linux-kernel - Re: Dealing with the NMI mess

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Message-ID: <20150724102826.GP25159@twins.programming.kicks-ass.net>
Date:	Fri, 24 Jul 2015 12:28:26 +0200
From:	Peter Zijlstra <peterz@...radead.org>
To:	Andy Lutomirski <luto@...capital.net>
Cc:	Linus Torvalds <torvalds@...ux-foundation.org>,
	X86 ML <x86@...nel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Willy Tarreau <w@....eu>, Borislav Petkov <bp@...en8.de>,
	Thomas Gleixner <tglx@...utronix.de>,
	Steven Rostedt <rostedt@...dmis.org>,
	Brian Gerst <brgerst@...il.com>
Subject: Re: Dealing with the NMI mess

On Thu, Jul 23, 2015 at 02:59:46PM -0700, Andy Lutomirski wrote:
> OK, new proposal:
> 
> In do_debug, if we trip an instruction breakpoint while
> !user_mode(regs) && ((regs->flags & X86_EFLAGS_IF) == 0), then disarm
> *that breakpoint*.

Doesn't !IF already imply that it must be kernel space? AFAIK user space
cannot clear IF.
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