linux-kernel - Re: [PATCH] uprobes tracer: Add stack/memory/retval access support

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Date:	Tue, 16 Oct 2012 20:55:22 +0900
From:	Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>
To:	Hyeoncheol Lee <hyc.lee@...il.com>
Cc:	acme@...stprotocols.net, LKML <linux-kernel@...r.kernel.org>,
	Srikar Dronamraju <srikar@...ux.vnet.ibm.com>,
	"yrl.pp-manager.tt@...achi.com" <yrl.pp-manager.tt@...achi.com>
Subject: Re: [PATCH] uprobes tracer: Add stack/memory/retval access support

(2012/10/16 18:02), Hyeoncheol Lee wrote:
> Event arguments except @SYM are supported. They are @ADDR,
> $stack, $stackN, $retval, and offs(arguments).
> 
> Cc: Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>
> Cc: Srikar Dronamraju <srikar@...ux.vnet.ibm.com>
> Signed-off-by: Hyeoncheol Lee <hyc.lee@...il.com>
> ---

[...]
>  #define DEFINE_FETCH_stack(type)					\
>  static __kprobes void FETCH_FUNC_NAME(stack, type)(struct pt_regs *regs,\
> -					  void *offset, void *dest)	\
> +					  void *offset, void *dest,	\
> +					  bool kprobe)			\
>  {									\
> -	*(type *)dest = (type)regs_get_kernel_stack_nth(regs,		\
> +	if (kprobe)							\
> +		*(type *)dest = (type)regs_get_kernel_stack_nth(regs,	\
>  				(unsigned int)((unsigned long)offset));	\
> +	else								\
> +		*(type *)dest = (type)regs_get_user_stack_nth(regs,	\
> +				(unsigned int)((unsigned long)offset)); \
>  }


Hmm, I don't think this is a good way to do that.
If fetching user space objects is different from the kernel one,
we'd better introduce new fetch handlers for it, instead of checking
a bool flag every time, because it will be done on every events.

Thank you,


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


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