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+/* SPDX-License-Identifier: GPL-2.0-or-later */
+//
+// Template to generate [V]PCLMULQDQ-based CRC functions for x86
+//
+// Copyright 2025 Google LLC
+//
+// Author: Eric Biggers <ebiggers@google.com>
+
+#include <linux/linkage.h>
+
+// Offsets within the generated constants table
+.set OFFSETOF_BSWAP_MASK, -5*16 // msb-first CRCs only
+.set OFFSETOF_FOLD_ACROSS_2048BIT_CONSTS, -4*16 // must precede next
+.set OFFSETOF_FOLD_ACROSS_1024BIT_CONSTS, -3*16 // must precede next
+.set OFFSETOF_FOLD_ACROSS_512BIT_CONSTS, -2*16 // must precede next
+.set OFFSETOF_FOLD_ACROSS_256BIT_CONSTS, -1*16 // must precede next
+.set OFFSETOF_FOLD_ACROSS_128BIT_CONSTS, 0*16 // must be 0
+.set OFFSETOF_SHUF_TABLE, 1*16
+.set OFFSETOF_BARRETT_REDUCTION_CONSTS, 4*16
+
+// Emit a VEX (or EVEX) coded instruction if allowed, or emulate it using the
+// corresponding non-VEX instruction plus any needed moves. The supported
+// instruction formats are:
+//
+// - Two-arg [src, dst], where the non-VEX form is the same.
+// - Three-arg [src1, src2, dst] where the non-VEX form is
+// [src1, src2_and_dst]. If src2 != dst, then src1 must != dst too.
+//
+// \insn gives the instruction without a "v" prefix and including any immediate
+// argument if needed to make the instruction follow one of the above formats.
+// If \unaligned_mem_tmp is given, then the emitted non-VEX code moves \arg1 to
+// it first; this is needed when \arg1 is an unaligned mem operand.
+.macro _cond_vex insn:req, arg1:req, arg2:req, arg3, unaligned_mem_tmp
+.if AVX_LEVEL == 0
+ // VEX not allowed. Emulate it.
+ .ifnb \arg3 // Three-arg [src1, src2, dst]
+ .ifc "\arg2", "\arg3" // src2 == dst?
+ .ifnb \unaligned_mem_tmp
+ movdqu \arg1, \unaligned_mem_tmp
+ \insn \unaligned_mem_tmp, \arg3
+ .else
+ \insn \arg1, \arg3
+ .endif
+ .else // src2 != dst
+ .ifc "\arg1", "\arg3"
+ .error "Can't have src1 == dst when src2 != dst"
+ .endif
+ .ifnb \unaligned_mem_tmp
+ movdqu \arg1, \unaligned_mem_tmp
+ movdqa \arg2, \arg3
+ \insn \unaligned_mem_tmp, \arg3
+ .else
+ movdqa \arg2, \arg3
+ \insn \arg1, \arg3
+ .endif
+ .endif
+ .else // Two-arg [src, dst]
+ .ifnb \unaligned_mem_tmp
+ movdqu \arg1, \unaligned_mem_tmp
+ \insn \unaligned_mem_tmp, \arg2
+ .else
+ \insn \arg1, \arg2
+ .endif
+ .endif
+.else
+ // VEX is allowed. Emit the desired instruction directly.
+ .ifnb \arg3
+ v\insn \arg1, \arg2, \arg3
+ .else
+ v\insn \arg1, \arg2
+ .endif
+.endif
+.endm
+
+// Broadcast an aligned 128-bit mem operand to all 128-bit lanes of a vector
+// register of length VL.
+.macro _vbroadcast src, dst
+.if VL == 16
+ _cond_vex movdqa, \src, \dst
+.elseif VL == 32
+ vbroadcasti128 \src, \dst
+.else
+ vbroadcasti32x4 \src, \dst
+.endif
+.endm
+
+// Load \vl bytes from the unaligned mem operand \src into \dst, and if the CRC
+// is msb-first use \bswap_mask to reflect the bytes within each 128-bit lane.
