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#!/usr/bin/env perl
#
# ====================================================================
# Written by Andy Polyakov <appro@openssl.org> for the OpenSSL
# project. The module is, however, dual licensed under OpenSSL and
# CRYPTOGAMS licenses depending on where you obtain it. For further
# details see http://www.openssl.org/~appro/cryptogams/.
# ====================================================================
#
# April 2010
#
# The module implements "4-bit" GCM GHASH function and underlying
# single multiplication operation in GF(2^128). "4-bit" means that it
# uses 256 bytes per-key table [+32 bytes shared table]. There is no
# experimental performance data available yet. The only approximation
# that can be made at this point is based on code size. Inner loop is
# 32 instructions long and on single-issue core should execute in <40
# cycles. Having verified that gcc 3.4 didn't unroll corresponding
# loop, this assembler loop body was found to be ~3x smaller than
# compiler-generated one...
#
# Note about "528B" variant. In ARM case it makes lesser sense to
# implement it for following reasons:
#
# - performance improvement won't be anywhere near 50%, because 128-
# bit shift operation is neatly fused with 128-bit xor here, and
# "538B" variant would eliminate only 4-5 instructions out of 32
# in the inner loop (meaning that estimated improvement is ~15%);
# - ARM-based systems are often embedded ones and extra memory
# consumption might be unappreciated (for so little improvement);
#
# Byte order [in]dependence. =========================================
#
# Caller is expected to maintain specific *dword* order in Htable,
# namely with *least* significant dword of 128-bit value at *lower*
# address. This differs completely from C code and has everything to
# do with ldm instruction and order in which dwords are "consumed" by
# algorithm. *Byte* order within these dwords in turn is whatever
# *native* byte order on current platform. See gcm128.c for working
# example...
while (($output=shift) && ($output!~/^\w[\w\-]*\.\w+$/)) {}
open STDOUT,">$output";
$Xi="r0"; # argument block
$Htbl="r1";
$inp="r2";
$len="r3";
$Zll="r4"; # variables
$Zlh="r5";
$Zhl="r6";
$Zhh="r7";
$Tll="r8";
$Tlh="r9";
$Thl="r10";
$Thh="r11";
$nlo="r12";
################# r13 is stack pointer
$nhi="r14";
################# r15 is program counter
$rem_4bit=$inp; # used in gcm_gmult_4bit
$cnt=$len;
sub Zsmash() {
my $i=12;
my @args=@_;
for ($Zll,$Zlh,$Zhl,$Zhh) {
# can be reduced to single "str $_,[$Xi,$i]" on big-endian platforms
$code.=<<___;
mov $Tlh,$_,lsr#8
strb $_,[$Xi,#$i+3]
mov $Thl,$_,lsr#16
strb $Tlh,[$Xi,#$i+2]
mov $Thh,$_,lsr#24
strb $Thl,[$Xi,#$i+1]
strb $Thh,[$Xi,#$i]
___
$code.="\t".shift(@args)."\n";
$i-=4;
}
}
$code=<<___;
.text
.code 32
.type rem_4bit,%object
.align 5
rem_4bit:
.short 0x0000,0x1C20,0x3840,0x2460
.short 0x7080,0x6CA0,0x48C0,0x54E0
.short 0xE100,0xFD20,0xD940,0xC560
.short 0x9180,0x8DA0,0xA9C0,0xB5E0
.size rem_4bit,.-rem_4bit
.type rem_4bit_get,%function
rem_4bit_get:
sub $rem_4bit,pc,#8
sub $rem_4bit,$rem_4bit,#32 @ &rem_4bit
b .Lrem_4bit_got
nop
.size rem_4bit_get,.-rem_4bit_get
.global gcm_ghash_4bit
.type gcm_ghash_4bit,%function
gcm_ghash_4bit:
sub r12,pc,#8
add $len,$inp,$len @ $len to point at the end
stmdb sp!,{r3-r11,lr} @ save $len/end too
sub r12,r12,#48 @ &rem_4bit
ldmia r12,{r4-r11} @ copy rem_4bit ...
