linux-kernel - RE: [PATCH v2 0/4] Intel MPX support

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Date:	Wed, 22 Jan 2014 08:51:14 +0000
From:	"Ren, Qiaowei" <qiaowei.ren@...el.com>
To:	David Rientjes <rientjes@...gle.com>
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 v2 0/4] Intel MPX support

> -----Original Message-----
> From: David Rientjes [mailto:rientjes@...gle.com]
> Sent: Wednesday, January 22, 2014 4:01 PM
> To: Ren, Qiaowei
> Cc: H. Peter Anvin; Thomas Gleixner; Ingo Molnar; x86@...nel.org;
> linux-kernel@...r.kernel.org
> Subject: Re: [PATCH v2 0/4] Intel MPX support
> 
> On Wed, 22 Jan 2014, Qiaowei Ren wrote:
> 
> > Changes since v1:
> >   * check to see if #BR occurred in userspace or kernel space.
> >   * use generic structure and macro as much as possible when
> >     decode mpx instructions.
> >
> > Qiaowei Ren (4):
> >   x86, mpx: add documentation on Intel MPX
> >   x86, mpx: hook #BR exception handler to allocate bound tables
> >   x86, mpx: add prctl commands PR_MPX_INIT, PR_MPX_RELEASE
> >   x86, mpx: extend siginfo structure to include bound violation
> >     information
> >
> >  Documentation/x86/intel_mpx.txt    |   76 +++++++
> >  arch/x86/Kconfig                   |    4 +
> >  arch/x86/include/asm/mpx.h         |   63 ++++++
> >  arch/x86/include/asm/processor.h   |   16 ++
> >  arch/x86/kernel/Makefile           |    1 +
> >  arch/x86/kernel/mpx.c              |  417
> ++++++++++++++++++++++++++++++++++++
> >  arch/x86/kernel/traps.c            |   61 +++++-
> >  include/uapi/asm-generic/siginfo.h |    9 +-
> >  include/uapi/linux/prctl.h         |    6 +
> >  kernel/signal.c                    |    4 +
> >  kernel/sys.c                       |   12 +
> >  11 files changed, 667 insertions(+), 2 deletions(-)  create mode
> > 100644 Documentation/x86/intel_mpx.txt  create mode 100644
> > arch/x86/include/asm/mpx.h  create mode 100644 arch/x86/kernel/mpx.c
> >
> 
> There's compiler warnings spread amongst the various patches with x86_64
> defconfig:
> 
> arch/x86/kernel/mpx.c: In function ‘do_mpx_bounds’:
> arch/x86/kernel/mpx.c:415:2: warning: format ‘%lx’ expects argument of
> type ‘long unsigned int’, but argument 3 has type ‘void *’ [-Wformat]
> arch/x86/kernel/mpx.c:415:2: warning: format ‘%lx’ expects argument of
> type ‘long unsigned int’, but argument 4 has type ‘void *’ [-Wformat]
> arch/x86/kernel/mpx.c: In function ‘do_mpx_bt_fault’:
> arch/x86/kernel/mpx.c:373:5: warning: ‘old_val’ may be used uninitialized in
> this function [-Wuninitialized]
> arch/x86/kernel/mpx.c:360:25: note: ‘old_val’ was declared here
> 
I will fix these warnings.
old_val will be set by user_atomic_cmpxchg_inatomic().

> and I had to resolve the second patch manually because of "x86/traps:
> Clean up error exception handler definitions" in the x86 tree.
> 
There is a conflict with latest kernel. I just fixed it and built successfully.

> With 32-bit, we get casting warnings:
> 
> arch/x86/kernel/mpx.c: In function ‘do_mpx_bounds’:
> arch/x86/kernel/mpx.c:407:3: warning: cast to pointer from integer of different
> size [-Wint-to-pointer-cast]
> arch/x86/kernel/mpx.c:409:3: warning: cast to pointer from integer of different
> size [-Wint-to-pointer-cast]
> 
> and I'm pretty sure you want this to be available for such a config.
> 
> There's also whitespace in the fourth patch.
Thanks much for your feedback.

Qiaowei