+.macro _load_data vl, src, bswap_mask, dst
+.if \vl < 64
+ _cond_vex movdqu, "\src", \dst
+.else
+ vmovdqu8 \src, \dst
+.endif
+.if !LSB_CRC
+ _cond_vex pshufb, \bswap_mask, \dst, \dst
+.endif
+.endm
+
+.macro _prepare_v0 vl, v0, v1, bswap_mask
+.if LSB_CRC
+ .if \vl < 64
+ _cond_vex pxor, (BUF), \v0, \v0, unaligned_mem_tmp=\v1
+ .else
+ vpxorq (BUF), \v0, \v0
+ .endif
+.else
+ _load_data \vl, (BUF), \bswap_mask, \v1
+ .if \vl < 64
+ _cond_vex pxor, \v1, \v0, \v0
+ .else
+ vpxorq \v1, \v0, \v0
+ .endif
+.endif
+.endm
+
+// The x^0..x^63 terms, i.e. poly128 mod x^64, i.e. the physically low qword for
+// msb-first order or the physically high qword for lsb-first order.
+#define LO64_TERMS 0
+
+// The x^64..x^127 terms, i.e. floor(poly128 / x^64), i.e. the physically high
+// qword for msb-first order or the physically low qword for lsb-first order.
+#define HI64_TERMS 1
+
+// Multiply the given \src1_terms of each 128-bit lane of \src1 by the given
+// \src2_terms of each 128-bit lane of \src2, and write the result(s) to \dst.
+.macro _pclmulqdq src1, src1_terms, src2, src2_terms, dst
+ _cond_vex "pclmulqdq $((\src1_terms ^ LSB_CRC) << 4) ^ (\src2_terms ^ LSB_CRC),", \
+ \src1, \src2, \dst
+.endm
+
+// Fold \acc into \data and store the result back into \acc. \data can be an
+// unaligned mem operand if using VEX is allowed and the CRC is lsb-first so no
+// byte-reflection is needed; otherwise it must be a vector register. \consts
+// is a vector register containing the needed fold constants, and \tmp is a
+// temporary vector register. All arguments must be the same length.
+.macro _fold_vec acc, data, consts, tmp
+ _pclmulqdq \consts, HI64_TERMS, \acc, HI64_TERMS, \tmp
+ _pclmulqdq \consts, LO64_TERMS, \acc, LO64_TERMS, \acc
+.if AVX_LEVEL < 10
+ _cond_vex pxor, \data, \tmp, \tmp
+ _cond_vex pxor, \tmp, \acc, \acc
+.else
+ vpternlogq $0x96, \data, \tmp, \acc
+.endif
+.endm
+
+// Fold \acc into \data and store the result back into \acc. \data is an
+// unaligned mem operand, \consts is a vector register containing the needed
+// fold constants, \bswap_mask is a vector register containing the
+// byte-reflection table if the CRC is msb-first, and \tmp1 and \tmp2 are
+// temporary vector registers. All arguments must have length \vl.
+.macro _fold_vec_mem vl, acc, data, consts, bswap_mask, tmp1, tmp2
+.if AVX_LEVEL == 0 || !LSB_CRC
+ _load_data \vl, \data, \bswap_mask, \tmp1
+ _fold_vec \acc, \tmp1, \consts, \tmp2
+.else
+ _fold_vec \acc, \data, \consts, \tmp1
+.endif
+.endm
+
+// Load the constants for folding across 2**i vectors of length VL at a time
+// into all 128-bit lanes of the vector register CONSTS.
+.macro _load_vec_folding_consts i
+ _vbroadcast OFFSETOF_FOLD_ACROSS_128BIT_CONSTS+(4-LOG2_VL-\i)*16(CONSTS_PTR), \
+ CONSTS
+.endm
+
+// Given vector registers \v0 and \v1 of length \vl, fold \v0 into \v1 and store
+// the result back into \v0. If the remaining length mod \vl is nonzero, also
+// fold \vl bytes from (BUF). For both operations the fold distance is \vl.
+// \consts must be a register of length \vl containing the fold constants.
+.macro _fold_vec_final vl, v0, v1, consts, bswap_mask, tmp1, tmp2
+ _fold_vec \v0, \v1, \consts, \tmp1
+ test $\vl, LEN8
+ jz .Lfold_vec_final_done\@
+ _fold_vec_mem \vl, \v0, (BUF), \consts, \bswap_mask, \tmp1, \tmp2
+ add $\vl, BUF
+.Lfold_vec_final_done\@:
+.endm
+
+// This macro generates the body of a CRC function with the following prototype:
+//
+// crc_t crc_func(crc_t crc, const u8 *buf, size_t len, const void *consts);
+//
+// |crc| is the initial CRC, and crc_t is a data type wide enough to hold it.
