linux-kernel - RE: [PATCH 2/5] x86, mpx: hook #BR exception handler to allocate bound tables

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Date:	Fri, 17 Jan 2014 14:47:15 +0000
From:	"Ren, Qiaowei" <qiaowei.ren@...el.com>
To:	Borislav Petkov <bp@...en8.de>
CC:	"H. Peter Anvin" <hpa@...or.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	"x86@...nel.org" <x86@...nel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: [PATCH 2/5] x86, mpx: hook #BR exception handler to allocate
 bound tables

> -----Original Message-----
> From: Borislav Petkov [mailto:bp@...en8.de]
> Sent: Monday, January 13, 2014 6:38 PM
> To: Ren, Qiaowei
> Cc: H. Peter Anvin; Thomas Gleixner; Ingo Molnar; x86@...nel.org;
> linux-kernel@...r.kernel.org
> Subject: Re: [PATCH 2/5] x86, mpx: hook #BR exception handler to allocate
> bound tables
> 
> On Mon, Jan 13, 2014 at 11:17:15AM +0800, Ren Qiaowei wrote:
> > Yes, I run this with lockdep enabled.
> 
> Ok, but you still are doing memory allocation in the exception handler,
> AFAICT:
> 
> do_bounds
> |->do_mpx_bt_fault
>    |->allocate_bt
>       |->sys_mmap_pgoff
>          |->vm_mmap_pgoff
>             |->do_mmap_pgoff
>                |->mmap_region
>                   |-> kmem_cache_zalloc(vm_area_cachep, GFP_KERNEL);
> 
Sorry for my late reply.

Petkov, could you please detail the problem? Memory allocation can't be done in the eception handler? I guess it is like do_page_fault(), right?

Thanks,
Qiaowei