linux-kernel - Re: [RFC 8/8] ARM64: Add uprobe support

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Message-ID: <20150109175936.GB13161@redhat.com>
Date:	Fri, 9 Jan 2015 18:59:36 +0100
From:	Oleg Nesterov <oleg@...hat.com>
To:	Pratyush Anand <panand@...hat.com>
Cc:	linux-arm-kernel@...ts.infradead.org, linux@....linux.org.uk,
	tixy@...aro.org, ananth@...ibm.com, sandeepa.prabhu@...aro.org,
	catalin.marinas@....com, will.deacon@....com,
	linux-kernel@...r.kernel.org, anil.s.keshavamurthy@...el.com,
	masami.hiramatsu.pt@...achi.com, wcohen@...hat.com
Subject: Re: [RFC 8/8] ARM64: Add uprobe support

On 12/31, Pratyush Anand wrote:
>
> +int arch_uprobe_analyze_insn(struct arch_uprobe *auprobe, struct mm_struct *mm,
> +		unsigned long addr)
> +{
> +	probe_opcode_t insn;
> +
> +	insn = *(probe_opcode_t *)(&auprobe->insn[0]);
> +
> +	switch (arm_probe_decode_insn(insn, &auprobe->ainsn)) {
> +	case INSN_REJECTED:
> +		return -EINVAL;
> +
> +	case INSN_GOOD_NO_SLOT:
> +		auprobe->simulate = true;
> +		if (auprobe->ainsn.prepare)
> +			auprobe->ainsn.prepare(insn, &auprobe->ainsn);
> +		break;
> +
> +	case INSN_GOOD:
> +	default:
> +		break;
> +	}
> +
> +	return 0;
> +}

forgot to mention... shouldn't it also check IS_ALIGNED(addr, AARCH64_INSN_SIZE) ?

I do not know if unaligned insn address is valid on arm64 or not, but please
note that at least it should not cross the page boundary, set_swbp() needs to
write AARCH64_INSN_SIZE == UPROBE_SWBP_INSN bytes and it assumes that this
should fit the single page.

Oleg.

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