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Date: Fri, 18 Aug 2023 19:56:45 +0900
From: Masami Hiramatsu (Google) <mhiramat@kernel.org>
To: Florent Revest <revest@chromium.org>
Cc: Alexei Starovoitov <alexei.starovoitov@gmail.com>, Steven Rostedt
 <rostedt@goodmis.org>, linux-trace-kernel@vger.kernel.org, LKML
 <linux-kernel@vger.kernel.org>, Martin KaFai Lau <martin.lau@linux.dev>,
 bpf <bpf@vger.kernel.org>, Sven Schnelle <svens@linux.ibm.com>, Alexei
 Starovoitov <ast@kernel.org>, Jiri Olsa <jolsa@kernel.org>, Arnaldo
 Carvalho de Melo <acme@kernel.org>, Daniel Borkmann <daniel@iogearbox.net>,
 Alan Maguire <alan.maguire@oracle.com>, Mark Rutland
 <mark.rutland@arm.com>, Peter Zijlstra <peterz@infradead.org>, Thomas
 Gleixner <tglx@linutronix.de>
Subject: Re: [PATCH v3 2/8] fprobe: Use fprobe_regs in fprobe entry handler
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On Thu, 17 Aug 2023 10:57:26 +0200
Florent Revest <revest@chromium.org> wrote:

> On Sat, Aug 12, 2023 at 7:37 AM Masami Hiramatsu (Google)
> <mhiramat@kernel.org> wrote:
> > --- a/kernel/trace/bpf_trace.c
> > +++ b/kernel/trace/bpf_trace.c
> > @@ -2467,7 +2467,7 @@ static int __init bpf_event_init(void)
> >  fs_initcall(bpf_event_init);
> >  #endif /* CONFIG_MODULES */
> >
> > -#ifdef CONFIG_FPROBE
> > +#ifdef CONFIG_DYNAMIC_FTRACE_WITH_REGS
> 
> Shouldn't this be #if defined(CONFIG_FPROBE) &&
> defined(CONFIG_DYNAMIC_FTRACE_WITH_REGS) ?

Oops, that's right!

> 
> I believe one could build a kernel with FTRACE_WITH_REGS and without
> FPROBE and then this code would have undefined references to fprobe
> functions, wouldn't it ?

Yeah, ftrace with regs doesn't mean fprobe is enabled.

> 
> And then patch 7 should be "Enable kprobe_multi feature even if
> FTRACE_WITH_REGS is disabled"

OK.

Thank you!


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