linux-kernel - Re: [RFC PATCH] x86 NMI-safe INT3 and Page Fault (v4)

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Message-ID: <48087217.50305@goop.org>
Date:	Fri, 18 Apr 2008 20:04:07 +1000
From:	Jeremy Fitzhardinge <jeremy@...p.org>
To:	Mathieu Desnoyers <mathieu.desnoyers@...ymtl.ca>
CC:	Andi Kleen <andi@...stfloor.org>, mingo@...e.hu, akpm@...l.org,
	"H. Peter Anvin" <hpa@...or.com>,
	Steven Rostedt <rostedt@...dmis.org>,
	"Frank Ch. Eigler" <fche@...hat.com>, linux-kernel@...r.kernel.org
Subject: Re: [RFC PATCH] x86 NMI-safe INT3 and Page Fault (v4)

Mathieu Desnoyers wrote:
> +/*
> + * Only returns from a trap or exception to a NMI context (intra-privilege
> + * level near return) to the same SS and CS segments. Should be used
> + * upon trap or exception return when nested over a NMI context so no iret is
> + * issued. It takes care of modifying the eflags, rsp and returning to the
> + * previous function.
> + *
> + * The stack, at that point, looks like :
> + *
> + * 0(rsp)  RIP
> + * 8(rsp)  CS
> + * 16(rsp) EFLAGS
> + * 24(rsp) RSP
> + * 32(rsp) SS
> + *
> + * Upon execution :
> + * Copy EIP to the top of the return stack
> + * Update top of return stack address
> + * Pop eflags into the eflags register
> + * Make the return stack current
> + * Near return (popping the return address from the return stack)
> + */
> +#define INTERRUPT_RETURN_NMI_SAFE	pushq %rax;		\
> +					mov %rsp, %rax;		\
> +					mov 24+8(%rax), %rsp;	\
> +					pushq 0+8(%rax);	\
> +					pushq 16+8(%rax);	\
> +					movq (%rax), %rax;	\
> +					popfq;			\
> +					ret;
>   

I got this right first go?  I must be getting good at this...

Anyway, trailing ';', and perhaps use a consistent form for mov (either 
movq or mov in all three instances).

    J
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