2018-05-04 16:08:28 +02:00
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/ This Source Code Form is subject to the terms of the Mozilla Public
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/ License, v. 2.0. If a copy of the MPL was not distributed with this
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/ file, You can obtain one at http://mozilla.org/MPL/2.0/.
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2015-10-21 05:03:22 +02:00
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/ ** ARCFOUR implementation optimized for AMD64.
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/ **
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/ ** The throughput achieved by this code is about 320 MBytes/sec, on
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/ ** a 1.8 GHz AMD Opteron (rev C0) processor.
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.text
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.align 16
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.globl ARCFOUR
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.type ARCFOUR,@function
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ARCFOUR:
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pushq %rbp
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pushq %rbx
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movq %rdi, %rbp / key = ARG(key)
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movq %rsi, %rbx / rbx = ARG(len)
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movq %rdx, %rsi / in = ARG(in)
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movq %rcx, %rdi / out = ARG(out)
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movq (%rbp), %rcx / x = key->x
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movq 8(%rbp), %rdx / y = key->y
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addq $16, %rbp / d = key->data
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incq %rcx / x++
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andq $255, %rcx / x &= 0xff
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leaq -8(%rbx,%rsi), %rbx / rbx = in+len-8
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movq %rbx, %r9 / tmp = in+len-8
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movq 0(%rbp,%rcx,8), %rax / tx = d[x]
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cmpq %rsi, %rbx / cmp in with in+len-8
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jl .Lend / jump if (in+len-8 < in)
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.Lstart:
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addq $8, %rsi / increment in
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addq $8, %rdi / increment out
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/ generate the next 8 bytes of the rc4 stream into %r8
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movq $8, %r11 / byte counter
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1: addb %al, %dl / y += tx
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movl 0(%rbp,%rdx,8), %ebx / ty = d[y]
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movl %ebx, 0(%rbp,%rcx,8) / d[x] = ty
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addb %al, %bl / val = ty + tx
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movl %eax, 0(%rbp,%rdx,8) / d[y] = tx
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incb %cl / x++ (NEXT ROUND)
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movl 0(%rbp,%rcx,8), %eax / tx = d[x] (NEXT ROUND)
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movb 0(%rbp,%rbx,8), %r8b / val = d[val]
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decb %r11b
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rorq $8, %r8 / (ror does not change ZF)
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jnz 1b
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/ xor 8 bytes
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xorq -8(%rsi), %r8
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cmpq %r9, %rsi / cmp in+len-8 with in
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movq %r8, -8(%rdi)
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jle .Lstart / jump if (in <= in+len-8)
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.Lend:
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addq $8, %r9 / tmp = in+len
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/ handle the last bytes, one by one
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1: cmpq %rsi, %r9 / cmp in with in+len
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jle .Lfinished / jump if (in+len <= in)
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addb %al, %dl / y += tx
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movl 0(%rbp,%rdx,8), %ebx / ty = d[y]
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movl %ebx, 0(%rbp,%rcx,8) / d[x] = ty
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addb %al, %bl / val = ty + tx
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movl %eax, 0(%rbp,%rdx,8) / d[y] = tx
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incb %cl / x++ (NEXT ROUND)
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movl 0(%rbp,%rcx,8), %eax / tx = d[x] (NEXT ROUND)
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movb 0(%rbp,%rbx,8), %r8b / val = d[val]
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xorb (%rsi), %r8b / xor 1 byte
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movb %r8b, (%rdi)
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incq %rsi / in++
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incq %rdi / out++
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jmp 1b
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.Lfinished:
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decq %rcx / x--
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movb %dl, -8(%rbp) / key->y = y
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movb %cl, -16(%rbp) / key->x = x
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popq %rbx
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popq %rbp
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ret
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.L_ARCFOUR_end:
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.size ARCFOUR,.L_ARCFOUR_end-ARCFOUR
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