From: Masami Hiramatsu <mhiramat@kernel•org>
To: Masami Hiramatsu <mhiramat@kernel•org>
Cc: "Naveen N. Rao" <naveen.n.rao@linux•vnet.ibm.com>,
Arnaldo Carvalho de Melo <acme@kernel•org>,
Steven Rostedt <rostedt@goodmis•org>,
Ingo Molnar <mingo@redhat•com>,
linux-kernel@vger•kernel.org, linuxppc-dev@lists•ozlabs.org,
Ananth N Mavinakayanahalli <ananth@linux•vnet.ibm.com>,
Michael Ellerman <mpe@ellerman•id.au>
Subject: Re: [PATCH v4 2/3] perf: kretprobes: offset from reloc_sym if kernel supports it
Date: Sat, 4 Mar 2017 11:38:25 +0900 [thread overview]
Message-ID: <20170304113825.bda12eb55495bfe8018638f7@kernel.org> (raw)
In-Reply-To: <20170304113551.6a008b969a3ed713729cbd57@kernel.org>
On Sat, 4 Mar 2017 11:35:51 +0900
Masami Hiramatsu <mhiramat@kernel•org> wrote:
> On Sat, 4 Mar 2017 09:49:11 +0900
> Masami Hiramatsu <mhiramat@kernel•org> wrote:
>
> > On Thu, 2 Mar 2017 23:25:06 +0530
> > "Naveen N. Rao" <naveen.n.rao@linux•vnet.ibm.com> wrote:
> >
> > > We indicate support for accepting sym+offset with kretprobes through a
> > > line in ftrace README. Parse the same to identify support and choose the
> > > appropriate format for kprobe_events.
> >
> > Could you give us an example of this change here? :)
> > for example, comment of commit 613f050d68a8 .
> >
> > I think the code is OK, but we need actual example of result.
>
> Hi Naveen,
>
> I've tried following commands
>
> $ grep "[Tt] user_read$" /proc/kallsyms
> 0000000000000000 T user_read
> 0000000000000000 t user_read
> $ sudo ./perf probe -D user_read%return
> r:probe/user_read _text+3539616
> r:probe/user_read_1 _text+3653408
>
> OK, looks good. However, when I set the retprobes, I got an error.
>
> $ sudo ./perf probe -a user_read%return
> Failed to write event: Invalid argument
> Error: Failed to add events.
>
> And kernel rejected that.
>
> $ dmesg -k | tail -n 1
> [ 850.315068] Given offset is not valid for return probe.
>
> Hmm, curious..
>
> I tried normal probes
>
> $ sudo ./perf probe -D user_read
> p:probe/user_read _text+3539616
> p:probe/user_read_1 _text+3653408
> $ sudo ./perf probe -a user_read
> Added new events:
> probe:user_read (on user_read)
> probe:user_read_1 (on user_read)
>
> You can now use it in all perf tools, such as:
>
> perf record -e probe:user_read_1 -aR sleep 1
>
> It works!
>
> $ sudo ./perf probe -l
> probe:user_read (on user_read@security/keys/user_defined.c)
> probe:user_read_1 (on user_read@selinux/ss/policydb.c)
> $ sudo cat /sys/kernel/debug/kprobes/list
> ffffffff9237bf20 k user_read+0x0 [DISABLED][FTRACE]
> ffffffff923602a0 k user_read+0x0 [DISABLED][FTRACE]
>
> So, the both "_text+3539616" and "_text+3653408" are correctly located
> on the entry address of user_read functions. It seems kernel-side
> symbol+offset check is wrong.
FYI, without this patch, perf probe returns same place for same-name
functions. So this patch itself looks good.