+// |buf| is the data to checksum. |len| is the data length in bytes, which must
+// be at least 16. |consts| is a pointer to the fold_across_128_bits_consts
+// field of the constants table that was generated for the chosen CRC variant.
+//
+// Moving onto the macro parameters, \n is the number of bits in the CRC, e.g.
+// 32 for a CRC-32. Currently the supported values are 8, 16, 32, and 64. If
+// the file is compiled in i386 mode, then the maximum supported value is 32.
+//
+// \lsb_crc is 1 if the CRC processes the least significant bit of each byte
+// first, i.e. maps bit0 to x^7, bit1 to x^6, ..., bit7 to x^0. \lsb_crc is 0
+// if the CRC processes the most significant bit of each byte first, i.e. maps
+// bit0 to x^0, bit1 to x^1, bit7 to x^7.
+//
+// \vl is the maximum length of vector register to use in bytes: 16, 32, or 64.
+//
+// \avx_level is the level of AVX support to use: 0 for SSE only, 2 for AVX2, or
+// 10 for AVX10 or AVX512.
+//
+// If \vl == 16 && \avx_level == 0, the generated code requires:
+// PCLMULQDQ && SSE4.1. (Note: all known CPUs with PCLMULQDQ also have SSE4.1.)
+//
+// If \vl == 32 && \avx_level == 2, the generated code requires:
+// VPCLMULQDQ && AVX2.
+//
+// If \vl == 32 && \avx_level == 10, the generated code requires:
+// VPCLMULQDQ && (AVX10/256 || (AVX512BW && AVX512VL))
+//
+// If \vl == 64 && \avx_level == 10, the generated code requires:
+// VPCLMULQDQ && (AVX10/512 || (AVX512BW && AVX512VL))
+//
+// Other \vl and \avx_level combinations are either not supported or not useful.
+.macro _crc_pclmul n, lsb_crc, vl, avx_level
+ .set LSB_CRC, \lsb_crc
+ .set VL, \vl
+ .set AVX_LEVEL, \avx_level
+
+ // Define aliases for the xmm, ymm, or zmm registers according to VL.
+.irp i, 0,1,2,3,4,5,6,7
+ .if VL == 16
+ .set V\i, %xmm\i
+ .set LOG2_VL, 4
+ .elseif VL == 32
+ .set V\i, %ymm\i
+ .set LOG2_VL, 5
+ .elseif VL == 64
+ .set V\i, %zmm\i
+ .set LOG2_VL, 6
+ .else
+ .error "Unsupported vector length"
+ .endif
+.endr
+ // Define aliases for the function parameters.
+ // Note: when crc_t is shorter than u32, zero-extension to 32 bits is
+ // guaranteed by the ABI. Zero-extension to 64 bits is *not* guaranteed
+ // when crc_t is shorter than u64.
+#ifdef __x86_64__
+.if \n <= 32
+ .set CRC, %edi
+.else
+ .set CRC, %rdi
+.endif
+ .set BUF, %rsi
+ .set LEN, %rdx
+ .set LEN32, %edx
+ .set LEN8, %dl
+ .set CONSTS_PTR, %rcx
+#else
+ // 32-bit support, assuming -mregparm=3 and not including support for
+ // CRC-64 (which would use both eax and edx to pass the crc parameter).
+ .set CRC, %eax
+ .set BUF, %edx
+ .set LEN, %ecx
+ .set LEN32, %ecx
+ .set LEN8, %cl
+ .set CONSTS_PTR, %ebx // Passed on stack
+#endif
+
+ // Define aliases for some local variables. V0-V5 are used without
+ // aliases (for accumulators, data, temporary values, etc). Staying
+ // within the first 8 vector registers keeps the code 32-bit SSE
+ // compatible and reduces the size of 64-bit SSE code slightly.
+ .set BSWAP_MASK, V6
+ .set BSWAP_MASK_YMM, %ymm6
+ .set BSWAP_MASK_XMM, %xmm6
+ .set CONSTS, V7
+ .set CONSTS_YMM, %ymm7
+ .set CONSTS_XMM, %xmm7
+
+#ifdef __i386__
+ push CONSTS_PTR
+ mov 8(%esp), CONSTS_PTR
+#endif
+
+ // Create a 128-bit vector that contains the initial CRC in the end
+ // representing the high-order polynomial coefficients, and the rest 0.
