linux-kernel - Re: [PATCH 2/2] kprobes: modify the copy

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Message-Id: <20220731234140.ad23f7d8c7c389112ac65487@kernel.org>
Date:   Sun, 31 Jul 2022 23:41:40 +0900
From:   Masami Hiramatsu (Google) <mhiramat@...nel.org>
To:     zhangduo <zduo006@....com>
Cc:     anil.s.keshavamurthy@...el.com, davem@...emloft.net,
        linux-kernel@...r.kernel.org, mhiramat@...nel.org,
        naveen.n.rao@...ux.ibm.com, zhangduo@...inos.cn
Subject: Re: [PATCH 2/2] kprobes: modify the copy_kprobe to make more
 clearly

On Thu, 28 Jul 2022 20:45:16 +0800
zhangduo <zduo006@....com> wrote:

> From: zhangduo <zhangduo@...inos.cn>
> 
>   copy_kprobe() are called in init_aggr_kprobe() to copy opcode
>   and insn from 'p' to 'ap',but in copy_kprobe(p,ap) implemtation
>   'p' pass to 'struct kprobe *ap' , 'ap' pass to 'struct kprobe *p',
>   it looks strange, because p means orig kprobe instance, ap
>   means aggregator kprobe, not the same.  and before the add_new_kprobe()
>   calling used the opposite copy from 'ap' to 'p', so modify copy_kprobe's
>   parameter name as 'p_src' and 'p_dst' to fit all.

Agreed, that was confusing.

This doesn not change the behavior, but better to be read
(the arguments are sorted as same as memcpy(dst, src))

Acked-by: Masami Hiramatsu (Google) <mhiramat@...nel.org>

Thanks!

> 
> Signed-off-by: zhangduo <zhangduo@...inos.cn>
> ---
>  kernel/kprobes.c | 10 +++++-----
>  1 file changed, 5 insertions(+), 5 deletions(-)
> 
> diff --git a/kernel/kprobes.c b/kernel/kprobes.c
> index 4f3e84343..8bcef7d3c 100644
> --- a/kernel/kprobes.c
> +++ b/kernel/kprobes.c
> @@ -405,10 +405,10 @@ static inline bool kprobe_unused(struct kprobe *p)
>  }
>  
>  /* Keep all fields in the kprobe consistent. */
> -static inline void copy_kprobe(struct kprobe *ap, struct kprobe *p)
> +static inline void copy_kprobe(struct kprobe *p_dst, struct kprobe *p_src)
>  {
> -	memcpy(&p->opcode, &ap->opcode, sizeof(kprobe_opcode_t));
> -	memcpy(&p->ainsn, &ap->ainsn, sizeof(struct arch_specific_insn));
> +	memcpy(&p_dst->opcode, &p_src->opcode, sizeof(kprobe_opcode_t));
> +	memcpy(&p_dst->ainsn, &p_src->ainsn, sizeof(struct arch_specific_insn));
>  }
>  
>  #ifdef CONFIG_OPTPROBES
> @@ -1277,7 +1277,7 @@ static int add_new_kprobe(struct kprobe *ap, struct kprobe *p)
>  static void init_aggr_kprobe(struct kprobe *ap, struct kprobe *p)
>  {
>  	/* Copy the insn slot of 'p' to 'ap'. */
> -	copy_kprobe(p, ap);
> +	copy_kprobe(ap, p);
>  	flush_insn_slot(ap);
>  	ap->addr = p->addr;
>  	ap->flags = p->flags & ~KPROBE_FLAG_OPTIMIZED;
> @@ -1350,7 +1350,7 @@ static int register_aggr_kprobe(struct kprobe *orig_p, struct kprobe *p)
>  	}
>  
>  	/* Copy the insn slot of 'ap' to 'p'. */
> -	copy_kprobe(ap, p);
> +	copy_kprobe(p, ap);
>  	ret = add_new_kprobe(ap, p);
>  
>  out:
> -- 
> 2.25.1
> 


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