mirror of https://gogs.blitter.com/RLabs/xs
96 lines
2.3 KiB
Go
96 lines
2.3 KiB
Go
// chacha20_amd64.go - AMD64 optimized chacha20.
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//
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// To the extent possible under law, Yawning Angel has waived all copyright
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// and related or neighboring rights to chacha20, using the Creative
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// Commons "CC0" public domain dedication. See LICENSE or
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// <http://creativecommons.org/publicdomain/zero/1.0/> for full details.
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// +build amd64,!gccgo,!appengine
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package chacha20
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import (
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"math"
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)
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var usingAVX2 = false
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func blocksAmd64SSE2(x *uint32, inp, outp *byte, nrBlocks uint)
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func blocksAmd64AVX2(x *uint32, inp, outp *byte, nrBlocks uint)
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func cpuidAmd64(cpuidParams *uint32)
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func xgetbv0Amd64(xcrVec *uint32)
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func blocksAmd64(x *[stateSize]uint32, in []byte, out []byte, nrBlocks int, isIetf bool) {
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// Probably unneeded, but stating this explicitly simplifies the assembly.
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if nrBlocks == 0 {
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return
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}
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if isIetf {
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var totalBlocks uint64
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totalBlocks = uint64(x[12]) + uint64(nrBlocks)
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if totalBlocks > math.MaxUint32 {
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panic("chacha20: Exceeded keystream per nonce limit")
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}
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}
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if in == nil {
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for i := range out {
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out[i] = 0
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}
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in = out
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}
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// Pointless to call the AVX2 code for just a single block, since half of
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// the output gets discarded...
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if usingAVX2 && nrBlocks > 1 {
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blocksAmd64AVX2(&x[0], &in[0], &out[0], uint(nrBlocks))
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} else {
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blocksAmd64SSE2(&x[0], &in[0], &out[0], uint(nrBlocks))
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}
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}
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func supportsAVX2() bool {
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// https://software.intel.com/en-us/articles/how-to-detect-new-instruction-support-in-the-4th-generation-intel-core-processor-family
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const (
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osXsaveBit = 1 << 27
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avx2Bit = 1 << 5
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)
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// Check to see if CPUID actually supports the leaf that indicates AVX2.
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// CPUID.(EAX=0H, ECX=0H) >= 7
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regs := [4]uint32{0x00}
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cpuidAmd64(®s[0])
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if regs[0] < 7 {
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return false
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}
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// Check to see if the OS knows how to save/restore XMM/YMM state.
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// CPUID.(EAX=01H, ECX=0H):ECX.OSXSAVE[bit 27]==1
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regs = [4]uint32{0x01}
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cpuidAmd64(®s[0])
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if regs[2]&osXsaveBit == 0 {
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return false
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}
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xcrRegs := [2]uint32{}
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xgetbv0Amd64(&xcrRegs[0])
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if xcrRegs[0]&6 != 6 {
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return false
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}
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// Check for AVX2 support.
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// CPUID.(EAX=07H, ECX=0H):EBX.AVX2[bit 5]==1
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regs = [4]uint32{0x07}
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cpuidAmd64(®s[0])
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return regs[1]&avx2Bit != 0
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}
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func init() {
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blocksFn = blocksAmd64
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usingVectors = true
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usingAVX2 = supportsAVX2()
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}
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