ref: 98c1cd7ae022efe276123898af6b892eade0732c
dir: /third_party/boringssl/src/crypto/fipsmodule/modes/asm/ghash-ssse3-x86.pl/
#!/usr/bin/env perl
# Copyright (c) 2019, Google Inc.
#
# Permission to use, copy, modify, and/or distribute this software for any
# purpose with or without fee is hereby granted, provided that the above
# copyright notice and this permission notice appear in all copies.
#
# THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
# WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
# MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY
# SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
# WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION
# OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN
# CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
# ghash-ssse3-x86.pl is a constant-time variant of the traditional 4-bit
# table-based GHASH implementation. It requires SSSE3 instructions.
#
# For background, the table-based strategy is a 4-bit windowed multiplication.
# It precomputes all 4-bit multiples of H (this is 16 128-bit rows), then loops
# over 4-bit windows of the input and indexes them up into the table. Visually,
# it multiplies as in the schoolbook multiplication diagram below, but with
# more terms. (Each term is 4 bits, so there are 32 terms in each row.) First
# it incorporates the terms labeled '1' by indexing the most significant term
# of X into the table. Then it shifts and repeats for '2' and so on.
#
# hhhhhh
# * xxxxxx
# ============
# 666666
# 555555
# 444444
# 333333
# 222222
# 111111
#
# This implementation changes the order. We treat the table as a 16×16 matrix
# and transpose it. The first row is then the first byte of each multiple of H,
# and so on. We then reorder terms as below. Observe that the terms labeled '1'
# and '2' are all lookups into the first row, etc. This maps well to the SSSE3
# pshufb instruction, using alternating terms of X in parallel as indices. This
# alternation is needed because pshufb maps 4 bits to 8 bits. Then we shift and
# repeat for each row.
#
# hhhhhh
# * xxxxxx
# ============
# 224466
# 113355
# 224466
# 113355
# 224466
# 113355
#
# Next we account for GCM's confusing bit order. The "first" bit is the least
# significant coefficient, but GCM treats the most sigificant bit within a byte
# as first. Bytes are little-endian, and bits are big-endian. We reverse the
# bytes in XMM registers for a consistent bit and byte ordering, but this means
# the least significant bit is the most significant coefficient and vice versa.
#
# For consistency, "low", "high", "left-shift", and "right-shift" refer to the
# bit ordering within the XMM register, rather than the reversed coefficient
# ordering. Low bits are less significant bits and more significant
# coefficients. Right-shifts move from MSB to the LSB and correspond to
# increasing the power of each coefficient.
#
# Note this bit reversal enters into the table's column indices. H*1 is stored
# in column 0b1000 and H*x^3 is stored in column 0b0001. It also means earlier
# table rows contain more significant coefficients, so we iterate forwards.
$0 =~ m/(.*[\/\\])[^\/\\]+$/; $dir=$1;
push(@INC,"${dir}","${dir}../../../perlasm");
require "x86asm.pl";
$output = pop;
open STDOUT, ">$output";
&asm_init($ARGV[0]);
my ($Xi, $Htable, $in, $len) = ("edi", "esi", "edx", "ecx");
&static_label("reverse_bytes");
&static_label("low4_mask");
my $call_counter = 0;
# process_rows emits assembly code to process $rows rows of the table. On
# input, $Htable stores the pointer to the next row. xmm0 and xmm1 store the
# low and high halves of the input. The result so far is passed in xmm2. xmm3
# must be zero. On output, $Htable is advanced to the next row and xmm2 is
# updated. xmm3 remains zero. It clobbers eax, xmm4, xmm5, and xmm6.
sub process_rows {
my ($rows) = @_;
$call_counter++;
# Shifting whole XMM registers by bits is complex. psrldq shifts by
# bytes, and psrlq shifts the two 64-bit halves separately. Each row
# produces 8 bits of carry, and the reduction needs an additional 7-bit
# shift. This must fit in 64 bits so reduction can use psrlq. This
# allows up to 7 rows at a time.
die "Carry register would overflow 64 bits." if ($rows*8 + 7 > 64);
&mov("eax", $rows);
&set_label("loop_row_$call_counter");
&movdqa("xmm4", &QWP(0, $Htable));
&lea($Htable, &DWP(16, $Htable));
