On Tue, 23 Aug 2016 21:13:00 -0400 Jessica Yu <jeyu@xxxxxxxxxx> wrote: > Hi Masami, Petr, > > I'm trying to figure out where we are exactly with fixing the problems with > livepatch + kprobes, and I was wondering if there will be any more updates to > the ipmodify patchset that was originally merged back in 2014 (See: > https://lkml.org/lkml/2014/11/20/808). It seems that patch 4/5 ("kprobes: Set > IPMODIFY flag only if the probe can change regs->ip") wasn't merged due to > other ongoing work, and this patch in particular was needed to enforce a hard > conflict between livepatch and jprobes while still enabling livepatch and > kprobes to co-exist. Hmm, it seems I have missed to follow it up. I'll try refresh it for the latest kernel again. > Currently, it looks like livepatch/kpatch and kprobes are still in direct > conflict, since both kprobe_ftrace_ops and klp_ops have FTRACE_OPS_FL_IPMODIFY > set. *But* it seems like this mutual exclusion wasn't 100% implemented; I'm > not sure if this was intentional, but kprobes registration will still return > success even when ftrace registration fails due to an ipmodify conflict, and > instead we just get WARNs (See: arm_kprobe_ftrace()). > > So we still end up with buggy situations like the following: > (1) livepatch patches meminfo_proc_show [ succeeds ] > (2) systemtap probes meminfo_proc_show (using kprobes) [ fails ] > * BUT from the user's perspective, it would look like systemtap succeeded, > since register_kprobe() returned success, but the handler will never fire > and only when we look at dmesg do we see that something went wrong > (i.e. ftrace registration had failed since livepatch already reserved > ipmodify in step 1). > > From what I understand though, there was work being planned to limit this > direct conflict to just livepatch and jprobes, since most of the time kprobes > doesn't change regs->ip. Just wondering what the current state of this work is. Right, jprobes and livepatch can not work together, but kprobe should be available. Thanks, -- Masami Hiramatsu <mhiramat@xxxxxxxxxx> -- To unsubscribe from this list: send the line "unsubscribe live-patching" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
