On Thu, Feb 07, 2019 at 09:51:57AM -0500, Steven Rostedt wrote: > On Thu, 7 Feb 2019 10:33:50 +0000 > Julien Thierry <julien.thierry@xxxxxxx> wrote: > > > I don't see really much documentation on that function. As far as I can > > tell it is only called once for each site (and if it didn't, we'd always > > be placing the same instruction, but I agree it wouldn't be nice). It > > could depend on how far you can expand the notion of "adjusting" :) . > > > > Steven, do you have an opinion on whether it would be acceptable to > > modify function entry code in ftrace_call_adjust() ? > > Just to make sure I'm on the same page as you are. You want to modify > the function entry code at the time of the ftrace_call_adjust()? Yes, this was the fiendish plan ;-) > I would update the rec->ip to the offset you want at > ftrace_call_adjust() but not do any modifications. It really isn't safe > to do it there. But right after that is called, you will have the arch > specific call of ftrace_make_nop() called with MCOUNT_ADDR as the > second parameter to let you know that this is the first time the call > is made at this address. This is where you can do that initial > modifications. Ok, so just substitute REC_IP_BRANCH_OFFSET arithmetic with ftrace_call_adjust() and keep the MCOUNT_ADDR logic. Thanks for the clarification. Torsten
