################################################################
	## PCLMULQDQ tables
	## Table is 128 entries x 2 words (8 bytes) each
	################################################################
.align 8
K_table:
	.long 0x493c7d27, 0x00000001
	.long 0xba4fc28e, 0x493c7d27
	.long 0xddc0152b, 0xf20c0dfe
	.long 0x9e4addf8, 0xba4fc28e
	.long 0x39d3b296, 0x3da6d0cb
	.long 0x0715ce53, 0xddc0152b
	.long 0x47db8317, 0x1c291d04
	.long 0x0d3b6092, 0x9e4addf8
	.long 0xc96cfdc0, 0x740eef02
	.long 0x878a92a7, 0x39d3b296
	.long 0xdaece73e, 0x083a6eec
	.long 0xab7aff2a, 0x0715ce53
	.long 0x2162d385, 0xc49f4f67
	.long 0x83348832, 0x47db8317
	.long 0x299847d5, 0x2ad91c30
	.long 0xb9e02b86, 0x0d3b6092
	.long 0x18b33a4e, 0x6992cea2
	.long 0xb6dd949b, 0xc96cfdc0
	.long 0x78d9ccb7, 0x7e908048
	.long 0xbac2fd7b, 0x878a92a7
	.long 0xa60ce07b, 0x1b3d8f29
	.long 0xce7f39f4, 0xdaece73e
	.long 0x61d82e56, 0xf1d0f55e
	.long 0xd270f1a2, 0xab7aff2a
	.long 0xc619809d, 0xa87ab8a8
	.long 0x2b3cac5d, 0x2162d385
	.long 0x65863b64, 0x8462d800
	.long 0x1b03397f, 0x83348832
	.long 0xebb883bd, 0x71d111a8
	.long 0xb3e32c28, 0x299847d5
	.long 0x064f7f26, 0xffd852c6
	.long 0xdd7e3b0c, 0xb9e02b86
	.long 0xf285651c, 0xdcb17aa4
	.long 0x10746f3c, 0x18b33a4e
	.long 0xc7a68855, 0xf37c5aee
	.long 0x271d9844, 0xb6dd949b
	.long 0x8e766a0c, 0x6051d5a2
	.long 0x93a5f730, 0x78d9ccb7
	.long 0x6cb08e5c, 0x18b0d4ff
	.long 0x6b749fb2, 0xbac2fd7b
	.long 0x1393e203, 0x21f3d99c
	.long 0xcec3662e, 0xa60ce07b
	.long 0x96c515bb, 0x8f158014
	.long 0xe6fc4e6a, 0xce7f39f4
	.long 0x8227bb8a, 0xa00457f7
	.long 0xb0cd4768, 0x61d82e56
	.long 0x39c7ff35, 0x8d6d2c43
	.long 0xd7a4825c, 0xd270f1a2
	.long 0x0ab3844b, 0x00ac29cf
	.long 0x0167d312, 0xc619809d
	.long 0xf6076544, 0xe9adf796
	.long 0x26f6a60a, 0x2b3cac5d
	.long 0xa741c1bf, 0x96638b34
	.long 0x98d8d9cb, 0x65863b64
	.long 0x49c3cc9c, 0xe0e9f351
	.long 0x68bce87a, 0x1b03397f
	.long 0x57a3d037, 0x9af01f2d
	.long 0x6956fc3b, 0xebb883bd
	.long 0x42d98888, 0x2cff42cf
	.long 0x3771e98f, 0xb3e32c28
	.long 0xb42ae3d9, 0x88f25a3a
	.long 0x2178513a, 0x064f7f26
	.long 0xe0ac139e, 0x4e36f0b0
	.long 0x170076fa, 0xdd7e3b0c
	.long 0x444dd413, 0xbd6f81f8
	.long 0x6f345e45, 0xf285651c
	.long 0x41d17b64, 0x91c9bd4b
	.long 0xff0dba97, 0x10746f3c
	.long 0xa2b73df1, 0x885f087b
	.long 0xf872e54c, 0xc7a68855
	.long 0x1e41e9fc, 0x4c144932
	.long 0x86d8e4d2, 0x271d9844
	.long 0x651bd98b, 0x52148f02
	.long 0x5bb8f1bc, 0x8e766a0c
	.long 0xa90fd27a, 0xa3c6f37a
	.long 0xb3af077a, 0x93a5f730
	.long 0x4984d782, 0xd7c0557f
	.long 0xca6ef3ac, 0x6cb08e5c
	.long 0x234e0b26, 0x63ded06a
	.long 0xdd66cbbb, 0x6b749fb2
	.long 0x4597456a, 0x4d56973c
	.long 0xe9e28eb4, 0x1393e203
	.long 0x7b3ff57a, 0x9669c9df
	.long 0xc9c8b782, 0xcec3662e
	.long 0x3f70cc6f, 0xe417f38a
	.long 0x93e106a4, 0x96c515bb
	.long 0x62ec6c6d, 0x4b9e0f71
	.long 0xd813b325, 0xe6fc4e6a
	.long 0x0df04680, 0xd104b8fc
	.long 0x2342001e, 0x8227bb8a
	.long 0x0a2a8d7e, 0x5b397730
	.long 0x6d9a4957, 0xb0cd4768
	.long 0xe8b6368b, 0xe78eb416
	.long 0xd2c3ed1a, 0x39c7ff35
	.long 0x995a5724, 0x61ff0e01
	.long 0x9ef68d35, 0xd7a4825c
	.long 0x0c139b31, 0x8d96551c
	.long 0xf2271e60, 0x0ab3844b
	.long 0x0b0bf8ca, 0x0bf80dd2
	.long 0x2664fd8b, 0x0167d312
	.long 0xed64812d, 0x8821abed
	.long 0x02ee03b2, 0xf6076544
	.long 0x8604ae0f, 0x6a45d2b2
	.long 0x363bd6b3, 0x26f6a60a
	.long 0x135c83fd, 0xd8d26619
	.long 0x5fabe670, 0xa741c1bf
	.long 0x35ec3279, 0xde87806c
	.long 0x00bcf5f6, 0x98d8d9cb
	.long 0x8ae00689, 0x14338754
	.long 0x17f27698, 0x49c3cc9c
	.long 0x58ca5f00, 0x5bd2011f
	.long 0xaa7c7ad5, 0x68bce87a
	.long 0xb5cfca28, 0xdd07448e
	.long 0xded288f8, 0x57a3d037
	.long 0x59f229bc, 0xdde8f5b9
	.long 0x6d390dec, 0x6956fc3b
	.long 0x37170390, 0xa3e3e02c
	.long 0x6353c1cc, 0x42d98888
	.long 0xc4584f5c, 0xd73c7bea
	.long 0xf48642e9, 0x3771e98f
	.long 0x531377e2, 0x80ff0093
	.long 0xdd35bc8d, 0xb42ae3d9
	.long 0xb25b29f2, 0x8fe4c34d
	.long 0x9a5ede41, 0x2178513a
	.long 0xa563905d, 0xdf99fc11
	.long 0x45cddf4e, 0xe0ac139e
	.long 0xacfa3103, 0x6c23e841
	.long 0xa51b6135, 0x170076fa