linux-kernel - Re: [RFC PATCH 18/32] function_graph: Fix to initalize ftrace_ops for fgraph with ftrace_graph

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Message-Id: <20231107104924.d992919b8277be36d6fa8455@kernel.org>
Date:   Tue, 7 Nov 2023 10:49:24 +0900
From:   Masami Hiramatsu (Google) <mhiramat@...nel.org>
To:     Masami Hiramatsu (Google) <mhiramat@...nel.org>
Cc:     Alexei Starovoitov <alexei.starovoitov@...il.com>,
        Steven Rostedt <rostedt@...dmis.org>,
        Florent Revest <revest@...omium.org>,
        linux-trace-kernel@...r.kernel.org,
        LKML <linux-kernel@...r.kernel.org>,
        Martin KaFai Lau <martin.lau@...ux.dev>,
        bpf <bpf@...r.kernel.org>, Sven Schnelle <svens@...ux.ibm.com>,
        Alexei Starovoitov <ast@...nel.org>,
        Jiri Olsa <jolsa@...nel.org>,
        Arnaldo Carvalho de Melo <acme@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Alan Maguire <alan.maguire@...cle.com>,
        Mark Rutland <mark.rutland@....com>,
        Peter Zijlstra <peterz@...radead.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Guo Ren <guoren@...nel.org>
Subject: Re: [RFC PATCH 18/32] function_graph: Fix to initalize ftrace_ops
 for fgraph with ftrace_graph_func

On Mon, 6 Nov 2023 19:04:16 +0900
Masami Hiramatsu (Google) <mhiramat@...nel.org> wrote:

> On Mon,  6 Nov 2023 01:10:10 +0900
> "Masami Hiramatsu (Google)" <mhiramat@...nel.org> wrote:
> 
> > From: Masami Hiramatsu (Google) <mhiramat@...nel.org>
> > 
> > Fix to initialize the ftrace_ops of fgraph_ops with ftrace_graph_func
> > instead of ftrace_stub.
> 
> I've changed this, because fprobe entry handler is not called via
> fgraph without this. But maybe I have to set correct gops->ops.func
> after init?

I confirmed that this is right because it is introduced by
0c0593b45c9b ("x86/ftrace: Make function graph use ftrace directly")
which replaces ftrace_stub with ftrace_graph_func (which automatically
switched by architecture)

Thanks,

> 
> Thank you,
> 
> > 
> > Signed-off-by: Masami Hiramatsu (Google) <mhiramat@...nel.org>
> > ---
> >  kernel/trace/fgraph.c |    4 ++--
> >  1 file changed, 2 insertions(+), 2 deletions(-)
> > 
> > diff --git a/kernel/trace/fgraph.c b/kernel/trace/fgraph.c
> > index 597250bd30dc..858fb73440ec 100644
> > --- a/kernel/trace/fgraph.c
> > +++ b/kernel/trace/fgraph.c
> > @@ -872,7 +872,7 @@ unsigned long ftrace_graph_ret_addr(struct task_struct *task, int *idx,
> >  void fgraph_init_ops(struct ftrace_ops *dst_ops,
> >  		     struct ftrace_ops *src_ops)
> >  {
> > -	dst_ops->func = ftrace_stub;
> > +	dst_ops->func = ftrace_graph_func;
> >  	dst_ops->flags = FTRACE_OPS_FL_PID | FTRACE_OPS_FL_STUB;
> >  
> >  #ifdef FTRACE_GRAPH_TRAMP_ADDR
> > @@ -1120,7 +1120,7 @@ int register_ftrace_graph(struct fgraph_ops *gops)
> >  
> >  	if (!gops->ops.func) {
> >  		gops->ops.flags |= FTRACE_OPS_FL_STUB;
> > -		gops->ops.func = ftrace_stub;
> > +		gops->ops.func = ftrace_graph_func;
> >  #ifdef FTRACE_GRAPH_TRAMP_ADDR
> >  		gops->ops.trampoline = FTRACE_GRAPH_TRAMP_ADDR;
> >  #endif
> > 
> 
> 
> -- 
> Masami Hiramatsu (Google) <mhiramat@...nel.org>


-- 
Masami Hiramatsu (Google) <mhiramat@...nel.org>