On Wed, 27 Dec 2017 19:45:42 -0800 Alexei Starovoitov <a...@fb.com> wrote:
> I don't think that's the case. My reading of current > trace_kprobe_ftrace() -> arch_check_ftrace_location() > is that it will not be true for old mcount case. In the old mcount case, you can't use ftrace to return without calling the function. That is, no modification of the return ip, unless you created a trampoline that could handle arbitrary stack frames, and remove them from the stack before returning back to the function. > > As far as the rest of your arguments it very much puzzles me that > you claim that this patch suppose to work based on historical > reasoning whereas you did NOT test it. I believe that Masami is saying that the modification of the IP from kprobes has been very well tested. But I'm guessing that you still want a test case for using kprobes in this particular instance. It's not the implementation of modifying the IP that you are worried about, but the implementation of BPF using it in this case. Right? -- Steve