+.if \n <= 32
+ _cond_vex movd, CRC, %xmm0
+.else
+ _cond_vex movq, CRC, %xmm0
+.endif
+.if !LSB_CRC
+ _cond_vex pslldq, $(128-\n)/8, %xmm0, %xmm0
+ _vbroadcast OFFSETOF_BSWAP_MASK(CONSTS_PTR), BSWAP_MASK
+.endif
+
+ // Load the first vector of data and XOR the initial CRC into the
+ // appropriate end of the first 128-bit lane of data. If LEN < VL, then
+ // use a short vector and jump to the end to do the final reduction.
+ // (LEN >= 16 is guaranteed here but not necessarily LEN >= VL.)
+.if VL >= 32
+ cmp $VL, LEN
+ jae 2f
+ .if VL == 64
+ cmp $32, LEN32
+ jb 1f
+ _prepare_v0 32, %ymm0, %ymm1, BSWAP_MASK_YMM
+ add $32, BUF
+ jmp .Lreduce_256bits_to_128bits\@
+1:
+ .endif
+ _prepare_v0 16, %xmm0, %xmm1, BSWAP_MASK_XMM
+ add $16, BUF
+ vmovdqa OFFSETOF_FOLD_ACROSS_128BIT_CONSTS(CONSTS_PTR), CONSTS_XMM
+ jmp .Lcheck_for_partial_block\@
+2:
+.endif
+ _prepare_v0 VL, V0, V1, BSWAP_MASK
+
+ // Handle VL <= LEN < 4*VL.
+ cmp $4*VL-1, LEN
+ ja .Lfold_4vecs_prepare\@
+ add $VL, BUF
+ // If VL <= LEN < 2*VL, then jump to the code at the end that handles
+ // the reduction from 1 vector. If VL==16 then
+ // fold_across_128bit_consts must be loaded first, as the final
+ // reduction depends on it and it won't be loaded anywhere else.
+ cmp $2*VL-1, LEN32
+.if VL == 16
+ _cond_vex movdqa, OFFSETOF_FOLD_ACROSS_128BIT_CONSTS(CONSTS_PTR), CONSTS_XMM
+.endif
+ jbe .Lreduce_1vec_to_128bits\@
+ // Otherwise 2*VL <= LEN < 4*VL. Load one more vector and jump to the
+ // code at the end that handles the reduction from 2 vectors.
+ _load_data VL, (BUF), BSWAP_MASK, V1
+ add $VL, BUF
+ jmp .Lreduce_2vecs_to_1\@
+
+.Lfold_4vecs_prepare\@:
+ // Load 3 more vectors of data.
+ _load_data VL, 1*VL(BUF), BSWAP_MASK, V1
+ _load_data VL, 2*VL(BUF), BSWAP_MASK, V2
+ _load_data VL, 3*VL(BUF), BSWAP_MASK, V3
+ sub $-4*VL, BUF // Shorter than 'add 4*VL' when VL=32
+ add $-4*VL, LEN // Shorter than 'sub 4*VL' when VL=32
+
+ // While >= 4 vectors of data remain, fold the 4 vectors V0-V3 into the
+ // next 4 vectors of data and write the result back to V0-V3.
+ cmp $4*VL-1, LEN // Shorter than 'cmp 4*VL' when VL=32
+ jbe .Lreduce_4vecs_to_2\@
+ _load_vec_folding_consts 2
+.Lfold_4vecs_loop\@:
+ _fold_vec_mem VL, V0, 0*VL(BUF), CONSTS, BSWAP_MASK, V4, V5
+ _fold_vec_mem VL, V1, 1*VL(BUF), CONSTS, BSWAP_MASK, V4, V5
+ _fold_vec_mem VL, V2, 2*VL(BUF), CONSTS, BSWAP_MASK, V4, V5
+ _fold_vec_mem VL, V3, 3*VL(BUF), CONSTS, BSWAP_MASK, V4, V5
+ sub $-4*VL, BUF
+ add $-4*VL, LEN
+ cmp $4*VL-1, LEN
+ ja .Lfold_4vecs_loop\@
+
+ // Fold V0,V1 into V2,V3 and write the result back to V0,V1.
+ // Then fold two vectors of data, if at least that much remains.
+.Lreduce_4vecs_to_2\@:
+ _load_vec_folding_consts 1
+ _fold_vec V0, V2, CONSTS, V4
+ _fold_vec V1, V3, CONSTS, V4
+ test $2*VL, LEN8
+ jz .Lreduce_2vecs_to_1\@
+ _fold_vec_mem VL, V0, 0*VL(BUF), CONSTS, BSWAP_MASK, V4, V5
+ _fold_vec_mem VL, V1, 1*VL(BUF), CONSTS, BSWAP_MASK, V4, V5
+ sub $-2*VL, BUF
+
+ // Fold V0 into V1 and write the result back to V0.
