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From: Randy Dunlap <rdunlap@infradead.org>
To: Masami Hiramatsu <mhiramat@kernel.org>,
	Thomas Gleixner <tglx@linutronix.de>,
	Ingo Molnar <mingo@kernel.org>
Cc: Ingo Molnar <mingo@redhat.com>, "H . Peter Anvin" <hpa@zytor.com>,
	linux-kernel@vger.kernel.org,
	Ananth N Mavinakayanahalli <ananth@linux.vnet.ibm.com>,
	Andrew Morton <akpm@linux-foundation.org>,
	Steven Rostedt <rostedt@goodmis.org>,
	linux-arch@vger.kernel.org, Jonathan Corbet <corbet@lwn.net>,
	linux-doc@vger.kernel.org
Subject: Re: [PATCH -tip v6 26/27] Documentation: kprobes: Add how to change the execution path
Date: Tue, 19 Jun 2018 09:31:49 -0700
Message-ID: <706832c5-dab4-f806-96d6-2cdc37203d9d@infradead.org> (raw)
In-Reply-To: <152942500680.15209.12374262914863044775.stgit@devbox>

On 06/19/2018 09:16 AM, Masami Hiramatsu wrote:
> Add a section that explaining how to change the execution
> path with kprobes and warnings for some arch.
> 
> Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org>
> Cc: Jonathan Corbet <corbet@lwn.net>
> Cc: linux-doc@vger.kernel.org
> ---
>  Documentation/kprobes.txt |   20 ++++++++++++++++++++
>  1 file changed, 20 insertions(+)
> 
> diff --git a/Documentation/kprobes.txt b/Documentation/kprobes.txt
> index 3e9e99ea751b..8a98eed1521b 100644
> --- a/Documentation/kprobes.txt
> +++ b/Documentation/kprobes.txt
> @@ -80,6 +80,26 @@ After the instruction is single-stepped, Kprobes executes the
>  "post_handler," if any, that is associated with the kprobe.
>  Execution then continues with the instruction following the probepoint.
>  

Hi,
I have a few small suggestions...


> +Changing Execution Path
> +-----------------------
> +
> +Since the kprobes can probe into a running kernel code, it can change

   Since kprobes can probe into running kernel code, it can change

> +the register set, including instruction pointer. This operation
> +requires maximum attention, such as keeping the stack frame, recovering
> +execution path etc. Since it is operated on running kernel and need deep

                       Since it operates on a running kernel and needs deep

> +knowladge of the archtecture and concurrent computing, you can easily

   knowledge of the architecture

> +shot your foot.

   shoot

> +
> +If you change the instruction pointer (and set up other related
> +registers) in pre_handler, you must return !0 so that the kprobes

                                                 so that kprobes

> +stops single stepping and just returns to given address.

                                          to the given address.

> +This also means post_handler should not be called anymore.
> +
> +Note that this operation may be harder on some architectures which
> +use TOC (Table of Contents) for function call, since you have to
> +setup new TOC for your function in your module, and recover old

   setup a new TOC for your function in your module, and recover the old

> +one after back from it.

   one after returning from it.

