linux-kernel - Re: [PATCH v12 05/10] arm64: Kprobes with single stepping support

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Message-ID: <20160517091009.GA5082@sha-win-210.asiapac.arm.com>
Date:	Tue, 17 May 2016 17:10:12 +0800
From:	Huang Shijie <shijie.huang@....com>
To:	David Long <dave.long@...aro.org>
CC:	Catalin Marinas <catalin.marinas@....com>,
	Will Deacon <will.deacon@....com>,
	Sandeepa Prabhu <sandeepa.s.prabhu@...il.com>,
	William Cohen <wcohen@...hat.com>,
	Pratyush Anand <panand@...hat.com>,
	Steve Capper <steve.capper@...aro.org>,
	<linux-arm-kernel@...ts.infradead.org>,
	<linux-kernel@...r.kernel.org>,
	Marc Zyngier <marc.zyngier@....com>,
	Mark Rutland <mark.rutland@....com>,
	Petr Mladek <pmladek@...e.com>,
	Viresh Kumar <viresh.kumar@...aro.org>,
	John Blackwood <john.blackwood@...r.com>,
	Feng Kan <fkan@....com>, Zi Shen Lim <zlim.lnx@...il.com>,
	Dave P Martin <Dave.Martin@....com>,
	Yang Shi <yang.shi@...aro.org>,
	Vladimir Murzin <Vladimir.Murzin@....com>,
	Kees Cook <keescook@...omium.org>,
	"Suzuki K. Poulose" <suzuki.poulose@....com>,
	Mark Brown <broonie@...nel.org>,
	Alex Bennée <alex.bennee@...aro.org>,
	Ard Biesheuvel <ard.biesheuvel@...aro.org>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Mark Salyzyn <salyzyn@...roid.com>,
	James Morse <james.morse@....com>,
	Christoffer Dall <christoffer.dall@...aro.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Robin Murphy <Robin.Murphy@....com>,
	Jens Wiklander <jens.wiklander@...aro.org>,
	Balamurugan Shanmugam <bshanmugam@....com>, <nd@....com>
Subject: Re: [PATCH v12 05/10] arm64: Kprobes with single stepping support

On Wed, Apr 27, 2016 at 02:53:00PM -0400, David Long wrote:
> From: Sandeepa Prabhu <sandeepa.s.prabhu@...il.com>
> +
> +static bool __kprobes aarch64_insn_is_steppable(u32 insn)

Could we add more comment for this function? In the comment, we can tell
that which type of instructions are steppable, which are not.

> +{
> +	if (aarch64_get_insn_class(insn) == AARCH64_INSN_CLS_BR_SYS) {
> +		if (aarch64_insn_is_branch(insn) ||
> +		    aarch64_insn_is_msr_imm(insn) ||
> +		    aarch64_insn_is_msr_reg(insn) ||
> +		    aarch64_insn_is_exception(insn))
> +			return false;
> +
> +		if (aarch64_insn_is_mrs(insn))
> +			return aarch64_insn_extract_system_reg(insn)
> +			     != AARCH64_INSN_SPCLREG_DAIF;
> +
> +		if (aarch64_insn_is_hint(insn))
> +			return aarch64_insn_is_nop(insn);
> +
> +		return true;
> +	}
> +
> +	if (aarch64_insn_uses_literal(insn) ||
> +	    aarch64_insn_is_exclusive(insn))
> +		return false;
> +
> +	return true;

Thanks
Huang Shijie