+ // Then fold one vector of data, if at least that much remains.
+.Lreduce_2vecs_to_1\@:
+ _load_vec_folding_consts 0
+ _fold_vec_final VL, V0, V1, CONSTS, BSWAP_MASK, V4, V5
+
+.Lreduce_1vec_to_128bits\@:
+ // Reduce V0 to 128 bits xmm0.
+.if VL == 64
+ // zmm0 => ymm0
+ vbroadcasti128 OFFSETOF_FOLD_ACROSS_256BIT_CONSTS(CONSTS_PTR), CONSTS_YMM
+ vextracti64x4 $1, %zmm0, %ymm1
+ _fold_vec_final 32, %ymm0, %ymm1, CONSTS_YMM, BSWAP_MASK_YMM, %ymm4, %ymm5
+.endif
+.if VL >= 32
+.Lreduce_256bits_to_128bits\@:
+ // ymm0 => xmm0
+ vmovdqa OFFSETOF_FOLD_ACROSS_128BIT_CONSTS(CONSTS_PTR), CONSTS_XMM
+ vextracti128 $1, %ymm0, %xmm1
+ _fold_vec_final 16, %xmm0, %xmm1, CONSTS_XMM, BSWAP_MASK_XMM, %xmm4, %xmm5
+.endif
+
+.Lcheck_for_partial_block\@:
+ and $15, LEN32
+ jz .Lpartial_block_done\@
+
+ // 1 <= LEN <= 15 data bytes remain. The polynomial is now
+ // A*(x^(8*LEN)) + B, where A = %xmm0 and B is the polynomial of the
+ // remaining LEN bytes. To reduce this to 128 bits without needing fold
+ // constants for each possible LEN, rearrange this expression into
+ // C1*(x^128) + C2, where C1 = floor(A / x^(128 - 8*LEN)) and
+ // C2 = A*x^(8*LEN) + B mod x^128. Then fold C1 into C2, which is just
+ // another fold across 128 bits.
+
+.if !LSB_CRC || AVX_LEVEL == 0
+ // Load the last 16 data bytes.
+ _load_data 16, "-16(BUF,LEN)", BSWAP_MASK_XMM, %xmm1
+.endif // Else will use vpblendvb mem operand later.
+.if !LSB_CRC
+ neg LEN // Needed for indexing shuf_table
+.endif
+
+ // tmp = A*x^(8*LEN) mod x^128
+ // lsb: pshufb by [LEN, LEN+1, ..., 15, -1, -1, ..., -1]
+ // i.e. right-shift by LEN bytes.
+ // msb: pshufb by [-1, -1, ..., -1, 0, 1, ..., 15-LEN]
+ // i.e. left-shift by LEN bytes.
+ _cond_vex movdqu, "OFFSETOF_SHUF_TABLE+16(CONSTS_PTR,LEN)", %xmm3
+ _cond_vex pshufb, %xmm3, %xmm0, %xmm2
+
+ // C1 = floor(A / x^(128 - 8*LEN))
+ // lsb: pshufb by [-1, -1, ..., -1, 0, 1, ..., LEN-1]
+ // i.e. left-shift by 16-LEN bytes.
+ // msb: pshufb by [16-LEN, 16-LEN+1, ..., 15, -1, -1, ..., -1]
+ // i.e. right-shift by 16-LEN bytes.
+ _cond_vex pshufb, "OFFSETOF_SHUF_TABLE+32*!LSB_CRC(CONSTS_PTR,LEN)", \
+ %xmm0, %xmm0, unaligned_mem_tmp=%xmm4
+
+ // C2 = tmp + B. This is just a blend of tmp with the last 16 data
+ // bytes (reflected if msb-first). The blend mask is the shuffle table
+ // that was used to create tmp. 0 selects tmp, and 1 last16databytes.
+.if AVX_LEVEL == 0
+ movdqa %xmm0, %xmm4
+ movdqa %xmm3, %xmm0
+ pblendvb %xmm1, %xmm2 // uses %xmm0 as implicit operand
+ movdqa %xmm4, %xmm0
+.elseif LSB_CRC
+ vpblendvb %xmm3, -16(BUF,LEN), %xmm2, %xmm2
+.else
+ vpblendvb %xmm3, %xmm1, %xmm2, %xmm2
+.endif
+
+ // Fold C1 into C2 and store the 128-bit result in xmm0.