# Right-shift xmm2 and xmm3 by 8 bytes.
&movdqa("xmm6", "xmm2");
&palignr("xmm6", "xmm3", 1);
&movdqa("xmm3", "xmm6");
&psrldq("xmm2", 1);
# Load the next table row and index the low and high bits of the input.
# Note the low (respectively, high) half corresponds to more
# (respectively, less) significant coefficients.
&movdqa("xmm5", "xmm4");
&pshufb("xmm4", "xmm0");
&pshufb("xmm5", "xmm1");
# Add the high half (xmm5) without shifting.
&pxor("xmm2", "xmm5");
# Add the low half (xmm4). This must be right-shifted by 4 bits. First,
# add into the carry register (xmm3).
&movdqa("xmm5", "xmm4");
&psllq("xmm5", 60);
&movdqa("xmm6", "xmm5");
&pslldq("xmm6", 8);
&pxor("xmm3", "xmm6");
# Next, add into xmm2.
&psrldq("xmm5", 8);
&pxor("xmm2", "xmm5");
&psrlq("xmm4", 4);
&pxor("xmm2", "xmm4");
&sub("eax", 1);
&jnz(&label("loop_row_$call_counter"));
# Reduce the carry register. The reduction polynomial is 1 + x + x^2 +
# x^7, so we shift and XOR four times.
&pxor("xmm2", "xmm3"); # x^0 = 0
&psrlq("xmm3", 1);
&pxor("xmm2", "xmm3"); # x^1 = x
&psrlq("xmm3", 1);
&pxor("xmm2", "xmm3"); # x^(1+1) = x^2
&psrlq("xmm3", 5);
&pxor("xmm2", "xmm3"); # x^(1+1+5) = x^7
&pxor("xmm3", "xmm3");
____
}
# gcm_gmult_ssse3 multiplies |Xi| by |Htable| and writes the result to |Xi|.
# |Xi| is represented in GHASH's serialized byte representation. |Htable| is
# formatted as described above.
# void gcm_gmult_ssse3(uint64_t Xi[2], const u128 Htable[16]);
&function_begin("gcm_gmult_ssse3");
&mov($Xi, &wparam(0));
&mov($Htable, &wparam(1));
&movdqu("xmm0", &QWP(0, $Xi));
&call(&label("pic_point"));
&set_label("pic_point");
&blindpop("eax");
&movdqa("xmm7", &QWP(&label("reverse_bytes")."-".&label("pic_point"), "eax"));
&movdqa("xmm2", &QWP(&label("low4_mask")."-".&label("pic_point"), "eax"));
# Reverse input bytes to deserialize.
&pshufb("xmm0", "xmm7");
# Split each byte into low (xmm0) and high (xmm1) halves.
&movdqa("xmm1", "xmm2");
&pandn("xmm1", "xmm0");
&psrld("xmm1", 4);
&pand("xmm0", "xmm2");
# Maintain the result in xmm2 (the value) and xmm3 (carry bits). Note
# that, due to bit reversal, xmm3 contains bits that fall off when
# right-shifting, not left-shifting.
&pxor("xmm2", "xmm2");
&pxor("xmm3", "xmm3");
# We must reduce at least once every 7 rows, so divide into three
# chunks.
&process_rows(5);
&process_rows(5);
&process_rows(6);
# Store the result. Reverse bytes to serialize.
&pshufb("xmm2", "xmm7");
&movdqu(&QWP(0, $Xi), "xmm2");
