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

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Date:   Tue, 8 Jan 2019 11:41:23 +0900
From:   Masami Hiramatsu <mhiramat@...nel.org>
To:     Steven Rostedt <rostedt@...dmis.org>
Cc:     Andrea Righi <righi.andrea@...il.com>,
        Masami Hiramatsu <mhiramat@...nel.org>,
        Ingo Molnar <mingo@...hat.com>, peterz@...radead.org,
        Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
        linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 2/2] kprobes: Mark ftrace mcount handler functions
 nokprobe

On Mon, 7 Jan 2019 12:29:51 -0500
Steven Rostedt <rostedt@...dmis.org> wrote:

> 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>
> 
> And zero day just caught it too.
> 
> Masami, want to fold this into your patch and send out a v2?

Yes, I'll do that.

Thank you,

> 
> -- Steve


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