linux-kernel - Re: [PATCH 1/2] uprobes: add comment with insn opcodes, mnemonics and why we dont support them

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Date:	Mon, 5 May 2014 21:41:00 +0200
From:	Oleg Nesterov <oleg@...hat.com>
To:	Denys Vlasenko <dvlasenk@...hat.com>
Cc:	linux-kernel@...r.kernel.org, Jim Keniston <jkenisto@...ibm.com>,
	Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>,
	Srikar Dronamraju <srikar@...ux.vnet.ibm.com>,
	Ingo Molnar <mingo@...nel.org>
Subject: Re: [PATCH 1/2] uprobes: add comment with insn opcodes, mnemonics
	and why we dont support them

On 05/05, Denys Vlasenko wrote:
>
> + * Opcodes we'll probably never support:
> + * 6c-6f - ins,outs. SEGVs if used in userspace
> + * e4-e7 - in,out imm. SEGVs if used in userspace
> + * ec-ef - in,out acc. SEGVs if used in userspace

Well. I have no idea why they are nacked, but this is not the reason.

SEGVs are fine. Plus we have ioperm().

> + * cc - int3. SIGTRAP if used in userspace

SIGTRAP is not the reason. We do not want to enter do_int3() in UTASK_SSTEP
state with utask->active_uprobe != NULL etc. Too many potential complications.

Oleg.

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