Messages in this thread | | | From | Rusty Russell <> | Subject | Re: [PATCH 1/5] ftrace: use module notifier for function tracer | Date | Sun, 19 Apr 2009 20:55:02 +0930 |
| |
On Thu, 16 Apr 2009 11:48:31 am Steven Rostedt wrote: > From: Steven Rostedt <srostedt@redhat.com> > > Impact: fix and clean up > > The hooks in the module code for the function tracer must be called > before any of that module code runs. The function tracer hooks > modify the module (replacing calls to mcount to nops). If the code > is executed while the change occurs, then the CPU can take a GPF. > > To handle the above with a bit of paranoia, I originally implemented > the hooks as calls directly from the module code. > > After examining the notifier calls, it looks as though the start up > notify is called before any of the module's code is executed. This makes > the use of the notify safe with ftrace.
Hi Steven,
Unfortunately not: we do parse_args, which can call into the module code. (Though it shouldn't do anything "significant", as it won't get a chance to clean up if module load fails later).
I think you need to do something else in general. Share the module_mutex for the ftrace code? The ksplice guys have a similar issue, so maybe we should generalize this into a "kernel_text" mutex?
Thanks, Rusty.
| |