On Thu, 22 Jun 2017 21:14:21 +1000 Michael Ellerman <m...@ellerman.id.au> wrote:
> Nicholas Piggin <npig...@gmail.com> writes: > > > On Thu, 22 Jun 2017 00:08:40 +0530 > > "Naveen N. Rao" <naveen.n....@linux.vnet.ibm.com> wrote: > > > >> It is actually safe to probe system_call() in entry_64.S, but only till > >> we unset MSR_RI. To allow this, add a new symbol system_call_exit() > >> after the mtmsrd and blacklist that. Though the mtmsrd instruction > >> itself is now whitelisted, we won't be allowed to probe on it as we > >> don't allow probing on rfi and mtmsr instructions (checked for in > >> arch_prepare_kprobe()). > > > > Can you add a little comment to say probes aren't allowed, and it's > > located after the mtmsr in order to avoid contaminating traces? > > > > Also I wonder if a slightly different name would be more instructive? > > I don't normally care, but the system_call_common code isn't trivial > > to follow. system_call_exit might give the impression that it is the > > entire exit path (which would pair with system_call for entry). > > It is the entire path in the happy case isn't it? I'm not sure I know > what you mean. Oh, yes you're right, I thought it was moved down further. Thanks, Nick