# Zero any registers which contain secrets.
&pxor("xmm0", "xmm0");
&pxor("xmm1", "xmm1");
&pxor("xmm2", "xmm2");
&pxor("xmm3", "xmm3");
&pxor("xmm4", "xmm4");
&pxor("xmm5", "xmm5");
&pxor("xmm6", "xmm6");
&function_end("gcm_gmult_ssse3");
# gcm_ghash_ssse3 incorporates |len| bytes from |in| to |Xi|, using |Htable| as
# the key. It writes the result back to |Xi|. |Xi| is represented in GHASH's
# serialized byte representation. |Htable| is formatted as described above.
# void gcm_ghash_ssse3(uint64_t Xi[2], const u128 Htable[16], const uint8_t *in,
# size_t len);
&function_begin("gcm_ghash_ssse3");
&mov($Xi, &wparam(0));
&mov($Htable, &wparam(1));
&mov($in, &wparam(2));
&mov($len, &wparam(3));
&movdqu("xmm0", &QWP(0, $Xi));
&call(&label("pic_point"));
&set_label("pic_point");
&blindpop("ebx");
&movdqa("xmm7", &QWP(&label("reverse_bytes")."-".&label("pic_point"), "ebx"));
# This function only processes whole blocks.
&and($len, -16);
# Reverse input bytes to deserialize. We maintain the running
# total in xmm0.
&pshufb("xmm0", "xmm7");
# Iterate over each block. On entry to each iteration, xmm3 is zero.
&pxor("xmm3", "xmm3");
&set_label("loop_ghash");
&movdqa("xmm2", &QWP(&label("low4_mask")."-".&label("pic_point"), "ebx"));
# Incorporate the next block of input.
&movdqu("xmm1", &QWP(0, $in));
&pshufb("xmm1", "xmm7"); # Reverse bytes.
&pxor("xmm0", "xmm1");
# Split each byte into low (xmm0) and high (xmm1) halves.
&movdqa("xmm1", "xmm2");
&pandn("xmm1", "xmm0");
&psrld("xmm1", 4);
&pand("xmm0", "xmm2");
# Maintain the result in xmm2 (the value) and xmm3 (carry bits). Note
# that, due to bit reversal, xmm3 contains bits that fall off when
# right-shifting, not left-shifting.
&pxor("xmm2", "xmm2");
# xmm3 is already zero at this point.
# We must reduce at least once every 7 rows, so divide into three
# chunks.
&process_rows(5);
&process_rows(5);
&process_rows(6);
&movdqa("xmm0", "xmm2");
# Rewind $Htable for the next iteration.
&lea($Htable, &DWP(-256, $Htable));
# Advance input and continue.
&lea($in, &DWP(16, $in));
&sub($len, 16);
&jnz(&label("loop_ghash"));
# Reverse bytes and store the result.
&pshufb("xmm0", "xmm7");
&movdqu(&QWP(0, $Xi), "xmm0");
# Zero any registers which contain secrets.
&pxor("xmm0", "xmm0");
&pxor("xmm1", "xmm1");
&pxor("xmm2", "xmm2");
&pxor("xmm3", "xmm3");
&pxor("xmm4", "xmm4");
&pxor("xmm5", "xmm5");
&pxor("xmm6", "xmm6");
&function_end("gcm_ghash_ssse3");
# reverse_bytes is a permutation which, if applied with pshufb, reverses the
# bytes in an XMM register.
&set_label("reverse_bytes", 16);
&data_byte(15, 14, 13, 12, 11, 10, 9, 8, 7, 6, 5, 4, 3, 2, 1, 0);
# low4_mask is an XMM mask which selects the low four bits of each byte.
&set_label("low4_mask", 16);
&data_word(0x0f0f0f0f, 0x0f0f0f0f, 0x0f0f0f0f, 0x0f0f0f0f);
&asm_finish();
close STDOUT or die "error closing STDOUT: $!";