linux-kernel - RE: [PATCH v6 04/10] x86, mpx: hook #BR exception handler to allocate bound tables

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Date:	Tue, 24 Jun 2014 01:53:18 +0000
From:	"Ren, Qiaowei" <qiaowei.ren@...el.com>
To:	Andy Lutomirski <luto@...capital.net>,
	"H. Peter Anvin" <hpa@...or.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	"Hansen, Dave" <dave.hansen@...el.com>
CC:	"x86@...nel.org" <x86@...nel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: [PATCH v6 04/10] x86, mpx: hook #BR exception handler to
 allocate bound tables

On 2014-06-24, Andy Lutomirski wrote:
> On 06/18/2014 02:44 AM, Qiaowei Ren wrote:
>> +	/*
>> +	 * The error code field of the BNDSTATUS register communicates status
>> +	 * information of a bound range exception #BR or operation involving
>> +	 * bound directory.
>> +	 */
>> +	switch (status & MPX_BNDSTA_ERROR_CODE) {
>> +	case 2:
>> +		/*
>> +		 * Bound directory has invalid entry.
>> +		 * No signal will be sent to the user space.
> 
> This comment is a lie.
> 
Hmm, thanks. 

>> +		 */
>> +		if (do_mpx_bt_fault(xsave_buf))
>> +			force_sig(SIGBUS, tsk);
> 
> Would it make sense to assign and use a new si_code value here?
> 
There is a new si_code SEGV_BNDERR for bounds violation reported by MPX. But in this case, it is mainly due to the failure caused by allocation of bounds table. I guess it is not necessary to add another new si_code value.

Thanks,
Qiaowei
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