(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. >> 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...) 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/