Messages in this thread | | | Date | Mon, 18 Nov 2013 12:25:05 +0530 | Subject | Re: Re: Re: [PATCH RFC 2/6] arm64: Kprobes with single stepping support | From | Sandeepa Prabhu <> |
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>> This is generic test module (samples/hw_breakpoint/data_breakpoint.ko) >> which places watchpoint for bothe read/write. >> Atleast watchpt should have triggered for Read right? I also tried >> with othe functions like do_fork, vfs_read etc but no hit. > > You'd need to place something for exec if you want to see anything on the > instruction side. A read by the instruction fetcher does not trigger a read > watchpoint on ARM. Hmm, then watchpoint cannot not be placed on text address (instruction fetch path) right? (Sorry I did not check debug spec fully for watchpoint/hw breakpoints, I should do that)
> >> >> 2. Placing text breakpoint (modified sample module with attr.bp_type >> >> = HW_BREAKPOINT_X) upon vfs_symlink, and run "ln -s /dev/null >> >> /tmp/foo". This time, breakpoint hit but exception is re-cursing >> >> infinitely! >> > >> > The problem here is that we expect the overflow handler to deal with the >> > stepping (like GDB does via ptrace). If you don't register a handler, the >> > kernel will do the step (like you would get if you used perf stat -e >> > mem:0xNNNN:x). >> [This test was done on upstream branch, without kprobes patches.] >> Hmm, then this is expected with test breakpoint right? is this >> handling to be done by perf and ptrace? > > perf stat doesn't register an overflow handler, so the hw_breakpoint > backend will handle the step. ptrace registers a handler which sends a > SIGTRAP to the debugger (e.g. gdb), which handles the step manually > (probably using a PTRACE_SINGLESTEP request). > >> I did not see arm64 support in linux/tools/perf/, there are multiple >> patches in mailing list though. Are you aware of any version of perf >> that work with arm64? > > The perf tool should work fine on arm64 using mainline. Are you seeing > problems? Hmm basically perf is working and I can run tests now. > > Will > -- > To unsubscribe from this list: send the line "unsubscribe linux-kernel" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html > Please read the FAQ at http://www.tux.org/lkml/
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