From: Eric Biggers <ebiggers@xxxxxxxxxx> Decrease the amount of code specific to the different AES variants by "right-aligning" the sequence of round keys, and for AES-128 and AES-192 just skipping irrelevant rounds at the beginning. This shrinks the size of aes-xts-avx-x86_64.o by 13.3%, and it improves the efficiency of AES-128 and AES-192. The tradeoff is that for AES-256 some additional not-taken conditional jumps are now executed. But these are predicted well and are cheap on x86. Note that the ARMv8 CE based AES-XTS implementation uses a similar strategy to handle the different AES variants. Signed-off-by: Eric Biggers <ebiggers@xxxxxxxxxx> --- arch/x86/crypto/aes-xts-avx-x86_64.S | 178 ++++++++++++++------------- 1 file changed, 92 insertions(+), 86 deletions(-) diff --git a/arch/x86/crypto/aes-xts-avx-x86_64.S b/arch/x86/crypto/aes-xts-avx-x86_64.S index 52f1997ed05a..f5e7ab739105 100644 --- a/arch/x86/crypto/aes-xts-avx-x86_64.S +++ b/arch/x86/crypto/aes-xts-avx-x86_64.S @@ -80,18 +80,19 @@ .byte 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80 .text // Function parameters .set KEY, %rdi // Initially points to crypto_aes_ctx, then is - // advanced to point directly to 7th round key + // advanced to point to 7th-from-last round key .set SRC, %rsi // Pointer to next source data .set DST, %rdx // Pointer to next destination data .set LEN, %rcx // Remaining length in bytes .set TWEAK, %r8 // Pointer to next tweak -// %r9d holds the AES key length in bytes. +// %r9 holds the AES key length in bytes. .set KEYLEN, %r9d +.set KEYLEN64, %r9 // %rax and %r10-r11 are available as temporaries. .macro _define_Vi i .if VL == 16 @@ -163,16 +164,22 @@ // V14 holds the constant from .Lgf_poly, copied to all 128-bit lanes. .set GF_POLY_XMM, %xmm14 .set GF_POLY, V14 - // V15 holds the first AES round key, copied to all 128-bit lanes. + // V15 holds the key for AES "round 0", copied to all 128-bit lanes. .set KEY0_XMM, %xmm15 .set KEY0, V15 // If 32 SIMD registers are available, then V16-V29 hold the remaining // AES round keys, copied to all 128-bit lanes. + // + // AES-128, AES-192, and AES-256 use different numbers of round keys. + // To allow handling all three variants efficiently, we align the round + // keys to the *end* of this register range. I.e., AES-128 uses + // KEY5-KEY14, AES-192 uses KEY3-KEY14, and AES-256 uses KEY1-KEY14. + // (All also use KEY0 for the XOR-only "round" at the beginning.) .if USE_AVX10 .set KEY1_XMM, %xmm16 .set KEY1, V16 .set KEY2_XMM, %xmm17 .set KEY2, V17 @@ -338,19 +345,19 @@ .set NEXT_TWEAK, NEXT_TWEAK2 .elseif \i == 15 .set PREV_TWEAK, NEXT_TWEAK2 .set NEXT_TWEAK, NEXT_TWEAK3 .endif -.if \i < 20 && \i % 5 == 0 +.if \i >= 0 && \i < 20 && \i % 5 == 0 vpshufd $0x13, PREV_TWEAK, V5 -.elseif \i < 20 && \i % 5 == 1 +.elseif \i >= 0 && \i < 20 && \i % 5 == 1 vpaddq