linux-kernel - Re: [PATCH 2/2] kprobe: fix: Add ftrace_ops_assist

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Message-ID: <20170714142900.1c91949c@gandalf.local.home>
Date:   Fri, 14 Jul 2017 14:29:00 -0400
From:   Steven Rostedt <rostedt@...dmis.org>
To:     Francis Deslauriers <francis.deslauriers@...icios.com>
Cc:     mhiramat@...nel.org, peterz@...radead.org,
        mathieu.desnoyers@...icios.com, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/2] kprobe: fix: Add ftrace_ops_assist_func to kprobe
 blacklist

On Fri, 14 Jul 2017 10:58:35 -0400
Francis Deslauriers <francis.deslauriers@...icios.com> wrote:

> This function is called when a kprobe is hit. Thus it should be
> blacklisted to prevent kprobe to be triggered by kprobes.
> 
> Signed-off-by: Francis Deslauriers <francis.deslauriers@...icios.com>
> ---
>  kernel/trace/ftrace.c | 2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
> index b308be3..c473d9b 100644
> --- a/kernel/trace/ftrace.c
> +++ b/kernel/trace/ftrace.c
> @@ -36,6 +36,7 @@
>  
>  #include <trace/events/sched.h>
>  
> +#include <asm/kprobes.h>
>  #include <asm/sections.h>
>  #include <asm/setup.h>
>  
> @@ -5739,6 +5740,7 @@ static void ftrace_ops_assist_func(unsigned long ip, unsigned long parent_ip,
>  	preempt_enable_notrace();
>  	trace_clear_recursion(bit);
>  }
> +NOKPROBE_SYMBOL(ftrace_ops_assist_func);

Continuing from what I said in the other email, this is fixing a
symptom and not the problem. The real fix will be much more involved. I
have a good idea on how to accomplish it too.

-- Steve


>  
>  /**
>   * ftrace_ops_get_func - get the function a trampoline should call