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Diffstat (limited to 'arch/x86/crypto/polyval-clmulni_asm.S')
| -rw-r--r-- | arch/x86/crypto/polyval-clmulni_asm.S | 321 |
1 files changed, 321 insertions, 0 deletions
diff --git a/arch/x86/crypto/polyval-clmulni_asm.S b/arch/x86/crypto/polyval-clmulni_asm.S new file mode 100644 index 000000000..a6ebe4e7d --- /dev/null +++ b/arch/x86/crypto/polyval-clmulni_asm.S @@ -0,0 +1,321 @@ +/* SPDX-License-Identifier: GPL-2.0 */ +/* + * Copyright 2021 Google LLC + */ +/* + * This is an efficient implementation of POLYVAL using intel PCLMULQDQ-NI + * instructions. It works on 8 blocks at a time, by precomputing the first 8 + * keys powers h^8, ..., h^1 in the POLYVAL finite field. This precomputation + * allows us to split finite field multiplication into two steps. + * + * In the first step, we consider h^i, m_i as normal polynomials of degree less + * than 128. We then compute p(x) = h^8m_0 + ... + h^1m_7 where multiplication + * is simply polynomial multiplication. + * + * In the second step, we compute the reduction of p(x) modulo the finite field + * modulus g(x) = x^128 + x^127 + x^126 + x^121 + 1. + * + * This two step process is equivalent to computing h^8m_0 + ... + h^1m_7 where + * multiplication is finite field multiplication. The advantage is that the + * two-step process only requires 1 finite field reduction for every 8 + * polynomial multiplications. Further parallelism is gained by interleaving the + * multiplications and polynomial reductions. + */ + +#include <linux/linkage.h> +#include <asm/frame.h> + +#define STRIDE_BLOCKS 8 + +#define GSTAR %xmm7 +#define PL %xmm8 +#define PH %xmm9 +#define TMP_XMM %xmm11 +#define LO %xmm12 +#define HI %xmm13 +#define MI %xmm14 +#define SUM %xmm15 + +#define KEY_POWERS %rdi +#define MSG %rsi +#define BLOCKS_LEFT %rdx +#define ACCUMULATOR %rcx +#define TMP %rax + +.section .rodata.cst16.gstar, "aM", @progbits, 16 +.align 16 + +.Lgstar: + .quad 0xc200000000000000, 0xc200000000000000 + +.text + +/* + * Performs schoolbook1_iteration on two lists of 128-bit polynomials of length + * count pointed to by MSG and KEY_POWERS. + */ +.macro schoolbook1 count + .set i, 0 + .rept (\count) + schoolbook1_iteration i 0 + .set i, (i +1) + .endr +.endm + +/* + * Computes the product of two 128-bit polynomials at the memory locations + * specified by (MSG + 16*i) and (KEY_POWERS + 16*i) and XORs the components of + * the 256-bit product into LO, MI, HI. + * + * Given: + * X = [X_1 : X_0] + * Y = [Y_1 : Y_0] + * + * We compute: + * LO += X_0 * Y_0 + * MI += X_0 * Y_1 + X_1 * Y_0 + * HI += X_1 * Y_1 + * + * Later, the 256-bit result can be extracted as: + * [HI_1 : HI_0 + MI_1 : LO_1 + MI_0 : LO_0] + * This step is done when computing the polynomial reduction for efficiency + * reasons. + * + * If xor_sum == 1, then also XOR the value of SUM into m_0. This avoids an + * extra multiplication of SUM and h^8. + */ +.macro schoolbook1_iteration i xor_sum + movups (16*\i)(MSG), %xmm0 + .if (\i == 0 && \xor_sum == 1) + pxor SUM, %xmm0 + .endif + vpclmulqdq $0x01, (16*\i)(KEY_POWERS), %xmm0, %xmm2 + vpclmulqdq $0x00, (16*\i)(KEY_POWERS), %xmm0, %xmm1 + vpclmulqdq $0x10, (16*\i)(KEY_POWERS), %xmm0, %xmm3 + vpclmulqdq $0x11, (16*\i)(KEY_POWERS), %xmm0, %xmm4 + vpxor %xmm2, MI, MI + vpxor %xmm1, LO, LO + vpxor %xmm4, HI, HI + vpxor %xmm3, MI, MI +.endm + +/* + * Performs the same computation as schoolbook1_iteration, except we expect the + * arguments to already be loaded into xmm0 and xmm1 and we set the result + * registers LO, MI, and HI directly rather than XOR'ing into them. + */ +.macro schoolbook1_noload + vpclmulqdq $0x01, %xmm0, %xmm1, MI + vpclmulqdq $0x10, %xmm0, %xmm1, %xmm2 + vpclmulqdq $0x00, %xmm0, %xmm1, LO + vpclmulqdq $0x11, %xmm0, %xmm1, HI + vpxor %xmm2, MI, MI +.endm + +/* + * Computes the 256-bit polynomial represented by LO, HI, MI. Stores + * the result in PL, PH. + * [PH : PL] = [HI_1 : HI_0 + MI_1 : LO_1 + MI_0 : LO_0] + */ +.macro schoolbook2 + vpslldq $8, MI, PL + vpsrldq $8, MI, PH + pxor LO, PL + pxor HI, PH +.endm + +/* + * Computes the 128-bit reduction of PH : PL. Stores the result in dest. + * + * This macro computes p(x) mod g(x) where p(x) is in montgomery form and g(x) = + * x^128 + x^127 + x^126 + x^121 + 1. + * + * We have a 256-bit polynomial PH : PL = P_3 : P_2 : P_1 : P_0 that is the + * product of two 128-bit polynomials in Montgomery form. We need to reduce it + * mod g(x). Also, since polynomials in Montgomery form have an "extra" factor + * of x^128, this product has two extra factors of x^128. To get it back into + * Montgomery form, we need to remove one of these factors by dividing by x^128. + * + * To accomplish both of these goals, we add multiples of g(x) that cancel out + * the low 128 bits P_1 : P_0, leaving just the high 128 bits. Since the low + * bits are zero, the polynomial division by x^128 can be done by right shifting. + * + * Since the only nonzero term in the low 64 bits of g(x) is the constant term, + * the multiple of g(x) needed to cancel out P_0 is P_0 * g(x). The CPU can + * only do 64x64 bit multiplications, so split P_0 * g(x) into x^128 * P_0 + + * x^64 * g*(x) * P_0 + P_0, where g*(x) is bits 64-127 of g(x). Adding this to + * the original polynomial gives P_3 : P_2 + P_0 + T_1 : P_1 + T_0 : 0, where T + * = T_1 : T_0 = g*(x) * P_0. Thus, bits 0-63 got "folded" into bits 64-191. + * + * Repeating this same process on the next 64 bits "folds" bits 64-127 into bits + * 128-255, giving the answer in bits 128-255. This time, we need to cancel P_1 + * + T_0 in bits 64-127. The multiple of g(x) required is (P_1 + T_0) * g(x) * + * x^64. Adding this to our previous computation gives P_3 + P_1 + T_0 + V_1 : + * P_2 + P_0 + T_1 + V_0 : 0 : 0, where V = V_1 : V_0 = g*(x) * (P_1 + T_0). + * + * So our final computation is: + * T = T_1 : T_0 = g*(x) * P_0 + * V = V_1 : V_0 = g*(x) * (P_1 + T_0) + * p(x) / x^{128} mod g(x) = P_3 + P_1 + T_0 + V_1 : P_2 + P_0 + T_1 + V_0 + * + * The implementation below saves a XOR instruction by computing P_1 + T_0 : P_0 + * + T_1 and XORing into dest, rather than separately XORing P_1 : P_0 and T_0 : + * T_1 into dest. This allows us to reuse P_1 + T_0 when computing V. + */ +.macro montgomery_reduction dest + vpclmulqdq $0x00, PL, GSTAR, TMP_XMM # TMP_XMM = T_1 : T_0 = P_0 * g*(x) + pshufd $0b01001110, TMP_XMM, TMP_XMM # TMP_XMM = T_0 : T_1 + pxor PL, TMP_XMM # TMP_XMM = P_1 + T_0 : P_0 + T_1 + pxor TMP_XMM, PH # PH = P_3 + P_1 + T_0 : P_2 + P_0 + T_1 + pclmulqdq $0x11, GSTAR, TMP_XMM # TMP_XMM = V_1 : V_0 = V = [(P_1 + T_0) * g*(x)] + vpxor TMP_XMM, PH, \dest +.endm + +/* + * Compute schoolbook multiplication for 8 