On Fri, 8 Jul 2016 22:24:55 +0200 Torsten Duwe <duwe@xxxxxx> wrote: > On Fri, Jul 08, 2016 at 11:57:10AM -0400, Steven Rostedt wrote: > > On Fri, 8 Jul 2016 10:48:24 -0500 > > Josh Poimboeuf <jpoimboe@xxxxxxxxxx> wrote: > > > > > > Here, with -fprolog-pad, it's already a nop, so no change is needed. > > > > > Yes, exactly. > > > That's what I was thinking. But as I stated in another email (probably > > in the air when you wrote this), the call to ftrace_modify_code() may be > > completely circumvented by ftrace_make_nop() if the addr is MCOUNT_ADDR. > > Only on the _first_ invocation. Later on, tracing can be switched on and off, > and then the instructions need to be changed just like with fentry (or > profile-kernel ;-) > Understood, but ftrace_modify_code() will only receive addr == MCOUNT_ADDR on boot up or when a module is loaded. In both cases, with -fprolog-pad it will already be a nop, hence no need to call ftrace_modify_code(), in those cases. In all other cases, addr will point to a ftrace trampoline. -- Steve -- To unsubscribe from this list: send the line "unsubscribe linux-arch" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
