linux-kernel - Re: [PATCH v3 2/4] x86, mpx: hook #BR exception handler to allocate bound tables

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Date:	Tue, 28 Jan 2014 14:46:57 +0800
From:	Ren Qiaowei <qiaowei.ren@...el.com>
To:	Andy Lutomirski <luto@...capital.net>
CC:	"H. Peter Anvin" <hpa@...or.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>, X86 ML <x86@...nel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v3 2/4] x86, mpx: hook #BR exception handler to allocate
 bound tables

On 01/28/2014 02:42 PM, Andy Lutomirski wrote:
> I just read it.  do_trap_no_signal presumably calls fixup_exception
> because #UD uses it and #UD needs that handling.  (I'm guessing that
> there is actually a legitimate use for a kernel fixup on #UD somewhere
> -- there's probably something that isn't covered by cpuid.)
>
> There should not be a #BR from the kernel using the fixup mechanism.
> IMO if the exception comes from the kernel, it should unconditionally
> call die.
>
Oh. I agree with you, and if a #BR from the kernel it should 
unconditionally call die.

	if (!user_mode(regs))
		die("bounds", regs, error_code);

Thanks,
Qiaowei
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