Hi Ravi, Sorry for replying later. On Mon, 11 Jun 2018 10:01:58 +0530 Ravi Bangoria <ravi.bangoria@xxxxxxxxxxxxx> wrote: > Hi Masami, > > >>> Hmm, it sounds simple... maybe we can increment refctr in install_breakpoint/ > >>> remove_breakpoint? > >> > >> Not really, it would be simpler if I can put it inside install_breakpoint(). > >> Consider an mmap() case. Probed instruction resides in the text section whereas > >> reference counter resides in the data section. These sections gets mapped using > >> separate mmap() calls. So, when process mmaps the text section we will change the > >> instruction, but section holding the reference counter may not have been mapped > >> yet in the virtual memory. If so, we will fail to update the reference counter. > > > > Got it. > > In such case, maybe we can hook the target page mmapped and do install_breakpoint() > > at that point. Since the instruction is protected by a refctr, unless mmap the > > page on where the refctr is, the program doesn't reach the tracepoint. Is that right? > > > > You mean, when mmap(text) happens, save the target page somewhere and when > mmap(data) happens, update both instruction and ref_ctr? Yes. I think you can just clone the target(text) page but not install breakpoint, and if mmap(data) happens, update both. > > This sounds feasible. Let me think on it. Thanks! > > Thanks for suggestion, > Ravi > -- Masami Hiramatsu <mhiramat@xxxxxxxxxx> -- To unsubscribe from this list: send the line "unsubscribe linux-doc" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
