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| author | Keith Randall <khr@golang.org> | 2013-03-12 10:47:44 -0700 |
|---|---|---|
| committer | Keith Randall <khr@golang.org> | 2013-03-12 10:47:44 -0700 |
| commit | a5d4024139231ca10b5347d17bbf702cfdf5fd5b (patch) | |
| tree | 5ac78c98317c3bcb2b881629d69b225f76afad5f /src/pkg/runtime/alg.c | |
| parent | 4e032ce301f980d238d876278d60a4937c772814 (diff) | |
| download | go-a5d4024139231ca10b5347d17bbf702cfdf5fd5b.tar.xz | |
runtime: faster & safer hash function
Uses AES hardware instructions on 386/amd64 to implement
a fast hash function. Incorporates a random key to
thwart hash collision DOS attacks.
Depends on CL#7548043 for new assembly instructions.
Update #3885
Helps some by making hashing faster. Go time drops from
0.65s to 0.51s.
R=rsc, r, bradfitz, remyoudompheng, khr, dsymonds, minux.ma, elias.naur
CC=golang-dev
https://golang.org/cl/7543043
Diffstat (limited to 'src/pkg/runtime/alg.c')
| -rw-r--r-- | src/pkg/runtime/alg.c | 35 |
1 files changed, 35 insertions, 0 deletions
diff --git a/src/pkg/runtime/alg.c b/src/pkg/runtime/alg.c index ad85b43aef..124723333f 100644 --- a/src/pkg/runtime/alg.c +++ b/src/pkg/runtime/alg.c @@ -467,6 +467,41 @@ runtime·algarray[] = // Runtime helpers. +// used in asm_{386,amd64}.s +byte runtime·aeskeysched[HashRandomBytes]; + +void +runtime·hashinit(void) +{ + // Install aes hash algorithm if we have the instructions we need + if((runtime·cpuid_ecx & (1 << 25)) != 0 && // aes (aesenc) + (runtime·cpuid_ecx & (1 << 9)) != 0 && // sse3 (pshufb) + (runtime·cpuid_ecx & (1 << 19)) != 0) { // sse4.1 (pinsr{d,q}) + byte *rnd; + int32 n; + runtime·algarray[AMEM].hash = runtime·aeshash; + runtime·algarray[AMEM8].hash = runtime·aeshash; + runtime·algarray[AMEM16].hash = runtime·aeshash; + runtime·algarray[AMEM32].hash = runtime·aeshash32; + runtime·algarray[AMEM64].hash = runtime·aeshash64; + runtime·algarray[AMEM128].hash = runtime·aeshash; + runtime·algarray[ASTRING].hash = runtime·aeshashstr; + + // Initialize with random data so hash collisions will be hard to engineer. + runtime·get_random_data(&rnd, &n); + if(n > HashRandomBytes) + n = HashRandomBytes; + runtime·memmove(runtime·aeskeysched, rnd, n); + if(n < HashRandomBytes) { + // Not very random, but better than nothing. + int64 t = runtime·nanotime(); + while (n < HashRandomBytes) { + runtime·aeskeysched[n++] = (int8)(t >> (8 * (n % 8))); + } + } + } +} + // func equal(t *Type, x T, y T) (ret bool) #pragma textflag 7 void |