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

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Message-ID: <4F4C4182.1040706@hitachi.com>
Date:	Tue, 28 Feb 2012 11:52:50 +0900
From:	Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>
To:	Ingo Molnar <mingo@...e.hu>
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: [PATCH v3 -tip] [BUGFIX] x86/kprobes: Fix to recover instructions
 on optimized path

(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?

> 
>> +
>> +/*
>> + * Recover the probed instruction at addr for further analysis.
>> + * Caller must lock kprobes by kprobe_mutex, or disable preemption
>> + * for preventing to release referencing kprobes.
>> + */
>> +static unsigned long recover_probed_instruction(kprobe_opcode_t *buf,
>> +						unsigned long addr)
>> +{
>> +	struct kprobe *kp;
>> +#ifdef CONFIG_OPTPROBES
>> +	int i;
>> +
>> +	for (i = 0; i < RELATIVEJUMP_SIZE; i++) {
>> +		kp = get_kprobe((void *)addr - i);
>> +		if (kp && kprobe_optready(kp))
>> +			return __recover_optprobed_insn(kp, buf, addr);
>> +	}
>> +#endif
> 
> This should be a separate, kprobes_recover_opt() method and be 
> inside kprobes-opt.c as well.

OK, I'll do that. But I think it should be separated work.
Just for the bugfix, I think this should go into this style,
because this should be pushed into stable tree too.

Thank you,

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