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

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Date:	Wed, 22 Jan 2014 00:00:43 -0800 (PST)
From:	David Rientjes <rientjes@...gle.com>
To:	Qiaowei Ren <qiaowei.ren@...el.com>
cc:	"H. Peter Anvin" <hpa@...or.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>, 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

and I had to resolve the second patch manually because of "x86/traps: 
Clean up error exception handler definitions" in the x86 tree.

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.