$ sudo ./perf probe -D user_read%return
r:probe/user_read user_read+0
r:probe/user_read_1 user_read+0
Thanks,
--
Masami Hiramatsu <mhiramat@kernel•org>
next prev parent reply other threads:[~2017-03-04 2:38 UTC|newest]
Thread overview: 57+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-02-22 13:53 [PATCH v2 0/5] kretprobe fixes Naveen N. Rao
2017-02-22 13:53 ` [PATCH v2 1/5] kretprobes: ensure probe location is at function entry Naveen N. Rao
2017-02-22 13:53 ` [PATCH v2 2/5] powerpc: kretprobes: override default function entry offset Naveen N. Rao
2017-02-24 19:57 ` Arnaldo Carvalho de Melo
2017-02-27 12:56 ` Michael Ellerman
2017-02-25 2:45 ` Ananth N Mavinakayanahalli
2017-02-22 13:53 ` [PATCH v2 3/5] trace/kprobes: allow return probes with offsets and absolute addresses Naveen N. Rao
2017-02-27 16:32 ` Steven Rostedt
2017-02-27 16:52 ` [PATCH v2 3.5/5] trace/kprobes: Add back warning about offset in return probes Steven Rostedt (VMware)
2017-02-28 0:01 ` Masami Hiramatsu
2017-03-01 15:16 ` Naveen N. Rao
2017-02-22 13:53 ` [PATCH v2 4/5] perf: kretprobes: offset from reloc_sym if kernel supports it Naveen N. Rao
2017-02-23 9:10 ` Masami Hiramatsu
2017-02-23 11:37 ` [PATCH v3 1/2] perf: probe: generalize probe event file open routine Naveen N. Rao
2017-02-24 16:46 ` Masami Hiramatsu
2017-02-24 20:07 ` Arnaldo Carvalho de Melo
2017-03-01 15:12 ` Naveen N. Rao
2017-02-23 11:37 ` [PATCH v3 2/2] perf: kretprobes: offset from reloc_sym if kernel supports it Naveen N. Rao
2017-02-24 17:12 ` Masami Hiramatsu
2017-03-01 15:11 ` Naveen N. Rao
2017-02-23 19:16 ` [PATCH v2 4/5] " Naveen N. Rao
2017-02-24 17:29 ` Masami Hiramatsu
2017-02-24 20:11 ` Arnaldo Carvalho de Melo
2017-02-24 23:55 ` Masami Hiramatsu
2017-03-01 15:14 ` Naveen N. Rao
2017-03-02 17:55 ` Naveen N. Rao
2017-03-02 17:55 ` [PATCH v4 1/3] perf: probe: factor out the ftrace README scanning Naveen N. Rao
2017-03-04 0:09 ` Masami Hiramatsu
2017-03-07 20:45 ` Steven Rostedt
2017-03-02 17:55 ` [PATCH v4 2/3] perf: kretprobes: offset from reloc_sym if kernel supports it Naveen N. Rao
2017-03-04 0:49 ` Masami Hiramatsu
2017-03-04 2:35 ` Masami Hiramatsu
2017-03-04 2:38 ` Masami Hiramatsu [this message]
2017-03-04 4:34 ` Masami Hiramatsu
2017-03-06 16:20 ` Naveen N. Rao
2017-03-06 17:49 ` Naveen N. Rao
2017-03-06 21:06 ` Masami Hiramatsu
2017-03-07 10:47 ` [PATCH v4 2/3] perf: kretprobes: offset from reloc_sym if kernel Naveen N. Rao
2017-03-07 10:47 ` [RESEND PATCH 1/6] trace/kprobes: fix check for kretprobe offset within function entry Naveen N. Rao
2017-03-07 20:47 ` Steven Rostedt
2017-03-08 8:01 ` Naveen N. Rao
2017-03-07 10:47 ` [RESEND PATCH 2/6] powerpc: kretprobes: override default function entry offset Naveen N. Rao
2017-03-07 10:47 ` [RESEND PATCH 3/6] perf: probe: factor out the ftrace README scanning Naveen N. Rao
2017-03-07 10:47 ` [RESEND PATCH 4/6] perf: kretprobes: offset from reloc_sym if kernel supports it Naveen N. Rao
2017-03-07 10:47 ` [PATCH 5/6] perf: probes: move ftrace README parsing logic into trace-event-parse.c Naveen N. Rao
2017-03-07 14:03 ` Masami Hiramatsu
2017-03-07 14:29 ` Naveen N. Rao
2017-03-07 15:51 ` Masami Hiramatsu
2017-03-07 16:31 ` Naveen N. Rao
2017-03-07 10:47 ` [RESEND PATCH 6/6] perf: powerpc: choose local entry point with kretprobes Naveen N. Rao
2017-03-07 16:49 ` [PATCH v2 " Naveen N. Rao
2017-03-06 15:04 ` [PATCH v4 2/3] perf: kretprobes: offset from reloc_sym if kernel supports it Naveen N. Rao
2017-03-06 21:14 ` Masami Hiramatsu
2017-03-02 17:55 ` [PATCH v4 3/3] perf: powerpc: choose local entry point with kretprobes Naveen N. Rao
2017-03-04 0:50 ` Masami Hiramatsu
2017-03-02 19:06 ` [PATCH v2 4/5] perf: kretprobes: offset from reloc_sym if kernel supports it Arnaldo Carvalho de Melo
2017-02-22 13:53 ` [PATCH v2 5/5] perf: powerpc: choose local entry point with kretprobes Naveen N. Rao
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