From: "Naveen N. Rao" <naveen.n.rao@linux.vnet.ibm.com>
To: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Steven Rostedt <rostedt@goodmis.org>,
Ananth N Mavinakayanahalli <ananth@linux.vnet.ibm.com>,
Michael Ellerman <mpe@ellerman.id.au>,
linux-kernel@vger.kernel.org, linuxppc-dev@lists.ozlabs.org
Subject: Re: [PATCH 2/2] selftests/ftrace: Update multiple kprobes test for powerpc
Date: Thu, 22 Jun 2017 22:33:25 +0530 [thread overview]
Message-ID: <20170622170325.qznheui7eydkdnmv@naverao1-tp.localdomain> (raw)
In-Reply-To: <20170622180738.e97092d4fa6458b9199a03d7@kernel.org>
On 2017/06/22 06:07PM, Masami Hiramatsu wrote:
> On Thu, 22 Jun 2017 00:20:28 +0530
> "Naveen N. Rao" <naveen.n.rao@linux.vnet.ibm.com> wrote:
>
> > KPROBES_ON_FTRACE is only available on powerpc64le. Update comment to
> > clarify this.
> >
> > Also, we should use an offset of 8 to ensure that the probe does not
> > fall on ftrace location. The current offset of 4 will fall before the
> > function local entry point and won't fire, while an offset of 12 or 16
> > will fall on ftrace location. Offset 8 is currently guaranteed to not be
> > the ftrace location.
>
> OK, these part seems good to me.
>
> >
> > Finally, do not filter out symbols with a dot. Powerpc Elfv1 uses dot
> > prefix for all functions and this prevents us from testing some of those
> > symbols. Furthermore, with the patch to derive event names properly in
> > the presence of ':' and '.', such names are accepted by kprobe_events
> > and constitutes a good test for those symbols.
>
> Hmm, the reason why I added such filter was to avoid symbols including
> gcc-generated suffixes like as .constprop or .isra etc.
I see.
I do wonder -- is there a problem if we try probing those symbols? On my
local x86 vm, I don't see an issue probing it especially with the
previous patch to enable probing with symbols having a '.' or ':'.
Furthermore, since this is for testing kprobe_events, I feel it is good
to try probing those symbols too to catch any weird errors we may hit.
Thanks for the review!
- Naveen
> So if the Powerpc Elfv1 use dot prefix, that is OK, in that case,
> could you update the filter as "^.*\\..*" ?
>
> Thank you,
>
> >
> > Signed-off-by: Naveen N. Rao <naveen.n.rao@linux.vnet.ibm.com>
> > ---
> > tools/testing/selftests/ftrace/test.d/kprobe/multiple_kprobes.tc | 8 ++++----
> > 1 file changed, 4 insertions(+), 4 deletions(-)
> >
> > diff --git a/tools/testing/selftests/ftrace/test.d/kprobe/multiple_kprobes.tc b/tools/testing/selftests/ftrace/test.d/kprobe/multiple_kprobes.tc
> > index f4d1ff785d67..d209c071b2c0 100644
> > --- a/tools/testing/selftests/ftrace/test.d/kprobe/multiple_kprobes.tc
> > +++ b/tools/testing/selftests/ftrace/test.d/kprobe/multiple_kprobes.tc
> > @@ -2,16 +2,16 @@
> > # description: Register/unregister many kprobe events
> >
> > # ftrace fentry skip size depends on the machine architecture.
> > -# Currently HAVE_KPROBES_ON_FTRACE defined on x86 and powerpc
> > +# Currently HAVE_KPROBES_ON_FTRACE defined on x86 and powerpc64le
> > case `uname -m` in
> > x86_64|i[3456]86) OFFS=5;;
> > - ppc*) OFFS=4;;
> > + ppc64le) OFFS=8;;
> > *) OFFS=0;;
> > esac
> >
> > echo "Setup up to 256 kprobes"
> > -grep t /proc/kallsyms | cut -f3 -d" " | grep -v .*\\..* | \
> > -head -n 256 | while read i; do echo p ${i}+${OFFS} ; done > kprobe_events ||:
> > +grep t /proc/kallsyms | cut -f3 -d" " | head -n 256 | \
> > +while read i; do echo p ${i}+${OFFS} ; done > kprobe_events ||:
> >
> > echo 1 > events/kprobes/enable
> > echo 0 > events/kprobes/enable
> > --
> > 2.13.1
> >
>
>
> --
> Masami Hiramatsu <mhiramat@kernel.org>
>
next prev parent reply other threads:[~2017-06-22 17:04 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-06-21 18:50 [PATCH 0/2] A couple of small updates/fixes for kprobes tracer Naveen N. Rao
2017-06-21 18:50 ` [PATCH 1/2] trace/kprobes: Sanitize derived event names Naveen N. Rao
2017-06-22 9:29 ` Masami Hiramatsu
2017-06-22 19:03 ` Naveen N. Rao
2017-06-23 17:30 ` Masami Hiramatsu
2017-06-21 18:50 ` [PATCH 2/2] selftests/ftrace: Update multiple kprobes test for powerpc Naveen N. Rao
2017-06-22 9:07 ` Masami Hiramatsu
2017-06-22 17:03 ` Naveen N. Rao [this message]
2017-06-23 17:30 ` Masami Hiramatsu
2017-06-24 11:06 ` Masami Hiramatsu
2017-06-28 9:28 ` Naveen N. Rao
2017-06-28 14:16 ` Masami Hiramatsu
2017-06-28 18:43 ` Naveen N. Rao
2017-06-29 0:57 ` Masami Hiramatsu
2017-06-29 13:08 ` Naveen N. Rao
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20170622170325.qznheui7eydkdnmv@naverao1-tp.localdomain \
--to=naveen.n.rao@linux.vnet.ibm.com \
--cc=ananth@linux.vnet.ibm.com \
--cc=linux-kernel@vger.kernel.org \
--cc=linuxppc-dev@lists.ozlabs.org \
--cc=mhiramat@kernel.org \
--cc=mpe@ellerman.id.au \
--cc=rostedt@goodmis.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).