linux-kernel - Re: [PATCH v2 2/3] kprobes: Mark ftrace mcount handler functions nokprobe

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Date:   Wed, 9 Jan 2019 09:31:21 -0500
From:   Steven Rostedt <rostedt@...dmis.org>
To:     Masami Hiramatsu <mhiramat@...nel.org>
Cc:     Ingo Molnar <mingo@...hat.com>, peterz@...radead.org,
        Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
        linux-kernel <linux-kernel@...r.kernel.org>,
        Andrea Righi <righi.andrea@...il.com>, stable@...r.kernel.org
Subject: Re: [PATCH v2 2/3] kprobes: Mark ftrace mcount handler functions
 nokprobe

On Tue,  8 Jan 2019 13:44:54 +0900
Masami Hiramatsu <mhiramat@...nel.org> wrote:

> Mark ftrace mcount handler functions nokprobe since
> probing on these functions with kretprobe pushes
> return address incorrectly on kretprobe shadow stack.
> 
> Signed-off-by: Masami Hiramatsu <mhiramat@...nel.org>
> Reported-by: Francis Deslauriers <francis.deslauriers@...icios.com>
> Tested-by: Andrea Righi <righi.andrea@...il.com>
> Cc: stable@...r.kernel.org

Acked-by: Steven Rostedt (VMware) <rostedt@...dmis.org>

-- Steve

> ---
>  - Changes in v2:
>    Fix to include kprobes.h (Thanks Andrea!)
> ---
>  kernel/trace/ftrace.c |    6 +++++-
>  1 file changed, 5 insertions(+), 1 deletion(-)
> 
> diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
> index f0ff24173a0b..b0774388d52b 100644
> --- a/kernel/trace/ftrace.c
> +++ b/kernel/trace/ftrace.c
> @@ -34,6 +34,7 @@
>  #include <linux/list.h>
>  #include <linux/hash.h>
>  #include <linux/rcupdate.h>
> +#include <linux/kprobes.h>
>  
>  #include <trace/events/sched.h>
>  
> @@ -6250,7 +6251,7 @@ void ftrace_reset_array_ops(struct trace_array *tr)
>  	tr->ops->func = ftrace_stub;
>  }
>  
> -static inline void
> +static nokprobe_inline void
>  __ftrace_ops_list_func(unsigned long ip, unsigned long parent_ip,
>  		       struct ftrace_ops *ignored, struct pt_regs *regs)
>  {
> @@ -6310,11 +6311,13 @@ static void ftrace_ops_list_func(unsigned long ip, unsigned long parent_ip,
>  {
>  	__ftrace_ops_list_func(ip, parent_ip, NULL, regs);
>  }
> +NOKPROBE_SYMBOL(ftrace_ops_list_func);
>  #else
>  static void ftrace_ops_no_ops(unsigned long ip, unsigned long parent_ip)
>  {
>  	__ftrace_ops_list_func(ip, parent_ip, NULL, NULL);
>  }
> +NOKPROBE_SYMBOL(ftrace_ops_no_ops);
>  #endif
>  
>  /*
> @@ -6341,6 +6344,7 @@ 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);
>  
>  /**
>   * ftrace_ops_get_func - get the function a trampoline should call