PREV_TWEAK, PREV_TWEAK, NEXT_TWEAK -.elseif \i < 20 && \i % 5 == 2 +.elseif \i >= 0 && \i < 20 && \i % 5 == 2 vpsrad $31, V5, V5 -.elseif \i < 20 && \i % 5 == 3 +.elseif \i >= 0 && \i < 20 && \i % 5 == 3 vpand GF_POLY, V5, V5 -.elseif \i < 20 && \i % 5 == 4 +.elseif \i >= 0 && \i < 20 && \i % 5 == 4 vpxor V5, NEXT_TWEAK, NEXT_TWEAK .elseif \i == 1000 vmovdqa NEXT_TWEAK0, TWEAK0 vmovdqa NEXT_TWEAK1, TWEAK1 vmovdqa NEXT_TWEAK2, TWEAK2 @@ -362,25 +369,25 @@ // (the same method _next_tweakvec uses for VL > 16). This means multiplying // each tweak by x^(4*VL/16) independently. Since 4*VL/16 is a multiple of 8 // when VL > 16 (which it is here), the needed shift amounts are byte-aligned, // which allows the use of vpsrldq and vpslldq to do 128-bit wide shifts. .macro _tweak_step_pclmul i -.if \i == 2 +.if \i == 0 vpsrldq $(128 - 4*VL/16) / 8, TWEAK0, NEXT_TWEAK0 -.elseif \i == 4 +.elseif \i == 2 vpsrldq $(128 - 4*VL/16) / 8, TWEAK1, NEXT_TWEAK1 -.elseif \i == 6 +.elseif \i == 4 vpsrldq $(128 - 4*VL/16) / 8, TWEAK2, NEXT_TWEAK2 -.elseif \i == 8 +.elseif \i == 6 vpsrldq $(128 - 4*VL/16) / 8, TWEAK3, NEXT_TWEAK3 -.elseif \i == 10 +.elseif \i == 8 vpclmulqdq $0x00, GF_POLY, NEXT_TWEAK0, NEXT_TWEAK0 -.elseif \i == 12 +.elseif \i == 10 vpclmulqdq $0x00, GF_POLY, NEXT_TWEAK1, NEXT_TWEAK1 -.elseif \i == 14 +.elseif \i == 12 vpclmulqdq $0x00, GF_POLY, NEXT_TWEAK2, NEXT_TWEAK2 -.elseif \i == 16 +.elseif \i == 14 vpclmulqdq $0x00, GF_POLY, NEXT_TWEAK3, NEXT_TWEAK3 .elseif \i == 1000 vpslldq $(4*VL/16) / 8, TWEAK0, TWEAK0 vpslldq $(4*VL/16) / 8, TWEAK1, TWEAK1 vpslldq $(4*VL/16) / 8, TWEAK2, TWEAK2 @@ -391,12 +398,12 @@ _vpxor NEXT_TWEAK3, TWEAK3, TWEAK3 .endif .endm // _tweak_step does one step of the computation of the next set of tweaks from -// TWEAK[0-3]. To complete all steps, this must be invoked with \i values 0 -// through at least 19, then 1000 which signals the last step. +// TWEAK[0-3]. To complete all steps, this is invoked with increasing values of +// \i that include at least 0 through 19, then 1000 which signals the last step. // // This is used to interleave the computation of the next set of tweaks with the // AES en/decryptions, which increases performance in some cases. .macro _tweak_step i .if VL == 16 @@ -404,26 +411,60 @@ .else _tweak_step_pclmul \i .endif .endm -// Load the round keys: just the first one if !USE_AVX10, otherwise all of them. -.macro _load_round_keys - _vbroadcast128 -7*16(KEY), KEY0 +.macro _setup_round_keys enc + + // Select either the encryption round keys or the decryption round keys. +.if \enc + .set OFFS, 0 +.else + .set OFFS, 240 +.endif + + // Load the round key for "round 0". + _vbroadcast128 OFFS(KEY), KEY0 + + // Increment KEY to make it so that 7*16(KEY) is the last round key. + // For AES-128, increment by 3*16, resulting in the 10 round keys (not + // counting the zero-th round key which was