On Tue 2019-10-08 15:35:34, Joe Lawrence wrote: > On Mon, Oct 07, 2019 at 10:17:11AM +0200, Miroslav Benes wrote: > > Livepatch uses ftrace for redirection to new patched functions. It is > > thus directly affected by ftrace sysctl knobs such as ftrace_enabled. > > Setting ftrace_enabled to 0 also disables all live patched functions. It > > is not a problem per se, because only administrator can set sysctl > > values, but it still may be surprising. > > > > Introduce PERMANENT ftrace_ops flag to amend this. If the > > FTRACE_OPS_FL_PERMANENT is set, the tracing of the function is not > > disabled. Such ftrace_ops can still be unregistered in a standard way. > > > > The patch set passes ftrace and livepatch kselftests. > > > > Miroslav Benes (3): > > ftrace: Make test_rec_ops_needs_regs() generic > > ftrace: Introduce PERMANENT ftrace_ops flag > > livepatch: Use FTRACE_OPS_FL_PERMANENT > > > > Documentation/trace/ftrace-uses.rst | 6 ++++ > > Documentation/trace/ftrace.rst | 2 ++ > > include/linux/ftrace.h | 8 +++-- > > kernel/livepatch/patch.c | 3 +- > > kernel/trace/ftrace.c | 47 ++++++++++++++++++++++++----- > > 5 files changed, 55 insertions(+), 11 deletions(-) > > > > -- > > 2.23.0 > > > > Hi Miroslav, > > I wonder if the opposite would be more intuitive: when ftrace_enabled is > not set, don't allow livepatches to register ftrace filters and > likewise, don't allow ftrace_enabled to be unset if any livepatches are > already registered. I guess you could make an argument either way, but > just offering another option. Perhaps livepatches should follow similar > behavior of other ftrace clients (like perf probes?) I am not sure that I understand it correctly. ftrace_enables is a global flag. My expectation is that it can be manipulated at any time. But it should affect only ftrace handlers without FTRACE_OPS_FL_PERMANENT flag. By other words, the handlers with FTRACE_OPS_FL_PERMANENT flag and only these handlers should ignore the global flag. To be even more precise. If a function has registered more ftrace handlers then the global ftrace_enable setting shold affect only the handlers without the flag. Is this the plan, please? Best Regards, Petr
