From: masami.hiramatsu.pt@hitachi•com (Masami Hiramatsu)
To: linux-arm-kernel@lists•infradead.org
Subject: [PATCH RFC 2/6] arm64: Kprobes with single stepping support
Date: Wed, 13 Nov 2013 23:07:17 +0900 [thread overview]
Message-ID: <52838795.2090106@hitachi.com> (raw)
In-Reply-To: <CA+b37P1sNsEXrJFfVL51sZ-SeGNCBiwXnOwCiFY8CBwSXPw+mQ@mail.gmail.com>
(2013/11/13 15:55), Sandeepa Prabhu wrote:
>>>> 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)
> Hi Will, Masami,
>
> I am not sure of 'perf' right now (my minimal rootfs doesn't have) but
> I tried to test hardware breakpoints using sample modules
> "samples/hw_breakpoint/" on arm64 upstream branch. This should use
> same kernel api as perf I believe.
>
> 1. Placing watchpoint ( attr.bp_type = HW_BREAKPOINT_W |
> HW_BREAKPOINT_R) upon vfs_symlink symbol, but seems watch-point is not
> triggering at all.
> 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!
Did you this without kprobes? If so, the hw_breakpoint porting
on arm64 may have a bug.
> I have attached the kernel logs for reference. So wanted to check if
> hw breakpoint/watch-points are working on the upstream branch? Has it
> been tested recently with sample modules or perf/ptrace?
I've tested on x86 with the latest tip-tree kernel and it worked.
Thank you,
--
Masami HIRAMATSU
IT Management Research Dept. Linux Technology Center
Hitachi, Ltd., Yokohama Research Laboratory
E-mail: masami.hiramatsu.pt at hitachi.com
next prev parent reply other threads:[~2013-11-13 14:07 UTC|newest]
Thread overview: 49+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-10-17 11:17 [PATCH RFC v2 0/6] ARM64: Add kernel probes(Kprobes) support Sandeepa Prabhu
2013-10-17 11:17 ` [PATCH RFC v4 1/6] arm64: support single-step and breakpoint handler hooks Sandeepa Prabhu
2013-10-25 15:22 ` Will Deacon
2013-12-03 14:33 ` Sandeepa Prabhu
2013-12-03 19:44 ` Will Deacon
2013-10-17 11:17 ` [PATCH RFC 2/6] arm64: Kprobes with single stepping support Sandeepa Prabhu
2013-11-08 16:56 ` Will Deacon
2013-11-09 9:10 ` Masami Hiramatsu
2013-11-11 5:39 ` Sandeepa Prabhu
2013-11-11 7:54 ` Masami Hiramatsu
2013-11-11 10:51 ` Masami Hiramatsu
2013-11-11 10:58 ` Will Deacon
2013-11-11 17:32 ` Masami Hiramatsu
2013-11-12 6:23 ` Sandeepa Prabhu
2013-11-12 7:27 ` Masami Hiramatsu
2013-11-12 8:44 ` Sandeepa Prabhu
2013-11-12 10:17 ` Masami Hiramatsu
2013-11-12 10:55 ` Sandeepa Prabhu
2013-11-12 14:11 ` Masami Hiramatsu
2013-11-12 16:59 ` Steven Rostedt
2013-11-13 16:05 ` Masami Hiramatsu
[not found] ` <CA+b37P1sNsEXrJFfVL51sZ-SeGNCBiwXnOwCiFY8CBwSXPw+mQ@mail.gmail.com>
2013-11-13 7:08 ` Sandeepa Prabhu
2013-11-13 14:07 ` Masami Hiramatsu [this message]
2013-11-13 14:31 ` Will Deacon
2013-11-13 15:55 ` Sandeepa Prabhu
2013-11-15 16:39 ` Will Deacon
2013-11-18 6:55 ` Sandeepa Prabhu
2013-11-18 8:51 ` Sandeepa Prabhu
2013-11-13 13:58 ` Peter Zijlstra
2013-11-13 14:20 ` Will Deacon
2013-11-11 5:35 ` Sandeepa Prabhu
2013-11-11 11:21 ` Will Deacon
2013-11-12 6:52 ` Sandeepa Prabhu
2013-11-15 16:37 ` Will Deacon
2013-11-18 6:43 ` Sandeepa Prabhu
2013-10-17 11:17 ` [PATCH RFC 3/6] arm64: Kprobes instruction simulation support Sandeepa Prabhu
2013-11-08 17:03 ` Will Deacon
2013-11-11 5:58 ` Sandeepa Prabhu
2013-10-17 11:17 ` [PATCH RFC 4/6] arm64: Add kernel return probes support(kretprobes) Sandeepa Prabhu
2013-11-08 17:04 ` Will Deacon
2013-11-11 4:29 ` Sandeepa Prabhu
2013-11-11 7:53 ` AKASHI Takahiro
2013-11-11 8:55 ` Sandeepa Prabhu
2013-10-17 11:17 ` [PATCH RFC 5/6] arm64: Enable kprobes support for arm64 platform Sandeepa Prabhu
2013-10-17 11:17 ` [PATCH RFC 6/6] kprobes: Add cases for arm and arm64 in sample module Sandeepa Prabhu
2013-10-25 15:24 ` Will Deacon
2013-11-06 11:05 ` Sandeepa Prabhu
2013-10-18 8:32 ` [PATCH RFC v2 0/6] ARM64: Add kernel probes(Kprobes) support Masami Hiramatsu
2013-10-21 4:17 ` Sandeepa Prabhu
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