just loaded into KEY0) being + // -2*16(KEY) through 7*16(KEY). For AES-192, increment by 5*16 and use + // 12 round keys -4*16(KEY) through 7*16(KEY). For AES-256, increment + // by 7*16 and use 14 round keys -6*16(KEY) through 7*16(KEY). + // + // This rebasing provides two benefits. First, it makes the offset to + // any round key be in the range [-96, 112], fitting in a signed byte. + // This shortens VEX-encoded instructions that access the later round + // keys which otherwise would need 4-byte offsets. Second, it makes it + // easy to do AES-128 and AES-192 by skipping irrelevant rounds at the + // beginning. Skipping rounds at the end doesn't work as well because + // the last round needs different instructions. + // + // An alternative approach would be to roll up all the round loops. We + // don't do that because it isn't compatible with caching the round keys + // in registers which we do when possible (see below), and also because + // it seems unwise to rely *too* heavily on the CPU's branch predictor. + lea OFFS-16(KEY, KEYLEN64, 4), KEY + + // If all 32 SIMD registers are available, cache all the round keys. .if USE_AVX10 + cmp $24, KEYLEN + jl .Laes128\@ + je .Laes192\@ _vbroadcast128 -6*16(KEY), KEY1 _vbroadcast128 -5*16(KEY), KEY2 +.Laes192\@: _vbroadcast128 -4*16(KEY), KEY3 _vbroadcast128 -3*16(KEY), KEY4 +.Laes128\@: _vbroadcast128 -2*16(KEY), KEY5 _vbroadcast128 -1*16(KEY), KEY6 _vbroadcast128 0*16(KEY), KEY7 _vbroadcast128 1*16(KEY), KEY8 _vbroadcast128 2*16(KEY), KEY9 _vbroadcast128 3*16(KEY), KEY10 - // Note: if it's AES-128 or AES-192, the last several round keys won't - // be used. We do the loads anyway to save a conditional jump. _vbroadcast128 4*16(KEY), KEY11 _vbroadcast128 5*16(KEY), KEY12 _vbroadcast128 6*16(KEY), KEY13 _vbroadcast128 7*16(KEY), KEY14 .endif @@ -464,26 +505,26 @@ .endif .endm // Do a single round of AES en/decryption on the blocks in registers V0-V3, // using the same key for all blocks. The round key is loaded from the -// appropriate register or memory location for round \i. In addition, does step -// \i of the computation of the next set of tweaks. May clobber V4. +// appropriate register or memory location for round \i. In addition, does two +// steps of the computation of the next set of tweaks. May clobber V4. .macro _vaes_4x enc, last, i .if USE_AVX10 - _tweak_step (2*(\i-1)) + _tweak_step (2*(\i-5)) _vaes \enc, \last, KEY\i, V0 _vaes \enc, \last, KEY\i, V1 - _tweak_step (2*(\i-1) + 1) + _tweak_step (2*(\i-5) + 1) _vaes \enc, \last, KEY\i, V2 _vaes \enc, \last, KEY\i, V3 .else _vbroadcast128 (\i-7)*16(KEY), V4 - _tweak_step (2*(\i-1)) + _tweak_step (2*(\i-5)) _vaes \enc, \last, V4, V0 _vaes \enc, \last, V4, V1 - _tweak_step (2*(\i-1) + 1) + _tweak_step (2*(\i-5) + 1) _vaes \enc, \last, V4, V2 _vaes \enc, \last, V4, V3 .endif .endm @@ -491,78 +532,62 @@ // then