linux-kernel - Re: [PATCH] kprobes: Fix to init kprobes in subsys

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Message-ID: <20190604050629.11c7ef12@oasis.local.home>
Date:   Tue, 4 Jun 2019 05:06:29 -0400
From:   Steven Rostedt <rostedt@...dmis.org>
To:     Masami Hiramatsu <mhiramat@...nel.org>
Cc:     Anders Roxell <anders.roxell@...aro.org>,
        Ingo Molnar <mingo@...nel.org>,
        "Naveen N . Rao" <naveen.n.rao@...ux.ibm.com>,
        Anil S Keshavamurthy <anil.s.keshavamurthy@...el.com>,
        "David S . Miller" <davem@...emloft.net>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] kprobes: Fix to init kprobes in subsys_initcall

On Mon,  3 Jun 2019 22:04:42 +0900
Masami Hiramatsu <mhiramat@...nel.org> wrote:

> Since arm64 kernel initializes breakpoint trap vector in arch_initcall(),
> initializing kprobe (and run smoke test) in postcore_initcall() causes
> a kernel panic.
> 
> To fix this issue, move the kprobe initialization in subsys_initcall()
> (which is called right afer the arch_initcall).
> 
> In-kernel kprobe users (ftrace and bpf) are using fs_initcall() which is
> called after subsys_initcall(), so this shouldn't cause more problem.
> 
> Reported-by: Anders Roxell <anders.roxell@...aro.org>
> Fixes: b5f8b32c93b2 ("kprobes: Initialize kprobes at postcore_initcall")

Hi Masami,

Is this really a fix, or is this just needed to add kprobes to the command line?

-- Steve


> Signed-off-by: Masami Hiramatsu <mhiramat@...nel.org>
> ---
>  kernel/kprobes.c |    2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/kernel/kprobes.c b/kernel/kprobes.c
> index 54aaaad00a47..5471efbeb937 100644
> --- a/kernel/kprobes.c
> +++ b/kernel/kprobes.c
> @@ -2289,7 +2289,7 @@ static int __init init_kprobes(void)
>  		init_test_probes();
>  	return err;
>  }
> -postcore_initcall(init_kprobes);
> +subsys_initcall(init_kprobes);
>  
>  #ifdef CONFIG_DEBUG_FS
>  static void report_probe(struct seq_file *pi, struct kprobe *p,