On Tue, 3 Nov 2020 08:42:44 +0100
Helge Deller <deller@xxxxxx> wrote:
> As noticed by Masami Hiramatsu, get_kprobe() must be called with preempt
> disabled.
Doesn't parisc ftrace implementation preempt off? Then it is required.
Steve, can we expect that op->func() is called under preempt off always
on any arch or is it arch dependent?
Thank you,
>
> Noticed-by: Masami Hiramatsu <mhiramat@xxxxxxxxxx>
> Signed-off-by: Helge Deller <deller@xxxxxx>
>
> diff --git a/arch/parisc/kernel/ftrace.c b/arch/parisc/kernel/ftrace.c
> index 63e3ecb9da81..dd356ad18aca 100644
> --- a/arch/parisc/kernel/ftrace.c
> +++ b/arch/parisc/kernel/ftrace.c
> @@ -207,13 +212,22 @@ void kprobe_ftrace_handler(unsigned long ip, unsigned long parent_ip,
> struct ftrace_ops *ops, struct pt_regs *regs)
> {
> struct kprobe_ctlblk *kcb;
> - struct kprobe *p = get_kprobe((kprobe_opcode_t *)ip);
> + struct kprobe *p;
> +
> + /*
> + * We don't want to be preempted for the entire
> + * duration of kprobe processing
> + */
> + preempt_disable();
> + p = get_kprobe((kprobe_opcode_t *)ip);
>
> if (unlikely(!p) || kprobe_disabled(p))
> + preempt_enable_no_resched();
> return;
>
> if (kprobe_running()) {
> kprobes_inc_nmissed_count(p);
> + preempt_enable_no_resched();
> return;
> }
>
> @@ -235,6 +249,8 @@ void kprobe_ftrace_handler(unsigned long ip, unsigned long parent_ip,
> }
> }
> __this_cpu_write(current_kprobe, NULL);
> +
> + preempt_enable_no_resched();
> }
> NOKPROBE_SYMBOL(kprobe_ftrace_handler);
>
--
Masami Hiramatsu <mhiramat@xxxxxxxxxx>
