Messages in this thread | | | From | Andy Lutomirski <> | Date | Mon, 3 Feb 2014 14:08:43 -0800 | Subject | Re: [PATCH] audit: Only use the syscall slowpath when syscall audit rules exist |
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On Mon, Feb 3, 2014 at 12:23 PM, Steve Grubb <sgrubb@redhat.com> wrote: > On Monday, February 03, 2014 09:53:23 AM Andy Lutomirski wrote: >> This toggles TIF_SYSCALL_AUDIT as needed when rules change instead of >> leaving it set whenever rules might be set in the future. This reduces >> syscall latency from >60ns to closer to 40ns on my laptop. > > Does this mean that we have processes that don't have the TIF_SYSCALL_AUDIT > flag set? When rules get loaded, how do we get the flag put back into all > processes?
By looping over all processes and setting the flag, which is what my patch does.
> > The theory of ops is supposed to be that for anyone not needing audit, there > is only the cost of "if (tif & TIF_SYSCALL_AUDIT)".
On current kernels *all* processes have TIF_SYSCALL_AUDIT, even if they don't need auditing because there's nothing to audit. So everything pays the full cost.
> That should be it. If you > have audit enabled or had it enabled (which means it might be loaded with new > rules), we want to inspect the syscall. >
My point is that there's nothing to inspect -- there are no rules. Unless the audit code needs to do something just in case a non-syscall audit event gets written, in which case the audit code should IMO be fixed. (This is what Eric is talking about, I think.)
--Andy
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