+ _fold_vec %xmm0, %xmm2, CONSTS_XMM, %xmm4
+
+.Lpartial_block_done\@:
+ // Compute the CRC as %xmm0 * x^n mod G. Here %xmm0 means the 128-bit
+ // polynomial stored in %xmm0 (using either lsb-first or msb-first bit
+ // order according to LSB_CRC), and G is the CRC's generator polynomial.
+
+ // First, multiply %xmm0 by x^n and reduce the result to 64+n bits:
+ //
+ // t0 := (x^(64+n) mod G) * floor(%xmm0 / x^64) +
+ // x^n * (%xmm0 mod x^64)
+ //
+ // Store t0 * x^(64-n) in %xmm0. I.e., actually do:
+ //
+ // %xmm0 := ((x^(64+n) mod G) * x^(64-n)) * floor(%xmm0 / x^64) +
+ // x^64 * (%xmm0 mod x^64)
+ //
+ // The extra unreduced factor of x^(64-n) makes floor(t0 / x^n) aligned
+ // to the HI64_TERMS of %xmm0 so that the next pclmulqdq can easily
+ // select it. The 64-bit constant (x^(64+n) mod G) * x^(64-n) in the
+ // msb-first case, or (x^(63+n) mod G) * x^(64-n) in the lsb-first case
+ // (considering the extra factor of x that gets implicitly introduced by
+ // each pclmulqdq when using lsb-first order), is identical to the
+ // constant that was used earlier for folding the LO64_TERMS across 128
+ // bits. Thus it's already available in LO64_TERMS of CONSTS_XMM.
+ _pclmulqdq CONSTS_XMM, LO64_TERMS, %xmm0, HI64_TERMS, %xmm1
+.if LSB_CRC
+ _cond_vex psrldq, $8, %xmm0, %xmm0 // x^64 * (%xmm0 mod x^64)
+.else
+ _cond_vex pslldq, $8, %xmm0, %xmm0 // x^64 * (%xmm0 mod x^64)
+.endif
+ _cond_vex pxor, %xmm1, %xmm0, %xmm0
+ // The HI64_TERMS of %xmm0 now contain floor(t0 / x^n).
+ // The LO64_TERMS of %xmm0 now contain (t0 mod x^n) * x^(64-n).
+
+ // First step of Barrett reduction: Compute floor(t0 / G). This is the
+ // polynomial by which G needs to be multiplied to cancel out the x^n
+ // and higher terms of t0, i.e. to reduce t0 mod G. First do:
+ //
+ // t1 := floor(x^(63+n) / G) * x * floor(t0 / x^n)
+ //
+ // Then the desired value floor(t0 / G) is floor(t1 / x^64). The 63 in
+ // x^(63+n) is the maximum degree of floor(t0 / x^n) and thus the lowest
+ // value that makes enough precision be carried through the calculation.
+ //
+ // The '* x' makes it so the result is floor(t1 / x^64) rather than
+ // floor(t1 / x^63), making it qword-aligned in HI64_TERMS so that it
+ // can be extracted much more easily in the next step. In the lsb-first
+ // case the '* x' happens implicitly. In the msb-first case it must be
+ // done explicitly; floor(x^(63+n) / G) * x is a 65-bit constant, so the
+ // constant passed to pclmulqdq is (floor(x^(63+n) / G) * x) - x^64, and
+ // the multiplication by the x^64 term is handled using a pxor. The
+ // pxor causes the low 64 terms of t1 to be wrong, but they are unused.
+ _cond_vex movdqa, OFFSETOF_BARRETT_REDUCTION_CONSTS(CONSTS_PTR), CONSTS_XMM
+ _pclmulqdq CONSTS_XMM, HI64_TERMS, %xmm0, HI64_TERMS, %xmm1
+.if !LSB_CRC
+ _cond_vex pxor, %xmm0, %xmm1, %xmm1
+.endif
+ // The HI64_TERMS of %xmm1 now contain floor(t1 / x^64) = floor(t0 / G).
