commit 8e765da941f4f0649aca2b28234ac31adde45f06
author Damian Gryski <dgryski@gmail.com> Thu Feb 02 14:09:27 2012 -0500
committer Russ Cox <rsc@golang.org> Thu Feb 02 14:09:27 2012 -0500
tree 1decf5c6f8e83df0c7ce68ba49f1dfa805a0804b
parent 16ce2f9369fd76334880a3883ca1def77d41c7e3

runtime: add runtime.cputicks() and seed fastrand with it

This patch adds a function to get the current cpu ticks.  This is
deemed to be 'sufficiently random' to use to seed fastrand to mitigate
the algorithmic complexity attacks on the hash table implementation.

On AMD64 we use the RDTSC instruction.  For 386, this instruction,
while valid, is not recognized by 8a so I've inserted the opcode by
hand.  For ARM, this routine is currently stubbed to return a constant
0 value.

Future work: update 8a to recognize RDTSC.

Fixes #2630.

R=rsc
CC=golang-dev
https://golang.org/cl/5606048