On Wed, 29 Jul 2020 00:59:33 +0800
Chengming Zhou <zhouchengm...@bytedance.com> wrote:
> > i.e.
> >
> > # echo some_module_function > set_ftrace_filter
> > # rmmod module_with_that_function
> > # insmod module_with_same_address_of_function
> > # echo function > current_tracer
> >
> > Now the tr->ops->hash would still have the function of the original
> > module.
>
> I thought all ftrace_ops has non empty func_hash are on the ftrace
> global list...
Nope, the two are disjoint.
>
> Well, so I just leave this function unmodified.
>
> Just call that new function register_ftrace_ops_hash() from
> ftrace_release_mod.
I would say to have anything that uses one of the
ftrace_set_filter/notrace* functions, to also register itself for
module removal.
register_ftrace_mod_removal(struct ftrace_ops *ops);
and then also have a unregister_ftrace_mod_removal() as there needs to
be a way to remove it from the list before the ops gets freed.
Then these functions would add the ops to a list, and this list is
traversed to remove modules. The trace_arrays can register their ops
too, so you can update that function.
-- Steve
>
> Thanks!
>
> >
> > Either have all owners of ftrace_ops handle this case, or add a helper
> > function to handle it for them. But using ftarce_ops_list is the wrong
> > place to do it.
> >
> > -- Steve
> >
> >
> >> + mutex_lock(&ftrace_lock);
> >> +
> >> + do_for_each_ftrace_op(op, ftrace_ops_list) {
> >> + if (!op->func_hash)
> >> continue;
> >> - mutex_lock(&tr->ops->func_hash->regex_lock);
> >> - clear_mod_from_hash(pg, tr->ops->func_hash->filter_hash);
> >> - clear_mod_from_hash(pg, tr->ops->func_hash->notrace_hash);
> >> - mutex_unlock(&tr->ops->func_hash->regex_lock);
> >> - }
> >> - mutex_unlock(&trace_types_lock);
> >> + mutex_lock(&op->func_hash->regex_lock);
> >> + clear_mod_from_hash(pg, op->func_hash->filter_hash);
> >> + clear_mod_from_hash(pg, op->func_hash->notrace_hash);
> >> + mutex_unlock(&op->func_hash->regex_lock);
> >> + } while_for_each_ftrace_op(op);
> >> +
> >> + mutex_unlock(&ftrace_lock);
> >> }
> >>
> >> static void ftrace_free_mod_map(struct rcu_head *rcu)
