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runtime: faster & safer hash function

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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
This commit is contained in:
Keith Randall 2013-03-12 10:47:44 -07:00
parent 4e032ce301
commit a5d4024139
23 changed files with 891 additions and 8 deletions
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35
src/pkg/runtime/alg.c
View file

@ -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