linux-kernel - Re: [PATCH] x86: kprobes remove fix

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Date:	Sun, 30 Dec 2007 01:37:33 -0500
From:	Masami Hiramatsu <mhiramat@...hat.com>
To:	Harvey Harrison <harvey.harrison@...il.com>,
	Ananth N Mavinakayanahalli <ananth@...ibm.com>,
	Jim Keniston <jkenisto@...ibm.com>
CC:	Ingo Molnar <mingo@...e.hu>, LKML <linux-kernel@...r.kernel.org>,
	"H. Peter Anvin" <hpa@...or.com>,
	Thomas Gleixner <tglx@...utronix.de>
Subject: Re: [PATCH] x86: kprobes remove fix_riprel #ifdef

Hello Harvey,

A similar idea was already nack-ed by Ananth.
http://sources.redhat.com/ml/systemtap/2007-q4/msg00468.html
And I agree his thought.

Especially, "riprel" does not exist on x86_32, so fix_riprel()
is meaningless on it.
Thus, I think it would better be ifdef'd in call-site.

Harvey Harrison wrote:
> Move #ifdef around function definiton into the function and
> unconditionally return on X86_32.  Saves an ifdef from the
> one callsite.
> 
> Signed-off-by: Harvey Harrison <harvey.harrison@...il.com>
> ---
> Ingo, Masami, final leftovers from some unsent kprobes unification work.
> 
> Net reduction of one #ifdef section.
> 
>  arch/x86/kernel/kprobes.c |   11 +++++++----
>  1 files changed, 7 insertions(+), 4 deletions(-)
> 
> diff --git a/arch/x86/kernel/kprobes.c b/arch/x86/kernel/kprobes.c
> index b1804e4..1ac532e 100644
> --- a/arch/x86/kernel/kprobes.c
> +++ b/arch/x86/kernel/kprobes.c
> @@ -263,15 +263,16 @@ static int __kprobes is_IF_modifier(kprobe_opcode_t *insn)
>  	return 0;
>  }
>  
> -#ifdef CONFIG_X86_64
>  /*
>   * Adjust the displacement if the instruction uses the %rip-relative
>   * addressing mode.
>   * If it does, Return the address of the 32-bit displacement word.
>   * If not, return null.
> + * Only applicable to X86_64
>   */
>  static void __kprobes fix_riprel(struct kprobe *p)
>  {
> +#ifdef CONFIG_X86_64
>  	u8 *insn = p->ainsn.insn;
>  	s64 disp;
>  	int need_modrm;
> @@ -335,15 +336,17 @@ static void __kprobes fix_riprel(struct kprobe *p)
>  			*(s32 *)insn = (s32) disp;
>  		}
>  	}
> -}
> +#else
> +	return;
>  #endif
> +}
>  
>  static void __kprobes arch_copy_kprobe(struct kprobe *p)
>  {
>  	memcpy(p->ainsn.insn, p->addr, MAX_INSN_SIZE * sizeof(kprobe_opcode_t));
> -#ifdef CONFIG_X86_64
> +
>  	fix_riprel(p);
> -#endif
> +
>  	if (can_boost(p->addr))
>  		p->ainsn.boostable = 0;
>  	else

-- 
Masami Hiramatsu

Software Engineer
Hitachi Computer Products (America) Inc.
Software Solutions Division

e-mail: mhiramat@...hat.com, masami.hiramatsu.pt@...achi.com

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