linux-kernel - Re: [RFC PATCH v3 15/26] early kprobes: x86: directly modify code.

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Message-ID: <54E6B172.7080604@hitachi.com>
Date:	Fri, 20 Feb 2015 13:00:50 +0900
From:	Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>
To:	Wang Nan <wangnan0@...wei.com>
Cc:	linux@....linux.org.uk, tglx@...utronix.de, mingo@...hat.com,
	hpa@...or.com, rostedt@...dmis.org, ananth@...ibm.com,
	anil.s.keshavamurthy@...el.com, davem@...emloft.net,
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	yalin.wang2010@...il.com, catalin.marinas@....com,
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	fabf@...net.be, hannes@...xchg.org, x86@...nel.org,
	linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
	lizefan@...wei.com,
	"yrl.pp-manager.tt@...achi.com" <yrl.pp-manager.tt@...achi.com>
Subject: Re: [RFC PATCH v3 15/26] early kprobes: x86: directly modify code.

(2015/02/13 14:40), Wang Nan wrote:
> When registering early kprobes, SMP should has not been enabled, so
> doesn't require synchronization in text_poke_bp(). Simply memcpy is
> enough.

BTW, we've already have text_poke_early for this purpose.

Thank you,

> 
> Signed-off-by: Wang Nan <wangnan0@...wei.com>
> ---
>  arch/x86/kernel/kprobes/opt.c | 12 ++++++++++--
>  1 file changed, 10 insertions(+), 2 deletions(-)
> 
> diff --git a/arch/x86/kernel/kprobes/opt.c b/arch/x86/kernel/kprobes/opt.c
> index 0dd8d08..21847ab 100644
> --- a/arch/x86/kernel/kprobes/opt.c
> +++ b/arch/x86/kernel/kprobes/opt.c
> @@ -36,6 +36,7 @@
>  #include <asm/alternative.h>
>  #include <asm/insn.h>
>  #include <asm/debugreg.h>
> +#include <asm/tlbflush.h>
>  
>  #include "common.h"
>  
> @@ -397,8 +398,15 @@ void arch_optimize_kprobes(struct list_head *oplist)
>  		insn_buf[0] = RELATIVEJUMP_OPCODE;
>  		*(s32 *)(&insn_buf[1]) = rel;
>  
> -		text_poke_bp(op->kp.addr, insn_buf, RELATIVEJUMP_SIZE,
> -			     op->optinsn.insn);
> +		if (unlikely(kprobes_is_early())) {
> +			BUG_ON(!(op->kp.flags & KPROBE_FLAG_EARLY));
> +			memcpy(op->kp.addr, insn_buf, RELATIVEJUMP_SIZE);
> +			local_flush_tlb();
> +			sync_core();
> +		} else {
> +			text_poke_bp(op->kp.addr, insn_buf, RELATIVEJUMP_SIZE,
> +				     op->optinsn.insn);
> +		}
>  
>  		list_del_init(&op->list);
>  	}
> 


-- 
Masami HIRAMATSU
Software Platform Research Dept. Linux Technology Research Center
Hitachi, Ltd., Yokohama Research Laboratory
E-mail: masami.hiramatsu.pt@...achi.com


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