Maxime Villard wrote: > Le 29/03/2017 ? 00:49, Alexander Nasonov a ?crit : > > I think this should be either all-or-nothing. You either have rdtsc as > > a time source or you don't. Similar for rdpmc (and other performance > > counters). > > Well, the idea was to make the availability more fine-grained. > > > Seeing the general skepticism that prevails, I guess we can just forget about > this idea.
There are two more or less independent things: fine-grained time source and userspace rdtsc. The latter is often used directly when vdso isn't available. If we implement vdso, I assume that software that needs rdtsc can be taught to call it via vdso. With vdso implemented, we can have a flag that enables/disables vdso globally as well as per process (paxctl?). Independetly, the kernel can be configured to use either fine-grained or hackerproof time source for regular (non-vdso) system calls. Alex