linux-kernel - Re: [RFC PATCH -tip 0/9] kprobes: Cleanup jprobe implementation

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Date:   Sat, 10 Mar 2018 09:24:44 +0100
From:   Ingo Molnar <mingo@...nel.org>
To:     Masami Hiramatsu <mhiramat@...nel.org>
Cc:     Thomas Gleixner <tglx@...utronix.de>, x86@...nel.org,
        Yang Bo <yangbo@...pin.com>, Ingo Molnar <mingo@...hat.com>,
        "H . Peter Anvin" <hpa@...or.com>, linux-kernel@...r.kernel.org,
        Ananth N Mavinakayanahalli <ananth@...ux.vnet.ibm.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Steven Rostedt <rostedt@...dmis.org>,
        Laura Abbott <labbott@...hat.com>, Josef Bacik <jbacik@...com>,
        Alexei Starovoitov <ast@...nel.org>
Subject: Re: [RFC PATCH -tip 0/9] kprobes: Cleanup jprobe implementation


* Masami Hiramatsu <mhiramat@...nel.org> wrote:

> Hello,
> 
> Since we decided to remove jprobe from kernel last year,
> its APIs are disabled and we worked on moving in-kernel
> jprobe users to kprobes or trace-events. And now no jprobe
> users are here anymore.
> 
> I think it is good time to get rid of jprobe implementation
> from the kernel. However, I need other arch developers help
> to complete it, since jprobe is implemented multi arch wide.
> I can remove those code, but can not test all of those.
> 
> Here is the series of patches to show how to do that.
> I tried to remove it from x86 tree. Basically we need to
> do 3 things;
> 
>  - Remove jprobe functions (register/unregister,
>    setjump/longjump) from generic/arch-dependent code.
>    [1/9][2/9][3/9]
>  - Remove break_handler related code.
>    [4/9][5/9][6/9]
>  - Do not disable preemption on exception handler
>    [7/9][8/9][9/9]
> 
> The [3/9] and [6/9] are destractive changes except for x86
> (means causes build errors) since those arch still have some
> references of those functions. So we need to write patches
> similar to [2/9] and [5/9] for each arch before applying those.
> In this series I sorted it as this order just for review,
> [3/9] and [6/9] should be applied after all archs have
> been fixed.
> 
> Also, [7/9] is a kind of destractive, which changes required
> behavior for the pre_handlers which changes regs->ip.
> So we also need a patch similar to [7/9] for each arch too.
> Fortunately, current in-tree such user is very limited, both
> works only on x86. So it is not hurry, but we need to change
> arch dependent code.
>
> Thank you,
> 
> ---
> 
> Masami Hiramatsu (9):
>       kprobes: Remove jprobe API implementation
>       x86: kprobes: Remove jprobe implementation
>       kprobes: Remove jprobe data structure and interfaces
>       kprobes: Ignore break_handler
>       x86: kprobes: Ignore break_handler
>       kprobes: Remove break_handler from struct kprobe
>       x86: kprobes: Do not disable preempt on int3 path
>       error-injection: Fix to not enabling preemption in pre_handler
>       tracing: kprobes: Fix to not enabling preemption
> 
> 
>  Documentation/kprobes.txt        |   13 ++--
>  arch/x86/include/asm/kprobes.h   |    3 -
>  arch/x86/kernel/kprobes/common.h |   10 ---
>  arch/x86/kernel/kprobes/core.c   |  114 ++------------------------------------
>  arch/x86/kernel/kprobes/ftrace.c |   21 +------
>  arch/x86/kernel/kprobes/opt.c    |    1 
>  include/linux/kprobes.h          |   54 ------------------
>  kernel/fail_function.c           |    1 
>  kernel/kprobes.c                 |  115 ++------------------------------------
>  kernel/trace/trace_kprobe.c      |    3 -
>  10 files changed, 20 insertions(+), 315 deletions(-)

Nice work, and I love the diffstat, but please do a series that works (builds and 
boots and has working kprobes) at every interim step.

Thanks,

	Ingo