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

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Message-Id: <20190108114050.25e64eeb80aab51fc70fc07d@kernel.org>
Date:   Tue, 8 Jan 2019 11:40:50 +0900
From:   Masami Hiramatsu <mhiramat@...nel.org>
To:     Andrea Righi <righi.andrea@...il.com>
Cc:     Ingo Molnar <mingo@...hat.com>, peterz@...radead.org,
        Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
        linux-kernel <linux-kernel@...r.kernel.org>,
        Steven Rostedt <rostedt@...dmis.org>
Subject: Re: [PATCH 2/2] kprobes: Mark ftrace mcount handler functions
 nokprobe

On Mon, 7 Jan 2019 15:55:36 +0100
Andrea Righi <righi.andrea@...il.com> wrote:

> On Mon, Jan 07, 2019 at 10:32:32PM +0900, Masami Hiramatsu 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>
> > ---
> >  kernel/trace/ftrace.c |    5 ++++-
> >  1 file changed, 4 insertions(+), 1 deletion(-)
> > 
> > diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
> > index f0ff24173a0b..ad4babad4a03 100644
> > --- a/kernel/trace/ftrace.c
> > +++ b/kernel/trace/ftrace.c
> > @@ -6250,7 +6250,7 @@ void ftrace_reset_array_ops(struct trace_array *tr)
> >  	tr->ops->func = ftrace_stub;
> >  }
> >  
> > -static inline void
> > +static nokprobe_inline void
> 
> I think we need to #include <linux/kprobes.h>, otherwise:
> 
>   CC      kernel/trace/ftrace.o
> kernel/trace/ftrace.c:6219:24: error: expected ‘=’, ‘,’, ‘;’, ‘asm’ or ‘__attribute__’ before ‘void’
>  static nokprobe_inline void
>                         ^~~~
> 
>  kernel/trace/ftrace.c | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
> index 3a58ad280d83..0333241034d5 100644
> --- a/kernel/trace/ftrace.c
> +++ b/kernel/trace/ftrace.c
> @@ -32,6 +32,7 @@
>  #include <linux/sort.h>
>  #include <linux/list.h>
>  #include <linux/hash.h>
> +#include <linux/kprobes.h>
>  #include <linux/rcupdate.h>
>  
>  #include <trace/events/sched.h>


Oops, I missed it while reordering other patches...

Thank you,

> 
> Thanks,
> -Andrea
> 
> >  __ftrace_ops_list_func(unsigned long ip, unsigned long parent_ip,
> >  		       struct ftrace_ops *ignored, struct pt_regs *regs)
> >  {
> > @@ -6310,11 +6310,13 @@ 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 +6343,7 @@ 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


-- 
Masami Hiramatsu <mhiramat@...nel.org>