> +
>  Return Probes
>  -------------


-- 
~Randy

  reply index

Thread overview: 33+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-06-19 16:04 [PATCH -tip v6 00/27] kprobes: Cleanup jprobe implementation Masami Hiramatsu
2018-06-19 16:04 ` [PATCH -tip v6 01/27] Documentation/kprobes: Fix to remove remaining jprobe Masami Hiramatsu
2018-06-19 16:05 ` [PATCH -tip v6 02/27] kprobes: Remove jprobe API implementation Masami Hiramatsu
2018-06-19 16:05 ` [PATCH -tip v6 03/27] kprobes/x86: Remove jprobe implementation Masami Hiramatsu
2018-06-19 16:06 ` [PATCH -tip v6 04/27] ARC: kprobes: " Masami Hiramatsu
2018-06-19 16:06 ` [PATCH -tip v6 05/27] ARM: kprobes: Remove jprobe arm implementation Masami Hiramatsu
2018-06-19 16:07 ` [PATCH -tip v6 06/27] arm64: kprobes: Remove jprobe implementation Masami Hiramatsu
2018-06-19 16:07 ` [PATCH -tip v6 07/27] powerpc/kprobes: Remove jprobe powerpc implementation Masami Hiramatsu
2018-06-19 16:08 ` [PATCH -tip v6 08/27] ia64: kprobes: Remove jprobe implementation Masami Hiramatsu
2018-06-19 16:08 ` [PATCH -tip v6 09/27] MIPS: " Masami Hiramatsu
2018-06-19 16:08 ` [PATCH -tip v6 10/27] s390/kprobes: " Masami Hiramatsu
2018-06-19 16:09 ` [PATCH -tip v6 11/27] sh: kprobes: " Masami Hiramatsu
2018-06-19 16:09 ` [PATCH -tip v6 12/27] sparc64: " Masami Hiramatsu
2018-06-19 16:10 ` [PATCH -tip v6 13/27] kprobes: Don't check the ->break_handler() in generic kprobes code Masami Hiramatsu
2018-06-19 16:10 ` [PATCH -tip v6 14/27] kprobes/x86: Don't call ->break_handler() in x86 kprobes Masami Hiramatsu
2018-06-19 16:11 ` [PATCH -tip v6 15/27] ARC: kprobes: Don't call the ->break_handler() in ARC kprobes code Masami Hiramatsu
2018-06-19 16:11 ` [PATCH -tip v6 16/27] ARM: kprobes: Don't call the ->break_handler() in arm " Masami Hiramatsu
2018-06-19 16:12 ` [PATCH -tip v6 17/27] arm64: kprobes: Don't call the ->break_handler() in arm64 " Masami Hiramatsu
2018-06-19 16:12 ` [PATCH -tip v6 18/27] powerpc/kprobes: Don't call the ->break_handler() in powerpc " Masami Hiramatsu
2018-06-19 16:13 ` [PATCH -tip v6 19/27] ia64: kprobes: Don't call the ->break_handler() in ia64 " Masami Hiramatsu
2018-06-19 16:13 ` [PATCH -tip v6 20/27] MIPS: kprobes: Don't call the ->break_handler() in MIPS " Masami Hiramatsu
2018-06-19 16:14 ` [PATCH -tip v6 21/27] s390/kprobes: Don't call the ->break_handler() in s390 " Masami Hiramatsu
2018-06-19 16:14 ` [PATCH -tip v6 22/27] sh: kprobes: Don't call the ->break_handler() in SH " Masami Hiramatsu
2018-06-19 16:15 ` [PATCH -tip v6 23/27] sparc64: kprobes: Don't call the ->break_handler() in sparc64 " Masami Hiramatsu
2018-06-19 16:15 ` [PATCH -tip v6 24/27] bpf: error-inject: kprobes: Clear current_kprobe and enable preempt in kprobe Masami Hiramatsu
2018-06-19 16:16 ` [PATCH -tip v6 25/27] kprobes/x86: Do not disable preempt on int3 path Masami Hiramatsu
2018-06-19 16:16 ` [PATCH -tip v6 26/27] Documentation: kprobes: Add how to change the execution path Masami Hiramatsu
2018-06-19 16:31   ` Randy Dunlap [this message]
2018-06-20  8:26     ` Masami Hiramatsu
2018-06-21 10:35       ` Ingo Molnar
2018-06-22  6:07         ` Masami Hiramatsu
2018-06-22  9:15           ` [tip:perf/core] kprobes/Documentation: Fix various typos tip-bot for Masami Hiramatsu
2018-06-19 16:17 ` [PATCH -tip v6 27/27] kprobes: Remove jprobe stub API Masami Hiramatsu

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