XOR with \tweak again) of the block(s) in \data. To process a single // block, use xmm registers and set \xmm_suffix=_XMM. To process a vector of // length VL, use V* registers and leave \xmm_suffix empty. May clobber V4. .macro _aes_crypt enc, xmm_suffix, tweak, data _xor3 KEY0\xmm_suffix, \tweak, \data + cmp $24, KEYLEN + jl .Laes128\@ + je .Laes192\@ _vaes_1x \enc, 0, 1, \xmm_suffix, \data _vaes_1x \enc, 0, 2, \xmm_suffix, \data +.Laes192\@: _vaes_1x \enc, 0, 3, \xmm_suffix, \data _vaes_1x \enc, 0, 4, \xmm_suffix, \data +.Laes128\@: _vaes_1x \enc, 0, 5, \xmm_suffix, \data _vaes_1x \enc, 0, 6, \xmm_suffix, \data _vaes_1x \enc, 0, 7, \xmm_suffix, \data _vaes_1x \enc, 0, 8, \xmm_suffix, \data _vaes_1x \enc, 0, 9, \xmm_suffix, \data - cmp $24, KEYLEN - jle .Laes_128_or_192\@ _vaes_1x \enc, 0, 10, \xmm_suffix, \data _vaes_1x \enc, 0, 11, \xmm_suffix, \data _vaes_1x \enc, 0, 12, \xmm_suffix, \data _vaes_1x \enc, 0, 13, \xmm_suffix, \data _vaes_1x \enc, 1, 14, \xmm_suffix, \data - jmp .Laes_done\@ -.Laes_128_or_192\@: - je .Laes_192\@ - _vaes_1x \enc, 1, 10, \xmm_suffix, \data - jmp .Laes_done\@ -.Laes_192\@: - _vaes_1x \enc, 0, 10, \xmm_suffix, \data - _vaes_1x \enc, 0, 11, \xmm_suffix, \data - _vaes_1x \enc, 1, 12, \xmm_suffix, \data -.Laes_done\@: _vpxor \tweak, \data, \data .endm .macro _aes_xts_crypt enc _define_aliases // Load the AES key length: 16 (AES-128), 24 (AES-192), or 32 (AES-256). movl 480(KEY), KEYLEN - // Advance KEY to point to the 7th encryption round key (if encrypting) - // or the 7th decryption round key (if decrypting). This makes the - // offset to any round key be in the range [-112, 112], fitting in a - // signed byte. This shortens VEX-encoded instructions that access the - // 8th and later round keys which otherwise would need 4-byte offsets. -.if \enc - add $7*16, KEY -.else - add $(15+7)*16, KEY - +.if !\enc // When decrypting a message whose length isn't a multiple of the AES // block length, exclude the last full block from the main loop by // subtracting 16 from LEN. This is needed because ciphertext stealing // decryption uses the last two tweaks in reverse order. We'll handle // the last full block and the partial block specially at the end. test $15, LEN jnz .Lneed_cts_dec\@ .Lxts_init\@: .endif - // Cache as many round keys as possible. - _load_round_keys + // Setup the pointer to the round keys and cache as many as possible. + _setup_round_keys \enc // Compute the first set of tweaks TWEAK[0-3]. _compute_first_set_of_tweaks sub $4*VL, LEN jl .Lhandle_remainder\@ .Lmain_loop\@: // This is the main loop, en/decrypting 4*VL bytes per iteration. - // XOR each source block with its tweak and the first round key. + // XOR each source block with its tweak and the zero-th round key. .if USE_AVX10 vmovdqu8 0*VL(SRC), V0 vmovdqu8 1*VL(SRC), V1 vmovdqu8 2*VL(SRC), V2 vmovdqu8 3*VL(SRC), V3 @@ -578,31 +603,31 @@ vpxor TWEAK0, V0, V0 vpxor TWEAK1, V1, V1 vpxor TWEAK2, V2, V2 vpxor TWEAK3, V3, V3 .endif + cmp $24, KEYLEN + jl .Laes128\@ + je .Laes192\@ // Do all the AES rounds on the data blocks, interleaved with // the computation of the next set of tweaks. _vaes_4x \enc, 0, 1 _vaes_4x \enc, 0, 2 +.Laes192\@: _vaes_4x \enc, 0, 3 _vaes_4x \enc, 0, 4 +.Laes128\@: _vaes_4x \enc, 0, 5 _vaes_4x \enc, 0, 6 _vaes_4x \enc, 0, 7 _vaes_4x \enc, 0, 8 _vaes_4x \enc, 0, 9 - // Try to optimize for AES-256 by keeping the code for AES-128 and - // AES-192 out-of-line. - cmp $24, KEYLEN - jle .Lencrypt_4x_aes_128_or_192\@ _vaes_4x \enc, 0, 10 _vaes_4x \enc, 0, 11 _vaes_4x \enc, 0, 12 _vaes_4x \enc, 0, 13 _vaes_4x \enc, 1, 14 -.Lencrypt_4x_done\@: // XOR in the tweaks again. _vpxor TWEAK0, V0, V0 _vpxor TWEAK1, V1, V1 _vpxor TWEAK2, V2, V2 @@ -676,21 +701,10 @@ // process the last 16 + LEN bytes. If LEN is zero, we're done. test LEN, LEN jnz .Lcts\@ jmp .Ldone\@ - // Out-of-line handling of AES-128 and AES-192 -.Lencrypt_4x_aes_128_or_192\@: - jz .Lencrypt_4x_aes_192\@ - _vaes_4x \enc, 1, 10 - jmp .Lencrypt_4x_done\@ -.Lencrypt_4x_aes_192\@: - _vaes_4x \enc, 0, 10 - _vaes_4x \enc, 0, 11 - _vaes_4x \enc, 1, 12 - jmp .Lencrypt_4x_done\@ - .if !\enc .Lneed_cts_dec\@: sub $16, LEN jmp .Lxts_init\@ .endif @@ -762,42 +776,34 @@ // void aes_xts_encrypt_iv(const struct crypto_aes_ctx *tweak_key, // u8 iv[AES_BLOCK_SIZE]); SYM_TYPED_FUNC_START(aes_xts_encrypt_iv) vmovdqu (%rsi), %xmm0 - add $7*16, %rdi - vpxor -7*16(%rdi), %xmm0, %xmm0 + vpxor (%rdi), %xmm0, %xmm0 + movl 480(%rdi), %eax // AES key length + lea -16(%rdi, %rax, 4), %rdi + cmp $24, %eax + jl .Lencrypt_iv_aes128 + je .Lencrypt_iv_aes192 vaesenc -6*16(%rdi), %xmm0, %xmm0 vaesenc -5*16(%rdi), %xmm0, %xmm0 +.Lencrypt_iv_aes192: vaesenc -4*16(%rdi), %xmm0, %xmm0 vaesenc -3*16(%rdi), %xmm0, %xmm0 +.Lencrypt_iv_aes128: vaesenc -2*16(%rdi), %xmm0, %xmm0 vaesenc -1*16(%rdi), %xmm0, %xmm0 vaesenc 0*16(%rdi), %xmm0, %xmm0 vaesenc 1*16(%rdi), %xmm0, %xmm0 vaesenc 2*16(%rdi), %xmm0, %xmm0 - cmpl $24, 480-(7*16)(%rdi) - jle .Lencrypt_iv_aes_128_or_192 vaesenc 3*16(%rdi), %xmm0, %xmm0 vaesenc 4*16(%rdi), %xmm0, %xmm0 vaesenc 5*16(%rdi), %xmm0, %xmm0 vaesenc 6*16(%rdi), %xmm0, %xmm0 vaesenclast 7*16(%rdi), %xmm0, %xmm0 -.Lencrypt_iv_done: vmovdqu %xmm0, (%rsi) RET - - // Out-of-line handling of AES-128 and AES-192 -.Lencrypt_iv_aes_128_or_192: - jz .Lencrypt_iv_aes_192 - vaesenclast 3*16(%rdi), %xmm0, %xmm0 - jmp .Lencrypt_iv_done -.Lencrypt_iv_aes_192: - vaesenc 3*16(%rdi), %xmm0, %xmm0 - vaesenc 4*16(%rdi), %xmm0, %xmm0 - vaesenclast 5*16(%rdi), %xmm0, %xmm0 - jmp .Lencrypt_iv_done SYM_FUNC_END(aes_xts_encrypt_iv) // Below are the actual AES-XTS encryption and decryption functions, // instantiated from the above macro. They all have the following prototype: // -- 2.44.0
