linux-kernel - Re: [PATCH 5/6] LoongArch: Add raw_show_trace to enable guess unwinder default

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Message-ID: <CAAhV-H4QwWV+q_ROSbw10n3mj64BPsiAoErR7k_wZ4v0zG3nhw@mail.gmail.com>
Date:   Thu, 15 Dec 2022 14:15:57 +0800
From:   Huacai Chen <chenhuacai@...nel.org>
To:     Jinyang He <hejinyang@...ngson.cn>
Cc:     WANG Xuerui <kernel@...0n.name>,
        Qing Zhang <zhangqing@...ngson.cn>, loongarch@...ts.linux.dev,
        linux-kernel@...r.kernel.org, Steven Rostedt <rostedt@...dmis.org>,
        Masami Hiramatsu <mhiramat@...nel.org>,
        Mark Rutland <mark.rutland@....com>
Subject: Re: [PATCH 5/6] LoongArch: Add raw_show_trace to enable guess
 unwinder default

Hi, Jinyang,

Is this patch really necessary?

Huacai

On Thu, Dec 15, 2022 at 12:02 PM Jinyang He <hejinyang@...ngson.cn> wrote:
>
> Inspired by MIPS, add cmdline parameter named 'raw_show_trace' to
> enable guess unwinder in prologue unwinder unwind_start() default.
> In some cases the guess is more efficient than prologue.
>
> Signed-off-by: Jinyang He <hejinyang@...ngson.cn>
> ---
>  arch/loongarch/kernel/unwind_prologue.c | 11 +++++++++++
>  1 file changed, 11 insertions(+)
>
> diff --git a/arch/loongarch/kernel/unwind_prologue.c b/arch/loongarch/kernel/unwind_prologue.c
> index 9677e13c4b4c..441641227c10 100644
> --- a/arch/loongarch/kernel/unwind_prologue.c
> +++ b/arch/loongarch/kernel/unwind_prologue.c
> @@ -122,11 +122,22 @@ static bool unwind_by_prologue(struct unwind_state *state)
>         return !!__kernel_text_address(state->pc);
>  }
>
> +static int raw_show_trace;
> +static int __init set_raw_show_trace(char *str)
> +{
> +       raw_show_trace = 1;
> +       return 1;
> +}
> +__setup("raw_show_trace", set_raw_show_trace);
> +
>  static void start(struct unwind_state *state, struct task_struct *task,
>                     struct pt_regs *regs)
>  {
>         state->first = true;
>
> +       if (raw_show_trace)
> +               unwind_register_unwinder(state, guard_unwinder);
> +
>         /*
>          * The current PC is not kernel text address, we cannot find its
>          * relative symbol. Thus, prologue analysis will be broken. Luckly,
> --
> 2.34.3
>