linux-kernel - Re: Re: Re: [PATCH v3 -tip] [BUGFIX] x86/kprobes: Fix to recover instructions on optimized path

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Date:	Tue, 28 Feb 2012 10:59:53 +0100
From:	Ingo Molnar <mingo@...e.hu>
To:	Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>
Cc:	linux-kernel@...r.kernel.org, yrl.pp-manager.tt@...achi.com,
	systemtap@...rceware.org, anderson@...hat.com,
	Thomas Gleixner <tglx@...utronix.de>,
	"H. Peter Anvin" <hpa@...or.com>,
	Ananth N Mavinakayanahalli <ananth@...ibm.com>
Subject: Re: Re: Re: [PATCH v3 -tip] [BUGFIX] x86/kprobes: Fix to recover
 instructions on optimized path


* Masami Hiramatsu <masami.hiramatsu.pt@...achi.com> wrote:

> (2012/02/28 17:48), Ingo Molnar wrote:
> > 
> > * Masami Hiramatsu <masami.hiramatsu.pt@...achi.com> wrote:
> > 
> >> (2012/02/27 18:34), Ingo Molnar wrote:
> >>>
> >>> * Masami Hiramatsu <masami.hiramatsu.pt@...achi.com> wrote:
> >>>
> >>>> +
> >>>> +#ifdef CONFIG_OPTPROBES
> >>>> +static unsigned long __recover_optprobed_insn(struct kprobe *kp,
> >>>> +					      kprobe_opcode_t *buf,
> >>>> +					      unsigned long addr)
> >>>> +{
> >>>> +	long offs = addr - (unsigned long)kp->addr - 1;
> >>>> +	struct optimized_kprobe *op = container_of(kp, struct optimized_kprobe, kp);
> >>>> +
> >>>> +	/*
> >>>> +	 * If the kprobe can be optimized, original bytes which can be
> >>>> +	 * overwritten by jump destination address. In this case, original
> >>>> +	 * bytes must be recovered from op->optinsn.copied_insn buffer.
> >>>> +	 */
> >>>> +	memcpy(buf, (void *)addr, MAX_INSN_SIZE * sizeof(kprobe_opcode_t));
> >>>> +	if (addr == (unsigned long)kp->addr) {
> >>>> +		buf[0] = kp->opcode;
> >>>> +		memcpy(buf + 1, op->optinsn.copied_insn, RELATIVE_ADDR_SIZE);
> >>>> +	} else
> >>>> +		memcpy(buf, op->optinsn.copied_insn + offs, RELATIVE_ADDR_SIZE - offs);
> >>>> +
> >>>> +	return (unsigned long)buf;
> >>>> +}
> >>>> +#endif
> >>>
> >>> Why not stick this into a new kprobes-opt.c file?
> >>
> >> Would you mean that I should split all optprobe stuffs into 
> >> new file?
> > 
> > Yeah, that would be sensible I think - and it might help avoid 
> > similar complications in the future.
> > 
> > Could (and probably should) be done in a separate patch - to 
> > keep the bits that you already fixed and tested intact.
> 
> OK, I'll make a separate patch.

Could be done on top of your existing patch, to keep things 
simpler for you - a split-up patch done before your fix would 
create a lot of conflicts in the fix patch.

Thanks,

	Ingo
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