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    SubjectRe: [PATCH 2/2] selftests/ftrace: Update multiple kprobes test for powerpc
    On Sat, 24 Jun 2017 02:30:21 +0900
    Masami Hiramatsu <mhiramat@kernel.org> wrote:

    > On Thu, 22 Jun 2017 22:33:25 +0530
    > "Naveen N. Rao" <naveen.n.rao@linux.vnet.ibm.com> wrote:
    >
    > > 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.
    >
    > Yes, and that is not what this testcase is aiming to. That testcase should
    > be a separated one, with correct error handling.

    Hi Naveen,

    Here is the testcase which I meant above. This may help if there is any
    regression related to this specific issue.

    Thank you,

    -----

    selftests: ftrace: Add a testcase for kprobe event naming

    From: Masami Hiramatsu <mhiramat@kernel.org>

    Add a testcase for kprobe event naming. This testcase
    checks whether the kprobe events can automatically ganerate
    its event name on normal function and dot-suffixed function.
    Also it checks whether the kprobe events can correctly
    define new event with given event name and group name.

    Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org>
    ---
    .../ftrace/test.d/kprobe/kprobe_eventname.tc | 28 ++++++++++++++++++++
    1 file changed, 28 insertions(+)
    create mode 100644 tools/testing/selftests/ftrace/test.d/kprobe/kprobe_eventname.tc

    diff --git a/tools/testing/selftests/ftrace/test.d/kprobe/kprobe_eventname.tc b/tools/testing/selftests/ftrace/test.d/kprobe/kprobe_eventname.tc
    new file mode 100644
    index 0000000..d259031
    --- /dev/null
    +++ b/tools/testing/selftests/ftrace/test.d/kprobe/kprobe_eventname.tc
    @@ -0,0 +1,28 @@
    +#!/bin/sh
    +# description: Kprobe event auto/manual naming
    +
    +disable_events
    +echo > kprobe_events
    +
    +:;: "Add an event on function without name" ;:
    +
    +FUNC=`grep -m 10 " [tT] [^.]*$" /proc/kallsyms | tail -n 1 | cut -f 3 -d " "`
    +echo p $FUNC > kprobe_events
    +test -d events/kprobes/p_${FUNC}_0 || exit_failure
    +
    +:;: "Add an event on function with new name" ;:
    +
    +echo p:event1 $FUNC > kprobe_events
    +test -d events/kprobes/event1 || exit_failure
    +
    +:;: "Add an event on function with new name and group" ;:
    +
    +echo p:kprobes2/event2 $FUNC > kprobe_events
    +test -d events/kprobes2/event2 || exit_failure
    +
    +:;: "Add an event on dot function without name" ;:
    +
    +FUNC=`grep -m 10 " [tT] .*\..*$" /proc/kallsyms | tail -n 1 | cut -f 3 -d " "`
    +echo p $FUNC > kprobe_events
    +EVENT=`grep $FUNC kprobe_events | cut -f 1 -d " " | cut -f 2 -d:` || exit_failure
    +test -d events/$EVENT || exit_failure
    --
    Masami Hiramatsu <mhiramat@kernel.org>
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