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

[Jeremy Fitzhardinge <jeremy@goop.org>]

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