linux-kernel - Re: [PATCH] selftests/ftrace: Add a testcase for many kprobe events

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Date:   Fri, 2 Jun 2017 15:37:09 -0600
From:   Shuah Khan <shuah@...nel.org>
To:     Masami Hiramatsu <mhiramat@...nel.org>,
        Ingo Molnar <mingo@...nel.org>
Cc:     Thomas Gleixner <tglx@...utronix.de>,
        Steven Rostedt <rostedt@...dmis.org>,
        Kees Cook <keescook@...omium.org>,
        LKML <linux-kernel@...r.kernel.org>, x86@...nel.org,
        "Luis R . Rodriguez" <mcgrof@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        linux-kselftest@...r.kernel.org, Shuah Khan <shuah@...nel.org>
Subject: Re: [PATCH] selftests/ftrace: Add a testcase for many kprobe events

On 05/25/2017 10:44 PM, Masami Hiramatsu wrote:
> Add a testcase to test kprobes via ftrace interface
> with many concurrent kprobe events.
> 
> This tries to add many kprobe events (up to 256) on
> kernel functions. To avoid making ftrace-based
> kprobes (kprobes on fentry), it skips first N bytes
> (on x86 N=5, on ppc or arm N=4) of function entry.
> After that, it enables all those events, disable it,
> and remove it.
> 
> Since the unoptimization buffer reclaiming will
> be delayed, after removing events, it will wait
> enough time.
> 
> Signed-off-by: Masami Hiramatsu <mhiramat@...nel.org>
> Suggested-by: Steven Rostedt <rostedt@...dmis.org>

Thanks. Applied to linux-kselftest next for 4.13-rc1

-- Shuah

> ---
>  This ensures following bug is fixed and no regression.
> 
>  https://lkml.org/lkml/2017/5/25/218
> ---
>  .../ftrace/test.d/kprobe/multiple_kprobes.tc       |   21 ++++++++++++++++++++
>  1 file changed, 21 insertions(+)
>  create mode 100644 tools/testing/selftests/ftrace/test.d/kprobe/multiple_kprobes.tc
> 
> diff --git a/tools/testing/selftests/ftrace/test.d/kprobe/multiple_kprobes.tc b/tools/testing/selftests/ftrace/test.d/kprobe/multiple_kprobes.tc
> new file mode 100644
> index 0000000..f4d1ff7
> --- /dev/null
> +++ b/tools/testing/selftests/ftrace/test.d/kprobe/multiple_kprobes.tc
> @@ -0,0 +1,21 @@
> +#!/bin/sh
> +# 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
> +case `uname -m` in
> +  x86_64|i[3456]86) OFFS=5;;
> +  ppc*) OFFS=4;;
> +  *) 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 ||:
> +
> +echo 1 > events/kprobes/enable
> +echo 0 > events/kprobes/enable
> +echo > kprobe_events
> +echo "Waiting for unoptimizing & freeing"
> +sleep 5
> +echo "Done"
> 
> 
>