stmdb sp!,{r4-r11} @ ... to stack
ldrb $nlo,[$inp,#15]
ldrb $nhi,[$Xi,#15]
.Louter:
eor $nlo,$nlo,$nhi
and $nhi,$nlo,#0xf0
and $nlo,$nlo,#0x0f
mov $cnt,#14
add $Zhh,$Htbl,$nlo,lsl#4
ldmia $Zhh,{$Zll-$Zhh} @ load Htbl[nlo]
ldrb $nlo,[$inp,#14]
add $Thh,$Htbl,$nhi
and $nhi,$Zll,#0xf @ rem
ldmia $Thh,{$Tll-$Thh} @ load Htbl[nhi]
mov $nhi,$nhi,lsl#1
eor $Zll,$Tll,$Zll,lsr#4
ldrh $Tll,[sp,$nhi] @ rem_4bit[rem]
eor $Zll,$Zll,$Zlh,lsl#28
ldrb $nhi,[$Xi,#14]
eor $Zlh,$Tlh,$Zlh,lsr#4
eor $Zlh,$Zlh,$Zhl,lsl#28
eor $Zhl,$Thl,$Zhl,lsr#4
eor $Zhl,$Zhl,$Zhh,lsl#28
eor $Zhh,$Thh,$Zhh,lsr#4
eor $nlo,$nlo,$nhi
eor $Zhh,$Zhh,$Tll,lsl#16
and $nhi,$nlo,#0xf0
and $nlo,$nlo,#0x0f
.Loop:
add $Thh,$Htbl,$nlo,lsl#4
subs $cnt,$cnt,#1
ldmia $Thh,{$Tll-$Thh} @ load Htbl[nlo]
and $nlo,$Zll,#0xf @ rem
add $nlo,$nlo,$nlo
eor $Zll,$Tll,$Zll,lsr#4
ldrh $Tll,[sp,$nlo] @ rem_4bit[rem]
eor $Zll,$Zll,$Zlh,lsl#28
eor $Zlh,$Tlh,$Zlh,lsr#4
eor $Zlh,$Zlh,$Zhl,lsl#28
eor $Zhl,$Thl,$Zhl,lsr#4
eor $Zhl,$Zhl,$Zhh,lsl#28
eor $Zhh,$Thh,$Zhh,lsr#4
ldrplb $nlo,[$inp,$cnt]
add $Thh,$Htbl,$nhi
eor $Zhh,$Zhh,$Tll,lsl#16 @ ^= rem_4bit[rem]
ldmia $Thh,{$Tll-$Thh} @ load Htbl[nhi]
and $nhi,$Zll,#0xf @ rem
add $nhi,$nhi,$nhi
eor $Zll,$Tll,$Zll,lsr#4
ldrh $Tll,[sp,$nhi] @ rem_4bit[rem]
eor $Zll,$Zll,$Zlh,lsl#28
ldrplb $nhi,[$Xi,$cnt]
eor $Zlh,$Tlh,$Zlh,lsr#4
eor $Zlh,$Zlh,$Zhl,lsl#28
eor $Zhl,$Thl,$Zhl,lsr#4
eor $Zhl,$Zhl,$Zhh,lsl#28
eor $Zhh,$Thh,$Zhh,lsr#4
eorpl $nlo,$nlo,$nhi
eor $Zhh,$Zhh,$Tll,lsl#16 @ ^= rem_4bit[rem]
andpl $nhi,$nlo,#0xf0
andpl $nlo,$nlo,#0x0f
bpl .Loop
ldr $len,[sp,#32] @ re-load $len/end
add $inp,$inp,#16
mov $nhi,$Zll
___
&Zsmash("cmp\t$inp,$len","ldrneb\t$nlo,[$inp,#15]");
$code.=<<___;
bne .Louter
add sp,sp,#36
ldmia sp!,{r4-r11,lr}
tst lr,#1
moveq pc,lr @ be binary compatible with V4, yet
bx lr @ interoperable with Thumb ISA:-)
.size gcm_ghash_4bit,.-gcm_ghash_4bit
.global gcm_gmult_4bit
.type gcm_gmult_4bit,%function
gcm_gmult_4bit:
