linux-kernel - Re: [PATCH] uprobes: fix scratch register selection for rip-relative fixups

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Message-ID: <20140501191123.GA17949@redhat.com>
Date:	Thu, 1 May 2014 21:11:23 +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] uprobes: fix scratch register selection for
	rip-relative fixups

On 05/01, Denys Vlasenko wrote:
>
> Before this patch, instructions such as div, mul,
> shifts with count in CL, cmpxchg are mishandled.

Thanks. I'll try to read this patch tomorrow, but you do know that I can't
review (or even understand ;) the change in riprel_analyze().

As for other changes, perhaps we can cleanup them later somehow, but I am
not going to discuss this now. I agree that the fix should be as simple
as possible.

Only on nit,

> -#define UPROBE_FIX_RIP_AX	0x08
> -#define UPROBE_FIX_RIP_CX	0x10
> +#define UPROBE_FIX_RIP_SI	0x08
> +#define UPROBE_FIX_RIP_DI	0x10
> +#define UPROBE_FIX_RIP_BX	0x20
> +#define UPROBE_FIX_RIP_ALL	0x38

OK, but please define UPROBE_FIX_RIP_ALL as

	#define UPROBE_FIX_RIP_ALL	\
		(UPROBE_FIX_RIP_SI | UPROBE_FIX_RIP_DI | UPROBE_FIX_RIP_BX)

Please do not bother to do this right now, lets wait for review.

Oleg.

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