+
+ // Second step of Barrett reduction: Cancel out the x^n and higher terms
+ // of t0 by subtracting the needed multiple of G. This gives the CRC:
+ //
+ // crc := t0 - (G * floor(t0 / G))
+ //
+ // But %xmm0 contains t0 * x^(64-n), so it's more convenient to do:
+ //
+ // crc := ((t0 * x^(64-n)) - ((G * x^(64-n)) * floor(t0 / G))) / x^(64-n)
+ //
+ // Furthermore, since the resulting CRC is n-bit, if mod x^n is
+ // explicitly applied to it then the x^n term of G makes no difference
+ // in the result and can be omitted. This helps keep the constant
+ // multiplier in 64 bits in most cases. This gives the following:
+ //
+ // %xmm0 := %xmm0 - (((G - x^n) * x^(64-n)) * floor(t0 / G))
+ // crc := (%xmm0 / x^(64-n)) mod x^n
+ //
+ // In the lsb-first case, each pclmulqdq implicitly introduces
+ // an extra factor of x, so in that case the constant that needs to be
+ // passed to pclmulqdq is actually '(G - x^n) * x^(63-n)' when n <= 63.
+ // For lsb-first CRCs where n=64, the extra factor of x cannot be as
+ // easily avoided. In that case, instead pass '(G - x^n - x^0) / x' to
+ // pclmulqdq and handle the x^0 term (i.e. 1) separately. (All CRC
+ // polynomials have nonzero x^n and x^0 terms.) It works out as: the
+ // CRC has be XORed with the physically low qword of %xmm1, representing
+ // floor(t0 / G). The most efficient way to do that is to move it to
+ // the physically high qword and use a ternlog to combine the two XORs.
+.if LSB_CRC && \n == 64
+ _cond_vex punpcklqdq, %xmm1, %xmm2, %xmm2
+ _pclmulqdq CONSTS_XMM, LO64_TERMS, %xmm1, HI64_TERMS, %xmm1
+ .if AVX_LEVEL < 10
+ _cond_vex pxor, %xmm2, %xmm0, %xmm0
+ _cond_vex pxor, %xmm1, %xmm0, %xmm0
+ .else
+ vpternlogq $0x96, %xmm2, %xmm1, %xmm0
+ .endif
+ _cond_vex "pextrq $1,", %xmm0, %rax // (%xmm0 / x^0) mod x^64
+.else
+ _pclmulqdq CONSTS_XMM, LO64_TERMS, %xmm1, HI64_TERMS, %xmm1
+ _cond_vex pxor, %xmm1, %xmm0, %xmm0
+ .if \n == 8
+ _cond_vex "pextrb $7 + LSB_CRC,", %xmm0, %eax // (%xmm0 / x^56) mod x^8
+ .elseif \n == 16
+ _cond_vex "pextrw $3 + LSB_CRC,", %xmm0, %eax // (%xmm0 / x^48) mod x^16
+ .elseif \n == 32
+ _cond_vex "pextrd $1 + LSB_CRC,", %xmm0, %eax // (%xmm0 / x^32) mod x^32
+ .else // \n == 64 && !LSB_CRC
+ _cond_vex movq, %xmm0, %rax // (%xmm0 / x^0) mod x^64
+ .endif
+.endif
+
+.if VL > 16
+ vzeroupper // Needed when ymm or zmm registers may have been used.
+.endif
+#ifdef __i386__
+ pop CONSTS_PTR
+#endif
+ RET
+.endm
+
+#ifdef CONFIG_AS_VPCLMULQDQ
+#define DEFINE_CRC_PCLMUL_FUNCS(prefix, bits, lsb) \
+SYM_FUNC_START(prefix##_pclmul_sse); \
+ _crc_pclmul n=bits, lsb_crc=lsb, vl=16, avx_level=0; \
+SYM_FUNC_END(prefix##_pclmul_sse); \
+ \
+SYM_FUNC_START(prefix##_vpclmul_avx2); \
+ _crc_pclmul n=bits, lsb_crc=lsb, vl=32, avx_level=2; \
+SYM_FUNC_END(prefix##_vpclmul_avx2); \
+ \
+SYM_FUNC_START(prefix##_vpclmul_avx10_256); \
+ _crc_pclmul n=bits, lsb_crc=lsb, vl=32, avx_level=10; \
+SYM_FUNC_END(prefix##_vpclmul_avx10_256); \
+ \
+SYM_FUNC_START(prefix##_vpclmul_avx10_512); \
+ _crc_pclmul n=bits, lsb_crc=lsb, vl=64, avx_level=10; \
+SYM_FUNC_END(prefix##_vpclmul_avx10_512);
+#else
+#define DEFINE_CRC_PCLMUL_FUNCS(prefix, bits, lsb) \