blocks + * m_0h^8 + ... + m_7h^1 + * + * If reduce is set, also computes the montgomery reduction of the + * previous full_stride call and XORs with the first message block. + * (m_0 + REDUCE(PL, PH))h^8 + ... + m_7h^1. + * I.e., the first multiplication uses m_0 + REDUCE(PL, PH) instead of m_0. + */ +.macro full_stride reduce + pxor LO, LO + pxor HI, HI + pxor MI, MI + + schoolbook1_iteration 7 0 + .if \reduce + vpclmulqdq $0x00, PL, GSTAR, TMP_XMM + .endif + + schoolbook1_iteration 6 0 + .if \reduce + pshufd $0b01001110, TMP_XMM, TMP_XMM + .endif + + schoolbook1_iteration 5 0 + .if \reduce + pxor PL, TMP_XMM + .endif + + schoolbook1_iteration 4 0 + .if \reduce + pxor TMP_XMM, PH + .endif + + schoolbook1_iteration 3 0 + .if \reduce + pclmulqdq $0x11, GSTAR, TMP_XMM + .endif + + schoolbook1_iteration 2 0 + .if \reduce + vpxor TMP_XMM, PH, SUM + .endif + + schoolbook1_iteration 1 0 + + schoolbook1_iteration 0 1 + + addq $(8*16), MSG + schoolbook2 +.endm + +/* + * Process BLOCKS_LEFT blocks, where 0 < BLOCKS_LEFT < STRIDE_BLOCKS + */ +.macro partial_stride + mov BLOCKS_LEFT, TMP + shlq $4, TMP + addq $(16*STRIDE_BLOCKS), KEY_POWERS + subq TMP, KEY_POWERS + + movups (MSG), %xmm0 + pxor SUM, %xmm0 + movaps (KEY_POWERS), %xmm1 + schoolbook1_noload + dec BLOCKS_LEFT + addq $16, MSG + addq $16, KEY_POWERS + + test $4, BLOCKS_LEFT + jz .Lpartial4BlocksDone + schoolbook1 4 + addq $(4*16), MSG + addq $(4*16), KEY_POWERS +.Lpartial4BlocksDone: + test $2, BLOCKS_LEFT + jz .Lpartial2BlocksDone + schoolbook1 2 + addq $(2*16), MSG + addq $(2*16), KEY_POWERS +.Lpartial2BlocksDone: + test $1, BLOCKS_LEFT + jz .LpartialDone + schoolbook1 1 +.LpartialDone: + schoolbook2 + montgomery_reduction SUM +.endm + +/* + * Perform montgomery multiplication in GF(2^128) and store result in op1. + * + * Computes op1*op2*x^{-128} mod x^128 + x^127 + x^126 + x^121 + 1 + * If op1, op2 are in montgomery form, this computes the montgomery + * form of op1*op2. + * + * void clmul_polyval_mul(u8 *op1, const u8 *op2); + */ +SYM_FUNC_START(clmul_polyval_mul) + FRAME_BEGIN + vmovdqa .Lgstar(%rip), GSTAR + movups (%rdi), %xmm0 + movups (%rsi), %xmm1 + schoolbook1_noload + schoolbook2 + montgomery_reduction SUM + movups SUM, (%rdi) + FRAME_END + RET +SYM_FUNC_END(clmul_polyval_mul) + +/* + * Perform polynomial evaluation as specified by POLYVAL. This computes: + * h^n * accumulator + h^n * m_0 + ... + h^1 * m_{n-1} + * where n=nblocks, h is the hash key, and m_i are the message blocks. + * + * rdi - pointer to precomputed key powers h^8 ... h^1 + * rsi - pointer to message blocks + * rdx - number of blocks to hash + * rcx - pointer to the accumulator + * + * void clmul_polyval_update(const struct polyval_tfm_ctx *keys, + * const u8 *in, size_t nblocks, u8 *accumulator); + */ +SYM_FUNC_START(clmul_polyval_update) + FRAME_BEGIN + vmovdqa .Lgstar(%rip), GSTAR + movups (ACCUMULATOR), SUM + subq $STRIDE_BLOCKS, BLOCKS_LEFT + js .LstrideLoopExit + full_stride 0 + subq $STRIDE_BLOCKS, BLOCKS_LEFT + js .LstrideLoopExitReduce +.LstrideLoop: + full_stride 1 + subq $STRIDE_BLOCKS, BLOCKS_LEFT + jns .LstrideLoop +.LstrideLoopExitReduce: + montgomery_reduction SUM +.LstrideLoopExit: + add $STRIDE_BLOCKS, BLOCKS_LEFT + jz .LskipPartial + partial_stride +.LskipPartial: + movups SUM, (ACCUMULATOR) + FRAME_END + RET +SYM_FUNC_END(clmul_polyval_update) |