stmdb sp!,{r4-r11,lr}
ldrb $nlo,[$Xi,#15]
b rem_4bit_get
.Lrem_4bit_got:
and $nhi,$nlo,#0xf0
and $nlo,$nlo,#0x0f
mov $cnt,#14
add $Zhh,$Htbl,$nlo,lsl#4
ldmia $Zhh,{$Zll-$Zhh} @ load Htbl[nlo]
ldrb $nlo,[$Xi,#14]
add $Thh,$Htbl,$nhi
and $nhi,$Zll,#0xf @ rem
ldmia $Thh,{$Tll-$Thh} @ load Htbl[nhi]
mov $nhi,$nhi,lsl#1
eor $Zll,$Tll,$Zll,lsr#4
ldrh $Tll,[$rem_4bit,$nhi] @ rem_4bit[rem]
eor $Zll,$Zll,$Zlh,lsl#28
eor $Zlh,$Tlh,$Zlh,lsr#4
eor $Zlh,$Zlh,$Zhl,lsl#28
eor $Zhl,$Thl,$Zhl,lsr#4
eor $Zhl,$Zhl,$Zhh,lsl#28
eor $Zhh,$Thh,$Zhh,lsr#4
and $nhi,$nlo,#0xf0
eor $Zhh,$Zhh,$Tll,lsl#16
and $nlo,$nlo,#0x0f
.Loop2:
add $Thh,$Htbl,$nlo,lsl#4
subs $cnt,$cnt,#1
ldmia $Thh,{$Tll-$Thh} @ load Htbl[nlo]
and $nlo,$Zll,#0xf @ rem
add $nlo,$nlo,$nlo
eor $Zll,$Tll,$Zll,lsr#4
ldrh $Tll,[$rem_4bit,$nlo] @ rem_4bit[rem]
eor $Zll,$Zll,$Zlh,lsl#28
eor $Zlh,$Tlh,$Zlh,lsr#4
eor $Zlh,$Zlh,$Zhl,lsl#28
eor $Zhl,$Thl,$Zhl,lsr#4
eor $Zhl,$Zhl,$Zhh,lsl#28
eor $Zhh,$Thh,$Zhh,lsr#4
ldrplb $nlo,[$Xi,$cnt]
add $Thh,$Htbl,$nhi
eor $Zhh,$Zhh,$Tll,lsl#16 @ ^= rem_4bit[rem]
ldmia $Thh,{$Tll-$Thh} @ load Htbl[nhi]
and $nhi,$Zll,#0xf @ rem
add $nhi,$nhi,$nhi
eor $Zll,$Tll,$Zll,lsr#4
ldrh $Tll,[$rem_4bit,$nhi] @ rem_4bit[rem]
eor $Zll,$Zll,$Zlh,lsl#28
eor $Zlh,$Tlh,$Zlh,lsr#4
eor $Zlh,$Zlh,$Zhl,lsl#28
eor $Zhl,$Thl,$Zhl,lsr#4
eor $Zhl,$Zhl,$Zhh,lsl#28
eor $Zhh,$Thh,$Zhh,lsr#4
andpl $nhi,$nlo,#0xf0
eor $Zhh,$Zhh,$Tll,lsl#16 @ ^= rem_4bit[rem]
andpl $nlo,$nlo,#0x0f
bpl .Loop2
___
&Zsmash();
$code.=<<___;
ldmia sp!,{r4-r11,lr}
tst lr,#1
moveq pc,lr @ be binary compatible with V4, yet
bx lr @ interoperable with Thumb ISA:-)
.size gcm_gmult_4bit,.-gcm_gmult_4bit
.asciz "GHASH for ARMv4, CRYPTOGAMS by <appro\@openssl.org>"
.align 2
___
$code =~ s/\`([^\`]*)\`/eval $1/gem;
$code =~ s/\bbx\s+lr\b/.word\t0xe12fff1e/gm; # make it possible to compile with -march=armv4
print $code;
close STDOUT; # enforce flush
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