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

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Message-ID: <20120227093421.GA10078@elte.hu>
Date:	Mon, 27 Feb 2012 10:34:21 +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: [PATCH v3 -tip] [BUGFIX] x86/kprobes: Fix to recover
 instructions on optimized path


* 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?

> +
> +/*
> + * 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.

Thanks,

	Ingo
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