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. > Perhaps system_call_exit_notrace? No that sucks too :( A bit :D If you're tracing etc. then you'll be in syscall_exit_work, isn't that sufficient to differentiate the two? cheers
