On 12 November 2013 12:57, Masami Hiramatsu <masami.hiramatsu...@hitachi.com> wrote: > (2013/11/12 15:23), Sandeepa Prabhu wrote: >>>>> OK, I've ensured that the hw_breakpoint (from perf) can work >>>>> with kprobes (from ftrace) at the same address on x86. >>>>> So if arm64 already support hw_breakpoint on perf, kprobes should >>>>> work with it. >>>> >>>> Single-stepping on x86 is different to the step behaviour on arm64 afaik. >>>> On >>>> ARM, we have to manually remove the breakpoint, perform a single-step, then >>>> add the breakpoint again. If we re-enable debug exceptions in the kprobe >>>> handler, the step will complete early and we'll never step off the >>>> breakpoint. >>> >>> I'm unsure about arm64's debug feature behavior, what does happen when >>> it performs a single-step on sw-breakpoint? >>> >>>> Sandeepa: I think you need to retry Masami's test on the arm64 model, since >>>> I'm fairly sure it won't work as expected without some additional code. >>> >>> OK, anyway, for testing same one, we need to port ftrace first. So the next > > Sorry for confusion, s/next/fallback is what I meant. Making a kprobe module > can be done without ftrace port. Yes, got it, all my verification until now are done using sample modules only, looking out for perf (or some other mechanism: ptrace?) that uses v8 hw breakpoint. > >>> plan is to make a kprobe module to put a probe (which just printk something) >>> on a specific function (e.g. vfs_symlink), and run perf record with >>> hw-breakpoint as below >>> >>> $ perf record -e "mem:0xXXXXXX:k" ln -s /dev/null /tmp/foo >>> >>> Note that 0xXXXXXX is the address of vfs_symlink. >>> >>> After that, you can see the message in dmesg and also check the perf result >>> with "sudo perf script --dump" (you can find a PERF_RECORD_SAMPLE entry if >>> it works) >> Thanks for steps, ARM64 ftrace patches are under review on arm mailing >> list, I can contact the (linaro) developer implementing ftrace on >> what's supported and then figure-out a way to test this concurrency of >> kprobes breakpoint and hardware breakpoint. > > Would you mean this? :) > http://www.spinics.net/lists/arm-kernel/msg278477.html > > Wow, it seems that this also has some works around instruction > manipulation (and confusable filenames...) I referred to: http://lwn.net/Articles/572323/ which is another implementation and on LAKML
> > Thank you, > > -- > Masami HIRAMATSU > IT Management Research Dept. Linux Technology Center > Hitachi, Ltd., Yokohama Research Laboratory > E-mail: masami.hiramatsu...@hitachi.com > > -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
