linux-kernel - Re: [PATCH 2/4] LoongArch: Add prologue unwinder support

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Date:   Tue, 2 Aug 2022 09:34:01 +0800
From:   Huacai Chen <chenhuacai@...nel.org>
To:     Youling Tang <tangyouling@...ngson.cn>
Cc:     Qing Zhang <zhangqing@...ngson.cn>,
        WANG Xuerui <kernel@...0n.name>, loongarch@...ts.linux.dev,
        LKML <linux-kernel@...r.kernel.org>,
        Jiaxun Yang <jiaxun.yang@...goat.com>,
        Jinyang He <hejinyang@...ngson.cn>
Subject: Re: [PATCH 2/4] LoongArch: Add prologue unwinder support

Hi, Youling,

On Tue, Aug 2, 2022 at 9:30 AM Youling Tang <tangyouling@...ngson.cn> wrote:
>
>
>
> On 08/01/2022 11:26 PM, Huacai Chen wrote:
> >> diff --git a/arch/loongarch/include/asm/unwind.h b/arch/loongarch/include/asm/unwind.h
> >> index 243330b39d0d..f9f73a26504e 100644
> >> --- a/arch/loongarch/include/asm/unwind.h
> >> +++ b/arch/loongarch/include/asm/unwind.h
> >> @@ -14,6 +14,14 @@
> >>  struct unwind_state {
> >>         struct stack_info stack_info;
> >>         struct task_struct *task;
> >> +#if defined(CONFIG_UNWINDER_PROLOGUE)
> >> +       unsigned long ra;
> >> +       bool enable;
> >> +       /*
> >> +        * Enable is the prologue analysis method
> >> +        * otherwise is the way to guess.
> >> +        */
> >> +#endif
> >>         unsigned long sp, pc;
> >>         bool first;
> >>         bool error;
> > This data struct makes me very uncomfortable, especially "enable" and
> > the #ifdef, maybe we can rework it like this?
> >
> > #define UNWINDER_GUESS     0
> > #define UNWINDER_PROLOGURE 1
>
> Maybe it's better to define with enum type?
> enum unwind_type {
>         UNWINDER_GUESS,
>         UNWINDER_PROLOGURE,
> };
Both macro and enum are acceptable, but enum is essentially "int",
while the "type" member is "char" here.

Huacai
>
> Youling
>
> > struct unwind_state {
> >         char type; /* UNWINDER_xxx */
> >         bool first, error;
> >         unsigned long sp, pc, ra;
> >         struct task_struct *task;
> >         struct stack_info stack_info;
> > };
> >
> > Huacai
>
>