On Wed, Mar 28, 2018 at 11:37:06AM -0400, Mathieu Desnoyers wrote: > ----- On Mar 28, 2018, at 11:28 AM, Peter Zijlstra peterz@xxxxxxxxxxxxx wrote: > > > On Wed, Mar 28, 2018 at 11:14:05AM -0400, Mathieu Desnoyers wrote: > > > >> > If at all possible I would make it SIGSEGV when issueing SYSCALL()s from > >> > within an RSEQ. > >> > >> What's the goal there ? rseq critical sections can technically do system calls > >> if they wish. Why prevent this ? > > > > This all started as a way to do 'small' _fast_ per-cpu ops, System calls > > do NOT fit in that pattern. If you're willing to do a system calls the > > cost of atomics is not a problem. > > I'm not arguing that a typical rseq would do a system call. I'm merely > pointing out that if we start putting arbitrary limitations like "SIGSEGV > when a fork or system call is encountered on top of rseq", this will cause > pain in user-space. I don't think disallowing system calls is arbitrary. And I think that is something we really want to enforce, because it's batshit insane to allow. And if we allow now, people _will_ use it and we can't ever take it away again. -- To unsubscribe from this list: send the line "unsubscribe linux-api" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