+SYM_FUNC_START(prefix##_pclmul_sse); \
+ _crc_pclmul n=bits, lsb_crc=lsb, vl=16, avx_level=0; \
+SYM_FUNC_END(prefix##_pclmul_sse);
+#endif // !CONFIG_AS_VPCLMULQDQ
new file mode 100644
@@ -0,0 +1,81 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+/*
+ * Macros for accessing the [V]PCLMULQDQ-based CRC functions that are
+ * instantiated by crc-pclmul-template.S
+ *
+ * Copyright 2025 Google LLC
+ *
+ * Author: Eric Biggers <ebiggers@google.com>
+ */
+#ifndef _CRC_PCLMUL_TEMPLATE_H
+#define _CRC_PCLMUL_TEMPLATE_H
+
+#include <asm/cpufeatures.h>
+#include <asm/simd.h>
+#include <crypto/internal/simd.h>
+#include <linux/static_call.h>
+#include "crc-pclmul-consts.h"
+
+#define DECLARE_CRC_PCLMUL_FUNCS(prefix, crc_t) \
+crc_t prefix##_pclmul_sse(crc_t crc, const u8 *p, size_t len, \
+ const void *consts_ptr); \
+crc_t prefix##_vpclmul_avx2(crc_t crc, const u8 *p, size_t len, \
+ const void *consts_ptr); \
+crc_t prefix##_vpclmul_avx10_256(crc_t crc, const u8 *p, size_t len, \
+ const void *consts_ptr); \
+crc_t prefix##_vpclmul_avx10_512(crc_t crc, const u8 *p, size_t len, \
+ const void *consts_ptr); \
+DEFINE_STATIC_CALL(prefix##_pclmul, prefix##_pclmul_sse)
+
+#define INIT_CRC_PCLMUL(prefix) \
+do { \
+ if (IS_ENABLED(CONFIG_AS_VPCLMULQDQ) && \
+ boot_cpu_has(X86_FEATURE_VPCLMULQDQ) && \
+ boot_cpu_has(X86_FEATURE_AVX2) && \
+ cpu_has_xfeatures(XFEATURE_MASK_YMM, NULL)) { \
+ if (boot_cpu_has(X86_FEATURE_AVX512BW) && \
+ boot_cpu_has(X86_FEATURE_AVX512VL) && \
+ cpu_has_xfeatures(XFEATURE_MASK_AVX512, NULL)) { \
+ if (boot_cpu_has(X86_FEATURE_PREFER_YMM)) \
+ static_call_update(prefix##_pclmul, \
+ prefix##_vpclmul_avx10_256); \
+ else \
+ static_call_update(prefix##_pclmul, \
+ prefix##_vpclmul_avx10_512); \
+ } else { \
+ static_call_update(prefix##_pclmul, \
+ prefix##_vpclmul_avx2); \
+ } \
+ } \
+} while (0)
+
+/*
+ * Call a [V]PCLMULQDQ optimized CRC function if the data length is at least 16
+ * bytes, the CPU has PCLMULQDQ support, and the current context may use SIMD.
+ *
+ * 16 bytes is the minimum length supported by the [V]PCLMULQDQ functions.
+ * There is overhead associated with kernel_fpu_begin() and kernel_fpu_end(),
+ * varying by CPU and factors such as which parts of the "FPU" state userspace
+ * has touched, which could result in a larger cutoff being better. Indeed, a
+ * larger cutoff is usually better for a *single* message. However, the
+ * overhead of the FPU section gets amortized if multiple FPU sections get
+ * executed before returning to userspace, since the XSAVE and XRSTOR occur only
+ * once. Considering that and the fact that the [V]PCLMULQDQ code is lighter on
+ * the dcache than the table-based code is, a 16-byte cutoff seems to work well.
+ */
+#define CRC_PCLMUL(crc, p, len, prefix, consts, have_pclmulqdq) \
+do { \
+ if ((len) >= 16 && static_branch_likely(&(have_pclmulqdq)) && \
+ crypto_simd_usable()) { \
+ const void *consts_ptr; \
+ \
+ consts_ptr = (consts).fold_across_128_bits_consts; \
+ kernel_fpu_begin(); \
+ crc = static_call(prefix##_pclmul)((crc), (p), (len), \
+ consts_ptr); \
+ kernel_fpu_end(); \
+ return crc; \
+ } \
+} while (0)
+
+#endif /* _CRC_PCLMUL_TEMPLATE_H */