Messages in this thread |  | | Date | Thu, 23 Aug 2018 10:18:31 +0900 | From | Masami Hiramatsu <> | Subject | Re: [BUGFIX PATCH] tracing/kprobes: Fix to check notrace function with correct range |
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On Wed, 22 Aug 2018 08:58:09 -0400 Steven Rostedt <rostedt@goodmis.org> wrote:
> On Tue, 21 Aug 2018 09:42:49 -0400 > Steven Rostedt <rostedt@goodmis.org> wrote: > > > On Tue, 21 Aug 2018 22:04:57 +0900 > > Masami Hiramatsu <mhiramat@kernel.org> wrote: > > > > > Fix within_notrace_func() to check notrace function correctly. > > > > > > Since the ftrace_location_range(start, end) function checks > > > the range inclusively (start <= ftrace-loc <= end), the end > > > address must not include the entry address of next function. > > > > > > However, within_notrace_func() uses kallsyms_lookup_size_offset() > > > to get the function size and calculate the end address from > > > adding the size to the entry address. This means the end address > > > is the entry address of the next function. > > > > > > In the result, within_notrace_func() fails to find notrace > > > function if the next function of the target function is > > > ftraced. > > > > > > Let's subtract 1 from the end address so that ftrace_location_range() > > > can check it correctly. > > > > > > Fixes: commit 45408c4f9250 ("tracing: kprobes: Prohibit probing on notrace function") > > > Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org> > > > Reported-by: Michael Rodin <michael@rodin.online> > > > --- > > > > > > > Applied. Thanks Masami! I'll start testing this and send it upstream > > when it's finished. > > > > Hmm, this fix shows the extent of not tracing functions with notrace > attched much deeper. For one thing, we can't hook kprobes to the > __schedule() function (which is now what all the main schedule > functions call). One of my tests used this function to test kprobes and > it failed. > > I'll push this to Linus, but I'm wondering if we want to perhaps add a > white list of functions marked "notrace" but still kprobes can trace?
Yes, that is what I'm thinking about. Maybe most of notrace function is safe for kprobes (like __schedule()). And if it is really critical, those functions must be marked by NOKPROBE_SYMBOL().
Thank you,
-- Masami Hiramatsu <mhiramat@kernel.org>
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